Substituent effect on the competition between hetero-Diels-Alder and cheletropic additions of sulfur dioxide to 1-substituted buta-1,3-dienes

Helvetica Chimica Acta Vol. 85 (2002)

733

Substituent Effect on the Competition between Hetero-Diels-Alder and

Cheletropic Additions of Sulfur Dioxide to 1-Substituted Buta-1,3-dienes

by Elena Roversi¹), Fre¬de¬ric Monnat²), and Pierre Vogel*

¬

¬ ¬

Institut de chimie moleculaire et biologique, Ecole Polytechnique Federale de Lausanne, BCH,

CH-1015 Lausanne-Dorigny

and Kurt Schenk and Pietro Roversi³)

¬

Institut de Cristallographie de l×Universite de Lausanne, BSP, CH-1015 Lausanne-Dorigny

The reactivity of sulfur dioxide toward variously substituted butadienes was explored in an effort to define

the factors affecting the competition between the hetero-Diels-Alder and cheletropic additions. At low

temperature (< À 708), 1-alkyl-substituted 1,3-dienes 1 that can adopt s-cis-conformations add to SO₂in the

hetero-Diels-Alder mode in the presence of CF₃COOH as promoter. In the case of (E)-1-ethylidene-2-

methylidenecyclohexane ((E)-4a), the [4 2] cycloaddition of SO₂is fast at À908 without acid catalyst. (E)-1-

(Acyloxy)buta-1,3-dienes (E)-1c, (E)-1y, and (E)-1z with AcO, BzO, and naphthalene-2-(carbonyloxy)

substituents, respectively also undergo the hetero-Diels-Alder addition with SO₂ CF₃COOH at low

temperatures, giving a 1 :10 mixture of the corresponding cis-and trans-6-(acyloxy)sultines c-2c,y,z and t-

2c,y,z, respectively). Above À508, the sultines undergo complete cycloreversion to the corresponding dienes

and SO₂, which that add in the cheletropic mode at higher temperature to give the corresponding 2-substituted

sulfolenes (2,5-dihydrothiophene 1,1-dioxides) 3. The hetero-Diels-Alder additions of SO₂follow the Alder

endo rule, giving first the 6-substituted cis-sultines that equilibrate then with the more stable trans-isomers. This

statement is based on the assumption that the SO group in the sultine prefers a pseudo-axial rather than a

pseudo-equatorial position, as predicted by quantum calculations. The most striking observation is that electron-

rich dienes such as 1-cyclopropyl-, 1-phenyl-, 1-(4-methoxyphenyl)-, 1-(trimethylsilyl)-, 1-phenoxy-, 1-(4-

chlorophenoxy)-, 1-(4-methoxyphenoxy)-, 1-(4-nitrophenoxy)-, 1-(naphthalen-2-yloxy)-, 1-(methylthio)-, 1-

(phenylthio)-, 1-[(4-chlorophenyl)thio]-, 1-[(4-methoxyphenyl)thio]-, 1-[(4-nitrophenyl)thio]-, and 1-(phenyl-

seleno)buta-1,3-diene, as well as 1-(methoxymethylidene)-2-methylidenecyclohexane (4f) do not equilibrate

with the corresponding sultines between À100 and À108, in the presence of a large excess of SO₂, with or

without acidic promoter. The hetero-Diels-Alder additions of SO₂to 1-substituted (E)-buta-1,3-dienes are

highly regioselective, giving exclusively the corresponding 6-substituted sultines. The 1-substituted (Z)-buta-1,3-

dienes do not undergo the hetero-Diels-Alder additions with sulfur dioxide.

Introduction. In the preceding report, we have evaluated the thermodynamics and

kinetics parameters of the hetero-Diels-Alder additions of sulfur dioxide to simple 1,2-

dimethylidenecycloalkanes and have compared them with those obtained for the

corresponding cheletropic additions [1]. Earlier, we had found that the competition

between the hetero-Diels-Alder and cheletropic additions of SO₂is strongly dependent

on the substitution of the conjugated dienes [2]. Whereas (E)-1-methyl- (1a) [3] (E)-1-

ethyl-( 1b) [4], and (E)-1-acetyloxy)butadiene [5] (1c) undergo the hetero-Diels-Alder

addition with SO₂below À508 in the presence of CF₃COOH, giving first the

1

)

Current address: Orgamol, CH-1902 Evionnaz.

Current address: Department of Chemistry and Biochemistry, University of California, Los Angeles.

Current address: Global Phasing Ltd., Sheraton House, Castle Park, Cambridge, CB3 0AX, UK.

2

3

734

Helvetica Chimica Acta Vol. 85 (2002)

corresponding cis-and then the trans-6-methyl-, trans-6-ethyl-, and trans-6-(acetyloxy)-

3,6-dihydro-1,2-oxathiin 2-oxides (6-substituted sultines) 2a c, respectively, (E)-1-

chloro-, (E)-2-bromo-, and (E)-1-methoxybutadienes 1d f) gave only the corre-

sponding 2-substituted 2,5-dihydrothiophene 1,1-dioxides (sulfolenes) 3d f, respec-

tively [2] (Scheme 1). Although 1-alkoxy- and 1-(silyloxy)-1,3-dienes equilibrate with

sulfolenes rather than with the corresponding sultines at low temperature [5], the latter

unstable heterocyclic compounds are believed to be formed as reactive intermediates in

our new CÀC forming reaction involving the cocondensation of electron-rich 1,3-

dienes and alkenes with SO₂[6][7].

Scheme 1

With the hope to learn more about the factors that affect the competition between

the hetero-Diels-Alder and the cheletropic additions of SO₂, we have explored the

behavior of 1-substituted (E)-and ( Z)-1,3-dienes 1g x, 4a, and 4f under various

conditions. As we shall see, the formation of sultines is observed only for (E)-1-alkyl-

and (E)-1-(acyloxy)butadienes. In all cases, the sultines are unstable above À508 and

undergo retro-Diels-Alder reactions, with the formation of the corresponding 1,3-dienes

that react then with SO₂to generate the corresponding sulfolenes 3. Dienes 1-

substituted with electron-rich groups such as cyclopropyl (1j), aryl (1k,l), trimethylsilyl

(1m), aryloxy (1n r), methylthio (1s), arylthio (1t w), or phenylseleno (1x) refuse to

equilibrate with the corresponding sultines at low temperature and form exclusively the

corresponding sulfolenes 3j x. Diene (E)-4a reacts with SO₂without catalyst, giving

the corresponding cis-, then trans-sultine, whereas the methoxy-substituted analogs

(E)-and ( Z)-4f equilibrate only with the corresponding sulfolene⁴).

4

)

Sultines fused with benzo groups [8] and other aromatic ring systems are stable compounds [9].

Helvetica Chimica Acta Vol. 85 (2002)

735

Synthesis of the Dienes. Pure (E)-1-(tert-butyl)butadiene (E)-1g was prepared

via the acid-catalyzed dehydratation of 2,2-dimethylhex-4-en-3-ol [10]. A 10 :1 mixture

of (E)-and ( Z)-1-cyclohexylbutadienes 1h was obtained by treatment of allyldiphe-

nylphosphine oxide with BuLi and quenching of the lithium derivative with cyclo-

hexanecarboxaldehyde, followed by H₂O elimination [11]. A 6 :1 mixture of (E)-and

(Z)-1-benzylbutadiene 1i was prepared by a similar route (Exper. Part) since the

reported synthesis for the reaction of phenylmagnesium bromide and 5-bromopenta-

1,3-diene [12] failed in our hands. The synthesis of 1-cyclopropylbutadiene 1j was by a

method similar to that described in [13]. Bromination of dicyclopropylmethanol [14]

with PBr₃, followed by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-induced HBr

elimination provided a 5 :1 mixture of (E)-and ( Z)-1-cyclopropylbutadienes 1j. Wittig

olefination of (E)-cinnamaldehyde produced pure (E)-1-phenylbutadiene (E)-1k [15].

A 4 :1 mixture of (E)-and ( Z)-1-(4-methoxyphenyl)butadiene 1l was obtained in 51%

yield by acid-promoted dehydratation of 1-(4-methoxyphenyl)but-3-en-1-ol, a com-

pound resulting from the addition of allylmagnesium chloride to p-anisaldehyde [16].

Pure (E)-1-(trimethylsilyl)butadiene (E)-1m was derived from propargyl alcohol

( prop-2-yn-1-ol) following a known procedure [17].

The syntheses of 1-(aryloxy)butadienes 1n r was according to the general

procedure shown in Scheme 2. The preparation of the (Z)-1,4-bis(aryloxy)but-2-enes

7n r according to the published procedure [18] from (Z)-1,4-dichlorobut-2-ene (5)

failed in our hands. We obtained 7n r in good yield (70 95%) by reactions of the

corresponding potassium phenolates 6 with 5 in EtOH or acetone [19]. Yields were the

highest in the presence of a catalytical amount of [18]crown-6. Base-promoted

elimination of 1 equiv. of phenol from 7 afforded the desired dienes with stereo-

selectivity ((E)/(Z) ratio) depending on the nature of the base and of the starting 1,4-

bis(aryloxy)butene 7 (Table 1).

Scheme 2

^a) See Scheme 1 for n r.

Table 1. Base-Induced Eliminations 7n r! 1n

r

Starting material

Diene

Reaction conditions

(E)/(Z)

< 1 : 100

> 100 : 1

3.2 : 1

12 : 1

3 : 1

> 100 : 1

Yield

7n

7o

7p

7q

7r

1n

1o

1p

1q

1r

t-BuOK [20], neat, sealed tube

BuLi, THF, À78 to 258

40%

78%

63%

52%

18%

26%

BuLi, THF, À78 to 258

Li tetramethylpiperidinide, THF

BuLi, THF, À78 to 258

Pure (E)-1-(methylthio)butadiene (E)-1s was prepared in a similar way by double

displacement of 5 with lithium methanethiolate, followed by BuLi-induced elimination

of 1 equiv. of methanethiol, a method that differs slightly from that published for the

synthesis of this diene [21]. The 1-(arylthio)butadienes 1t w were obtained by addition

736

Helvetica Chimica Acta Vol. 85 (2002)

of the corresponding arylsulfenyl chlorides 8t w to butadiene followed by DBU-

induced eliminations of HCl from 9t w (Scheme 3). This produced mixtures of (E)-

and (Z)-1-(arylthio)butadiene ((E)/(Z) ratio 2 :1 to 3.5 :1).

Scheme 3

^a) See Scheme 1 for t w.

The reaction of benzeneselenyl chloride with butadiene gave a 5 :1 mixture of

adducts 10 and 11 (Scheme 4). Treatment of this mixture with DBU led to a 1:0.8 :0.5

mixture of (E)-1-(phenylseleno)butadiene (E)-1x, its (Z)-isomer (Z)-1x, and 2-

(phenylseleno)butadiene 12 that was used as such in our exploratory studies with SO₂

(see below).

Scheme 4

The 1-(acyloxy)butadienes 1y and 1z were prepared by reaction of (E)-1-

[(trimethylsilyl)oxy]buta-1,3-diene with benzoyl fluoride and naphthalene-2-carbonyl

fluoride in the presence of a catalytical amount of Bu₄NF [22]. This furnished a 10 :1

mixture of (E)-and ( Z)-1y and a 5 :1 mixture of (E)-and ( Z)-1z, respectively, in good

yield. A 2 :1 mixture of (1E)-and (1 Z)-1-ethylidene-2-methylidenecyclohexane ((E)-

and (Z)-4a, resp.) was obtained via the Wittig olefination of 2-[(dimethylamino)-

methyl]cyclohexanone (13) [23] by [EtPPh₃]Br and t-BuOK ([18]crown-6, THF) that

produced 14a (Scheme 5). When BuLi/LiBr was used [24] as a base for the Wittig

olefination, (E)-14a was formed exclusively. Quaternization of 14a with MeI, followed

by treatment with Ag₂O gave the exocyclic dienes (E)-and ( Z)-4a. Similarly, a 1:1.5

mixture of (E)-and ( Z)-4f was prepared by Wittig olefination of 13 with

[MeOCH₂PPh₃]Cl and lithium diisopropylamide in THF via 14f (Scheme 5).

Scheme 5

Helvetica Chimica Acta Vol. 85 (2002)

737

Competition between the Diels-Alder and Cheletropic Additions. Except for the

most reactive diene (E)-4a (Scheme 6), none of the other dienes 1a z and 4f did

undergo the hetero-Diels-Alder addition of SO₂without an acidic promoter. When SO₂

(10 20 fold excess) was premixed with CF₃COOH (1 2 equiv.), hetero-Diels-Alder

additions of SO₂were observed below À 758 only for the (E)-1-alkylbutadienes (E)-1a

[3], (E)-1b [4], (E)-1g, (E)-1h, and (E)-1i, and for the (E)-1-(acyloxy)butadienes (E)-

1c [2a], (E)-1y, and (E)-1z (Table 2). Compared with the non-acid-catalyzed Diels-

Alder addition of SO₂to 1,2-dimethylidenecyclohexane [1], that of (E)-4a was at least

60 times faster at À 758.

Scheme 6

Table 2. Competition between the Hetero-Diels-Alder (D.-A.) and Cheletropic (CHE) Additions of SO₂Premixed with CF₃COOH (1 2 equiv.)

for 1-Substituted (E)-Dienes 1a z, 4a, and 4f (0.2 0.4m in CFCl₃/CDCl₂/SO₂1 : 1.5 : 2): Temperatures^a) at Which the Reactions are Observed (half-

lives of 0.5 10 h, by ¹H-NMR)^b)^c)

1a [3] 1b [4] 1c [2a] 1d

À 808 À 808 À 758

1e

1f

1g

1h

1i

1j

1k

1l

1m

1y

1z

4a

4f

f

g

f

D.-A.

)

À 708 À 708 À 808

À 508 À 508 À 508

À 408 À 308 À 408

)

À 758 À758 <À 908 )

)

d

cis>trans ) À 608 À 608 À 758

À 758 À 758

À 308 À 308

À 858

À 408

Cyclo-

À 408 À 408 À 208

e

reversion )

CHE

À 408 À 408 À 108 À 508 À 508 À 808 )^g) À 258 À 308 À 308 À 508 ) À 108 À 308 À 108 258

258

À 308

À 808 )^g)

f

g

f

^a) Æ58. ^b) All other dienes 1n x do not undergo the hetero-Diels-Alder addition with SO₂. They react with SO₂to give the

corresponding sulfolenes only. None of the 1-substituted (Z)-butadienes adds in the hetero-Diels-Alder mode. ^c) Butadiene

has not reacted yet with SO₂in the hetero-Diels-Alder mode. ^d) Isomerization of the cis-sultine formed first to its more stable

f

trans-isomer (see text). ^e) Temperature at which less than 5% of sultines are at equilibrium with the diene. ) Polymerization

in the presence of acids. ^g) Reaction without acidic promoter.

None of the (Z)-isomeric dienes added to SO₂in the Diels-Alder mode (for

mixtures of (E)-and ( Z)-1). In the case of the expectedly highly reactive 1-

(cyclopropyl)butadiene 1j, only polymerization was observed at low temperature in the

presence of SO₂containing CF₃COOH. With BF₃¥ Et₂O, polymerizaton was even

faster. The same behavior was observed for the electron-rich 1-substituted dienes 1n r

(R ArO), 1s w (R MeS or ArS), and 1x (R PhSe). All the latter dienes

underwent the expected cheletropic additions of SO₂between À 40 and 208. In the case

of the 1-arylbutadienes 1k (R Ph) and 1l (R 4-MeOC₆H₄) and 1-(trimethylsilyl)-

butadiene 1m that were stable under acidic conditions below À 108, no hetero-Diels-

Alder additon of SO₂(several days at À 100 to À 108) could be observed before the

cheletropic addition. This is surprising, as these dienes are not expected to be less

reactive than (E)-1-alkylbutadienes in Diels-Alder cycloadditions. This suggests that

SO₂is different in nature compared with other dienophiles (see below).

738

Helvetica Chimica Acta Vol. 85 (2002)

As for the hetero-Diels-Alder addition of (E)-1a [3] and (E)-1b [4] discussed

earlier, the reactions of (E)-1g, (E)-1h, (E)-1i, and (E)-4a with SO₂gave first the

corresponding cis-sultines c-2g, c-2h, c-2i, and c-15, respectively, in agreement with the

endo-Alder rule [25] (see Schemes 1 and 6). With prolonged reaction times or at higher

temperatures, these cis-sultines were equilibrated with their more stable trans-isomers

t-2g, t-2h, t-2i, and t-15, respectively. In the case of the hetero-Diels-Alder additions of

the (E)-1-(acyloxy)butadienes (E)-1c [2a], (E)-1y, and (E)-1z, 1:10 mixtures of the

corresponding cis-and trans-sultines were formed immediately, and the 1:10 product

ratio did not change until their conversion into the corresponding sulfolenes 3c [2a], 3y,

and 3z, respectively. The thermodynamic data for the reactions of SO₂with 1-

(acyloxy)butadienes are collected in Table 3. They show that the cheletropic additions

of these dienes to SO₂is ca. 4 kcal mol^À1more exothermic than the corresponding

hetero-Diels-Alder additions. This is significantly less than (ca. 10 kcal mol^À1) the

difference in exothermicity of hetero-Diels-Alder and cheletropic additions of alkyl-

subsituted dienes [1][26]. All our attempts to crystallize the sultines presented here

1

failed. Thus their structures were inferred from their H-and ¹³C-NMR spectra (see

below).

Table 3. Thermodynamic Data for the Hetero-Diels-Alder Additions of 1c, 1y, and 1z and of the Cheletropic

Additions of 1c and 1y to SO₂(10 20 fold excess, 1 equiv. of CF₃COOH)

Diels Alder

K(À 758)

DH_r(À 758)

[kcal mol^À1

Cheletropic

K(258)

[1 mol^À1

DH_r(258)

[kcal mol^À1

]

[10³l mol^À1

]

SO₂ 1c>c-2c

SO₂ 1c>t-2c

SO₂ 1y>c-2y

SO₂ 1y>t-2y

SO₂ 1z>c-2z

SO₂ 1z>t-2z

2.3 Æ 0.4

21 Æ 3

À 6.0 Æ 1.5^a)

À 6.3 Æ 0.2^a)

À 5.0 Æ 0.2^b)

À 5.9 Æ 0.2^b)

À 5.0 Æ 0.2^b)

À 5.8 Æ 0.2^b)

SO₂ 1c>3c

SO₂ 1y>3y

0.19 Æ 0.01

À 10.9 Æ 0.2^b)

À 10.5 Æ 0.3^b)

0.57 Æ 0.08

5.4 Æ 1.2

0.6 Æ 0.2

5 Æ 1

0.092 Æ 0.002

^a) See Van×t Hoff plots, [2a]; DS_r(SO₂ 1c>c-2c) À43 Æ 7 cal mol^À1K^À1; DS_r(SO₂ 1c>t-2c) À 39.7 Æ 0.8

cal mol^À1K^À1

.

^b) DS_r À40 cal mol^À1K^À1used for the calculation.

Except for the 2-oxy-substituted sulfolenes 3n s and 16f, the thio analogs 3s,r, and

the seleno analog 3x that were unstable at room temperature, all derivatives 3g m, t, u,

w, y, z and 16a were fully characterized by their spectral data and, in the cases of 3u

(Fig. 1) and 3y (Fig. 2), by single-crystal X-ray-diffraction studies. Sulfolene 3a was

hydrogenated into sulfolane 17, the structure of which was also determined by single-

crystal X-ray crystallography (Fig. 3). The structure of 3m was confirmed by derivation

of this compound from unsubstituted sulfolene (2,5-dihydrothiophene 1,1-dioxide)

via lithiation with BuLi and subsequent treatment with Me₃SiCl [26].

Structures of Sultines. We have shown that ¹⁷O-NMR chemical shifts of sultines

are quite different from those of the isomeric sulfolenes in the case of corresponding

alkyl-substituted derivatives [2b]. This method of identification is not practical for

systems of high molecular mass because of severe line broadening in the ¹⁷O-NMR

spectra of sultines that have to be measured at very low temperature (< À 708). For

instance, with t-15, two very broad signals at d(¹⁷O) 141 (w_1/2 800 Hz) and 88 (w_1/2

1200 Hz) are observed at À658. For the isomeric sulfolene 16, its ¹⁷O-NMR spectrum

Helvetica Chimica Acta Vol. 85 (2002)

739

Fig. 1. ORTEP Representation of 2-[(4-chlorophenyl)thio]-2,5-dihydrothiophene 1,1-dioxide (3u) showing

non-H-atoms with 50% probability⁴)

Fig. 2. ORTEP Representation of 2,5-dihydro-1,1-dioxidothiophen-2-yl benzoate (3y) showing non-H-atoms

with 50% probability⁵)

⁵) The IUPAC numbering of atoms is not followed for reasons of convenience. Crystallographic data (excluding

structure factors) have been deposited with the Cambridge Crystallographic Data Center as Supplementary

Publication No. 171082 for 3u, No. 171083 for 3y, and No. 170963 for 17. Copies of the data can be obtained

on application to CCDC, 12 Union Road, Cambridge CB21EZ, UK (Fax: 441223336-033; e-mail:

deposit@ccdc.cam.ac.uk.

740

Helvetica Chimica Acta Vol. 85 (2002)

Fig. 3. ORTEP Representation of 2-(4-chlorophenoxy)-2,3,4,5-tetrahydrothiophene 1,1-dioxide (17) showing

non-H-atoms with 50% probability⁴)

Scheme 7

shows two broad lines also at 258 at d(¹⁷O) 155.8 and 149.4 (w_1/2 300 Hz).

Furthermore, and as discussed earlier [26], distinction between sultine and sulfolene

structures with alkyloxy and acyloxy substituents based on their ¹⁷O-NMR data is not

trivial. Comparison of the ¹H-NMR data of 6-substituted sultines (Table 4) with those

of their isomeric 2-substituted sulfolenes (Table 5) shows that these compounds can be

distinguished by the coupling constants of their vicinal olefinic protons. As expected for

cyclohexene (³J(1,2) 8.8 Hz) and cyclopentene (³J(1,2) 5.1 Hz) [27], the vicinal

3

coupling constants J(4,5) of sultines 2 (11.0 11.8 Hz) are found to be larger than

³J(3,4) 8.5 8.8 Hz of sulfolenes 3.

Comparison of ¹³C-NMR data of sultines and isomeric sulfolenes show that the

C(5) of sulfolenes resonates at lower field (8 10 ppm) than C(6) of the corresponding

sultines (see Exper. Part).

High-level quantum calculations predicted that unsubstituted sultine and the cis-

and trans-6-methylsultines (c-and t-2a) adopt pseudo-chair conformations in their

ground-states with pseudo-axial SO bonds [2a][28]. Calculations on 6-fluorosultines

and preliminary experimental results suggested, however, that sultines substituted at

C(6) by polar groups can adopt sofa conformations in which the O-atom lies in the

average plane of the four C-atoms [29]. If one assumes that sultine c-2g adopts a

Helvetica Chimica Acta Vol. 85 (2002)

741

a

Table 4. ¹H-NMR Data (400 MHz, SO₂/CDCl₂/CFCl₃, <À 708) of 6-Substituted Sultines 2a c, 2g i, and 2y, d(H) in ppm, J in Hz. )

b

c

d

d(H) H_aÀC(3) ) H_eÀC(3) ) HÀC(4) HÀC(5) HÀC(6) ²J(3a,3e) ³J(3a,4) ³J(3e,4) ³J(4,5) ³J(5,6) ⁵J(3a,6) ⁵J(3e,6) ) R at C(6) )

e

c-2a ) 3.25

3.37

2.95

3.38

3.00

3.86

3.57

3.56

3.04

3.46

3.03

?

5.90

5.60

5.80

5.70

6.17

6.26

?

5.75

?

5.67

5.80

?

6.00

5.80

6.20

5.80

6.00

6.14

6.18

5.95

?

4.60

4.65

4.45

4.55

6.69

6.48

4.07

4.24

4.43

4.64

?

16.5

17.0

16.5

17.5

17.3

17.0

15.5

17.2

16.6

17.3

?

2.5

2.0

3.0

2.5

4.0

3.3

?

2.7

3.3

2.6

?

7.0

5.5

7.0

6.0

4.8

5.7

6.5

7.0

6.3

?

11.5

11.0

?

11.2

?

11.0

?

11.4

11.8

ca. 12

?

2.0

1.0

2.0

?

1.9

2.4

2.1

?

3.0

4.0

3.5

4.5

2.1

?

< 0.5

2.5

< 0.5

3.0

2.1

?

1.0

2.1

?

2.6

?

2.7

1.8

?

Me(ax)

Me(eq)

Et(ax)

Et(eq)

AcO

t-2a

c-2b

t-2b

c-2c

t-2c

c-2g

t-2g

c-2h

t-2h

c-2i

t-3i

3.45

3.28

3.45

3.34

3.61

3.08

3.41

3.14

3.39

?

AcO

?

t-Bu(ax)

t-Bu(eq)

c-Hex(ax)

c-Hex(eq)

Bn(ax)

Bn(eq)

BzO

4.2

2.3

4.4

?

4.1

1.8

?

6.05

?

3.36

3.87

3.62

3.00

3.38

3.58

17.5

17.0

2.5

3.8

?

6.2

4.5

?

c-1y

t-1y

6.23

6.30

6.16

6.25

6.94

6.69

BzO

^a) See Exper. Part for data of other compounds described in this report. Spectral assignments were confirmed by 2D-COSY

and NOESYexperiments. ^b) H_aÀC(3) occupies a pseudo-axial, H_eÀC(3) a pseudo-equatorial position in a supposed pseudo-

c

chair conformation of the sultine (Fig. 4). ) See Exper. Part for J values. ^d) Pseudo-axial (ax) and pseudo-equatorial (eq)

position of the 6-substituent, average pseudo-chair conformation when assignment was possible. ^e) The c corresponds to the

sultine of kinetic control, assigned to the cis stereoisomer, and t corresponds to the more stable stereoisomer, assigned to the

trans-sultine, see text.

4

Table 5. ¹H-NMR Data (400 MHz, SO₂/CDCl₂/CFCl₃, 0 208) of Selected 2-Substituted Sulfolenes 3a, 3c k, 3m, 3s, and 3x y. d(H) in ppm, J in

Hz.

b

d(H) HÀC(2) HÀC(3) HÀC(4) H_aÀC(5) ) H_bÀC(5) ) ²J(5a,6b) ³J(2,3) ³J(3,4) ³J(4,5a) ³J(4,5b) ⁴J(2,5a) ⁴J(2,5b) R at C(2)

3a

3c

3d

3e

3f

3g

3h

3i

3.70

5.93

5.28

5.36

4.65

3.51

3.46

3.94

3.19

4.97

3.40

4.61

4.92

6.24

5.92

6.16

6.26

6.23

5.95

6.13

6.12

5.93

6.04

6.21

5.95

6.11

5.95

6.29

5.96

6.43

6.29

6.32

6.18

6.16

6.09

6.04

6.09

6.31

6.02

6.25

6.16

6.46

3.67

3.77

3.85

3.83

3.68

3.62

3.46

3.74

3.67

3.84

3.65

3.77

3.40

3.84

3.72

3.80

3.85

3.88

3.75

3.67

3.62

3.80

3.72

3.89

3.74

3.83

3.65

3.89

8.8

8.6

8.5

8.8

8.6

8.7

8.5

8.6

8.5

8.6

Me

AcO

Cl

17.2

?

2.9

2.0

2.3

3.0

2.1

1.8

2.3

2.2

2.3

2.4

?

3.0

2.7

2.3

2.7

2.9

2.7

3.0

3.2

3.4

3.0

2.9

2.5

2.7

2.3

2.7

2.2

2.7

2.4

2.5

2.7

1.1

0.8

1.0

0.5

1.1

?

1.3

1.5

2.2

1.3

1.0

0.6

0.9

2.4

2.5

1.5

1.0

2.1

?

2.3

2.2

2.4

2.2

2.4

1.8

16.9

17.5

16.5

17.3

16.7

14.5

16.6

16.7

17.0

16.8

18.0

Br

MeO

t-Bu

c-Hex

Bn

c-C₃H₅

Ph

Me₃Si

MeS

PhSe

BzO

3j

3k

3m

3s

3x

3y

2.7

^a) See Exper. Part for further data of these sulfolenes and other derivatives. Spectral assignments were confirmed by 2D-

COSY and NOESY experiments. ^b) H_aÀC(5) is trans to HÀC(2); H_bÀC(5) is cis to HÀC(2).

742

Helvetica Chimica Acta Vol. 85 (2002)

pseudo-chair conformation as shown in Fig. 4, both the SO and t-Bu groups reside in

pseudo-axial positions, thus making c-2g less stable than its trans isomer t-2g for steric

reasons, as observed. These hypothetical structures and conformations (Fig. 4) are

1

consistent with the H-NMR data collected for these two sultines (Table 4, Exper.

Part). Assuming the validity of the ⁵J(H,H) 4.99 sin²fsin²f' relationship [30] for the

homoallylic coupling constants between proton pairs HÀC(3)/HÀC(6) (f and f' being

the angles these protons make with the p-plane C(3)ÀC(4)ÀC(5)ÀC(6)), the ⁵J(3,6)

coupling constants measured for c-2g and t-2g are in agreement with the conformers

3

shown in Fig. 4. The proposed conformers are also consistent with the J(3,4) and

³J(5,6) vicinal coupling constants measured (Karplus relationship [31]). The ¹H-NMR

data (Table 4) collected for the other 6-alkyl substituted sultines suggest that similar

structures and conformations to those shown in Fig. 4 can be proposed for 2a, 2b, 2h,

4

and 2i. Because of Jand ⁵J coupling constants involving the protons of the cyclohexeno

moiety of bicyclic sultines c-and t-15, only complicated ms were seen in the ¹H-NMR

spectra for HÀC(1) and 2 HÀC(4) of these compounds. Distinction between c-and

1

t-15 and signal assignments were based on their 2D H,¹H-NOESY data obtained at

À858.

Fig. 4. Proposed structures and conformations for cis- and trans-6-(tert-butyl)sultines 2g (H,H coupling

constants in Hz)

Structures of 6-(acyloxy)sultines 1y and 1z were not established unambiguously

because of insufficient NMR data. Nevertheless, the coupling constants observed in

their ¹H-NMR spectra suggested that these sultines adopt similar structures and

conformation than those of c-and t-2c for which equilibria of several conformers have

been proposed [2a]. Distinction betwen cis-and trans-sultines 2c, 2y, and 2z relied on

2D ¹H,¹H-NOESY experiments.

Discussion. The most surprising result of our exploratory studies is that electron-

rich dienes such as 1-alkoxy, 1-(aryloxy)-, 1-thio-, 1-seleno-, 1-cyclopropyl-, and 1-

arylbutadiene do not equilibrate with the corresponding sultines at low temperatures,

although analogs less reactive towards all kind of dienophiles do add SO₂in the hetero-

Diels-Alder mode. These dienes are alkyl-substituted and (Z)-1-(acyloxy)butadienes. It

is possible that the failure to observe sultines arising from the hetero-Diels-Alder

additions of SO₂to electron-rich dienes is due to too low an exothermicity of the [4

2] cycloaddition or to too negative an entropy of condensation. Both hypotheses will

Helvetica Chimica Acta Vol. 85 (2002)

743

have to be tested by further experimentation and, possibly, by high-level calculations.

On mixing dienes with SO₂at low temperature, colors are immediately formed; they

vanish once the dienes have reacted with SO₂. These colors are probably due to the

formation of charge-transfer complexes between the dienes and SO₂[32]. The more

electronrich the diene is, the deeper the color formed on mixing it with SO₂. It is thus

possible that differential solvation effects intervene and affect both the enthalpy and

entropy of the equilibria diene SO₂ sultines. One is tempted to explain the failure

to observe sultine formation with the most electron-rich dienes as being due to specific

solvation of the latter by SO₂, which reduces significantly the heat of their hetero-Diels-

Alder additions. This hypothesis can be tested, in principle, by measuring the heats and

entropies of dissolution of dienes and their sultines (or models of them) in solutions

containing a large excess of SO₂. No such data is available for closely related systems.

As already demonstrated with (E)-piperylene [3], the hetero-Diels-Alder addition

of SO₂to (E)-1-alkylbutadienes and (E)-1-(acyloxy)butadienes are suprafacial and

obey the Alder endo rule [25]. This affirmation is based on the assumption that the 6-

substituted trans sultines are more stable than their cis-isomers in solution, as predicted

by high-level quantum calculations [2b]. To put these conclusions on firmer grounds, X-

ray diffraction studies of crystalline sultines are required. This has been possible at the

moment for one case only (1RS,3SR)-1-fluoronaphth[2,1-d][2,3]oxathiin 3-oxide, the

product of Diels-Alder addition of SO₂to (Z)-1-(fluoromethylidene) 1,2,3,4-tetrahy-

dro-2-methylidene naphthalene [29].

The hetero-Diels-Alder additions of SO₂to 1-substituted (E)-buta-1,3-dienes are

highly regioselective and give exclusively the corresponding 6-substituted sultines.

Even after remaining for a prolonged time at equilibrium with their cycloaddents, the 6-

substituted sultines were not equilibrated with their 3-substituted isomers. This was the

case also with the most reactive system (E)-4a SO₂ t-15 when left at À608 for one

week in the presence of CF₃COOH. It appears, therefore, that the activation energy of

the hetero-Diels-Alder additions of SO₂to 1-substituted buta-1,2-dienes giving 3-

substituted sultines are much higher than those leading to the corresponding 6-

substituted sultines. They are higher also than the energy barriers of the corresponding

cheletropic additions with SO₂. Alternatively, one can invoke a thermodynamic control

that would imply that the 6-substituted sultines are significantly more stable (by at least

2 kcal/mol) than their 3-substituted isomers. This might well be the case for the

reactions with (E)-1-(acyloxy)buta-1,3-dienes giving 6-(acyloxy)sultines in which a

possible enthalpy anomeric effect [2a][33] is expected to stabilize them compared with

their 3-(acyloxy)-substituted isomers.

Conclusions. The 1-substituted (E)-butadiene derivatives 1 with Me, Et, t-Bu,

cyclohexyl and benzyl groups as well as (E)-1-(acyloxy) derivatives (AcO, BzO, and

(naphthalen-2-ylcarbonyl)oxy) add to SO₂below À708 in the hetero-Diels-Alder mode

in the presence of an acidic promoter such as CF₃COOH. These dienes do not undergo

the [4

2] cycloadditions with SO₂without acid catalyst, contrary to 1,2-

dimethylidenecycloalkanes [1] and (E)-1-ethylidene-2-methylidenecyclohexane ((E)-

4a). The uncatalyzed hetero-Diels-Alder addition of the latter diene (E)-4a to SO₂is at

least 60 times more rapid than that of 1,2-dimethylidenecyclohexane. More electron-

richer 1,3-dienes such 1-cyclopropyl-, 1-phenyl-, 1-[4-methoxyphenyl)-, 1-(trimethyl-

744

Helvetica Chimica Acta Vol. 85 (2002)

silyl)-, 1-phenoxy-, 1-(4-chlorophenoxy)-, 1-(4-methoxyphenoxy)-, 1-(4-nitrophen-

oxy)-, 1-(naphthalen-2-yloxy)-, 1-(methylthio)-, 1-(phenylthio)-, 1-[(4-chlorophen-

yl)thio], 1-[(4-methoxyphenyl)thio], 1-[(4-nitrophenyl)thio]-, and 1-(phenylseleno)-

butadiene did not equilibrate with the corresponding sultines between À100 and À108,

in the presence or absence of acidic promoter, but underwent the expected cheletropic

additions to give the corresponding 2-substituted sulfolenes. Both (E)-and ( Z)-1-

(methoxymethylidene)-2-methylidenecyclohexanes (4f) add quickly to SO₂at À808 in

the cheletropic mode exclusively. The failure to observe sultine formation with the most

electron-rich 1,3-dienes is a surprise. The reasons for it are unclear at the moment.

Perhaps differential solvation effects affect the heat and entropy of the hetero-Diels-

Alder additions of SO₂to dienes in excess of SO₂. Based on high-level quantum

calculations, the SO moiety of sultines is assumed to occupy pseudo-axial positions in

pseudo-chair conformers. With these hypotheses, all the adducts resulting from the

hetero-Diels-Alder addition of 1-substituted (E)-butadienes under conditions of

kinetic control are 6-substituted cis-sultines that are then equilibrated with their more

stable 6-substituted trans-stereoisomers, in agreement with the Alder endo rule. These

cycloadditions are highly regioselective, and the 6-substituted sultines could not be

equilibrated with their 3-substituted isomers.

Experimental Part

General. See [1][34]. ¹⁷O-NMR Spectra: Bruker spectrometers DPX-400 and DRX-400 at 54.2 MHz, and

AMX600 at 81.3 MHz, with 5-mm tubes, see [26].

(E)-1-(tert-Butyl)buta-1,3-diene ((3E)-5,5-Dimethylhexa-1,3-diene; (E)-1g). Obtained in 40% yield,

according to [10]. Colorless liquid. UV (MeCN): 226 (10500). IR (film): 2960, 2865, 1780, 1650, 1605, 1475,

1485, 1365, 1265, 1210, 1005, 955, 895, 650. ¹H-NMR (400 MHz, CDCl₃): 6.33 (ddd, ³J(3,4) 16.1, 10.2, ³J(2,3)

10.2, HÀC(3)); 6.00 (dd, ³J(1,2) 15.5, ³J(2,3) 10.2, HÀC(2)); 5.75 (d, ³J(1,2) 15.5, HÀC(1)); 5.13

(dm, ³J(3,4) 10.2, HÀC(4)); 4.98 (dm, ³J(3,4) 16.1, HÀC(4)); 1.05 (s, t-Bu). ¹³C-NMR (100.6 MHz, CDCl₃):

146.3 (d, ¹J(C,H) 148, C(1)); 137.7 (d, ¹J(C,H) 156, C(3)); 125.7 (d, ¹J(C,H) 149, C(2)); 114.7 (t, ¹J(C,H)

154, C(4)); 33.1 (s, Me₃C); 29.4 (q, ¹J(C,H) 134, 3 C, Me₃C).

10 :1 Mixture of (E)- and (Z)-1-Cyclohexylbuta-1,3-diene (1h). Obtained in 53% yield, according to [11].

Colorless oil. UV (MeCN): 231 (5000). IR (film): 2925, 2850, 1720, 1650, 1605, 1450, 1310, 1260, 1145, 1005, 895,

845. ¹H-NMR (400 MHz, CDCl₃): (E)-1h: 6.31 (ddd, ³J(3,4) 16.9, 10.1, ³J(2,3) 10.2, HÀC(3)); 6.03

(dd, ³J(1,2) 15.3, ³J(2,3) 10.2, HÀC(2)); 5.67 (dd, ³J(1,2) 15.3, ³J(1,Chx) 6.9, HÀC(1)); 5.10

(dm, ³J(3,4) 16.9, HÀC(4)); 4.96 (dm, ³J(3,4) 10.1, HÀC(4)); 2.20 1.00 (m, 11 H, Chx); (Z)-1h: 6.66

(ddd, ³J(3,4) 16.8, 10.8, ³J(2,3) 10.8, HÀC(3)); 6.02 (dd, ³J(1,2) 10.9, ³J(2,3) 10.8, HÀC(2)); 5.31

(dd, ³J(1,2) 10.9, ³J(1,Chx) 10.8, HÀC(1)); 5.23 (dm, ³J(3,4) 16.8, HÀC(4)); 5.07 (dm, ³J(3,4) 10.8,

HÀC(4)); 2.20 1.00 (m, 11 H, Chx). ¹³C-NMR (100.6 MHz, CDCl₃): (E)-1h: 141.1 (d, ¹J(C,H) 148, C(3));

138.8 (d, ¹J(C,H) 152, C(1)); 128.3 (d, ¹J(C,H) 150, C(2)); 114.6 (t, ¹J(C,H) 159, C(4)); 40.6 (d, ¹J(C,H)

125, CH(Chx)); 32.7 (t, ¹J(C,H) 126, 2 C(Chx)); 27.9 (t, ¹J(C,H) 127, 1 C(Chx)); 25.8 (t, ¹J(C,H) 125,

2 C(Chx)); (Z)-1h: 138.8 (d, ¹J(C,H) 151, C(3)); 132.5 (d, ¹J(C,H) 151, C(1)); 127.2 (d, ¹J(C,H) 153,

C(2)); 116.6 (t, ¹J(C,H) 160, C(4)); 40.6 (d, ¹J(C,H) 125, CH(Chx)); 32.7 (t, ¹J(C,H) 126, 2 C(Chx)); 27.9

(t, ¹J(C,H) 127, 1 C(Chx)); 25.8 (t, ¹J(C,H) 125, 2 C(Chx)).

6 :1 Mixture of (E)- and (Z)-1-Benzylbuta-1,3-diene ((3E)- and (3Z)-5-Phenylpenta-1,3-diene; 1i). BuLi

(1.6m in hexane; 4.5 ml, 7.2 mmol) was added dropwise to a stirred soln. of allyldiphenylphosphine oxide (1.8 g,

7.4 mmol) in THF (25 ml) and hexamethylphosphoric triamide (HMPA; 3 ml) at À788. The resulting soln. was

stirred at À788 for 10 min. Phenylacetaldehyde (740 mg, 6.2 mmol) in dry THF (5 ml) was added within 15 min,

and the resulting soln. was stirred at À788 for 10 min, at 08 for 30 min, and at 258 for 20 h. THF was evaporated,

pentane (25 ml) added to the residue, and the precipitate filtered off (Celite). The filtrate was evaporated and

the residue purified by FC (petroleum ether): 150 mg (14%) of 1i. Colorless oil (see [12]). UV (MeCN): 278

(1000), 240 (3400), 200 (2200). IR (film): 3030, 2925, 1650, 1605, 1455, 1430, 1305, 1075, 1030, 1000, 950, 900,

Helvetica Chimica Acta Vol. 85 (2002)

745

745. ¹H-NMR (400 MHz, CDCl₃): (E)-1i: 7.35 7.20 (m, 5 arom. H); 6.38 (ddd, ³J(3,4) 17.0, 10.2, ³J(2,3)

10.2, HÀC(3)); 6.15 (dd, ³J(1,2) 16.8, ³J(2,3) 10.2, HÀC(2)); 5.89 (ddd, ³J(1,2) 16.8, ³J(1,Bn) 6.9,

HÀC(1)); 5.17 (d, ³J(3,4) 17.0, HÀC(4)); 5.01 (d, ³J(3,4) 10.2, HÀC(4)); 3.46 (d, ³J(1,Bn) 6.9, PhCH₂);

(Z)-1i: 7.35 7.20 (m, 5 arom. H); 6.81 (ddd, ³J(3,4) 16.9, 9.8, ³J(2,3) 11.0, HÀC(3)); 6.18 (m, HÀC(2));

5.66 (ddd, ³J(1,2) 8.0, ³J(1,Bn) 7.7, H ÀC(1)); 5.32 (d, ³J(3,4) 16.9, HÀC(4)); 5.21 (d, ³J(3,4) 9.8,

HÀC(4)); 3.58 (d, ³J(1,H(Bn)) 7.7, PhCH₂). ¹³C-NMR (100.6 MHz, CDCl₃): (E)-1i: 140.1 (s, arom. C);

136.9 (d, ¹J(C,H) 157, C(3)); 133.4 (d, ¹J(C,H) 147, C(1)); 132.1 (d, ¹J(C,H) 147, C(2)); 128.6 (d, ¹J(C,H)

157, 2 arom. C); 128.4 (d, ¹J(C,H) 158, 2 arom. C); 126.1 (d, ¹J(C,H) 160, arom. C); 115.7 (t, ¹J(C,H) 155,

C(4)); 38.9 (t, ¹J(C,H) 127, PhCH₂); (Z)-1i: detected signals 131.9, 130.6, 129.9 (3 C); 118.0 (t, ¹J(C,H) 159,

.

C(4)); 33.9 (PhCH₂). CI-MS (NH₃): 145 (4, M ), 129 (100), 115 (35), 103 (7), 91 (21).

5 :1 Mixture of (E)- and (Z)-1-Cyclopropylbuta-1,3-diene (1j). By syringe, 4-bromo-1-cyclopropylbut-1-

ene [14] (1.0 g, 10.6 mmol) was added to DBU (5 ml, 5.1 g, 33.5 mmol) heated to 1508. After 5 min, the mixture

was distilled at 35 408/10 Torr (Vigreux column) yielding 240 mg (30%) of (E)/(Z)-1j 5 :1. B.p. 107 1098.

Colorless liquid [35]. UV (MeCN): 235 (4100). IR (film): 3085, 3010, 1650, 1420, 1200, 1050, 1000, 965, 945, 895,

860, 810. ¹H-NMR (400 MHz, CDCl₃): (E)-1j: 6.29 (ddd, ³J(3,4) 15.5, 10.5, ³J(2,3) 10.5, HÀC(3)); 6.16

(dd, ³J(1,2) 14.9, ³J(2,3) 10.5, HÀC(2)); 5.25 (dd, ³J(1,2) 14.9, ³J(1,1') 9.0, HÀC(1)); 5.07 (dm, ³J(3,4)

15.5, HÀC(4)); 4.92 (dm, ³J(3,4) 10.5, HÀC(4)); 1.44 (m, HÀC(1')); 0.78 (m, 2 H); 0.43 (m, 2 H); (Z)-1j:

6.81 (ddd, ³J(3,4) 16.9, 10.2, ³J(2,3) 11.2, HÀC(3)); 5.97 (dd, ³J(2,3) 11.2, ³J(1,2) 10.8, HÀC(2)); 5.14

(dm, ³J(3,4) 16.9, HÀC(4)); 5.11 (dm, ³J(3,4) 10.2, HÀC(4)); 4.82 (dd, ³J(1,2) 10.8, ³J(1,1') 9.5,

HÀC(1)); 1.77 (m, HÀC(1')); 0.78 (m, 2 H); 0.43 (m, 2 H). ¹³C-NMR (100.6 MHz, CDCl₃): (E)-1j: 139.0

(d, ¹J(C,H) 151, C(1)); 136.9 (d, ¹J(C,H) 153, C(3)); 128.6 (d, ¹J(C,H) 148, C(2)); 113.7 (t, ¹J(C,H) 159,

C(4)); 13.9 (d, ¹J(C,H) 158, C(1')); 7.21 (t, ¹J(C,H) 162, C(2'), C(3')); (Z)-1j: 136.9 (d, ¹J(C,H) 153, C(1));

132.6 (d, ¹J(C,H) 152, C(3)); 127.5 (d, ¹J(C,H) 149, C(2)); 116.2 (t, ¹J(C,H) 155, C(4)); 10.3 (d, ¹J(C,H)

160, C(1')); 7.45 (t, ¹J(C,H) 162, C(2'), C(3')). CI-MS (NH₃): 95 (35, [M 1] ), 79 (100).

(E)-1-Phenylbuta-1,3-diene ((E)-1k). Prepared according to [15][36]. Colorless oil. UV (MeCN): 278

(24200), 232 (8800), 225 (12300), 219 (12500), 209 (13800), 197 (10300). IR (film): 3025, 1600, 1495, 1450, 1000,

1

945, 890, 755, 690. H-NMR (400 MHz, CDCl₃): 7.42 (m, 2 arom. H); 7.32 (m, 2 arom. H); 7.22 (m, arom. H);

3

6.81 (dd, ³J(1,2) 16.8, J(2,3) 10.5, HÀC(2)); 6.58 (d, ³J(1,2) 16.8, HÀC(1)); 6.52 (ddd, ³J(3,4) 16.8, 9.9,

³J(2,3) 10.5, HÀC(3)); 5.35 (dm, ³J(3,4) 16.8, HÀC(4)); 5.19 (dm, ³J(3,4) 9.9, HÀC(4)). ¹³C-NMR

(100.6 MHz, CDCl₃): 137.3 (d, ¹J(C,H) 153, C(3)); 137.2 (s, arom. C); 132.0 (d, ¹J(C,H) 148, C(1)); 129.7

(d, ¹J(C,H) 148, C(2)); 128.7 (d, ¹J(C,H) 160, arom. C); 127.7 (d, ¹J(C,H) 161, arom. C); 126.5

(d, ¹J(C,H) 158, arom. C); 117.7 (t, ¹J(C,H) 151, C(4)). CI-MS (NH₃): 131 (100, [M 1] ), 115 (17), 103

(50), 77 (84).

4 :1 Mixture of (E)- and (Z)-1-(4-Methoxyphenyl)buta-1,3-diene (1l). A mixture of 1-(4-methoxyphenyl)-

but-3-en-1-ol [16] (3.6 g, 20 mmol), KHSO₄(0.36 g, 2.6 mmol), and hydroquinone (0.1 g) was heated to 808.

After stirring at 808 for 30 min, the mixture was cooled to 208 and the mixture distilled at 808/0.5 Torr (Vigreux

column). The distillate was diluted in pentane (15 ml) and dried (MgSO₄). Solvent evaporation gave 1.7 g

(51%) of (E)/(Z)-1l 4 :1. White solid. M.p. 45 468. UV (MeCN): 291 (13500), 285 (13500), 256 (1300), 225

(12300). IR (KBr): 3030, 2910, 2835, 1605, 1510, 1245, 1175, 1035, 825, 640. ¹H-NMR (400 MHz, CDCl₃): (E)-1l.

7.40 (m, 2 arom. H); 6.90 (m, 2 arom. H); 6.76 (dd, ³J(1,2) 14.9, ³J(2,3) 10.9, HÀC(2)); 6.60 (d, ³J(1,2)

14.9, HÀC(1)); 6.57 (ddd, ³J(3,4) 15.4, 9.2, ³J(2,3) 10.9, HÀC(3)); 5.37 (d, ³J(3,4) 15.4, HÀC(4)); 5.21

(d, ³J(3,4) 9.2, HÀC(4)); 3.84 (s, MeO); (Z)-1l: 7.35 (m, 2 arom. H); 7.00 (ddd, ³J(3,4) 16.3, 9.3, ³J(2,3)

11.4, HÀC(3)); 6.95 (m, 2 arom. H); 6.48 (d, ³J(1,2) 11.3, HÀC(1)); 6.28 (dd, ³J(2,3) 11.4, ³J(1,2) 11.3,

HÀC(2)); 5.44 (d, ³J(3,4)) 16.3, HÀC(4)); 5.29 (d, ³J(3,4) 9.3, HÀC(4)); 3.84 (s, MeO). ¹³C-NMR

(100.6 MHz, CDCl₃): (E)-1l: 159.2 (s, arom. C); 137.3 (d, ¹J(C,H) 155, C(3)); 132.3 (d, ¹J(C,H) 146,

C(1)); 129.8 (s, arom. C); 127.7 (d, ¹J(C,H) 158, arom. C); 127.5 (d, ¹J(C,H) 160, C(2)); 116.4 (t, ¹J(C,H)

155, C(4)); 114.0 (d, ¹J(C,H) 161, arom. C); 55.0 (q, ¹J(C,H) 144, MeO); (Z)-1l: 158.6 (s, arom. C); 133.2

(d, ¹J(C,H) 153, C(3)); 130.2 (d, ¹J(C,H) 158, arom. C); 129.9 (d, ¹J(C,H) 155, C(1)); 129.2 (d, ¹J(C,H)

157, C(2)); 128.2 (s, arom. C); 118.8 (t, ¹J(C,H) 155, C(4)); 113.6 (d, ¹J(C,H) 159, arom. C); 55.0

.

(q, ¹J(C,H) 144, MeO). CI-MS (NH₃): 160 (100, M ), 144 (44), 129 (63), 115 (82), 102 (12), 91 (50).

(E)-1-(Trimethylsilyl)buta-1,3-diene ((E)-1m). The tetrahydro-2H-pyran-2-yl ether derived from prop-2-

yn-1-ol was converted [37] into (E)-1m according to [17]. Colorless liquid. UV (MeCN): 236 (8900). IR (film):

2965, 1815, 1570, 1250, 1125, 1010, 905, 865, 840, 690, 615. ¹H-NMR (400 MHz, CDCl₃): 6.53 (dd, ³J(1,2) 18.2,

³J(2,3) 10.1, HÀC(2)); 6.36 (dddd, ³J(3,4) 16.8, 10.0, ³J(2,3) 10.1, HÀC(3)); 5.89 (d, ³J(1,2) 18.2,

HÀC(1)); 5.24 (dm, ³J(3,4) 16.8, HÀC(4)); 5.13 (dm, ³J(3,4) 10.0, HÀC(4)); 0.11 (s, Me₃Si). ¹³C-NMR

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Helvetica Chimica Acta Vol. 85 (2002)

(100.6 MHz, CDCl₃): 144.5 (C(2)); 139.8 (C(3)); 134.8 (C(1)); 117.6 (C(4)); À1.4 (3 C, Me₃Si). CI-MS (NH₃):

.

126 (2, M ), 111 (21), 90 (100).

(Z)-1,4-Di(phenoxy)but-2-ene (7n). A mixture of PhOH (21 mmol) and KOH (1.2 g, 21 mmol) was heated

under reflux in EtOH (30 ml) for 15 min. Then (Z)-1,4-dichlorobut-2-ene (5; 1.4 g, 11 mmol) was added slowly

under stirring at 08. After stirring at 08 for 6 h, then at 208 for 15 h, the precipitate was filtered off (Celite) and

washed with EtOH (5 ml, twice). It was then dissolved in CH₂Cl₂(60 ml) and the soln. washed with H₂O (3 Â

20 ml) and dried (MgSO₄). Solvent evaporation gave 3.8 g (75%) of 7n. White solid. M.p. 31 328. UV

(MeCN): 276 (4500), 269 (5200), 225 (6800), 199 (4800). IR (KBr): 1600, 1495, 1300, 1240, 1170, 1030, 750, 690.

¹H-NMR (400 MHz, CDCl₃): 7.35 (m, 4 arom. H); 7.34 (m, 6 arom. H); 5.99 (t, ³J 3.5, HÀC(2), HÀC(3));

4.73 (d, ³J 3.5, CH₂(1), CH₂(4)). ¹³C-NMR (100.6 MHz, CDCl₃): 159.0 (s, arom. C); 129.5 (d, ¹J(C,H) 159,

arom. C); 128.5 (d, ¹J(C,H) 164, C(2), C(3)); 121.0 (d, ¹J(C,H) 161, arom. C); 114.6 (d, ¹J(C,H) 159,

arom. C); 64.0 (t, ¹J(C,H) 137, C(1), C(4)). CI-MS (NH₃): 258 (100, [M 18] ), 241 (26, [M 1] ), 147 (30),

131 (1), 107 (3), 91 (9). Anal. calc. for C₁₆H₁₆O₂(240.30): C 79.97, H 6.71; found: C 79.88, H 6.68.

(Z)-1,4-Bis(4-chlorophenoxy)but-2-ene (7o). As described for 7n, with 4-chlorophenol (12.9 g, 0.1 mol),

KOH (5.6g, 0.1 mol), and 5 (4.8 g, 38 mmol): 8.0 g (68%) of 7o. White solid. M.p. 36 388. UV (MeCN): 280

(4800), 230 (17400), 204 (12400), 187 (2300). IR (KBr): 1595, 1490, 1285, 1235, 1170, 1095, 1005, 825, 740.

¹H-NMR (400 MHz, CDCl₃): 7.24 (m, 4 arom. H); 6.85 (m, 4 arom. H); 5.92 (t, ³J 3.6, HÀC(2), HÀC(3));

4.66 (d, ³J 3.6, CH₂(1), CH₂(4)). ¹³C-NMR (100.6 MHz, CDCl₃): 156.9 (s, arom. C); 129.5 (d, ¹J(C,H) 164,

arom. C); 128.4 (d, ¹J(C,H) 165, 2 C, C(2), C(3)); 126.0 (s, arom. C); 115.9 (d, ¹J(C,H) 161, arom. C); 64.5

.

(t, ¹J(C,H) 144, C(1), C(4)). CI-MS (NH₃): 326 (100, [M 18] ), 308 (39, M ), 181 (44), 146 (17), 99 (13).

(Z)-1,4-Bis(4-methoxyphenoxy)but-2-ene (7p). As described for 7n, with 4-methoxyphenol (2 g, 16 mmol),

KOH (0.87 g, 16 mmol), and 5 (0.74 g, 5.9 mmol): 1.2 g (70%) of 7p. Brownish solid. M.p. 48 528. UV (MeCN):

296 (8600), 289 (9500), 226 (26200), 199 (52600). IR (KBr): 2950, 2830, 1510, 1455, 1295, 1230, 1110, 1035, 825,

770. ¹H-NMR (400 MHz, CDCl₃): 6.86 (m, 8 arom. H); 5.93 (t, ³J 3.5, HÀC(2), HÀC(3)); 4.63 (d, ³J 3.5,

CH₂(1), CH₂(4)). ¹³C-NMR (100.6 MHz, CDCl₃): 154.0, 152.5 (2s, 2 arom. C); 128.6 (d, ¹J(C,H) 164, C(2),

C(3)); 115.7 (d, ¹J(C,H) 160, arom. C); 144.6 (d, ¹J(C,H) 159, arom. C); 64.8 (t, ¹J(C,H) 137, C(1), C(4));

.

55.7 (q, ¹J(C,H) 143, MeO). CI-MS (NH₃): 300 (18, M ), 177 (71), 123 (100), 109 (11), 95 (32). Anal. calc.

for C₁₈H₂₀O₄(300.35): C 71.98. H 6.71; found: C 71.91, H 6.82.

(Z)-1,4-Bis(4-nitrophenoxy)but-2-ene (7q). A mixture of 4-nitrophenol (6.7 g, 48 mmol), KOH (2.7 g,

48 mmol), and [18]crown-6 (0.1 g) in acetone (100 ml) was heated under reflux for 15 min. Then 5 (2.0 g, 2.4 ml,

16 mmol) was added slowly under stirring. After heating under reflux for 24 h, the solvent was evaporated and

the residue dissolved in AcOEt (100 ml). The org. phase was washed in 1n NaOH (3 Â 30 ml), dried (MgSO₄),

and evaporated: 3.8 g (95%) of 7q. White solid. M.p. 133 1348. UV (MeCN): 306 (27900), 226 (17800), 200

(25300), 194 (21300). IR (KBr): 1590, 1505, 1450, 1330, 1260, 1170, 1105, 1025, 850, 750, 650, 495. ¹H-NMR

(400 MHz, CDCl₃): 8.20 (m, 4 arom. H); 6.98 (m, 4 arom. H); 6.01 (t, ³J 3.6, HÀC(2), HÀC(3)); 4.80 (d, ³J

3.6, CH₂(1), CH₂(4)). ¹³C-NMR (100.6 MHz, CDCl₃): 163.2 (s, arom. C); 141.8 (s, arom. C); 128.1 (d, ¹J(C,H)

162, C(2), C(3)); 126.0 (d, ¹J(C,H) 168, arom. C); 114.6 (d, ¹J(C,H) 164, arom. C); 64.7 (t, ¹J(C,H) 137,

2 C, C(1), C(4)). CI-MS (NH₃): 348 (100, [M 18] ), 331 (2, [M 1] ), 301 (3), 191 (4), 131 (5). Anal. calc. for

C₁₆H₁₄N₂O₆(330.30): C 58.18, H 4.27; found: C 58.22, H 4.15.

(Z)-1,4-Bis(naphthalen-2-yloxy)but-2-ene (7r). As described for 7n, with naphthalen-2-ol (14.4 g, 0.1 mol),

KOH (5.6 g, 0.1 mol), and 5 (4.8 g, 38 mmol): 10.4 g (80%) of 7r. White solid. M.p. 77 808. UV (MeCN): 327

(6300), 313 (5400), 270 (14800), 232 (47900). IR (KBr): 2920, 1625, 1595,1460, 1390, 1255, 1215, 1180, 1005, 840,

750, 470. ¹H-NMR (400 MHz, CDCl₃): 7.81 7.20 (m, 14 arom. H); 6.08 (t, ³J 3.5, HÀC(2), HÀC(3)); 4.88

(d, ³J 3.5, CH₂(1), CH₂(4)). ¹³C-NMR (100.6 MHz, CDCl₃): 156.4 (s, arom. C); 134.5 (s, arom. C); 129.6

(d, ¹J(C,H) 159, arom. C); 129.1 (s, arom. C); 128.6 (d, ¹J(C,H) 165, C(2), C(3)); 127.6 (d, ¹J(C,H) 164,

arom. C); 126.8 (d, ¹J(C,H) 159, arom. C); 126.4 (d, ¹J(C,H) 160, arom. C); 123.8 (d, ¹J(C,H) 158,

arom. C); 118.9 (d, ¹J(C,H) 161, arom. C); 106.9 (d, ¹J(C,H) 158, arom. C); 64.2 (t, ¹J(C,H) 144, C(1),

C(4)). CI-MS (NH₃): 358 (30, [M 18] ), 341 (100, [M 1] ), 197 (78), 179 (8), 115 (47). Anal. calc. for

C₂₄H₂₀O₂(340.42): C 84.68, H 5.92; found: C 84.52, H 5.91.

(E)-1-Phenoxybuta-1,3-diene ((E)-1n). BuLi (1.6m in hexane; 10 ml, 16 mmol) was added dropwise to a soln. of

7n (2 g, 8.3 mmol) in dry THF (50 ml) at À788. The mixture was stirred at À788 for 0.5 h, then it was gradually

warmed up to 258 and stirred for another 2 h. Et₂O (50 ml) was added, the org. phase washed with brine (3 Â

30 ml), dried (MgSO₄), and evaporated, and the residue purified by FC (AcOEt/petroleum ether 1 :9): 950 mg

(78%) of (E)-1n. Colorless oil. UV (MeCN): 245 (17800), 205 (10900), 187 (2700). IR (film): 3045, 1655, 1590,

1490, 1420, 1230, 1175, 1115, 995, 920, 890, 755, 690. ¹H-NMR (400 MHz, CDCl₃): 7.38 (m, 2 arom. H); 7.12

(m, arom. H); 7.07 (m, 2 arom. H); 6.82 (d, ³J(1,2) 12.0, HÀC(1)); 6.38 (ddd, ³J(3,4) 16.9, 8.9, ³J(2,3) 11.2,

Helvetica Chimica Acta Vol. 85 (2002)

747

HÀC(3)); 6.06 (dd, ³J(1,2) 12.0, ³J(2,3) 11.2, HÀC(2)); 5.19 (dm, ³J(3,4) 16.9, HÀC(4)); 5.04

(dm, ³J(3,4) 8.9, HÀC(4)). ¹³C-NMR (100.6 MHz, CDCl₃): 156.9 (s, arom. C); 146.2 (d, ¹J(C,H) 181,

C(1)); 132.1 (d, ¹J(C,H) 152, C(3)); 129.6 (d, ¹J(C,H) 165, arom. C); 123.2 (d, ¹J(C,H) 160, arom. C);

116.9 (d, ¹J(C,H) 161, arom. C); 114.5 (t, ¹J(C,H) 155, C(4)); 114.3 (d, ¹J(C,H) 154, C(2)). CI-MS (NH₃):

.

146 (100, M ), 131 (33), 117 (58), 105 (10), 91 (54).

3.2:1 Mixture of ( E)- and (Z)-1-(4-Chlorophenoxy)buta-1,3-diene (1o). As described for (E)-1n, with 7o

(1 g, 3.2 mmol): 0.35 g (63%) of 1o. Colorless oil. UV (MeCN): 251 (13000), 212 (9200). IR (film): 2960, 1660,

1590, 1485, 1430, 1240, 1090, 1010, 995, 920, 830, 655. ¹H-NMR (400 MHz, CDCl₃): (E)-1o: 7.28 (m, 2 arom. H);

6.96 (m, 2 arom. H); 6.72 (d, ³J(1,2) 11.8, HÀC(1)); 6.31 (ddd, ³J(3,4) 16.9, 10.3, ³J(2,3) 11.8, HÀC(3));

6.02 (dd, ³J(1,2) 11.8, ³J(2,3) 11.8, HÀC(2)); 5.17 (dm, ³J(3,4) 16.9, HÀC(4)); 5.02 (dm, ³J(3,4) 10.3,

HÀC(4)); (Z)-1o: 7.27 (m, 2 arom. H); 6.96 (m, 2 arom. H); 6.81 (ddd, ³J(3,4) 9.5, 17.2, ³J(2,3) 10.9,

HÀC(3)); 6.33 (d, ³J(1,2) 6.1, HÀC(1)); 5.51 (dd, ³J(2,3) 10.9, ³J(1,2) 6.1, HÀC(2)); 5.25 (dm, ³J(3,4)

17.2, HÀC(4)); 5.09 (dm, ³J(3,4) 9.5, HÀC(4)). ¹³C-NMR (100.6 MHz, CDCl₃): (E)-1o: 155.4 (s, arom. C);

145.6 (d, ¹J(C,H) 182, C(1)); 131.8 (d, ¹J(C,H) 153, C(3)); 129.6 (d, ¹J(C,H) 166, arom. C); 128.2

(s, arom. C); 118.2 (d, ¹J(C,H) 163, arom. C); 115.2 (t, ¹J(C,H) 154, C(4)); 115.0 (d, ¹J(C,H) 152, C(2));

(Z)-1o: 155.8 (s, arom. C); 140.7 (d, ¹J(C,H) 180, C(1)); 129.5 (d, ¹J(C,H) 165, arom. C); 129.0

(d, ¹J(C,H) 152, C(3)); 128.0 (s, arom. C); 117.7 (d, ¹J(C,H) 163, arom. C); 116.6 (t, ¹J(C,H) 153, C(4));

112.9 (d, ¹J(C,H) 150, C(2)). CI-MS (NH₃): 197 (50), 180 (27), 169 (6), 145 (18), 128 (73), 111 (34), 99 (47),

85 (100).

12:1 Mixture of ( E)- and (Z)-1-(4-Methoxyphenoxy)buta-1,3-diene (1p). As described for (E)-1n, with 7p

(0.2 g, 0.7 mmol): 60 mg (52%) of 1p. Colorless oil. UV (MeCN): 247 (54300), 215 (43700). IR (film): 2835,

1655, 1505, 1465, 1440, 1225, 1175, 1115, 1035, 825. ¹H-NMR (400 MHz, CDCl₃): (E)-1p: 6.97 (m, 2 arom. H);

6.88 (m, 2 arom. H); 6.75 (d, ³J(1,2) 8.8, HÀC(1)); 6.30 (ddd, ³J(3,4) 13.0, 7.9, ³J(2,3) 8.6, HÀC(3)); 5.97

(dd, ³J(1,2) 8.8, ³J(2,3) 8.6, HÀC(2)); 5.18 (dm, ³J(3,4) 13.0, HÀC(4)); 5.03 (dm, ³J(3,4) 7.9, HÀC(4));

3

3.90 (s, MeO); (Z)-1p: 6.97 (m, 2 arom. H); 6.88 (m, 2 arom. H); 6.84 (ddd, ³J(3,4) 17.3, 10.4, J(2,3) 10.9,

HÀC(3)); 6.30 (d, ³J(1,2) 6.1, HÀC(1)); 5.47 (dd, ³J(2,3) 10.9, ³J(1,2) 6.1, HÀC(2)); 5.22 (dm, ³J(3,4)

17.3, HÀC(4)); 5.06 (dm, ³J(3,4) 10.4, HÀC(4)); 3.90 (s, MeO). ¹³C-NMR (100.6 MHz, CDCl₃): (Z)-1p: 155.6

(s, arom. C); 150.6 (s, arom. C); 147.6 (d, ¹J(C,H) 181, C(1)); 132.2 (d, ¹J(C,H) 152, C(3)); 118.4

(d, ¹J(C,H) 160, arom. C); 114.6 (d, ¹J(C,H) 161, arom. C); 114.0 (t, ¹J(C,H) 158, C(4)); 113.1

(d, ¹J(C,H) 160, C(2)); 55.6 (q, ¹J(C,H) 135, MeO); (Z)-1p: 155.6 (s, arom. C); 150.6 (s, arom. C); 142.4

(d, ¹J(C,H) 181, C(1)); 129.3 (d, ¹J(C,H) 158, C(3)); 115.9 (d, ¹J(C,H) 161, arom. C); 115.3 (t, ¹J(C,H)

158, C(4)); 114.7 (d, ¹J(C,H) 161, arom. C); 111.2 (d, ¹J(C,H) 160, C(2)); 55.6 (q, ¹J(C,H) 135, MeO). CI-

.

MS (NH₃): 176 (100, M ), 159 (69), 144 (31), 124 (80), 105 (55), 91 (30).

3 :1 Mixture of (E)- and (Z)-1-(4-Nitrophenoxy)buta-1,3-diene (1q). BuLi (1.6m in hexane; 3.8 ml,

6.0 mmol) was added slowly under stirring to a soln. of tetramethylpiperidine (0.85 g, 1 ml, 6.0 mmol) in dry

THF (30 ml) at 08 (flame-dried flask). After 15 min at 08, the soln. was added slowly via a syringe to 7q (1 g,

3.0 mmol) in dry THF (50 ml) cooled to À158. The mixture was then gradually warmed up to 258 and stirred at

this temp. for 2 h. Et₂O (30 ml) was added to the dark soln. The org. phase was washed with brine (3 Â 30 ml),

dried (MgSO₄), and evaporated. FC (AcOEt/pentane 1:8) gave 100 mg (18%) of 1q. Yellow oil. UV (MeCN):

313 (22800), 231 (34000), 203 (26000). IR (film): 2930, 2860, 1655, 1610, 1590, 1520, 1490, 1345, 1255, 1115, 850,

750, 630, 615, 600. ¹H-NMR (400 MHz, CDCl₃): (E)-1q: 8.22 (m, 2 arom. H); 7.11 (m, 2 arom. H); 6.81

(d, ³J(1,2) 11.9, HÀC(1)); 6.35 (ddd, ³J(3,4) 16.7, 10.3, ³J(2,3) 10.6, HÀC(3)); 6.17 (dd, ³J(1,2) 11.9,

³J(2,3) 10.6, HÀC(2)); 5.26 (dm, ³J(3,4) 16.7, HÀC(4)); 5.12 (dm, ³J(3,4) 10.3, HÀC(4)); (Z)-1q: 8.22

(m, 2 arom. H); 7.11 (m, 2 arom. H); 6.79 (ddd, ³J(3,4) 17.2, 11.9, ³J(2,3) 10.1, HÀC(3)); 6.44 (d, ³J(1,2)

6.0, HÀC(1)); 5.67 (dd, ³J(2,3) 10.1, ³J(1,2) 6.0, HÀC(2)); 5.31 (dm, ³J(3,4) 17.2, HÀC(4)); 5.16

(dm, ³J(3,4) 11.9, HÀC(4)). ¹³C-NMR (100.6 MHz, CDCl₃): (E)-1q: 161.5 (s, arom. C); 143.2 (d, ¹J(C,H)

183, C(1)); 142.9 (s, arom. C); 131.1 (d, ¹J(C,H) 154, C(3)); 125.9 (d, ¹J(C,H) 169, arom. C); 117.8

(d, ¹J(C,H) 158, C(2)); 117.1 (t, ¹J(C,H) 158, C(4)); 116.3 (d, ¹J(C,H) 169, arom. C); (Z)-1q: 161.7

(s, arom. C); 143.0 (s, arom. C); 138.8 (d, ¹J(C,H) 189, C(1)); 128.4 (d, ¹J(C,H) 152, C(3)); 125.9

(d, ¹J(C,H) 169, arom. C); 118.0 (t, ¹J(C,H) 157, C(4)); 116.1 (d, ¹J(C,H) 168, arom. C); 115.4

.

(d, ¹J(C,H) 149, C(2)). CI-MS (NH₃): 191 (48, M ), 174 (14), 139 (50), 109 (100), 93 (47), 81 (29).

(E)-1-(Naphthalen-2-yloxy)buta-1,3-diene ((E)-1r). As described for (E)-1n, with 7r (0.1 g, 0.3 mmol):

8 mg (26%) of (E)-1r. Yellowish solid. M.p. 40 428. UV (MeCN): 245 (21400). IR (KBr): 2930, 1655, 1630,

1595, 1510, 1465, 1440, 1255, 1215, 1175, 1130, 1095, 995, 850, 820, 750. ¹H-NMR (400 MHz, CDCl₃): 7.81

(m, 2 arom. H); 7.78 (m, arom. H); 7.45 (m, arom. H); 7.43 (m, arom. H); 7.28 (m, arom. H); 7.22 (m, arom. H);

6.92 (d, ³J(1,2) 12.0, HÀC(1)); 6.39 (ddd, ³J(3,4) 16.9, 10.3, ³J(2,3) 11.4, HÀC(3)); 6.10 (dd, ³J(1,2) 12.0,

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Helvetica Chimica Acta Vol. 85 (2002)

³J(2,3) 11.4, HÀC(2)); 5.19 (dm, ³J(3,4) 16.9, HÀC(4)); 5.04 (dm, ³J(3,4) 10.3, HÀC(4)). ¹³C-NMR

(100.6 MHz, CDCl₃): 154.7 (s, arom. C); 146.0 (d, ¹J(C,H) 182, C(1)); 134.2 (s, arom. C); 132.1 (d, ¹J(C,H)

153, C(3)); 130.2 (s, arom. C); 129.9 (d, ¹J(C,H) 154, arom. C); 127.8 (d, ¹J(C,H) 160, arom. C); 127.1

(d, ¹J(C,H) 159, arom. C); 126.7 (d, ¹J(C,H) 160, arom. C); 124.7 (d, ¹J(C,H) 159, arom. C); 118.7

(d, ¹J(C,H) 162, arom. C); 114.9 (d, ¹J(C,H) 154, C(2)); 114.9 (t, ¹J(C,H) 160, C(4)); 111.4 (d, ¹J(C,H)

159, arom. C). CI-MS (NH₃): 197 (28, [M 1] ), 115 (1), 87 (9).

(E)-1-(Methylthio)buta-1,3-diene ((E)-1s). As described for (E)-1n, with (Z)-1,4-bis(methylthio)but-2-

ene [21] (0.9 g, 8 mmol): 240 mg (30%) of (E)-1s. Yellowish oil. Data identical with those reported [38].

2:1 Mixture of ( E)- and (Z)-1-(Phenylthio)buta-1,3-diene (1t). Following [39]. Pale yellow oil. UV

(MeCN): 280 (12700), 207 (14200), 203 (14000). IR (film): 3060, 1805, 1620, 1585, 1440, 1230, 1090, 995, 905,

740, 690. ¹H-NMR (400 MHz, CDCl₃): (E)-1t: 7.42 7.20 (m, 5 arom. H); 6.47 6.33 (m, HÀC(1), HÀC(2),

HÀC(3)); 5.17 (d, ³J(3,4) 17.2, HÀC(4)); 5.08 (d, ³J(3,4) 9.6, HÀC(4)); (Z)-1t: 7.42 7.20 (m, 5 arom. H);

6.79 (ddd, ³J(3,4) 16.9, 10.1, ³J(2,3) 10.4, HÀC(3)); 6.41 (m, HÀC(2)); 6.29 (d, ³J(1,2) 9.4, HÀC(1)); 5.35

(d, ³J(3,4) 16.9, HÀC(4)); 5.27 (d, ³J(3,4) 10.1, HÀC(4)). ¹³C-NMR (100.6 MHz, CDCl₃): (E)-1t: 135.5

(d, ¹J(C,H) 154, C(1)); 134.7 (s, arom. C); 132.2 (d, ¹J(C,H) 155, C(3)); 130.0 (d, ¹J(C,H) 162, arom. C);

129.0 (d, ¹J(C,H) 161, arom. C); 127.0 (d, ¹J(C,H) 162, arom. C); 127.2 (C(2)); 116.3 (t, ¹J(C,H) 157, C(4));

(Z)-1t: 134.7 (s, arom. C); 132.2 (d, ¹J(C,H) 155, C(3)); 130.4 (d, ¹J(C,H) 157, C(2)); 129.2 (d, ¹J(C,H)

160, arom. C); 129.1 (d, ¹J(C,H) 160, arom. C); 126.6 (d, ¹J(C,H) 162, arom. C); 125.4 (d, ¹J(C,H) 157,

.

C(1)); 118.8 (t, ¹J(C,H) 155, C(4)). CI-MS (NH₃): 162 (1, M ), 157 (54), 129 (14), 117 (17), 107 (11), 89 (44).

2:1 Mixture of ( E)- and (Z)-1-[(4-Chlorophenyl)thio]buta-1,3-diene (1u). Pure 3-chloro-4-[(4-chlorophe-

nyl)thio]but-1-ene (9u) [40] (5.8 g, 15 mmol) was added slowly to stirred DBU (7.6 g, 50 mmol) heated to 1008.

After 10 min at 1008, the mixture was cooled to 258 and diluted with 2% aq. HCl soln. (100 ml). Extraction with

Et₂O (100 ml), washing of the extract with brine (3 Â 30 ml), drying (MgSO₄), and evaporation gave a residue

that was distilled under reduced pressure: 3.6 g (76%) of 1u. Pale yellow oil. B.p. 808/0.1 Torr. UV (MeCN): 286

1

(11600), 201 (11500). IR (film): 2920, 1675, 1475, 1390, 1095, 1010, 815. H-NMR (400 MHz, CDCl₃): (E)-1u:

7.31 7.27 (m, 4 arom. H); 6.42 6.34 (m, HÀC(1), HÀC(2), HÀC(3)); 5.18 (d, ³J(3,4) 12.6, HÀC(4)); 5.09

(d, ³J(3,4) 8.4, HÀC(4)); (Z)-1u: 7.31 7.27 (m, 4 arom. H); 6.76 (ddd, ³J(3,4) 13.5, 7.9, ³J(2,3) 8.7,

HÀC(3)); 6.38 (m, HÀC(2)); 6.20 (d, ³J(1,2) 7.2, H ÀC(1)); 5.35 (d, ³J(3,4) 13.5, HÀC(4)); 5.25

³J(d, 3,4) 7.9, HÀC(4)). ¹³C-NMR (100.6 MHz, CDCl₃): (E)-1u: 135.2 (d, ¹J(C,H) 156, C(3)); 133.4

(s, arom. C); 133.0 (d, ¹J(C,H) 158, C(2)); 132.9 (s, arom. C); 131.0 (d, ¹J(C,H) 167, arom. C); 129.2

(d, ¹J(C,H) 168, arom. C); 126.3 (d, ¹J(C,H) 173, C(1)); 116.9 (t, ¹J(C,H) 157, C(4)); (Z)-1u: 134.3

(s, arom. C); 132.5 (s, arom. C); 131.9 (d, ¹J(C,H) 156, C(3)); 131.2 (d, ¹J(C,H) 158, C(2)); 130.2

(d, ¹J(C,H) 167, arom. C); 128.8 (d, ¹J(C,H) 168, arom. C); 124.4 (d, ¹J(C,H) 186, C(1)); 119.3

.

(t, ¹J(C,H) 161, C(4)). CI-MS (NH₃): 196 (2, M ), 166 (88), 129 (37), 119 (17), 97 (74), 84 (100).

2.3 :1 Mixture of (E)- and (Z)-1-[(4-Methoxyphenyl)thio]buta-1,3-diene (1v). As described for 1u, with 9v

(17.4 g, 76 mmol) and DBU (22.3 g, 0.15 mmol): 9.9 g (68%) of 1v. Pale yellow oil. B.p. 1008/0.1 Torr. UV

(MeCN): 254 (12000), 228 (14200), 207 (13000), 197 (11000). IR (film): 2955, 2835, 1620, 1590, 1570, 1495, 1460,

1440, 1410, 1290, 1250, 1175, 1030, 930, 900, 825. ¹H-NMR (400 MHz, CDCl₃): (E)-1v: 7.37 (m, 2 arom. H); 6.90

(m, 2 arom. H); 6.40 (d, ³J(1,2) 13.0, HÀC(1)); 6.34 (ddd, ³J(3,4) 13.0, 8.0, ³J(2,3) 7.9, HÀC(3)); 6.14

(dd, ³J(1,2) 13.0, ³J(2,3) 7.9, HÀC(2)); 5.07 (d, ³J(3,4) 13.0, HÀC(4)); 4.98 (d, ³J(3,4) 8.0, HÀC(4));

3.80 (s, MeO); (Z)-1v: 7.35 (m, 2 arom. H); 6.88 (m, 2 arom. H); 6.75 (ddd, ³J(3,4) 13.0, 7.9, ³J(2,3) 7.9,

HÀC(3)); 6.22 (dd, ³J(2,3) 7.9, ³J(1,2) 7.2, HÀC(2)); 6.17 (d, ³J(1,2) 7.2, HÀC(1)); 5.29 (d, ³J(3,4) 13.0,

HÀC(4)); 5.22 (d, ³J(3,4) 7.9, HÀC(4)); 3.81 (s, MeO). ¹³C-NMR (100.6 MHz, CDCl₃): (E)-1v: 159.6

(s, arom. C); 135.7 (d, ¹J(C,H) 149, C(3)); 133.6 (d, ¹J(C,H) 162, arom. C); 129.6 (d, ¹J(C,H) 160, C(1),

C(2)); 124.0 (s, arom. C); 115.2 (t, ¹J(C,H) 156, C(4)); 114.8 (d, ¹J(C,H) 160, arom. C); 55.3 (q, ¹J(C,H)

144, MeO); (Z)-1v: 159.2 (s, arom. C); 132.3 (d, ¹J(C,H) 162, arom. C); 132.2 (d, ¹J(C,H) 151, C(3)); 128.4

(d, ¹J(C,H) 157, C(2)); 128.0 (d, ¹J(C,H) 168, C(1)); 126.0 (s, arom. C); 118.3 (t, ¹J(C,H) 160, C(4)); 114.7

.

(d, ¹J(C,H) 160, arom. C); 55.3 (q, ¹J(C,H) 144, MeO). CI-MS (NH₃): 192 (7, M ), 140 (100), 125 (24), 108

(52), 96 (15), 79 (12), 70 (7).

3.5 :1 Mixture of (E)- and (Z)-1-[(4-Nitrophenyl)thio]buta-1,3-diene (1w). As described for 1u, with 3-

chloro-4-[(4-nitrophenyl)thio]but-1-ene (9w; 2.0 g, 8 mmol) and DBU (2.4 g, 16 mmol). FC (Et₂O/light

petroleum ether 1:9): 1.2 g (69%) of 1w. Yellow solid. M.p. 39 408. UV (MeCN): 340 (9100), 275 (6700), 203

(12400). IR (KBr): 1575, 1510, 1340, 1090, 1000, 850. ¹H-NMR (400 MHz, CDCl₃): (E)-1w: 8.15 (m, 2 arom. H);

3

7.40 (m, 2 arom. H); 6.64 (dd, ³J(1,2) 11.5, J(2,3) 8.1, HÀC(2)); 6.43 (ddd, ³J(3,4) 12.8, 8.1, J(2,3) 8.1,

HÀC(3)); 6.42 (d, ³J(1,2) 11.5, HÀC(1)); 5.33 (d, ³J(3,4) 12.8, HÀC(4)); 5.27 (d, ³J(3,4) 8.1, HÀC(4));

(Z)-1w: 8.15 (m, 2 arom. H); 7.40 (m, 2 arom. H); 6.80 (ddd, ³J(3,4) 12.9, 8.5, ³J(2,3) 7.2, HÀC(3)); 6.61

Helvetica Chimica Acta Vol. 85 (2002)

749

3

(dd, ³J(2,3) 7.2, J(1,2) 7.1, H ÀC(2)); 6.27 (d, ³J(1,2) 7.1, H ÀC(1)); 5.51 (d, ³J(3,4) 12.9, HÀC(4)); 5.40

(d, ³J(3,4) 8.5, HÀC(4)). ¹³C-NMR (100.6 MHz, CDCl₃): (E)-1w: 146.1 (s, arom. C); 145.5 (s, arom. C); 138.1

(d, ¹J(C,H) 157, C(2)); 134.8 (d, ¹J(C,H) 161, C(3)); 126.9 (d, ¹J(C,H) 173, arom. C); 124.0 (d, ¹J(C,H)

173, arom. C); 121.7 (d, ¹J(C,H) 154, C(1)); 119.4 (t, ¹J(C,H) 165, C(4)); (Z)-1w: 146.1 (s, arom. C); 145.5

(s, arom. C); 135.4 (d, ¹J(C,H) 157, C(2)); 131.50 (d, ¹J(C,H) 160, C(3)); 126.9 (d, ¹J(C,H) 173, arom. C);

124.0 (d, ¹J(C,H) 173, arom. C); 121.3 (d, ¹J(C,H) 154, C(1)); 119.9 (t, ¹J(C,H) 164, C(4)). CI-MS (NH₃):

.

207 (23, M ), 190 (1), 160 (3), 128 (17), 115 (8), 85 (100). Anal. calc. for C₁₀H₉NO₂S (207.25): C 57.96, H 4.38,

N 15.44, S 6.76; found: C 57.85, H 4.33, N 15.45, S 6.71.

(Æ)-3-Chloro-4-[(4-methoxyphenyl)thio]but-1-ene (9v). To a rapidly stirred suspension of N-chlorosuccin-

imide (9.9 g, 74 mmol) in dry CH₂Cl₂(70 ml), a soln. of 4-methoxybenzenethiol (10.0 g, 71 mmol) in dry

CH₂Cl₂(30 ml) was added slowly at 258. Initiation of sulfenyl chloride formation is indicated by the intense

orange coloration of the mixture accompanied by gentle boiling of the solvent. Once initiated, the vessel was

immersed in an ice bath, and the remaining 4-methoxybenzenethiol was added dropwise at a rate sufficient to

maintain the solvent under reflux. When the addition was complete, the ice bath was removed and the orange

soln. stirred at 258 for additional 30 min. During this time, N-succinimide precipitated. Buta-1,3-diene (30 ml,

18.6 g, 0.34 mol) was condensed in a graduate funnel at À788 and quickly transferred into the above soln. of 4-

methoxybenzenesulfenyl chloride (0.71m in CH₂Cl₂; 100 ml, 71 mmol) at À788. The mixture was allowed to

warm to 258, stirred at 258 for 1 h, and evaporated. The residue was diluted with CCl₄(40 ml). Filtration and

concentration of the filtrate gave 17.4 g (88%) of 9v. Pale yellow oil. UV (MeCN): 256 (10700), 229 (12600), 203

(18300). IR (film): 2940, 1590, 1495, 1460, 1440, 1285, 1245, 1175, 1030, 930, 830, 720, 640. ¹H-NMR (400 MHz,

CDCl₃): 7.40 (m, 2 arom. H); 6.90 (m, 2 arom. H); 5.88 (ddd, ³J(1,2) 16.9, 10.1, ³J(2,3) 8.6, HÀC(2)); 5.35

(d, ³J(1,2) 16.9, HÀC(1)); 5.27 (d, ³J(1,2) 10.1, HÀC(1)); 4.35 (ddd, ³J(3,4) 8.7, 5.7, ³J(2,3) 8.6, HÀC(2));

3

3.80 (s, MeO); 3.29 (dd, ²J 13.7, J(1,2) 5.7, HÀC(4)); 3.11 (dd, ²J 13.7, J(1,2) 8.7, HÀC(4)). ¹³C-NMR

(100.6 MHz, CDCl₃): 159.5 (s, arom. C); 136.7 (d, ¹J(C,H) 161, C(2)); 134.5 (d, ¹J(C,H) 162, arom. C); 124.7

(s, arom. C); 118.5 (t, ¹J(C,H) 160, C(1)); 114.7 (d, ¹J(C,H) 160, arom. C); 60.4 (d, ¹J(C,H) 148, C(3));

.

55.3 (q, ¹J(C,H) 144, MeO); 43.6 (t, ¹J(C,H) 142, C(4)). CI-MS (NH₃): 228 (20, M ), 193 (62), 139 (100),

108 (26). Anal. calc. for C₁₁H₁₃ClOS (228.74): C 57.76, H 5.73; found: C 57.95, H 5.69.

(Æ)-3-Chloro-4-[(4-nitrophenyl)thio]but-1-ene (9w). As described for 9v, with 4-nitrobenzenethiol (5.0 g,

32 mmol): 4.8 g (76%) of 9w. Red oil. UV (MeCN): 336 (13600), 332 (13800), 199 (20500). IR (film): 3095,

1715, 1595, 1580, 1515, 1340, 1185, 1090, 930, 855, 840, 740, 680. ¹H-NMR (400 MHz, CDCl₃): 8.17

(m, 2 arom. H); 7.40 (m, 2 arom. H); 5.90 (ddd, ³J(1,2) 16.8, 10.2, ³J(1,2) 8.2, HÀC(2)); 5.37 (d, ³J(1,2)

16.8, HÀC(1)); 5.28 (d, ³J(1,2) 10.2, HÀC(1)); 4.50 (ddd, ³J(2,3) 8.2, ³J(3,4) 8.1, 5.8, HÀC(3)); 3.53

(dd, ²J 13.7, ³J(3,4) 5.8, HÀC(4)); 3.37 (dd, ²J 13.7, ³J(3,4) 8.1, HÀC(4)). ¹³C-NMR (100.6 MHz,

CDCl₃): 145.5 (s, arom. C); 135.9 (d, ¹J(C,H) 165, C(2)); 127.1 (d, ¹J(C,H) 165, arom. C); 126.3 (s, arom. C);

124.4 (d, ¹J(C,H) 165, arom. C); 119.2 (t, ¹J(C,H) 157, C(1)); 59.6 (d, ¹J(C,H) 158, C(3)); 39.7

.

(t, ¹J(C,H) 143, C(4)). CI-MS (NH₃): 244 (4, M ), 208 (100), 168 (11), 122 (23). Anal. calc. for C₁₀H₁₀ClNO₂S

(243.71): C 49.28, H 4.14; found: C 49.37, H 4.28.

1:0.8 :0.5 Mixture of (E)-1-(Phenylseleno)buta-1,3-diene ((E)-1x), (Z)-1x, and 2-(Phenylseleno)buta-1,3-

diene (12). As described for 1u, with 10/11 5 :1 (455 mg, 1.9 mmol) and DBU (580 mg, 3.8 mmol): 163 mg

(41%). Spectroscopic data identical with those reported for these compounds [41].

5 :1 Mixture of (Æ)-3-Chloro-4-(phenylseleno)but-1-ene (10) and (Æ)-4-Chloro-3-(phenylseleno)but-1-ene

(11). Buta-1,3-diene (0.5 ml, 310 mg, 5.7 mmol) was condensed into a stirred soln. of benzeneselenenyl chloride

(0.46 g, 2.4 mmol) in anh. CH₂Cl₂(3 ml) cooled to À788. The mixture was allowed to reach 258 in a few hours.

After an additional hour of stirring, solvent evaporation gave a residue that was taken up in CCl₄(2 ml).

Filtration and evaporation yielded 565 mg (96%) of 10/11 5 :1. Deep orange oil. 10: UV (MeCN): 198 (15400).

IR (film): 3070, 3055, 1580, 1480, 1440, 1020, 1020, 985, 965, 930, 740, 690, 670. ¹H-NMR (400 MHz, CDCl₃): 7.54

(m, 2 arom. H); 7.30 (m, 3 arom. H); 5.90 (ddd, ³J(1,2) 16.9, 10.1, ³J(2,3) 8.4, HÀC(2)); 5.32 (d, ³J(1,2)

16.9, HÀC(1)); 5.24 (d, ³J(1,2) 10.1, HÀC(1)); 4.50 (ddd, ³J(3,4) 9.3, 5.4, ³J(2,3) 8.4, HÀC(3)); 3.39

3

(dd, ²J 12.5, J(3,4) 5.4, HÀC(4)); 3.23 (dd, ²J 12.5, 9.3, HÀC(4)). ¹³C-NMR (100.6 MHz, CDCl₃): 139.2

(s, arom. C); 136.9 (d, ¹J(C,H) 161, C(2)); 133.4 (d, ¹J(C,H) 161, arom. C); 129.3 (d, ¹J(C,H) 161,

arom. C); 127.6 (d, ¹J(C,H) 160, arom. C); 118.5 (t, ¹J(C,H) 157, C(1)); 61.2 (d, ¹J(C,H) 159, C(3)); 34.9

.

(t, ¹J(C,H) 146, C(4)). CI-MS (NH₃): 264 (4, [M 18] ), 246 (57, M ), 211 (100), 157 (25), 89 (25), 78 (31).

9 :1 Mixture of (E)- and (Z)-Buta-1,3-dien-1-yl Benzoate (1y). As described for 1z (see below), with benzoyl

chloride instead of naphthalene-2-carbonyl chloride [22]. Colorless liquid. ¹H-NMR (400 MHz, CDCl₃): 8.1

(m, 2 H, HÀC(2), HÀC(6)); 7.67 (d, 0.9 H, ³J(1',2') 12.0, HÀC(1')); 7.62 (m, 1 H, HÀC(4)); 7.49 (m, 2 H,

HÀC(3), HÀC(5)); 7.34 (dm, ³J(1',2') 6.4, 0.1 H, HÀC(1')); 6.89 (ddd, ³J(3',4'cis) 17.5, ³J(2',3') 10.5,

750

Helvetica Chimica Acta Vol. 85 (2002)

³J(3',4'trans) 10.1, 0.1 H, HÀC(3')); 6.38 (ddd, ³J(3',4'cis) 17.0, ³J(2',3') 11.1, ³J(3',4'trans) 10.4, 0.9 H,

HÀC(3')); 6.25 (dd, ³J(1',2') 12.0, ³J(2',3') 11.1, 0.9 H, HÀC(2')); 5.67 (ddm, ³J(2',3') 10.5, ³J(1',2') 6.4,

0.1 H, HÀC(2')); 5.33 (dm, ³J(3',4'cis) 17.5, 0.1 H, H_cisÀC(4')); 5.28 (dm, ³J(3',4'cis) 17.0, 0.9 H, H_cisÀC(4'));

5.19 (dm, ³J(3',4'trans) 10.1, 0.1 H, H_transÀC(4')); 5.15 (dm, ³J(3',4'trans) 10.4, 0.9 H, H_transÀC(4')).

¹³C-NMR (100.6 MHz, CDCl₃): (E)-1y: 163.5 (s, CO); 138.9 (d, ¹J(C,H) 195, C(1')); 133.6 (d, ¹J(C,H)

161, C(4)); 131.7 (d, ¹J(C,H) 155, C(3')); 130.0 (d, ¹J(C,H) 163, C(2), C(6)); 128.8 (s, C(1)); 128.6

(d, ¹J(C,H) 155, C(3), C(5)); 117.4 (t, ¹J(C,H) 160, C(4')); 116.6 (d, ¹J(C,H) 162, C(2')). ¹⁷O-NMR

(81.34 MHz, CD₂Cl₂): 359.5 (OC, (Z)); 342.8 (OC, (E)); 186.8 (OÀC(1), (E)); 171.9 (OÀC(1), (Z)).

8 :1 Mixture of (E)- and (Z)-Buta-1,3-dien-1-yl Naphthalene-2-carboxylate (1z). A mixture of KF (3.66 g),

H₂O (6 ml), CH₂Cl₂(30 ml), naphthalene-2-carbonyl chloride (6 g, 31.5 mmol) and Bu₃N (0.37 ml) was stirred

at 08 for 4 h. The aq. layer was extracted with CH₂Cl₂(2 Â 15 ml). The combined org. extract was dried (MgSO₄)

and evaporated, giving naphthalene-2-carbonyl fluoride (¹⁹F-NMR (CDCl₃, 376 MHz): 17.5), which was used as

such in the next step. To a soln. of this carbonyl fluoride in anh. THF (44 ml); (E)/(Z)-1-[(trimethylsilyl)-

oxy]buta-1,3-diene (5.06 g, 3.07 mmol) and Bu₃NF ¥ 3 H₂O (225 mg) were added, and the mixture was stirred at

08 for 3 h under Ar. Sat. aq. NaHCO₃soln. (50 ml) was added (pH 7), the org. phase washed with sat. aq. NaHCO₃

soln. (2 Â 20 ml), then with H₂O (2 Â 20 ml), dried (MgSO₄), and evaporated. FC (AcOEt/light petroleum ether

1:12): 5.45 g (76%) of 1z. White solid. M.p. 37 408. UV (MeCN): 281 (40000), 241 (140000), 193 (88000). IR

(KBr): 3085, 1725, 1650, 1630, 1600, 1265, 1225, 1195, 1135, 1115, 1005, 930, 890, 775, 760, 475. ¹H-NMR

(400 MHz, CDCl₃): (E)-1z: 8.69 (s, HÀC(1)); 8.11 (dm, ³J(3,4) 8.3, HÀC(3)); 7.99 (dm, ³J(7,8) 7.7,

HÀC(8)); 7.74 (d, ³J(1',2') 11.7, HÀC(1')); 7.94 7.90 (m, HÀC(4), HÀC(5)); 7.56 7.65 (m, HÀC(6),

HÀC(7)); 6.41 (ddd, ³J(2',3') 11.1, ³J(3',4'cis)) 16.5, ³J(3',4'trans) 10.2, HÀC(3')); 6.32 (dd, ³J(2',3')

11.1, ³J(1',2') 11.7, HÀC(2')); 5.32 (d, ³J(3',4'cis) 16.5, H_cisÀC(4')); 5.32 (ddm, ³J(3',4'trans) 10.2,

²J(4'cis,4'trans) 1.8, H_transÀC(4')); (Z)-1z: 8.71 (s, HÀC(1)); 8.14 (dm, ³J(3,4) 8.3, HÀC(3)); 8.01

(dm, ³J(7,8) 7.7, H ÀC(8)); 7.90 7.94 (m, HÀC(4), HÀC(5)); 7.65 7.56 (m, HÀC(6), HÀC(7)); 7.40

(dddd, ³J(1',2') 6.2, ⁵J(1',4'trans) 1.7, ⁴J(1',3') 1.0, ⁵J(1',4'cis) 0.9, HÀC(1')); 6.99 (dddd, ³J(2',3') 10.7,

³J(3',4'cis) 17.3, ³J(3',4'trans) 10.5, ⁴J(1',3') 1.0, HÀC(3')); 5.70 (dddd, ³J(2',3') 10.7, ³J(1',2'cis) 6.2,

4

⁴J(2',4'cis) 0.8, J(2',4'trans) 0.8, HÀC(2')); 5.37 (dddd, ³J(3',4'cis) 17.3, ²J(4'cis,4'trans) 1.8, ⁵J(1',4'cis)

0.9, ⁴J(2',4'trans) 0.8, H_cisÀC(4')); 5.24 (dddd, ³J(3',4'trans) 10.5, ²J(4'cis,4'trans) 1.8, ⁵J(1',4'trans) 1.7,

⁴J(2',4'trans) 0.8, H_transÀC(4')). ¹³C-NMR (100.6 MHz, CDCl₃): (E)-1z: 163.6 (s, CO); 139.0 (d, ¹J(C,H)

190, C(1')); 135.8 (s, C(4a)); 132.4 (s, C(8a)); 131.8 (d, ¹J(C,H) 158, C(1), C(3')); 129.4 (d, ¹J(C,H) 161,

C(8)); 128.7 (d, ¹J(C,H) 160, C(6)); 128.4 (d, ¹J(C,H) 160, C(4)); 127.8 (d, ¹J(C,H) 160, C(5)); 126.8

(d, ¹J(C,H) 161, C(7)); 125.9 (s, C(2)); 125.1 (d, ¹J(C,H) 164, C(3)); 117.4 (d, ¹J(C,H) 158, C(4')); 116.6

(d, ¹J(C,H) 158, C(2')); (Z)-1z: 163.6 (s, CO); 139.0 (d, ¹J(C,H) 190, C(1')); 135.8 (s, C(4a)); 134.4

(d, ¹J(C,H) 194, C(2')); 132.4 (s, C(8a)); 131.8 (d, ¹J(C,H) 158, C(1)); 129.4 (d, ¹J(C,H) 161, C(8)); 129.0

(d, ¹J(C,H) 156, C(3')); 128.7 (d, ¹J(C,H) 160, C(6)); 128.4 (d, ¹J(C,H) 160, C(4)); 127.8 (d, ¹J(C,H) 160,

C(5)); 126.8 (d, ¹J(C,H) 161, C(7)); 126.1 (s, C(2)); 125.1 (d, ¹J(C,H) 164, C(3)); 118.0 (d, ¹J(C,H) 158,

C(4')); 114.0 (d, ¹J(C,H) 158, C(2')). CI-MS (NH₃): 242 (9, [M NH₄] ), 225 (32, [M H] ), 172 (11, [M

.

H À C₄H₅] ), 156 (44, [M H À OC₄H₅] ), 155 (100, [M À OC₄H₅] ), 127 (27, [M À C(O)OC₄H₅] ), 99 (16),

76 (58). Anal. calc. for C₁₅H₁₂O₂¥ 0.5 H₂O (224.26 9.01): C 77.24, H 5.62; found: C 77.05, H 5.63.

2:1 Mixture of (1 E)- and (1Z)-Ethylidene-2-methylidenecyclohexane (4a). At 08, 2-[(dimethylamino)-

methyl]cyclohexanone (13) [23] (5 g, 32.5 mmol) was added dropwise to a stirred soln. of (EtPPh₃)Br (13.2 g,

35.5 mmol), t-BuOK (3.98 g, 35.5 mmol), and [18]crown-6 (30 mg) in anh. THF (50 ml) under Ar. After stirring

at 258 for 5.5 h, the solvent was evaporated. The oily residue was filtered through a pad of silica gel, rinsing with

light petroleum ether, the filtrate evaporated, and the oily residue added dropwise to a stirred soln. of MeI

(3.85 ml) in anh. Et₂O (55 ml) under Ar. After stirring at 258 for 12 h, the precipitate was collected and washed

with Et₂O. The white solid so obtained was dissolved in H₂O (171 ml), then Ag₂O (10 g, 43 mmol) was added

portionwise under stirring and Ar. After stirring at 258 for 6 h, the brownish soln. was filtered, the filtrate

evaporated (<408), and the residue heated in a B¸chi −Kugelrohr× (1508/130 Torr) for 1 h. The residue was

extracted with pentane (2 Â 15 ml), the combined extract washed with 0.7n aq. HCl (15 ml), then with H₂O (2 Â

20 ml), dried (MgSO₄), and evaporated at 308/600 mbar, and the residue distilled bulb-to-bulb (B¸chi

−Kugelrohr×) at 70 808/30 mbar: 1.97 g (585) of (E)/(Z)-4a 2 :1. Colorless liquid. UV (MeCN): 227 (5700). IR

(film): 3080, 2930, 2855, 1625, 1440, 890, 830. ¹H-NMR (400 MHz, CDCl₃): (E)-4a: 5.54 (q, ³J 6.9, HÀC(1'));

4.79 (d, ²J 2.7, H_cisÀC(1'')); 4.56 (dm, ²J 2.7, H_transÀC(1'')); 2.25 2.22 (m, CH₂(3), CH₂(6)); 1.64 (d, ³J 6.9,

Me(2')); 1.67 1.59 (m, CH₂(4), CH₂(5)); (Z)-4a: 5.29 (q, ³J 6.9, HÀC(1')); 4.96 (dm, ²J 2.7, H_cisÀC(1''));

4.65 (d, ²J 2.7, H_transÀC(1'')); 2.20 2.16 (m, CH₂(3), CH₂(6)); 1.70 (d, ³J 6.9, Me(2')); 1.67 1.59 (m, CH₂(4),

CH₂(5)); distinctions between (E)-and ( Z)-4a and signal assignments based on 2D ¹H,¹H-NOESY. ¹³C-NMR

Helvetica Chimica Acta Vol. 85 (2002)

751

(100.6 MHz, CDCl₃): (E)-4a: 151.4 (s, C(2)); 140.7 (s, C(1)); 117.2 (d, ¹J(C,H) 150, CHC(1)); 106.8

(t, ¹J(C,H) 156, CH₂C(2)); 35.5 (t, ¹J(C,H) 126, C(3)); 28.1 (t, ¹J(C,H) 128, C(6)); 27.2 (t, ¹J(C,H) 128,

C(4) or C(5)); 26.1 (t, ¹J(C,H) 128, C(5) or C(4)); 13.0 (q, ¹J(C,H) 126, Me); (Z)-4a: 151.4 (s, C(2)); 140.7

(s, C(1)); 117.8 (d, ¹J(C,H) 151, CHC(1)); 110.2 (t, ¹J(C,H) 156, CH₂C(2)); 37.9 (t, ¹J(C,H) 126, C(3)

or C(6)); 36.8 (t, ¹J(C,H) 126, C(6) or C(3)); 28.0 (t, ¹J(C,H) 128, C(4) or C(5)); 27.7 (t, ¹J(C,H) 128, C(5)

.

or C(4)); 14.3 (q, ¹J(C,H) 126, Me). CI-MS (NH₃): 140 (100, [M NH₄] ), 123 (17, [M H] ), 122 (15, M ),

110 (34), 83 (56).

1.5 :1 Mixture of (1E)- and (1Z)-1-(Methoxymethylidene)-2-methylidenecyclohexane (4f). Ag₂O (3.5 g,

15 mmol) and (E)/(Z)-14f 1.5 :1 (3.9 g, 12 mmol) in H₂O (100 ml) were stirred at 258 for 4 h. The precipitate

was filtered off and the solvent evaporated (408/1 mbar). The yellow residue was heated in a B¸chi −Kugelrohr×

at 1508/0.1 mbar yielding 620 mg (38%) of (E)/(Z)-4f 1.5 :1. Colorless oil. UV (MeCN): 202 (3900), 198 (4300).

IR (film): 2930, 2860, 1655, 1620, 1445, 1225, 1130, 985, 885, 715. ¹H-NMR (400 MHz, CDCl₃): (E)-4f: 6.13

(t, J 1.4, MeOCH); 4.71, 4.49 (2 br. s, CH₂C(2)); 3.63 (s, MeO); 2.24 (m, CH₂(3), HÀC(6)); 2.03

(m, HÀC(6)); 1.60 (m, CH₂(5), CH₂(4)); (Z)-4f: 5.88 (s, MeOCH); 5.06, 5.05 (2m, CH₂C(2)); 3.60

(s, MeO); 2.24 (m, CH₂(6), CH₂(3)); 1.60 (m, CH₂(5), CH₂(4)). ¹³C-NMR (100.6 MHz, CDCl₃): (E)-4f:

146.8 (s, C(2)); 140.6 (d, ¹J(C,H) 184, MeOCH); 119.5 (s, C(1)); 105.3 (t, ¹J(C,H) 156, CH₂C(2)); 59.6

(q, ¹J(C,H) 143, MeO); 35.2 (t, ¹J(C,H) 128, C(3)); 26.9 (t, ¹J(C,H) 128); 25.5 (t, ¹J(C,H) 127); 25.2

(t, ¹J(C,H) 127); (Z)-4f: 143.1 (s, C(2)); 141.6 (d, ¹J(C,H) 176, MeOCH); 116.4 (s, C(1)); 111.5 (t, ¹J(C,H)

159, CH₂C(2)); 59.9 (q, ¹J(C,H) 143, MeO); 35.7 (t, ¹J(C,H) 131, C(3)); 31.0 (t, ¹J(C,H) 126); 26.9

(t, ¹J(C,H) 127); 26.8 (t, ¹J(C,H) 128). CI-MS (NH₃): 139 (100, [M 1] ), 125 (43), 109 (50), 95 (40), 81

(46), 75 (37).

1.5 :1 Mixture of (2E)- and (2Z)-N,N-Dimethyl-2-(methoxymethylidene)cyclohexanemethanamine (14f).

BuLi (1.6m in hexane; 4.4 ml, 7 mmol) was added slowly to a stirred soln. of (i-Pr)₂NH (708 mg, 1 ml, 7 mmol) in

anh. THF (5 ml) under Ar at 08. After stirring at 08 for 15 min, this soln. was cooled to À788 and added dropwise

to a stirred suspension of (methoxymethyl)triphenylphosphonium chloride (2.0 g, 6 mmol) in anh. THF (40 ml)

cooled to À788 under Ar. The resulting orange soln. was allowed to warm to 08 and stirred at 08 for 1 h. Then a

soln. of 13 [23] (1 g, 6 mmol) in anh. THF (5 ml) was added slowly (syringe). After stirring at 258 for 1 h, the

precipitate was filtered off, the solvent evaporated, the residue extracted with Et₂O (10 ml, 5 Â ), the combined

Et₂O extract dried (MgSO₄) and evaporated, and the residue distilled bulb-to-bulb in a B¸chi oven at 908/

0.02 mbar :1.2 g (89%) of (E)/(Z)-14f 1.5 :1. Colorless liquid. UV (MeCN): 204 (6500). IR (film): 2925, 2855,

2765, 1680, 1460, 1235, 1200, 1130, 1010, 835. ¹H-NMR (400 MHz, CDCl₃): (E)-14f: 5.79 (s, MeOCH); 3.55

(s, MeO); 2.34 (dd, ²J 11.9, ³J(CH₂N,1) 8.5, 1 H, CH₂N); 2.21 (s, Me₂N); 2.24 1.38 (m, 1 H of CH₂N,

HÀC(1), CH₂(3), CH₂(4), CH₂(5), CH₂(6)); (Z)-14f: 5.84 (d, J 1.6, MeOCH); 3.53 (s, MeO); 3.06

(m, HÀC(1)); 2.46 (dd, ²J 11.9, ³J 9.0, 1 H, CH₂N); 2.24 (s, Me₂N); 2.24 1.38 (m, 1 H of CH₂N, CH₂(3),

CH₂(4), CH₂(5), CH₂(6)). ¹³C-NMR (100.6 MHz, CDCl₃): (E)-14f: 139.3 (d, ¹J(C,H) 171, MeOCH); 119.5

(s, C(2)); 59.1 (q, ¹J(C,H) 143, MeO); 61.9 (t, ¹J(C,H) 130, CH₂N); 45.8 (q, ¹J(C,H) 133, 2 CMe₂N); 36.8

(d, ¹J(C,H) 124, C(1)); 31.2 (t, ¹J(C,H) 128); 27.2 (t, ¹J(C,H) 126); 23.3 (t, ¹J(C,H) 127); 23.2

(t, ¹J(C,H) 127); (Z)-14f: 139.9 (d, ¹J(C,H) 181, MeOCH); 119.0 (s, C(2)); 60.8 (t, ¹J(C,H) 130, CH₂N);

59.0 (q, ¹J(C,H) 143, MeO); 45.8 (q, ¹J(C,H) 133, 2 C, Me₂N); 30.8 (d, ¹J(C,H) 124, C(1)); 28.4

(t, ¹J(C,H) 126); 28.8 (t, ¹J(C,H) 126); 26.6 (t, ¹J(C,H) 125); 21.5 (t, ¹J(C,H) 127). CI-MS (NH₃): 184

(100, [M 1] ), 157 (7), 139 (16), 123 (10), 107 (5), 91 (10), 77 (7). Anal. calc. for C₁₁H₂₁NO (183.29): C 72.08,

H 11.55; found: C 72.31, H 11.22.

(2RS,6SR)-cis-6-(tert-Butyl)-3,6-dihydro-1,2-oxathiin 2-Oxide (c-2g) and (2RS,6RS)-trans-6-(tert-Butyl)-

3,6-dihydro-1,2-oxathiin 2-Oxide (t-2g). In a 5-mm NMR Pyrex tube, pure (E)-1g (40 mg, 0.4 mmol), CD₂Cl₂

(0.15 ml), and CFCl₃(100 mg) were mixed at 258. After degassing by several freeze-thaw cycles at 10^À2mbar on

the vacuum line, degassed SO₂(ca. 0.2 ml, 4 6 mmol) and CF₃COOH (23 mg, 0.2 mmol) were transferred to

the above mixture. The NMR tube was sealed under vacuum at À1968, warmed to À808, and left at À808 for 6 h.

The tube was then transferred to a Bruker ARX-400 spectrometer probe cooled to À808 and analyzed: traces of

c-2g could be detected. After additional 12 h at À808, isomerization to t-2g took place. ¹H-NMR (400 MHz,

CD₂Cl₂/CFCl₃/SO₂, 193 K): c-2g, detected signals: 6.18 (dd, ³J(4,5) 11.0, ⁴J(3ax,5) 2.4, HÀC(5)); 4.07

(m, HÀC(6)); 3.56 (ddd, ²J 16.4, ³J(3eq,4) 6.5, J 1.0, H_eqÀC(3)); 3.08 (m, H_axÀC(3)); t-2g: 5.95

(dm, ³J(4,5) 11.7, HÀC(5)); 5.75 (m, HÀC(4)); 4.24 (dddd, ⁵J(3ax,6)) 4.2, ⁵J(3eq,6) 2.8, ³J(5,6) 2.1,

⁴J(4,6) 2.1, HÀC(6)); 3.41 (dddd, ²J 17.2, ⁵J(3ax,6) 4.2, ³J(3ax,4) 2.7, ⁴J(3ax,5) 2.7, H_axÀC(3)); 3.04

(dddd, ²J 17.2, ³J(3eq,4) 6.5, ⁵J(3eq,6) 2.8, ⁴J(3eq,5) 1.1, H_eqÀC(3)); 0.86 (s, Me₃C). ¹³C-NMR

(100.6 MHz, CD₂Cl₂/CFCl₃/SO₂, 223 K): t-2g, detected signals: 125.9 (d, ¹J(C,H) 161, C(5)); 125.7

(d, ¹J(C,H) 151, C(4)); 77.6 (d, ¹J(C,H) 150, C(6)); 45.3 (t, ¹J(C,H) 141, C(3)).

752

Helvetica Chimica Acta Vol. 85 (2002)

(2RS,6RS)-cis-6-Cyclohexyl-3,6-dihydro-1,2-oxathiin 2-Oxide (c-2h) and (2RS,6SR)-trans-6-Cyclohexyl-

3,6-dihydro-1,2-oxathiin 2-Oxide (t-2h). As described for 2g, with (E)/(Z)-1h 10 :1 (40 mg, 0.3 mmol). After

15 h at 808, traces of c/t-2h 1:2 were observed by ¹H-NMR. After 12 h at À508, complete isomerization of c-2h to

t-2h occurred. ¹H-NMR (400 MHz, CD₂Cl₂/CFCl₃/SO₂, 193 K): c-2h, detected signals: 4.24 (br. s, HÀC(6)); 3.46

(dd, ²J 16.6, ³J(3ax,4) 4.2, H_axÀC(3)); 3.14 (dddd, ²J 16.6, ⁵J(3eq,6) 2.3, ³J(3eq,4) 2.3, ⁴J(3eq,5) 2.3,

H_eqÀC(3)); 1.90 0.80 (m, 11 H, Chx); t-2h, detected signals: 5.12 (dm, ³J(4,5) 11.5, HÀC(5)); 4.43 (br. s,

HÀC(6)); 3.39 (dddd, ²J 17.3, ⁵J(3ax,6) 4.4, ³J(3ax,4) 2.6, ⁴J(3ax,5) 2.6, H_axÀC(3)); 3.03 (ddd, ²J 17.3,

³J(3eq,4) 6.3, ⁵J(3eq,6) 2.6, H_eqÀC(3)); 1.90 0.80 (m, 11 H, Chx). ¹³C-NMR (100.6 MHz, CD₂Cl₂/CFCl₃/

SO₂, 223 K): t-2h detected signals: 130.5 (d, ¹J(C,H) 151, C(5)); 119.3 (C(4)); 74.8 (d, ¹J(C,H) 146, C(6));

46.2 (t, ¹J(C,H) 143, C(3)).

(2RS,6RS)-cis-6-Benzyl-3,6-dihydro-1,2-oxathiin 2-Oxide (c-2i) and (2RS,6SR)-trans-6-Benzyl-3,6-dihy-

dro-1,2-oxathiin 2-Oxide (t-2i). As described for 2g, with (E)/(Z)-1i 6 :1 (20 mg, 0.14 mmol). After 6 h at À808,

traces of c-2i were detected by ¹H-NMR. After 12 h at À508, total isomerization of c-2i into t-2i was observed.

¹H-NMR (400 MHz, CD₂Cl₂/CFCl₃/SO₂, 193 K): c-2i: 7.50 7.10 (m, 5 arom. H), 6.05 (dm, ³J(4,5) 11.8,

HÀC(5)); 5.80 (dm, ³J(4,5) 11.8, HÀC(4)); 4.64 (m, HÀC(6)); 3.50 2.80 (m, CH₂(3)); 2.94 (dd, ²J 14.0,

³J 9.6, 1 H, PhCH₂); 2.88 (dd, ²J 14.0, ³J 5.9, 1 H, PhCH₂); t-2i: 7.50 7.10 (m, 5 arom. H); 5.88

(dm, ³J(4,5) 11.8, HÀC(5)); 5.67 (dddd, ³J(4,5) 11.8, ³J(3eq,4) 6.2, ³J(3ax,4) 2.5, ⁴J(4,6) 2.1,

HÀC(4)); 4.82 (m, HÀC(6)); 3.36 (dddd, ²J 17.5, ⁵J(3ax,6) 4.1, ³J(3ax,4) 2.5, ⁴J(3ax,5) 2.5, HaxÀC(3));

3.00 (dddd, ²J 17.5, ³J(3eq,4) 6.2,⁵J(3eq,6) 2.7, ⁴J(3eq,5) 1.1,H_eqÀC(3)); 2.96 (dd, ²J 14.1, ³J 5.3, 1 H,

PhCH₂); 2.86 (dd, ²J 14.1, ³J 7.9, 1 H, PhCH₂). ¹³C-NMR (100.6 MHz, CD₂Cl₂/CFCl₃/SO₂, 193 K): c-2i: 145

110 (6 arom. C); 129.4 (C(5)); 120.6 (C(4)); 78.2 (C(6)); 45.4 (C(3)); 42.5 (CH₂Ph); t-2i: 145 110 (6 arom. C);

129.8 (C(5)); 117.1 (C(4)); 70.5 (C(6)); 45.0 (C(3)); 39.7 (PhCH₂).

(2RS,6SR)-cis-3,6-Dihydro-2-oxido-1,2-oxathiin-6-yl Benzoate (c-2y) and (2RS,6SR)-trans-3,6-Dihydro-2-

oxido-1,2-oxathiin-6-yl Benzoate (t-2y). As described for 2g, with (E)/(Z)-1y 9 :1 (54 mg, 0.31 mmol), CD₂Cl₂

(248 mg), CF₃COOH (25.7 mg, 0.23 mmol), CFCl₃(268 mg), SO₂(218 mg, 3.4 mmol), and MeCN (5.6 mg) as

internal reference. Both sultines c-and t-2y were formed simultaneously at À758 in a 1:10 ratio. Equilibrium

with diene (E)-1y (K((E)-1y SO₂>t-2y) 6.58 ¥ 10^À3lmol^À1and K((E)-1y SO₂>c-2y) 6.4 ¥ 10^À4lmol^À1at

À758) was reached after 10 h at À758. Diene (Z)-1y did not add to SO₂at À758. ¹H-NMR (400 MHz, CD₂Cl₂/

CFCl₃/SO₂, 198 K): c-2y, detected signals: 6.94 (m, HÀC(6')); 6.23 (dm, ³J(4,5) ꢀ 12, HÀC(4)); 6.16

(dm, ³J(4,5) ꢀ 12, HÀC(3), HÀC(5)); 3.87 (dddd, ²J 17.0, ³J(3'a,4') 3.8, ⁴J(3'a,5') 2.0, ⁵J(3'a,6') 1.8,

4

5

H_aÀC(3')); 3.38 (dddd, ²J 17.0, ³J(3',4') 4.5, J(3'b,5') 2.4, J(3'b,6') 1.8, H_bÀC(3')). 2D ¹H,¹H-NOESY

of c-2y: correlation peaks for signals H_aÀC(3')/H_bÀC(3'), H_aÀC(3')/HÀC(4'), H_aÀC(3')/HÀC(5'), H_bÀC(3')/

1

HÀC(4'), HÀC(4')/HÀC(6'), HÀC(5')/HÀC(6')). H-NMR (600 MHz, CD₂Cl₂/CFCl₃/SO₂, 198 K): t-2y: 8.08

(dm, ³J 8.0, 7.9, HÀC(2), HÀC(6)); 7.70 (m, HÀC(4)); 7.56 (m, HÀC(3), HÀC(5)); 6.69 (m, HÀC(6')); 6.30

(m, HÀC(4')); 6.25 (m, HÀC(5')); 3.62 (dm, ²J 17.0, H_aÀC(3')); 3.58 (dm, ²J 17.0, H_bÀC(3')); signals for

HÀC(4') and HÀC(5') were detected by 1D-COSY-DQF and TOCSY measurements with selective irradiation

of the signals of CH₂(3') and HÀC(6'). 2D ¹H,¹H-NOESY of t-2y: correlation peaks for signal pairs H_aÀC(3')/

HÀC(6'). ¹³C-NMR (100.6 MHz, CD₂Cl₂/CFCl₃/SO₂, 198 K): c-2y, detected signals: 124.3 (C(5')); 121.8 (C(4'));

84.1 (C(6')); 45.5 (C(3')); t-2y: 165.5 (s, CO); 134.8 (d, ¹J(C,H) 162, C(4)); 130.4 (d, ¹J(C,H) 162, C(2),

C(6)); 129.1 (d, ¹J(C,H) 162, C(3), C(5)); 128.0 (s, C(1)); 123.3 (d, ¹J(C,H) 170, C(5')); 119.3 (d, ¹J(C,H)

175, C(4')); 84.1 (d, ¹J(C,H) 180, C(6')); 45.5 (t, ¹J(C,H) 139, C(3')).

(2RS,6SR)-cis-3,6-Dihydro-2-oxido-1,2-oxathiin-6-yl Naphthalene-2-carboxylate (c-2z) and (2RS,6RS)-trans-

3,6-Dihydro-2-oxido-1,2-oxathiin-6-yl Naphthalene-2-carboxylate (t-2z). As described for 2y, with (E)/(Z)-1z

8 :1 (49 mg, 0.22 mmol), CD₂Cl₂(248 mg), CF₃COOH (25 mg, 0.22 mmol), CFCl₃(250 mg), and SO₂(0.3 ml,

400 mg, 6.2 mmol). ¹H-NMR (400 MHz, CD₂Cl₂/CFCl₃/SO₂, 198 K): c-2z, detected signals: 6.94 (m, HÀC(6'));

3.88 (dm, ²J 17.0, H_aÀC(3')); 3.37 (dm, ²J 17.0, H_bÀC(3')); t-2z, detected signals: 6.72 (m, HÀC(6')); 6.30

(m, HÀC(4')); 6.25 (m, HÀC(5')); 3.63 (dm, ²J 16.5, H_aÀC(3')); 3.58 (dm, ²J 16.5, H_bÀC(3')). ¹³C-NMR

(100.6 MHz, CD₂Cl₂/CFCl₃/SO₂, 198 K): t-2z, detected signals: 84.2 (d, ¹J(C,H) 180, C(6')); 45.5 (t, ¹J(C,H)

139, C(3')). (Æ)-2-(tert-Butyl)-2,5-dihydrothiophene 1,1-Dioxide (3g). A mixture of 1g (40 mg, 0.36 mmol) and

SO₂(ca. 0.2 ml, 4 6 mmol) was placed in a Pyrex tube and degassed on the vacuum line. After sealing the tube

under vacuum, the mixture was left at 258 for 15 h. After cooling in liq. N₂, the tube was opened and SO₂

evaporated. The residue was purified by FC (silica gel, CH₂Cl₂) affording 36 mg (57%) of 3g. Colorless oil. UV

1

(MeCN): 270 (350), 195 (1800). IR (film): 2965, 1370, 1310, 1255, 1235, 1135, 1120, 770. H-NMR (400 MHz,

CDCl₃): 6.16 (dtd, ³J(3,4) 8.8, ³J(4,5) 2.7, ⁴J(2,4) 2.7, HÀC(4)); 6.13 (dtd, ³J(3,4) 8.8, ³J(2,3) 2.1,

⁴J(3,5) 2.1, 2.0, HÀC(3)); 3.67 (dddd, ²J 16.5, ³J(4,5) 2.7, ⁴J(3,5) 2.1, ⁴J(2,5) 2.1, HÀC(5)); 3.62

(dddd, ²J 16.5, ³J(4,5) 2.7, ⁴J(3,5) 2.0, ⁴J(2,5) 1.1, HÀC(5)); 3.51 (m, HÀC(2)); 1.17 (s, t-Bu). ¹³C-NMR

Helvetica Chimica Acta Vol. 85 (2002)

753

(100.6 MHz, CDCl₃): 128.9 (d, ¹J(C,H) 171, C(3)); 124.0 (d, ¹J(C,H) 174, C(4)); 74.2 (d, ¹J(C,H) 144,

C(2)); 56.3 (t, ¹J(C,H) 136, C(5)); 34.4 (s, Me₃C); 26.92 (q, ¹J(C,H) 131, 3 C, Me₃C). ¹⁷O-NMR (54 MHz,

CDCl₃, 295 K): 167, 158. CI-MS (NH₃): 192 (100, [M 18] ), 175 (3, [M 1] ), 128 (26), 110 (95), 95 (92), 82

(26). Anal. calc. for C₈H₁₄O₂S (174.26): C 55.14, H 8.10; found: C 55.15, H 8.05.

(Æ)-2-Cyclohexyl-2,5-dihydrothiophene 1,1-Dioxide (3h). As described for 3g, with (E)/(Z)-1h 10 :1

(40 mg, 0.29 mmol). FC (CH₂Cl₂): 32 mg (55%) of 3h. Yellowish oil. UV (MeCN): 277 (500), 197 (2200). IR

1

(film): 2925, 1440, 1295, 1250, 1135, 1110, 890, 735, 655, 615, 580, 480, 410. H-NMR (400 MHz, CDCl₃): 6.11

(m, HÀC(4), HÀC(3)); 3.69 (dm, ²J 17.3, HÀC(5)); 3.62 (dm, ²J 17.3, HÀC(5)); 3.46 (dm, ³J 7.2,

HÀC(2)); 2.00 1.13 (m, 11 H, Chx). ¹³C-NMR (100.6 MHz, CDCl₃): 128.7 (d, ¹J(C,H) 169, C(3)); 124.1

(d, ¹J(C,H) 175, C(4)); 70.4 (d, ¹J(C,H) 140, C(2)); 56.3 (t, ¹J(C,H) 144, C(5)); 37.9 (d, ¹J(C,H) 135,

CH(Chx)); 31.9 (t, ¹J(C,H) 125, CH₂(Chx)); 29.7 (t, ¹J(C,H) 117, CH₂(Chx)); 26.4, 26.30, 26.27

(3t, ¹J(C,H) 122, 3 CH₂(chx)). ¹⁷O-NMR (54 MHz, CD₂Cl₂/SO₂, 295 K): 169, 156. CI-MS (NH₃): 218 (100,

[M 18] ), 201 (1, [M 1] ), 154 (13), 136 (83), 121 (35), 107 (53), 94 (45), 81 (49). Anal. calc. for C₁₀H₁₆O₂S

(200.30): C 59.97, H 8.06; found: C 59.95, H 8.11.

(Æ)-2-Benzyl-2,5-dihydrothiophene 1,1-Dioxide (3i). As described for 3g, with (E)/(Z)-1i 6 :1 (20 mg,

0.14 mmol). FC (CH₂Cl₂): 20 mg (69%) of 3i. Yellowish oil. UV (MeCN): 193 (11200), 198 (11400). IR (film):

3065, 3030, 1495, 1455, 1405, 1305, 1245, 1135, 1080, 920, 755. ¹H-NMR (400 MHz, CDCl₃): 7.36 (m, 2 arom. H);

7.27 (m, 3 arom. H); 6.04 (dddd, ³J(3,4) 8.6, ³J(4,5) 2.7, 2.7, ⁴J(2,4) 2.7, HÀC(4)); 5.93 (dddd, ³J(3,4) 8.6,

³J(2,3) 2.3, ⁴J(3,5) 2.3, 2.3, HÀC(3)); 3.94 (m, HÀC(2)); 3.80 (dddd, ²J 16.7, ³J(4,5) 2.7, ⁴J(3,5) 2.3,

⁴J(2,5) 2.3, HÀC(5)); 3.74 (dddd, ²J 16.7, ³J(4,5) 2.7, ⁴J(3,5) 2.3, ⁴J(2,5) 1.3, HÀC(5)); 3.38 (dd, ²J

14.0, ³J 5.7, 1 H, PhCH₂); 2.82 (dd, ²J 14.0, ³J 9.9, 1 H, PhCH₂). ¹³C-NMR (100.6 MHz, CDCl₃): 136.3

(s, arom. C); 129.7 (d, ¹J(C,H) 177, C(3)); 129.0 (d, ¹J(C,H) 153, arom. C); 128.8 (d, ¹J(C,H) 169,

arom. C); 127.1 (d, ¹J(C,H) 169, arom. C); 123.2 (d, ¹J(C,H) 175, C(4)); 65.2 (d, ¹J(C,H) 144, C(2));

55.7 (t, ¹J(C,H) 134, C(5)); 34.5 (t, ¹J(C,H) 132, PhCH₂). CI-MS (NH₃): 226 (100, [M 18] ), 209 (6, [M

1] ), 143 (98), 128 (73), 115 (63), 91 (84). Anal. calc. for C₁₁H₁₂O₂S (208.28): C 63.44, H 5.81; found: C 63.52,

H 5.87.

(Æ)-2-Cyclopropyl-2,5-dihydrothiophene 1,1-Dioxide (3j). As described for 3g, with (E)/(Z)-1j 5 :1 (30 mg,

0.32 mmol). FC (CH₂Cl₂): 50 mg (99%) of 3j. White solid. M.p. 66 678. UV (MeCN): 193 (1100). IR (KBr):

3070, 3010, 2960, 1620, 1470, 1435, 1420, 1355, 1305, 1255, 1130, 1105, 1050, 1020, 675. ¹H-NMR (400 MHz,

CDCl₃): 6.09 (dddd, ³J(3,4) 8.7, ³J(4,5) 2.9, 2.2, ⁴J(2,4) 2.7, HÀC(4)); 6.04 (dddd, ³J(3,4) 8.7, ³J(2,3)

2.2, ⁴J(3,5) 2.2, 2.0, HÀC(3)); 3.72 (dddd, ²J 14.5, ³J(4,5) 2.2, ⁴J(3,5) 2.0, ⁴J(2,5) 1.5, HÀC(5)); 3.67

(dddd, ²J 14.5, ³J(4,5) 2.9, ⁴J(3,5) 2.2, ⁴J(2,5) 2.2, HÀC(5)); 3.19 (dm, ³J 9.0, HÀC(2)); 1.03 (m, 1 H);

0.73 (m, 2 H); 0.51 (m, 1 H); 0.36 (m, 1 H). ¹³C-NMR (100.6 MHz, CDCl₃): 129.5 (d, ¹J(C,H) 178, C(3));

124.1 (d, ¹J(C,H) 175, C(4)); 69.5 (d, ¹J(C,H) 143, C(2)); 55.5 (t, ¹J(C,H) 144, C(5)); 8.9 (d, ¹J(C,H) 169,

CH(cycloprop.)); 3.5 (t, ¹J(C,H) 163, CH₂(cycloprop.)); 2.5 (t, ¹J(C,H) 161, CH₂(cycloprop.)). ¹⁷O-NMR

(54 MHz, CDCl₃, 295 K): 164, 157. CI-MS (NH₃): 94 (32), 79 (100). Anal. calc. for C₇H₁₀O₂S (158.22): C 53.14,

H 6.37; found: C 53.13, H 6.23.

(Æ)-2,5-Dihydro-2-phenylthiophene 1,1-Dioxide (3k). As described for 3g, with (E)-1k (80 mg,

0.62 mmol). FC (CH₂Cl₂): 50 mg (42%) of 3k. Colorless oil. UV (MeCN): 281 (1500), 216 (9800). IR (film):

1

3630, 3030, 1495, 1455, 1405, 1310, 1240, 1135, 1115, 910, 775, 735, 700, 640, 615. H-NMR (400 MHz, CDCl₃):

7.45 (m, 3 arom. H); 7.31 (m, 2 arom. H); 6.31 (dddd, ³J(3,4) 8.5, ³J(4,5) 2.7, 2.7, ⁴J(2,4) 2.7, HÀC(4)); 6.21

(dddd, ³J(3,4) 8.5, ³J(2,3) 2.3, ⁴J(3,5) 2.3, 2.3, HÀC(3)); 4.96 (m, HÀC(2)); 3.87 (dddd, ²J 16.6,

³J(4,5) 2.7, ⁴J(3,5) 2.3, ⁴J(2,5) 2.2, HÀC(5)); 3.81 (dddd, ²J 16.6, ³J(4,5) 2.7, ⁴J(3,5) 2.3, ⁴J(2,5))

2.2, HÀC(5)). ¹³C-NMR (100.6 MHz, CDCl₃): 130.0 (s, arom. C); 129.4 (d, ¹J(C,H) 174, C(3)); 129.2

(d, ¹J(C,H) 161, arom. C); 129.0 (d, ¹J(C,H) 161, arom. C); 128.8 (d, ¹J(C,H) 161, arom. C); 124.8

(d, ¹J(C,H) 175, C(4)); 69.7 (d, ¹J(C,H) 143, C(2)); 54.8 (t, ¹J(C,H) 137, C(5)). ¹⁷O-NMR (54 MHz,

CDCl₃): 162, 158. CI-MS (NH₃): 212 (65, [M 18] ), 130 (100), 115 (56).

(Æ)-2,5-Dihydro-2-(4-methoxyphenyl)thiophene 1,1-Dioxide (3l). As described for 3g, with (E)/(Z)-1l 4 :4

(20 mg, 0.13 mmol). FC (CH₂Cl₂): 16 mg (55%) of 3l. Colorless oil. UV (MeCN): 266 (4400), 230 (7400), 200

(13400). IR (film): 2900, 1610, 1515, 1465, 1315, 1250, 1175, 1035, 835. ¹H-NMR (400 MHz, CDCl₃): 7.24

(m, 2 arom. H); 6.95 (m, 2 arom. H); 6.29 (dddd, ³J(3,4) 8.5, ³J(4,5) 2.7, 2.7, ⁴J(2,4) 2.7, HÀC(4)); 6.19

(dddd, ³J(3,4) 8.5, ³J(2,3) 2.2, 2.2, ⁴J(3,5) 2.2, HÀC(3)); 4.46 (m, HÀC(2)); 3.86 (m, CH₂(5)); 3.82

(s, MeO). ¹³C-NMR (100.6 MHz, CDCl₃): 160.4 (s, arom. C); 130.3 (d, ¹J(C,H) 158, arom. C); 129.9

(d, ¹J(C,H) 174, C(3)); 124.5 (d, ¹J(C,H) 174, C(4)); 121.8 (s, arom. C); 114.4 (d, ¹J(C,H) 160, arom. C);

69.4 (d, ¹J(C,H) 143, C(2)); 55.3 (q, ¹J(C,H) 144, MeO); 54.7 (t, ¹J(C,H) 137, C(5)). CI-MS (NH₃): 224 (3,

.

M

), 199 (14), 161 (85), 135 (34), 121 (100).

754

Helvetica Chimica Acta Vol. 85 (2002)

(Æ)-2,5-Dihydro-2-(trimethylsilyl)thiophene 1,1-Dioxide (3m). As described for 3g, with (E)-1m [17]. Yield

75%. Identical to 3m obtained by silylation of 2,5-dihydrothiophene 1,1-dioxide [26].

(Æ)-2,5-Dihydro-2-(phenoxy)thiophene 1,1-Dioxide (3n). As described for 3g, with (E)-1n (23 mg,

0.31 mmol), CD₂Cl₂(0.15 ml), CFCl₃(100 mg), and SO₂(0.2 ml) in a 5-mm NMR tube, reaction followed by

¹H-NMR, complete reaction after 24 h at À108. Sulfolene 3n was unstable at 208 after SO₂evaporation.

¹H-NMR (400 MHz, CD₂Cl₂/SO₂, 263 K): 7.40 (m, arom. H); 6.80 (m, 4 arom. H); 6.41 (dddd, ³J(3,4) 8.8,

³J(4,5) 3.0, 2.5, ⁴J(2,4) 1.5, HÀC(4)); 6.26 (dddd, ³J(3,4) 8.8, ³J(2,3) 2.5, ⁴J(3,5) 2.5, 2.5, HÀC(3));

5.63 (m, HÀC(2)); 3.87 (dddd, ²J 17.1, ³J(4,5), HÀC(4)) 2.5, ⁴J(3,5) 2.5, ⁴J(2,5) 2.5, HÀC(5)); 3.80

(dddd, ²J 17.1, ³J(4,5) 3.0, ⁴J(3,5) 2.5, ⁴J(2,5) 0.8, HÀC(5)). ¹³C-NMR (100.6 MHz, CD₂Cl₂/SO₂, 263 K):

157.2 (s, arom. C); 130.5 (d, ¹J(C,H) 161, arom. C); 129.6 (d, ¹J(C,H) 177, C(4)); 126.0 (d, ¹J(C,H) 175,

C(3)); 123.7 (d, ¹J(C,H) 161, arom. C); 115.8 (d, ¹J(C,H) 158, arom. C); 89.7 (d, ¹J(C,H) 166, C(2)); 54.8

(t, ¹J(C,H) 138, C(5)).

(Æ)-2-(4-Chlorophenoxy)-2,5-dihydrothiophene 1,1-Dioxide (3o). As described for 3n, with (E)/(Z)-1o

3.2 :1 (23 mg, 0.31 mmol). Sulfolene 3o was unstable at 208. ¹H-NMR (400 MHz, CD₂Cl₂/SO₂, 263 K): 7.38

(m, 2 arom. H); 7.12 (m, 2 arom. H); 6.42 (dddd, ³J(3,4) 8.8, ³J(4,5) 3.0, 2.5, ⁴J(2,4) 1.5, HÀC(4)); 6.22

(dddd, ³J(3,4) 8.8, ³J(2,3) 2.5, ⁴J(3,5) 2.5, 2.5, HÀC(3)); 5.57 (m, HÀC(2)); 3.87 (dddd, ²J 17.2,

³J(4,5) 2.5, ⁴J(3,5) 2.5, ⁴J(2,5) 2.5, HÀC(5)); 3.81 (dddd, ²J 17.2, ³J(4,5) 3.0, ⁴J(3,5) 2.5, ⁴J(2,5)

0.7, HÀC(5)). ¹³C-NMR (100.6 MHz, CD₂Cl₂/SO₂, 263 K): 155.9 (s, arom. C); 130.2 (d, ¹J(C,H) 173,

arom. C); 129.9 (d, ¹J(C,H) 177, C(4)); 129.7 (s, arom. C); 126.1 (d, ¹J(C,H) 183, C(3)); 116.4

(d, ¹J(C,H) 163, arom. C); 90.1 (d, ¹J(C,H) 173, C(2)); 54.9 (t, ¹J(C,H) 138, C(5)). ¹⁷O-NMR (48.9 MHz,

CD₂Cl₂/SO₂, 253 K): 161.

(Æ)-2,5-Dihydro-2-(4-methoxyphenoxy)thiophene 1,1-Dioxide (3p). As described for 3n, with (E)/(Z)-1p

3 :1. Complete reaction after 24 h at À108 (NMR). Sulfolene 3p decomposed at 258. ¹H-NMR (400 MHz,

CD₂Cl₂/SO₂, 263 K): 7.00 (m, 2 arom. H); 6.83 (m, 2 arom. H); 6.38 (dddd, ³J(3,4) 8.8, ³J(4,5) 3.0, 2.5,

3

4

⁴J(2,4) 1.5, HÀC(4)); 6.23 (dddd, ³J(3,4) 8.8, J(2,3) 2.5, J(3,5) 2.5, 2.5, HÀC(3)); 5.53 (m, HÀC(2));

3.86 (dddd, ²J 17.2, ³J(4,5) 2.5, ⁴J(3,5) 2.5, ⁴J(2,5) 2.5, HÀC(5)); 3.79 (dddd, ²J 17.2, ³J(4,5) 3.0,

⁴J(3,5) 2.5, ⁴J(2,5) 0.7, HÀC(5)); 3.73 (s, MeO). ¹³C-NMR (100.6 MHz, CD₂Cl₂/SO₂, 263 K): 156.9, 153.0

(2s, arom. C); 129.5 (d, ¹J(C,H) 176, C(4)); 126.5 (d, ¹J(C,H) 177, C(3)); 117.4 (d, ¹J(C,H) 162, arom. C);

115.2 (d, ¹J(C,H) 157, arom. C); 91.0 (d, ¹J(C,H) 164, C(2)); 55.2 (q, ¹J(C,H) 145, MeO); 54.8

(t, ¹J(C,H) 145, C(5)). ¹⁷O-NMR (48.9 MHz, CD₂Cl₂/SO₂, 253 K): 158, 76, 43.

(Æ)-2,5-Dihydro-2-(4-nitrophenoxy)thiophene 1,1-Dioxide (3q). As described for 3n, with (E)/(Z)-1q 3 :1

(17 mg, 0.09 mmol). Complete conversion into 3q at 108 after 24 h. Sulfolene 3q was unstable at 208. ¹H-NMR

(400 MHz, CD₂Cl₂/SO₂, 273 K): 8.25 (m, 2 arom. H); 7.13 (m, 2 arom. H); 6.51 (dddd, ³J(3,4) 8.8, ³J(4,5)

3.0, 2.5, ⁴J(2,4) 1.5, HÀC(4)); 6.28 (dddd, ³J(3,4) 8.8, ³J(2,3) 2.5, ⁴J(3,5) 2.5, 2.5, HÀC(3)); 5.77

(m, HÀC(2)); 3.96 (dddd, ²J 17.4, ³J(4,5) 2.5, ⁴J(3,5) 2.5, ⁴J(2,5) 2.5, HÀC(5)); 3.90 (dddd, ²J 17.4,

³J(4,5) 3.0, ⁴J(3,5) 2.5, ⁴J(2,5) 0.9, HÀC(5)). ¹³C-NMR (100.6 MHz, CD₂Cl₂/SO₂, 273 K): detected

signals: 130.6 (d, ¹J(C,H) 177, C(4)); 125.9 (d, ¹J(C,H) 178, C(3)); 89.4 (d, ¹J(C,H) 164, C(2)); 55.3

(t, ¹J(C,H) 145, C(5)).

(Æ)-2,5-Dihydro-2-(naphthalen-2-yloxy)thiophene 1,1-Dioxide (3r). As described for 3n, with (E)-1r

(12 mg, 0.04 mmol). Sulfolene 3r was unstable at 258. ¹H-NMR (400 MHz, CD₂Cl₂/SO₂, 263 K): 7.85 7.23

(m, 7 arom. H); 6.44 (dddd, ³J(3,4) 8.8, ³J(4,5) 3.0, 2.5, ⁴J(2,4) 1.5, HÀC(4)); 6.29 (dddd, ³J(3,4) 8.8,

³J(2,3) 2.5, ⁴J(3,5) 2.5, 2.5, HÀC(3)); 5.77 (m, HÀC(2)); 3.91 (dddd, ²J 17.1, ³J(4,5) 2.5, ⁴J(3,5) 2.5,

⁴J(2,5) 2.5, HÀC(5)); 3.85 (dddd, ²J 17.1, ³J(4,5) 3.0, ⁴J(3,5) 2.5, ⁴J(2,5) 0.8, HÀC(5)). ¹³C-NMR

(100.6 MHz, CD₂Cl₂/SO₂, 263 K): 155.4, 134.5 (2s, arom. C); 130.8 (d, ¹J(C,H) 162, arom. C); 129.9

(d, ¹J(C,H) 170, C(4)); 128.5, 127.9, 127.8 (3 arom. C); 126.4 (d, ¹J(C,H) 151, C(3)); 125.8 (d, ¹J(C,H)

161, arom. C); 125.6 (s, arom. C); 119.0 (d, ¹J(C,H) 163, arom. C); 109.6 (d, ¹J(C,H) 159, arom. C); 90.0

(d, ¹J(C,H) 165, C(2)); 55.0 (t, ¹J(C,H) 146, C(5)).

(Æ)-2,5-Dihydro-2-(methylthio)thiophene 1,1-Dioxide (3s). As described for 3g, with (E)-1s (124 mg,

1.2 mmol). FC (CH₂Cl₂): 94 mg (48%) of 3s. Pale yellow oil that decomposed on staying at 208. UV (MeCN):

202 (2400). IR (film): 2920, 1715, 1680, 1435, 1305, 1245, 1175, 1135, 970. ¹H-NMR (400 MHz, CDCl₃): 6.25

(dddd, ³J(3,4) 8.6, ³J(4,5) 3.2, 2.5, ⁴J(2,4) 2.0, HÀC(4)); 6.11 (dddd, ³J(3,4) 8.6, ³J(2,3) 3.0, ⁴J(3,5)

2.3, 2.3, HÀC(3)); 4.61 (dddd, ³J(2,3) 3.0, ⁴J(2,5) 2.0, 1.0, HÀC(2)); 3.83 (dddd, ²J 17.0, ³J(4,5) 3.2,

⁴J(3,5) 2.3, ⁴J(2,5) 1.0, HÀC(5)); 3.77 (dddd, ²J 17.0, ³J(4,5) 2.5, ⁴J(3,5) 2.3, ⁴J(2,5) 2.0, HÀC(5));

2.20 (s, MeS). ¹³C-NMR (100.6 MHz, CDCl₃): 127.7 (d, ¹J(C,H) 177, C(4)); 125.4 (d, ¹J(C,H) 169, C(3));

68.0 (d, ¹J(C,H) 155, C(2)); 53.4 (t, ¹J(C,H) 144, C(5)); 13.7 (q, ¹J(C,H) 136, MeS). ¹⁷O-NMR (54 MHz,

.

CDCl₃, 295 K): 162, 160. CI-MS (NH₃): 163 (3, M ), 147 (19), 133 (17), 96 (9), 83 (3).

Helvetica Chimica Acta Vol. 85 (2002)

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(Æ)-2,5-Dihydro-2-(phenylthio)thiophene 1,1-Dioxide (3t). As described for 3g, with (E)/(Z)-1t 2 :1 [39]

(1.0 g, 6.2 mmol) and SO₂(10 g, 0.16 mol), without solvent. FC (CH₂Cl₂): 550 mg (39%) of 3t. White solid. M.p.

55 568 (pentane). UV (MeCN): 204 (17600), 199 (20200). IR (KBr): 3070, 2935, 1575, 1480, 1400, 1320, 1250,

1185, 1145, 1110, 1095, 815, 740, 685. ¹H-NMR (400 MHz, CDCl₃): 7.60 (m, 2 arom. H); 7.30 (m, arom. H); 7.16

(m, 2 arom. H); 6.10 (dddd, ³J(3,4) 8.6, ³J(4,5) 3.2, 2.5, ⁴J(2,4) 1.9, HÀC(4)); 6.00 (dddd, ³J(3,4) 8.6,

³J(3,5) 2.5, ³J(2,3) 2.2, ⁴J(3,5) 1.8, HÀC(3)); 4.80 (m, HÀC(2)); 3.70 (dddd, ²J 17.0, ³J(4,5) 3.2,

⁴J(3,5) 1.8, ⁴J(2,5) 1.0, HÀC(5)); 3.50 (dddd, ²J 17.0, ³J(4,5) 2.5, ⁴J(3,5) 2.5, ⁴J(2,5) 2.2, HÀC(5)).

¹³C-NMR (100.6 MHz, CDCl₃): 133.7 (d, ¹J(C,H) 161, arom. C); 130.5 (s, arom. C); 129.1 (d, ¹J(C,H) 161,

arom. C); 128.8 (d, ¹J(C,H) 161, arom. C); 127.4 (d, ¹J(C,H) 177, C(4)); 125.4 (d, ¹J(C,H) 175, C(3)); 70.4

(d, ¹J(C,H) 157, C(2)); 54.1 (t, ¹J(C,H) 144, C(5)). ¹⁷O-NMR (48.9 MHz, CDCl₃, 295 K): 160. CI-MS (NH₃):

.

226 (6, M ), 162 (53), 129 (92), 104 (14), 85 (100). Anal. calc. for C₁₀H₁₀O₂S₂(226.31): C 53.07, H 4.45, S 28.33;

found: C 53.15, H 4.55, S 28.15.

(Æ)-2-[(4-Chlorophenyl)thio]-2,5-dihydrothiophene 1,1-Dioxide (3u). As described for 3g, with (E)/(Z)-1u

2 :1 (1.2 g, 6.1 mmol) and SO₂(9.9 g, 0.15 mol), without solvent. FC (CH₂Cl₂): 1.2 g (60%) of 3u. White solid.

M.p. 86 878 (pentane). UV (MeCN): 263 (4300), 260 (4300), 223 (9500), 201 (18300). IR (KBr): 1475, 1310,

1240, 1140, 1120, 740, 650, 625, 580, 475. ¹H-NMR (400 MHz, CDCl₃): 7.51 (m, 2 arom. H); 7.24 (m, 2 arom. H);

6.13 (dddd, ³J(3,4) 8.6, ³J(4,5) 3.0, 2.3, ⁴J(2,4) 1.9, HÀC(4)); 6.08 (dddd, ³J(3,4) 8.6, ³J(2,3) 2.5,

⁴J(3,5) 1.8, 1.5, HÀC(3)); 4.80 (m, HÀC(2)); 3.70 (dddd, ²J 16.9, ³J(4,5) 3.0, ⁴J(3,5) 1.8, ⁴J(2,5) 1.0,

HÀC(5)); 3.60 (dddd, ²J 16.9, ³J(4,5) 2.3, ⁴J(3,5) 2.5, ⁴J(2,5) 2.3, HÀC(5)). ¹³C-NMR (100.6 MHz,

CDCl₃): detected signals: 135.6 (d, ¹J(C,H) 165, arom. C); 129.4 (d, ¹J(C,H) 166, arom. C); 128.8

(s, arom. C); 127.4 (d, ¹J(C,H) 175, C(4)); 125.7 (d, ¹J(C,H) 165, C(3)); 70.1 (d, ¹J(C,H) 157, C(2)); 54.2

(t, ¹J(C,H) 137, C(5)). ¹⁷O-NMR (48.9 MHz, CD₂Cl₂, 295 K): 161. CI-MS (NH₃): 196 (33), 144 (31), 108 (36),

85 (100). Anal. calc. for C₁₀H₉ClO₂S₂(260.75): C 46.06, H 3.48, Cl 13.60, S 24.59; found: C 46.11, H 3.47, Cl 13.67,

S 24.68.

(Æ)-2,5-Dihydro-2-[(4-methoxyphenyl)thio]thiophene 1,1-Dioxide (3v). As described for 3g, with (E)/(Z)-

1v 2.3 :1 (2.0 g, 10 mmol) and SO₂(20 g, 0.31 mol), without solvent. FC (CH₂Cl₂): 1.0 g (39%) of 3v. Pale yellow

oil, unstable at 258. UV (MeCN): 263 (11200), 257 (11400), 232 (16000), 202 (23300). IR (film): 2835, 1590,

1570, 1495, 1465, 1440, 1315, 1290, 1250, 1175, 1135, 1105, 1030, 830, 790, 735, 640. ¹H-NMR (400 MHz, CDCl₃):

7.60 (m, 2 arom. H); 6.86 (m, 2 arom. H); 6.09 (dddd, ³J(3,4) 8.5, ³J(4,5) 3.2, 2.5, ⁴J(2,4) 2.4, HÀC(4));

6.02 (dddd, ³J(3,4) 8.5, ³J(2,3) 3.4, ⁴J(3,5) 2.4, 1.8, HÀC(3)); 4.71 (m, HÀC(2)); 3.81 (s, MeO); 3.64

(dddd, ²J 16.9, ³J(4,5) 3.2, ⁴J(3,5) 1.8, ⁴J(2,5) 0.7, HÀC(5)); 3.44 (dddd, ²J 16.9, ³J(4,5) 2.4, ⁴J(3,5)

2.4, ⁴J(2,5) 2.4, HÀC(5)). ¹³C-NMR (100.6 MHz, CDCl₃): 137.4 (d, ¹J(C,H) 164, arom. C); 133.5 (s, ar-

om. C); 127.8 (d, ¹J(C,H) 177, C(4)); 125.2 (d, ¹J(C,H) 175, C(3)); 119.9 (s, arom. C); 114.7 (d, ¹J(C,H)

161, arom. C); 71.0 (d, ¹J(C,H) 156, C(2)); 55.3 (q, ¹J(C,H) 144, MeO); 54.0 (t, ¹J(C,H) 145, C(5)). ¹⁷O-

NMR (48.9 MHz, CDCl₃, 295 K): 162, 53. CI-MS (NH₃): 274 (8, [M 18] ), 144 (31), 209 (14), 193 (94), 159

(17), 139 (100), 124 (13), 96 (17), 85 (10).

(Æ)-2,5-Dihydro-2-[(4-nitrophenyl)thio]thiophene 1,1-Dioxide (3w). As described for 3g, with (E)/(Z)-1w

3.5 :1 (0.8 g, 3.9 mmol) and SO₂(5 g, 0.08 mol), without solvent, left at 258 for 7 days. FC (CH₂Cl₂): 240 mg

(23%) of 3w. Yellow solid. M.p. 109 1108. UV (MeCN): 321 (9100), 260 (4200), 217 (7100), 197 (16400). IR

(KBr): 1505, 1340, 1335, 1300, 1140, 855, 840, 740, 640, 595. ¹H-NMR (400 MHz, CDCl₃): 8.21 (m, 2 arom. H);

7.65 (m, 2arom. H); 6.30 (dddd, ³J(3,4) 8.6, ³J(4,5) 3.2, 2.7, ⁴J(2,4) 2.0, HÀC(4)); 6.10 (dddd, ³J(3,4) 8.6,

³J(2,3) 2.8,⁴J(3,5) 2.3, 2.0, HÀC(3)); 5.08 (m, HÀC(2)); 3.87 (dddd, ²J 17.0, ³J(4,5) 3.2, ⁴J(3,5) 2.0,

⁴J(2,5) 1.0, HÀC(5)); 3.85 (dddd, ²J 17.0, ³J(4,5) 2.7, ⁴J(3,5) 2.3, ⁴J(2,5) 2.3, HÀC(5)). ¹³C-NMR

(100.6 MHz, CDCl₃): 146.9 (s, arom. C); 141.2 (s, arom. C); 130.7 (d, ¹J(C,H) 167, arom. C); 126.8

(d, ¹J(C,H) 170, C(4)); 126.3 (d, ¹J(C,H) 172, C(3)); 124.2 (d, ¹J(C,H) 170, arom. C); 68.9 (d, ¹J(C,H)

158, C(2)); 54.5 (t, ¹J(C,H) 145, C(5)). ¹⁷O-NMR (48.9 MHz, CDCl₃, 295 K): 570, 161. CI-MS (NH₃): 271 (1,

.

M

), 207 (29), 128 (11), 115 (6), 85 (100). Anal. calc. for C₁₀H₉NO₄S₂(271.31): C 44.27, H 3.34, N 5.16, S 23.63;

found: C 44.31, H 3.35, N 5.11, S 23.64.

(Æ)-2,5-Dihydro-2-(phenylseleno)thiophene 1,1-Dioxide (3x) and (Æ)-2,5-Dihydro-3-(phenylseleno)thio-

phene 1,1-Dioxide. As described for 3g, with (E)-1x/(Z)-1x/12 1:0.8 :0.5 (270 mg, 1.29 mmol) and SO₂(1.4 g,

22 mmol). FC (CH₂Cl₂) gave 40 mg (19%) of 3x and 25 mg (19%) of 2,5-dihydro-3-(phenylseleno)thiophene

1,1-dioxide.

Data of 3x: Yellow oil that decomposed at 258. UV (MeCN): 224 (26900), 208 (17300). IR (film): 3060,

1580, 1480, 1320, 1245, 1140, 1100, 740, 690, 645. ¹H-NMR (400 MHz, CDCl₃): 7.73 (m, 2 arom. H); 7.35

(m, 3 arom. H); 6.16 (dddd, ³J(3,4) 8.5, ³J(2,3) 2.7, ⁴J(3,5) 2.5, 1.8, HÀC(3)); 5.95 (dddd, ³J(3,4) 8.5,

³J(4,5) 3.4, 2.5, ⁴J(2,4) 1.9, HÀC(4)); 4.92 (m, HÀC(2)); 3.65 (dddd, ²J 16.8, ³J(4,5) 3.4,⁴J(3,5) 2.5,

756

Helvetica Chimica Acta Vol. 85 (2002)

⁴J(2,5) 2.5, HÀC(5)); 3.40 (dddd, ²J 16.8, ³J(4,5) 2.5, ³J(3,5) 2.5, ⁴J(2,5) 2.5, HÀC(5)). ¹³C-NMR

(100.6 MHz, CDCl₃): 136.5 (t, ¹J(C,H) 165, arom. C); 129.3 (d, ¹J(C,H) 161, arom. C); 129.2 (d, ¹J(C,H)

161, arom. C); 128.8 (d, ¹J(C,H) 178, C(4)); 124.2 (d, ¹J(C,H) 164, C(3)); 63.0 (d, ¹J(C,H) 158, C(2)); 53.7

(t, ¹J(C,H) 144, C(5)). ¹⁷O-NMR (54 MHz, CDCl₃): 163, 157.

Data of 2,5-Dihydro-3-(phenylseleno)thiophene 1,1-Dioxide: Yellow solid. M.p. 49 508. UV (MeCN): 251

(7100), 198 (14300). IR (film): 1580, 1450, 1435, 1315, 1300, 1125, 1020, 905, 735, 590. ¹H-NMR (400 MHz,

CDCl₃): 7.39 (m, 2 arom. H); 7.30 (m, 3 arom. H); 6.00 (dddd, ³J(4,5) 2.0, 2.0, ⁴J(2,4) 2.0, 2.0, HÀC(4)); 3.86

(m, CH₂); 3.74 (m, CH₂). ¹³C-NMR (100.6 MHz, CDCl₃): 134.9 (d, ¹J(C,H) 160, arom. C); 129.8

(d, ¹J(C,H) 163, arom. C); 129.1 (d, ¹J(C,H) 162, arom. C); 127.1 (s); 125.5 (s); 123.4 (d, ¹J(C,H) 176,

C(4)); 59.1 (t, ¹J(C,H) 139, CH₂); 58.3 (t, ¹J(C,H) 151, CH₂). ¹⁷O-NMR (54 MHz, CDCl₃): 168. CI-MS

(NH₃): 292 (18, [M 1 18] ), 274 (45, [M 1] ), 210 (57), 158 (35), 129 (100). Anal. calc. for C₁₀H₁₀O₂SSe

(273.21): C 43.96; H 3.69; found: C 44.11, H 3.74.

(Æ)-2,5-Dihydro-1,1-dioxidothiophen-2-yl Benzoate (3y). A mixture of (E)/(Z)-1y 10 :1 (597 mg,

3.43 mmol) and pure SO₂(3.52 g, 54.9 mmol) was placed in a sealed Pyrex tube and left at 258 for 7 days.

After freezing the tube in liq. N₂and opening, SO₂was evaporated. The residue was purified by FC (AcOEt/

light petroleum ether 1:1, then gradually up to 4 :1): 446 mg (55%) of 3y, soluble in CHCl₃only.

Recrystallization from CHCl₃/pentane gave colorless needles submitted to X-ray analysis. M.p. 112 1158

(dec.). UV (MeCN): 271 (2600), 236 (9800). IR (KBr): 3090, 3070, 3000, 2940, 1730, 1600, 1455, 1405, 1315,

1255, 1185, 1130, 1085, 1070, 755, 710. ¹H-NMR (400 MHz, CDCl₃): 8.11 (dm, ³J 8.0, HÀC(2), HÀC(6)); 7.63

(tm, ³J 8.0, HÀC(4)); 7.48 (tm, ³J 8.0, HÀC(3), HÀC(5)); 6.46 (dddd, ³J 8.6, ³J(4',5b)) 3.0, ³J(4',5a)

4

3

4

2.7, J(2,4') 0.9, HÀC(4')); 6.29 (dddd, ³J(3',4') 8.6, J(2',3') 2.7, J(3',5'a) 2.7, ⁴J(3',5'b) 2.1, HÀC(3'));

6.24 (dddd, ³J(2',3') 2.7, ⁵J(2',5'a) 1.8, ⁴J(2',4') 0.9, ⁵J(2',5'b) 0.9, HÀC(2')); 3.89 (dddd, ²J(5'a,5'b) 18.0,

³J(4',5'a) 2.7, ⁴J(3',5'a) 2.7, ⁵J(2',5'a) 1.8, H_aÀC(5')); 3.84 (dddd, ²J(5'a,5'b) 18.0, ³J(4',5'b) 3.0,

⁴J(3',5'b) 2.1, ⁵J(2',5'b) 0.9, H_bÀC(5')). ¹³C-NMR (100.6 MHz, CDCl₃): 165.0 (s, CO); 134.0

(d, ¹J(C,H) 162, C(4)); 130.2 (d, ¹J(C,H) 170, C(4')); 130.2 (d, ¹J(C,H) 162, C(2), C(6)); 128.6

(d, ¹J(C,H) 162, C(3), C(5)); 128.1 (s, C(1)); 125.5 (d, ¹J(C,H) 177, C(3')); 83.9 (d, ¹J(C,H) 168, C(2'));

54.4 (t, ¹J(C,H) 145, C(5')). ¹⁷O-NMR (81.3 MHz, MeCN/CDCl₃/CHCl₃, 258): 341 (CO); 161.5 (OÀC(2));

.

153.5 (O(a)S); 152.1 (O(b)S). CI-MS (NH₃): 238 (0.1, M ), 174 (1.1, [M À SO₂] ), 166 (3), 164 (2), 122

(2), 106 (13), 105 (100), 78 (5), 77 (24). Anal. calc. for C₁₁H₁₀O₄S (238.26): C 55.45, H 4.23, S 13.46; found:

C 55.39, H 4.20, S 13.38.

(Æ)-2,5-Dihydro-1,1-dioxidothiophen-2-yl Naphthalene-2-carboxylate (3z). As described for 3y, with (E)/

(Z)-1z 8 :1 (2.0 g, 8.9 mmol) and pure SO₂(5 ml), at 08 for 4 days. FC (CH₂Cl₂/light petroleum ether 1:1, then

pure CH₂Cl₂): 770 mg of (E)/(Z)-1z and 563 mg (22%) of 3z as colorless needles. M.p. 128 1308 (dec.). UV

(MeCN): 337 (8600), 325 (8600), 290 (23000), 281 (31000), 274 (26000), 240 (118000), 211 (63000). IR (KBr):

3070, 2985, 1725, 1305, 1195, 1145, 1080, 780, 675, 585, 470, 410. ¹H-NMR (400 MHz, CDCl₃): 8.69 (br. s,

HÀC(1)); 8.10 (dd, ³J(3,4) 8.6, ⁴J(1,3) 1.7, HÀC(3)); 7.98 (ddm, ³J(7,8) 8.1, ⁴J(6,8) 1.4, HÀC(8)); 7.92

(d, ³J(3,4) 8.6, HÀC(4)); 7.90 (ddm, ³J(5,6) 8.1, ⁴J(5,7) 1.3, HÀC(5)); 7.64 (ddd, ³J(5,6) 8.1, ³J(6,7) 6.9,

⁴J(6,8) 1.4, HÀC(6)); 7.57 (ddd, ³J(7,8) 8.1, ³J(6,7) 6.9, ⁴J(5,7) 1.3, HÀC(7)); 6.49 (ddm, ³J(3',4') 8.6,

⁴J(2',4') 1.0, HÀC(4')); 6.34 (ddm, ³J(3',4') 8.6, ³J(2',3') 3.0, HÀC(3')); 6.32 (ddm, ³J(2',3') 3.0, ⁴J(2',4')

1.0, HÀC(2')); 3.93 (dm, ²J(5'a,5'b) 17.0, H_aÀC(5')); 3.86 (dm, ²J(5'a,5'b) 17.0, H_bÀC(5)). ¹³C-NMR

(100.6 MHz, CDCl₃): 165.6 (s, CO); 136.0 (s, C(4a)); 132.3 (s, C(8a)); 132.2 (d, ¹J(C,H) 162, C(1)); 130.3

(d, ¹J(C,H) 173, C(4')); 129.5 (d, ¹J(C,H) 161, C(8)); 128.9 (d, ¹J(C,H) 162, C(4)); 128.5 (d, ¹J(C,H) 162,

C(6)); 127.8 (d, ¹J(C,H) 162, C(5)); 126.9 (d, ¹J(C,H) 162, C(7)); 125.6 (d, ¹J(C,H) 177, C(3')); 125.2

(d, ¹J(C,H) 172, C(3)); 125.1 (s, C(2)); 84.0 (d, ¹J(C,H) 168, C(2')); 54.5 (t, ¹J(C,H) 144, C(5')). CI-MS

.

(NH₃): 306 (15,[M NH₄] ), 289 (3, [M H] ), 288 (0.2, M ), 242 (5, [M NH₄À SO₂] ), 225 (34, [M H À

SO₂] ), 172 (9), 156 (37), 155 (100), 127 (38), 98 (18).

(1RS,3RSi)-cis-1,4,5,6,7,8-Hexahydro-1-methyl-2,3-benzoxathiin 3-Oxide (c-15) and (1RS,3SR)-trans-

1,4,5,6,7,8-Hexahydro-1-methyl-2,3-benzoxathiin 3-Oxide (t-15). As described for 2g, with (E)/(Z)-4a 2 :1,

without CF₃COOH. After 5 min at À758, the equilibrium (E)-4a SO₂>cis-sultine c-15 was reached. After

14 h at À758, c/t-15 5 :95 was obtained.

1

Data of c-15: H-NMR (400 MHz, CD₂Cl₂/CFCl₃/SO₂, À858): 4.51 (qm, ³J 7.0, HÀC(1)); 3.32 (dm, ²J

15.7, H_aÀC(4)); 2.99 (dm, ²J 15.7, H_bÀC(4)); 2.08 1.99 (m, H_aÀC(8)); 2.04 1.93 (m, CH₂(5)); 1.82 1.75

(m, H_bÀC(8)); 1.80 1.75 (m, H_aÀC(7) or H_aÀC(6)); 1.76 (m, H_aÀC(6) or H_aÀC(7)); 1.57 1.44 (m, H_bÀC(6)

or H_bÀC(7)); 1.55 1.45 (m, H_bÀC(7) or H_bÀC(6)); 1.43 (d, ³J 7.0, Me). ¹³C-NMR (100.6 MHz, CD₂Cl₂/

CFCl₃/SO₂, À858): 130.6 (s, C(8a)); 117.3 (s, C(4a)); 76.1 (d, ¹J(C,H) 150, C(1)); 51.7 (t, ¹J(C,H) 139, C(4));

Helvetica Chimica Acta Vol. 85 (2002)

757

30.3 (t, ¹J(C,H) 127, C(5)); 25.9 (t, ¹J(C,H) 127, C(8)); 22.1 (t, ¹J(C,H) 127, C(6) or C(7)); 21.9

(t, ¹J(C,H) 127, C(7) or C(6)); 20.7 (q, ¹J(C,H) 130, Me).

1

Data of t-15: H-NMR (400 MHz, CD₂Cl₂/CFCl₃/SO₂, À658): 4.46 (qm, ³J 6.8, HÀC(1)); 3.39 (dm, ²J

16.7, H_aÀC(4)); 2.74 (dm, ²J 16.7, H_bÀC(4)); 1.94 1.90 (m, H_aÀC(8)); 1.91 1.80 (m, CH₂(5)); 1.72 (m,

H_aÀC(6), H_aÀC(7)); 1.72 1.67 (m, H_bÀC(8)); 1.41 (m, H_bÀC(6), H_bÀC(7)); 1.38 (d, ³J 6.8, Me);

1.53 1.43 (m, H_bÀC(6), H_bÀC(7)). ¹³C-NMR (100.6 MHz, CD₂Cl₂/CFCl₃/SO₂, À658): 129.8 (s, C(8a));

117.4 (s, C(4a)); 68.8 (d, ¹J(C,H) 149, C(1)); 49.9 (t, ¹J(C,H) 138, C(4)); 30.0 (t, ¹J(C,H) 127, C(5));

25.4 (t, ¹J(C,H) 127, C(8)); 22.1, 22.0 (2t, ¹J(C,H) 127, C(6), C(7)); 18.3 (q, ¹J(C,H) 129, Me):

¹⁷O-NMR (54.2 MHz, CD₂Cl₂/CFCl₃/SO₂, À658): 141 (br. s, w_1/2 800, OS(3)); 88 (br. s, w_1/2 1200,

O(2)).

(Æ)-1,3,4,5,6,7-Hexahydro-1-methylbenzo[c]thiophene 2,2-Dioxide (16a). As described for 3g, with (E)/

(Z)-4a 2 :1 (200 mg, 1.03 mmol), SO₂(2 ml), no solvent (258, 14 h). FC (CH₂Cl₂): 300 mg (98%) of 16a.

Colorless oil. UV (MeCN): 202 (4000). IR (KBr): 2935, 2860, 2840, 1450, 1410, 1380, 1305, 1240, 1145, 1105, 785.

¹H-NMR (400 MHz, CDCl₃): 3.64 (dm, ²J 17.7, H_aÀC(3)); 3.60 (dm, ²J 17.7, H_bÀC(3)); 3.59 (qm, ³J 7.2,

HÀC(1)); 2.08 1.90 (m, CH₂(7)); 2.02 (m, CH₂(4)); 1.73 1.62 (m, CH₂(5), CH₂(6)); 1.35 (d, ³J 7.2, Me).

¹³C-NMR (100.6 MHz, CDCl₃): 133.0 (s, C(7a)); 126.3 (s, C(3a)); 62.8 (d, ¹J(C,H) 141, C(1)); 57.8

(t, ¹J(C,H) 142, C(3)); 25.6 (t, ¹J(C,H) 127, C(7)); 23.8 (t, ¹J(C,H) 127, C(4)); 21.7 (2t, ¹J(C,H) 129,

C(5), C(6)); 12.0 (q, ¹J(C,H) 130, Me). ¹⁷O-NMR (54.2 MHz, CDCl₃, 298 K): 155.8 (br. s, w_1/2 300,

O(a)S); 149.4 (br. s, w_1/2 300, O(b)S). CI-MS (NH₃): 205 (28, [M H NH₄] ), 204 (100, [M NH₄] ),

122 (15, [M À SO₂] ), 107 (4), 93 (5), 76 (3).

(Æ)-1,3,4,5,6,7-Hexahydro-1-methoxybenzo[c]thiophene 2,2-Dioxide (16f). As described for 2g, with (E)/

(Z)-4f 1.5 :1 (36 mg, 2.6 mmol), without CF₃COOH. By ¹H-NMR the cheletropic addition was complete after

15 h at À808. Sulfolene 16f was decomposed as a result of attempts to eliminate the excess SO₂or raising the

temp. above À108. ¹H-NMR (400 MHz, CD₂Cl₂/SO₂, 203 K): 4.55 (br. s, HÀC(2)); 3.68 (dm, ²J 16.6,

HÀC(4)); 3.57 (s, MeO); 3.52 (dm, ²J 16.6, HÀC(4)); 2.05 (m, CH₂(6), CH₂(9)); 1.68 (m, CH₂(7),

CH₂(8)). ¹³C-NMR (100.6 MHz, CD₂Cl₂/SO₂, 203 K): 133.9 (s, C(1)); 129.6 (s, C(5)); 96.8 (d, ¹J(C,H) 162,

C(2)); 59.1 (q, ¹J(C,H) 140, MeO); 59.5 (t, ¹J(C,H) 144, C(4)); 25.8 (t, ¹J(C,H) 128); 23.7

(t, ¹J(C,H) 128); 21.4 (t, ¹J(C,H) 144); 21.2 (t, ¹J(C,H) 144). ¹⁷O-NMR (54 MHz, CD₂Cl₂/SO₂, 263 K):

159, 156.

(Æ)-2-(4-Chlorophenoxy)-2,3,4,5-tetrahydrothiophene 1,1-Dioxide (17). A mixture of (E)/(Z)-1o 3.2 :1

(0.2 g, 0.9 mmol), CD₂Cl₂(0.3 ml), and SO₂(0.3 ml) was kept at À158 for 12 h. After cooling to À308, the

solvent was evaporated and dry MeOH (4 ml) added slowly. After the addition of 10% Pd/C (30 mg), the

mixture was degassed at À308 and pressurized with H₂(1 atm). After shaking at À308 for 1 h, the precipitate

(catalyst) was filtered off and the filtrate evaporated. The residue was triturated with dry pentane at 208 for 3 h:

30 mg (14%) of 17. White solid. M.p. 77 788. IR (KBr): 2950, 1585, 1490, 1310, 1230, 1140, 1100, 1000, 720, 660.

¹H-NMR (400 MHz, CDCl₃): 7.28 (m, 2 arom. H); 7.00 (m, 2 arom. H); 5.08 (dd, ³J(2,3) 6.3, 4.2, HÀC(2));

3.12 (m, CH₂(5)); 2.59 (m, 1 H, HÀC(3)); 2.37 (m, 2 H, HÀC(4), HÀC(3)); 2.21 (m, 1 H, HÀC(4)). ¹³C-NMR

(100.6 MHz, CDCl₃): 155.5 (s, arom. C); 129.6 (d, ¹J(C,H) 166, arom. C); 128.0 (s, arom. C); 117.0

(d, ¹J(C,H) 162, arom. C); 88.9 (d, ¹J(C,H) 164, C(2)); 50.0 (t, ¹J(C,H) 142, C(5)); 29.8 (t, ¹J(C,H) 136,

.

C(3)); 18.6 (t, ¹J(C,H) 139, C(4)). CI-MS (NH₃): 248 (6, [M 2] ), 246 (15, M ), 182 (13), 154 (63), 128

(100), 119 (56), 99 (13), 91 (48). Anal. calc. for C₁₀H₁₁ClO₃S (246.71): C 48.68, H 4.49, Cl 14.27, S 13.00; found:

C 48.6, H 4.40, Cl 14.27, S 12.89.

X-Ray Crystal-Structure Determinations⁴). For (Æ)-2-[(4-chlorophenyl)thio]-2,5-dihydrothiophene 1,1-

dioxide (3u), see Table 6; for (Æ)-2,5-dihydro-1,1-dioxidothiophen-2-yl benzoate (3y), see Table 7; for 2-(4-

chlorophenoxy)-2,3,4,5-tetrahydrothiophene 1,1-dioxide (17), see Table 8.

758

Helvetica Chimica Acta Vol. 85 (2002)

Table 6. Crystal Data and Structure Refinement of (Æ)-3u

Empirical formula

M_r

C₁₀H₉ClO₂S₂Morphology Pinacoids

{010}, {001}

(^À, 1 01)

260.74

Pedions

Temperature [K]

Wavelength [ä]

Crystal system

Space group

Unit-cell dimensions a [ä] 6.9453(12)

b [ä] 7.1057(13)

c [ä] 11.463(2)

203 (2)

0.71073

triclinic

Fracture plane (314)

2.95 to 27.81

q Range [8]

Index ranges

À 8ꢁ hꢁ 8, À9ꢁ kꢁ 9, À14ꢁ lꢁ 15

≈

P1

Reflect. collected

Independent reflect.

Refinement method

Data/restraints/parameters

Goodness-of-fit on F²

Final R indices (I > 2s(I))

R indices (all data)

Weights

4997

2325 (R(int) 0.0280)

Full-matrix least-squares on F²

2325/0/172

a [8] 102.43(2)

b [8] 92.67(2)

g [8] 94.85(2)

V [ä³] 549.3(2)

0.712

R₁ 0.0313, wR₂ 0.900

R₁ 0.0388,wR₂ 0.0982

[s²(F²)]^À1

Z

2

R indices (all data)

Weights

R₁ 0.0592, wR₂ 0.1918

[s²(F_o,²) (0.1 ¥ P)² 0.00 ¥ P]^À1

(Max(F_o²0) 2 ¥ F_c,²)/3

0.794 and À0.442

Density calc. [Mgm^À3

]

1.577

0.702

268

Absorption coeff. [mm^À1

F(000)

Crystal size [mm]

]

where P

Largest difference peak

0.6 Â 0.2 Â 0.14 and hole [e ¥ A^À3

]

Table 7. Crystal Data and Structure Refinement of (Æ)-3y

Empirical formula

M_r

Temperature [K]

Wavelength [ä]

Crystal system

Space group

C₁₁H₁₀O₄S

238.25

293 (2)

0.71073

monoclinic

P2₁/n

q Range [8]

Index ranges

Reflect. collected

Independent reflect.

Absorption correction

Refinement method

1.81 to 23.29

À 7 ꢁ h ꢁ 7, À24 ꢁ k ꢁ 24, À8 ꢁ l ꢁ 5

4102

1548 (R(int) 0.0234)

none

Full-matrix least-squares on F²

Unit cell dimensions a [ä] 6.9190(7)

b [ä] 22.441(2)

Data/restraints/parameters 1548/0/187

Goodness-of-fit on F²

3.236

c [ä] 7.2236

a [8] 90

Final R indices (I > 2s(I)) R₁ 0.0219, wR₂ 0.0711

R indices (all data)

Weights

R₁ 0.0318, wR₂ 0.0716

b [8]

g [8]

105.138(2)

90

[s²(F_o,²)]^À1

Extinction coeff.

Largest difference

peak and hole [e ¥ A^À3

0.022(2)

0.177 and À0.239

V [ä³] 1082.7(2)

]

Z

4

Density calc. (Mgm^À3

]

1.462

0.294

496

Absorption coeff. [mm^À1

F(000)

]

Crystal size [mm]

0.6 Â 0.4 Â 0.2

Helvetica Chimica Acta Vol. 85 (2002)

759

Table 8. Crystal Data and Structure Refinement of (Æ)-17

Empirical formula

M_r

Temperature [K]

Wavelength [ä]

Crystal system

Space group

C₁₀H₁₁ClO₃S q Range [8]

2.12 to 22.5

246.70

Index ranges

À 6 ꢁ h ꢁ 6, À12 ꢁ k ꢁ 12, À16 ꢁ l ꢁ 16

293 (2)

0.71073

triclinic

Reflect. collected

Independent reflect.

Absorption correction

Refinement method

5786

2893 (R(int) 0.032)

none

P1

Full-matrix least-squares on F²

≈

Unit-cell dimensions a [ä] 6.387(1)

b [ä] 11.500(2)

Data/restraints/parameters 1896/0/359

Goodness-of-fit on F²

0.839

c [ä] 15.377(2)

a [8] 84.14(1)

b [8] 81.20(1)

Final R indices (I > 2s(I)) R₁ 0.0407, wR₂ 0.1006

R indices (all data)

Weights

R₁ 0.0644, wR₂ 0.1095

{s²(F_o²) [0.075(F_o² 2 F_c²)/3]²}^À1

none

g [8] 88.56(1)

Extinction coeff.

Largest difference

peak and hole [e ¥ A^À3

Volume [ä³] 1110

0.2 [e ¥ A^À3] À0.3 [e ¥ A^À3

]

Z

4

Density calc. (Mgm^À3

]

1.476

0.51

512

Absorption coeff. [mm^À1

F(000)

]

Crystal size [mm]

0.4 Â 0.3 Â 0.2

We are grateful to the Swiss National Science Foundation and to the Fonds Herbette (Lausanne) for

»

financial support. We thank also Miss Carinne B¸hlmann, Mr. Raphael Estoppey, Martial Rey, and Francisco

¬

Sepulveda for their technical help and Prof. J. A. Sordo (Oviedo, Spain) for helpful discussions.

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Received September 28, 2001

Article Doi

Substituent effect on the competition between hetero-Diels-Alder and cheletropic additions of sulfur dioxide to 1-substituted buta-1,3-dienes

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