Efficient synthesis of new phosphono-substituted dihydrothiopyrans via hetero Diels-Alder reaction, under thermal and high pressure conditions

Article abstract of DOI:10.1016/S0040-4020(00)00297-0

New α-phosphono-β-aryl- or β-heteroaryl-substituted α,β-unsaturated dithioesters 2 were easily prepared from diethyl phosphonodithioacetate 1 and used as thiadienes in thermal or high pressure hetero Diels-Alder cycloadditions with enol and thioenol ethers. The resulting new phosphono 3,4-dihydro 2H-thiopyrans 3 were isolated in excellent yields and with a cis- or trans-diastereoselectivity depending on the conditions of the reaction as well as the structure of the reagents. Some of the thiopyrans 3 were also favourably synthesized via a domino Knoevenagel-hetero Diels-Alder sequence. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00297-0

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 3909±3919
Ef®cient Synthesis of New Phosphono-Substituted
Dihydrothiopyrans via Hetero Diels±Alder Reaction, under
Thermal and High Pressure Conditions
a
Hashim Al-Badri, Noel Collignon, Jacques Maddaluno and Serge Masson
b,
a
c
*
È
a
   Â
Laboratoire des Fonctions Azotees et Oxygenees Complexes de l'IRCOF, UPRES-A 6014 CNRS, Universite de Rouen,
76821 Mont-Saint-Aignan Cedex, France
Laboratoire d'Heterochimie Organique de l'IRCOF, UPRES-A 6014 CNRS, INSA de Rouen, Place E. Blondel, BP 08,
76131 Mont-Saint-Aignan Cedex, France
b
 Â
c
  Â
Laboratoire de Chimie Moleculaire et Thioorganique, UMR 6507 CNRS, Universite de Caen et ISMRA, 6 Boulevard du Marechal Juin,
14050 Caen Cedex, France
Received 3 February 2000; accepted 17 April 2000
AbstractÐNew a-phosphono-b-aryl- or b-heteroaryl-substituted a,b-unsaturated dithioesters 2 were easily prepared from diethyl phos-
phonodithioacetate 1 and used as thiadienes in thermal or high pressure hetero Diels±Alder cycloadditions with enol and thioenol ethers. The
resulting new phosphono 3,4-dihydro 2H-thiopyrans 3 were isolated in excellent yields and with a cis- or trans-diastereoselectivity
depending on the conditions of the reaction as well as the structure of the reagents. Some of the thiopyrans 3 were also favourably synthesized
via a domino Knoevenagel±hetero Diels±Alder sequence. q 2000 Elsevier Science Ltd. All rights reserved.
Introduction
phosphono-6-ethylthio-3,4-dihydro-2H-thiopyrans 3 variously
substituted at the 2 and 4 positions, as shown in the retro-
synthetic Scheme 1. Following this strategy, compounds 3
were obtained by [412] cycloadditions of vinyl ethers or
thioethers with a,b-unsaturated carbodithioic acid esters 2,
preparedÐor in situ generatedÐby Knoevenagel-type
reactions of the readily available triethyl phosphonodithio-
acetate 1.16
In contrast to their carboxylic analogues, which rarely react
as dienes in hetero Diels±Alder reactions,1 a,b-unsaturated
carbodithioic acid esters generally show good reactivity as
heterodienes in cycloadditions with various dienophiles,
under thermal and Lewis acid conditions.2±5 Moreover,
and as previously described by us, the ®rst members of
the series readily dimerize at low temperature through a
head-to-tail [412] cyclocondensation, leading to the corre-
sponding dihydrothiopyrans with high stereoselectivity.6
As observed for the phosphono oxadienes,15 the presence of
the electron-withdrawing phosphono group at the carbon 2
of the thiadienes 2 should favour their reactivity with elec-
tron-rich dienophiles (inverse-electron-demand)17 such as
enol or thioenol ethers (XˆO or S), by lowering the energy
Its ef®ciency and versatility combined with its regio and
stereochemical control render the thia Diels±Alder route
an extremely attractive approach to dihydrothiopyrans,7,8
which are potential precursors of a wide range of thiohetero-
cycles exhibiting a variety of interesting biological
properties.9±14
To the best of our knowledge, no example of phosphono-
substituted dihydrothiopyrans has been reported to date.
As an extension to our recent work on the hetero Diels±
Alder reaction of a-carbonylated styrylphosphonates,15 we
decided to study a similar synthetic way to new 5-diethyl-
Keywords: diastereoselection; hetero Diels±Alder reactions; phosphonates;
thiopyrans; domino reactions.
* Corresponding author. Fax: 133-235-522959;
e-mail: ncollign@ircof.insa-rouen.fr
Scheme 1.
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00297-0

3910
H. Al-Badri et al. / Tetrahedron 56 (2000) 3909±3919
Table 1. Synthesis and 31P NMR data of phosphonates 2
Producta
31P (CDCl3) d (ppm)
Yield (%)b
(E)-2a
(E)-2b
(E)-2c
(E)-2d
(E)-2e
(E)-2f
13.1
11.5
12.1
13.8
11.9
11.4
86
88
85
73
89
81
a The (E)-geometry of the C2vC3 double bond in 2 was assigned by 3JPH3
(,24 Hz) coupling constant measurements in 1H NMR spectra23,24 (see
Experimental).
b Yield in pure product, isolated in an oily form. Puri®cation by column
chromatography over silica gel [eluent: Et2O/CH2Cl2 (95:5), for 2a, 2b,
2d; Et2O, for 2c; Et2O/CH2Cl2 (90:10), for 2e, 2f]. Purity controlled and
structures con®rmed by 1H and 13C NMR spectroscopy. Satisfactory
microanalyses were obtained.
Hetero Diels±Alder reaction of phosphonates 2 with enol
and thioenol ethers
Scheme 2.
We have considered the cycloaddition of phosphonates
2a±f with the two vinyl ethers 5a and 5b, and that of phos-
phonate 2b with the vinyl thioether 5c. The reactions were
performed under different conditions of temperature and
pressure, leading to new 5-diethylphosphonyl-3,4-dihydro-
2H-thiopyrans 3a±m (Scheme 3), isolated as a mixture of
trans- and cis-diastereomers (t-3a±m and c-3a±m in Table
2). The progress of the reaction was monitored by 31P NMR
spectroscopy. Generally, the commercially available dieno-
philes were used in large excess (10 mol equiv.) and thus
served as the reaction solvent.
of the LUMO of the diene, which facilitates its overlap with
the HOMO of the dienophile.18
Results and Discussion
Synthesis of a-phosphono-a,b-unsaturated dithio-
esters 2
First, we wish to report here the (E)-stereoselective synthe-
sis of several new a-diethylphosphonyl-b-aryl- or b-hetero-
aryl-substituted a,b-unsaturated dithioesters 2 by reacting
²
triethyl phosphonodithioacetate 1 with aromatic or hetero-
aromatic bis-morpholino aminal derivatives 4, following the
conditions described by Sakoda et al.21 (Scheme 2 and
Table 1). The reaction can be conveniently monitored by
31P NMR spectroscopy.
It is worthy of note that phosphonates 2 could be obtained
directly from 1 and the corresponding aldehydes by using
the conventional Knoevenagel reaction conditions,22 but the
yield of puri®ed product was often lowered by the presence
of impurities such as the corresponding Horner±
Wadsworth±Emmons ole®nation derivatives. Moreover,
the aminal method was totally (E)-stereoselective, whereas
the formation of a few percentage of the (Z)-isomer of 2 was
occasionally observed using the conventional conditions.
Having a representative range of the new phosphono-substi-
tuted a,b-unsaturated carbodithioic acid esters 2 of homo-
geneous (E)-con®guration available, we studied their
cycloaddition with some electron-rich dienophiles.
²
Ethyl O,O-diethylphosphonodithioacetate 1 was synthesized in multi-
gram scale from the commercially available O,O-diethylcyanomethylpho-
sphonate, by addition of EtSH and dry HCl, followed by sulfhydrolysis of
the intermediate thioimidoester hydrochloride, using the procedure devel-
oped by Marvel et al.,19 for the synthesis of aliphatic dithioesters. The
physical and analytical data of the prepared compound 1 were in full agree-
ment with an earlier report.20
Scheme 3.

H. Al-Badri et al. / Tetrahedron 56 (2000) 3909±3919
Table 2. Conditions, selectivities and yields of the synthesis of cycloadducts 3a±m
3911
Entry
XR
Ar
Productsa
t-3a/c-3a
t-3b/c-3b
t-3c/c-3c
t-3d/c-3d
t-3e/c-3e
t-3f/c-3f
t-3g/c-3g
t-3h/c-3h
t-3i/c-3i
Methodb
Timec (t/h)
Selectivityd trans/cis
Yielde (%)
1
2
3
4
5
6
7
8
OEt
Ph
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
10
48
2
24
3
60
12
96
6
15:85
68:32
15:85
64:36
16:84
75:25
16:84
60:40
19:81
15:85
81:19
15:85f
22:78
25:75
21:79
24:76
32:68
39:61
±
85
88
86
90
87
87
79
85
87
89
82
84
79
84
85
88
82
85
±
4-NO2-C6H4
4-CF3-C6H4
4-MeO-C6H4
3-Pyr
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
18
2.5
52
24
72
11
48
12
72
4-Pyr
OBut
Ph
4-NO2-C6Hub 4
4-CF3-C6H4
4-MeO-C6H4
3-Pyr
g
t-3j/c-3j
t-3k/c-3k
t-3l/c-3l
±
192
6
48
4
24
6
48
22:78
31:69
16:84
80:20
15:85g
7:93
76
90
82
88
88
89
83
4-Pyr
SEt
4-NO2-C6H4
t-3m/c-3m
86:14
a Products isolated as a mixture of trans- and cis-diastereomers.
b A: reaction is sealed tube, at 1258C; B: reaction under 11 kbar, at 208C.
c Time for the complete consumption of phosphonate 2, monitored by 31P NMR spectroscopy.
d Determined on the crude mixture, by 31P and/or 1H NMR integration measurements.
e Yield of puri®ed oily products. Puri®cation by ¯ash chromatography over silica gel [eluent: Et2O/MeOH (95:5) for 3a±l; Et2O/CH2Cl2 (70:30) for 3m].
1
Purity checked and structures established by H and 13C NMR spectroscopy. Satisfactory microanalyses or HRMS were obtained.
f During the work-up, the excess of reagents has to be removed at room temperature in order to avoid the thermal alteration of the diastereomeric ratio of the
product.
g Incomplete reaction, after 10 days.
In the ®rst set of experiments, we examined the ability of
phosphonates 2 to react with ethyl vinyl ether 5a (entries
1±12, Table 2), either under thermal conditions in a sealed
tube at 1258C (method A), or at high pressure (11 kbar) at
208C (method B). For example, the reaction between the
p-nitrophenyl-substituted phosphonothiadiene 2b and an
excess of dienophile 5a reached completion after 2 h
following method A, giving quantitatively the crude
cycloadduct 3b, as a mixture of diastereomers t-3b/c-3b in
the ratio 15:85 (entry 3); this ratio was not altered after
puri®cation by ¯ash chromatography over silica gel (eluent:
ether/methanol, 95:5), yielding 86% of the puri®ed product.
The dihydrothiopyran structure of the cycloadduct was
unambiguously assigned by 1H and 13C NMR spectroscopy
(see Experimental), and the relative con®guration of each
1
diastereomer was deduced from H±1H NOESY experi-
ments. Thus, in the above example, an NOE effect was
observed between the anomeric proton H-2 and proton
H-4 for the major component, establishing its cis-con®gura-
tion; conversely, the NOE effect between the proton H-2 and
the ortho-aromatic protons for the minor component
con®rmed its relative trans-con®guration. Moreover, as
commonly accepted,25±27 we assume that each diastereomer
adopts a half-chair form in a rapid and equilibrated inter-
³
conversion (Scheme 4).
Then, in order to evaluate the effect of reaction conditions,
we exposed the same starting reagent mixture (2b15a) to
high pressure (method B): the reaction was complete after
24 h at room temperature; more interestingly, the diastereo-
selectivity was reversed in favour of the trans-diastereomer
(entry 4).
³
As we observed in the case of phosphonodihydropyrans,15 we veri®ed
here too that the 13C NMR chemical shift of the C-2 anomeric carbon can be
used as a criterion for the relative con®gurational assignment of the phos-
phonodihydrothiopyrans of type 3, by using the previously established
relationship dC-2trans,dC-2cis (see Experimental).
Scheme 4.

3912
H. Al-Badri et al. / Tetrahedron 56 (2000) 3909±3919
Scheme 6.
renders the congested endo-approach less favourable than
the exo-one. However, as expected and as observed in the
case of phosphonooxadienes, the endo-approach was
preferred anew for the phosphonothiadiene, under high
pressure (entry 4), which usually favours the more compact
transition state.29±32
The other thiabutadienes of the aromatic series (2a, 2c and
2d) reacted with 5a to give the expected adducts 3a, 3c and
3d in excellent yields and with a selectivity very similar to
that characterizing the pair 2b/5a, i.e. a cis-diastereoselec-
tivity under thermal conditions, and a trans one at high
pressure. Only the reaction time varied signi®cantly with
the nature of the substituent on the aromatic ring. As
expected for such an inverse-electron-demand cycloaddition
reaction, an electron-withdrawing substituent as NO2 or CF3
increases the rate of the reaction (compare entry 1 with entry
3 or 5), whereas an electron-donating group as MeO slowed
the reaction down (entries 7 and 8). We veri®ed here too the
thermal stability of the related cycloadducts.
More contrasted results were obtained with the pyridyl-
substituted dienes 2e±f, which showed a good reactivity
with 5a (entries 9±12), leading to the corresponding adducts
3e±f, but with an unexpected selectivity. Thus, under
thermal conditions, whereas the cis-isomer of the 3-pyri-
dyl-substituted adduct 3e (entry 9) predominated as for
the above aromatic series, the 4-pyridyl-substituted 3f was
formed with a trans-diastereoselectivity (entry 11); just as
surprising, under high pressure, the predominance of the cis-
isomers was observed for these two adducts, which were
obtained in an identical 15:85 trans/cis ratio (entries 10
and 12). However, we found that the trans/cis ratio of the
4-pyridyl adduct obtained at high pressure (entry 12)
changed from 15:85 to 80:20, when heated for 3 h at
1258C. This result proves the thermal lability of the cyclo-
adduct 3f and suggests that the 81:19 trans/cis ratio
observed using method A (entry 11) represents the ratio of
the thermodynamical mixture, in which the trans-isomer
allows the anomeric effect33 to take place with a minimum
of steric hindrance, as shown in the left-side conformation
of trans-3 (Scheme 4). The easy isomerization of c-3f into
the more stable t-3f adduct under thermal conditions seems
to be due to a retro Diels±Alder reaction, rather than a base-
promoted deprotonation process.§ Moreover, in order to
Scheme 5.
In order to check the thermal stability of the cycloadducts
3b, we heated the diastereomeric mixture resulting from the
above experiment (entry 4); the corresponding 64:36 trans/
cis ratio remained unchanged after several hours at 1258C.
Moreover, having veri®ed beforehand the con®gurational
stability of the starting phosphonates (E)-2 under the same
thermal conditions, we could assume that the studied
cycloadditions of 2b with 5a were kinetically controlled,
and that the trans-cycloadduct was formed via an endo-tran-
sition state (path a), whereas the cis-isomer resulted from an
exo-transition state (path b), as represented in Scheme 5.
The preferred exo-approach observed for the pair of
reagents 2b/5a under thermal conditions is worth under-
lying. Actually, with the same dienophile and under the
same reaction conditions, a-keto-(E)-styrylphosphonates
generally reacted via a preferred endo-transition structure,
but with a poor diastereoselectivity;15 in the system studied
here, the weakness of the secondary orbital interactions
between the oxygen atom of the dienophile and the weakly
polarized CvS double bond28 of the thiadiene 2a, possibly
§
The 15:85 t-3f/c-3f diastereomeric mixture proved to be unchanged, at
room temperature, in the presence of bases as pyridine, 4-picoline, or
piperidine. We gratefully acknowledge one of the referees, who suggested
to us such an experiment.

H. Al-Badri et al. / Tetrahedron 56 (2000) 3909±3919
3913
explain the unexpected predominance of the cis-isomers in
the mixtures resulting from the synthesis of cycloadducts 3e
and 3f at high pressure, we considered a possible isomeriza-
tion of the corresponding dienes, under the reaction condi-
tions. Actually, whereas the dienes (E)-2a±d of the aromatic
series were con®gurationally stable at 11 kbar and 208C
after 48 h, the pure dienes (E)-2e and (E)-2f were trans-
formed, under the same conditions, into a mixture of
(E)-2e/(Z)-2ek and (E)-2f/(Z)-2f,¶ respectively, in a ratio of
,98:2, measured after pressure release. If we assume that
the (Z)-isomers of these mixtures, taken to be equilibrated at
11 kbar,pp reacted more readily, for steric reasons, than their
(E)-partners, and that the related addition occured via
the endo-approach (path d, Scheme 5) as usually proposed
at high pressure, we could thus explain the cis-stereo-
selectivity of the reactions.
reaction with the diene 2b. A very good reactivity and an
excellent cis-diastereoselectivity were observed for this pair
of reagents under thermal conditions (entry 25), giving
access to a new interesting 3,4-dihydro-2H-thiopyran 3m
²²
bearing the ethylthio substituent at the position 2. As
expected, under 11 kbar, the selectivity was reversed in
favour of the trans-isomer (entry 26). Having veri®ed the
stability of the 86:14 t-3m/c-3m mixture obtained at high
pressure, when heated for 6 h at 1258C, we concluded that
the remarkable cis-diastereoselectivity observed under ther-
mal conditions resulted from an exo-approach of the two
reagents, which preferred an endo-one at high pressure, as
usually accepted.
One-pot synthesis of phosphonodihydrothiopyrans 3
from 1, through a domino Knoevenagel±hetero
Diels±Alder sequence
Next, we studied the cycloaddition of dienes 2 with tert-
butyl vinyl ether 5b (entries 13±24, Table 2). As expected,
the bulky dienophile 5b reacted generally more slowly than
its ethyl analogue 5a under thermal, as well as high pressure
conditions. Moreover, for the aromatic series (entries 13±
20) the cis-adducts predominated under thermal conditions,
probably owing to the steric hindrance of the But group,
which favours the exo-approach (path b, Scheme 5).34
This same argument probably accounts for the exo-approach
preference under 11 kbar, and the trans/cis ratios very simi-
lar to the ones recorded under thermal conditions. In the
heteroaromatic series at last (entries 21±24), the cis-isomer
of the 3-pyridyl-substituted adduct 3k predominated under
conditions A or B (entries 21 and 22), as in the above
aromatic series, but for the entry 22, the cis-isomer could
result also from the endo-cycloaddition (path d, Scheme 5)
of the (Z)-2e diene formed in situ under high pressure, as
established above. The 4-pyridyl-substituted diene 2f
reacted rapidly and completely with 5b to give the expected
cycloadduct 3l, but with a trans-diastereoselectivity under
thermal conditions and with a cis-one at 11 kbar. Moreover,
when the t-3l/c-3l mixture obtained under high pressure
(entry 24) was heated for 4 h at 1258C, its diastereomeric
ratio changed from 15:85 into 80:20, which likely represents
the thermodynamical trans/cis ratio for this adduct, as it was
discussed above for 3f. Consequently, we assume that the
preferred transition state for the cycloaddition of (E)-2f with
the bulky dienophile 5b was still the exo-one, using method
A or B. However, the predominant cis-isomer formed in the
®rst case likely isomerized under the thermal conditions into
the more stable t-3l isomer. Such an isomerization did not
occur at high pressure and 208C, but in this case, the c-3l
isomer might result too from the endo-addition of the diene
(Z)-2f formed in situ.
As ®rstly introduced by Tietze et al.,36 the synthesis of some
dihydropyrans can be performed by a three-component
reaction protocol, leading to the expected cycloadduct
through the so called domino Knoevenagel±hetero Diels±
Alder reaction, by using an activated methylene compound,
an aldehyde and an electron-rich alkene as reagents.37
Recently, this procedure allowed us to improve signi®cantly
the yield of the synthesis of phosphonodihydropyrans.15 To
the best of our knowledge, such a sequence has not been
previously employed in thia Diels±Alder syntheses,7 and
therefore we decided to use it for a one-pot synthesis of
phosphonodihydrothiopyrans 3 from phosphonodithio-
acetate 1, as represented in Scheme 6.
A toluene solution of the phosphonate 1, of the suitable
aldehyde 6 and dienophile 5 was introduced into a reactor
equipped with a Dean±Stark separator, then a few drops of
piperidine were added and the mixture was re¯uxed, while
the progress of the reaction was monitored by 31P NMR
spectroscopy. The procedure has been exploited for the
synthesis of the cycloadducts 3b, 3c, 3e, 3f and 3m and
the results are reported in the Table 3.
The yields of isolated cycloadducts 3 synthesized by the
domino-sequences were excellent and higher than the over-
all yields calculated for the corresponding sequences in two
separated reactions. As expected, the selectivities observed
by using this one-pot protocol were very similar to that
reported for the corresponding separate cycloadditions,
carried out under thermal conditions (method A, Table 2).
Moreover, the excellent cis-diastereoselectivity (deˆ88%)
obtained for the synthesis of the cycloadduct 3m deserves to
be underlined (entry 5).
Finally, we tested the behaviour of the dienophile 5c in its
Conclusion
k
In 31P NMR spectroscopy, the signal of the (Z)-isomer of 2e was
observed at 10 ppm.
In this work, we studied a thia-hetero Diels±Alder approach
to new 5-diethylphosphono-6-ethylthio-3,4-dihydro-2H-
thiopyrans 3, variously substituted at 2 and 4 positions.
Ef®cient and diastereoselective syntheses of the cyclo-
adducts 3 were achieved starting from the readily available
¶
In 31P NMR spectroscopy, the signal of the (Z)-isomer of 2f was observed
at 9.4 ppm.
The (Z)-isomers of the pyridyl-substituted dienes 2e and 2f might be
pp
formed by the decomposition of a transient ionic dimer resulting from
the Michael self-condensation of the corresponding (E)-isomers, the overall
process being equilibrated under 11 kbar. Such unusual high-pressure-
promoted Michael/retro-Michael isomerizations are currently being studied
in our laboratory; results will be published in due course.
²²
In carbohydrate chemistry, such alkylthio substituent have been favour-
ably used in glycosylation reactions.35

3914
H. Al-Badri et al. / Tetrahedron 56 (2000) 3909±3919
Table 3. Synthesis of cycloadducts 3b, 3c, 3e, 3f and 3m by domino Knoevenagel±hetero Diels±Alder reaction
Entry
Productsa
Timeb (t/h)
Selectivityc trans/cis
Yield (%)d (Calcd Yield)e
1
2
3
4
5
t-3b/c-3b
t-3c/c-3c
t-3e/c-3e
t-3f/c-3f
48
120
48
48
120
14:86
15:85
17:83
81:19
6:94
89 (74.8)
81 (73.9)
89 (77.4)
86 (66.4)
87 (78.3)
t-3m/c-3m
a Products isolated as a mixture of trans- and cis-diastereomers.
b Time for the complete consumption of phosphonate 1, monitored by 31P NMR spectroscopy.
c Determined on the crude mixture, by 31P and/or 1H NMR integration measurements.
d Yield of puri®ed oily products. Puri®cation by ¯ash chromatography over silica gel [eluent: Et2O/MeOH (95:5) for 3b, 3c, 3e, 3f; Et2O/CH2Cl2 (70:30) for
1
3m]. Purity checked and structures established by H and 13C NMR spectroscopy. Satisfactory microanalyses or HRMS were obtained.
e Calculated overall yield for the sequence in two separate reactions.
diethyl phosphonodithioacetate 1, either in two separate
reactions via the new a-phosphono-a,b-unsaturated carbo-
dithioesters 2, or in a sole reactor, by a domino
Knoevenagel±hetero Diels±Alder reaction sequence.
CH3CH2OP), 3.23 (2H, q, Jˆ7.4 Hz, CH3CH2S), 4.10 (4H,
qui, Jˆ7.2 Hz, CH3CH2OP), 7.42 (1H, d, Jˆ23.8 Hz,
H-C3), 7.18±7.30 and 7.44±7.51 (5H, 2m, Harom.); dC
11.52 (s, CH3CH2S), 15.95 (d, Jˆ7.1 Hz, CH3CH2OP),
30.60 (s, CH3CH2S), 62.79 (d, Jˆ5.1 Hz, CH3CH2OP),
128.20, 129.80 and 130.10 (3s, o-, m-, p-Carom.), 133.10
(d, Jˆ20.1 Hz, i-Carom.), 137.30 (d, Jˆ177.3 Hz, C2),
142.45 (d, Jˆ8.7 Hz, C3), 227.50 (d, Jˆ9.4 Hz, CvS);
Anal. Calcd for C15H21O3PS2: C, 52.31; H, 6.15; S 18.62.
Found: C, 51.92; H, 5.98; S 18.42.
Experimental
General
Solvents and reagents were purchased from common
commercial suppliers and puri®ed by conventional methods
prior to use. High-pressure cycloaddition reactions were
performed in a Unipress piston-cylinder apparatus for
pressures up to 14 kbar. TLC was performed on Merck
60F-254 silica gel plates and column chromatography
over silica gel SI 60 (230±400 mesh). Gas-liquid chromato-
graphy (GLC) was performed on a Varian 3300 chromato-
graph with a 15 m Megabore OV 101 column. Elemental
microanalyses were carried out on a Carlo Erba EA 1110
analyser. HRMS measurements were performed under elec-
tronic impact at 70 eV on a JEOL AX 500 spectrometer.
NMR spectra were recorded on a Bruker DPX-300 spectro-
meter operating at 300 MHz for proton, 75.4 MHz for
carbon, and 121.5 MHz for phosphorus; chemical shift (d)
are expressed in ppm relative to TMS for 1H and 13C nuclei
and to H3PO4 for 31P nucleus; coupling constants (J) are
given in Hz; coupling multiplicities are reported using
conventional abbreviations.
Ethyl (E)-2-diethoxyphosphoryl-3-(4-nitrophenyl)pro-
pendithioate (E)-2b. dP 11.50; dH 1.22±1.38 (9H, m,
CH3CH2S and CH3CH2OP), 3.20 (2H, q, Jˆ7.4 Hz,
CH3CH2S), 4.12 (4H, qui, Jˆ7.2 Hz, CH3CH2OP), 7.50
(1H, d, Jˆ23.5 Hz, H-C3), 7.60 and 8.10 (4H, 2d,
Jˆ8.8 Hz, Harom.); dC 11.65 (s, CH3CH2S), 16.10 (d,
Jˆ6.9 Hz, CH3CH2OP), 30.87 (s, CH3CH2S), 63.30 (d,
Jˆ5.4 Hz, CH3CH2OP), 123.56 and 130.50 (2s, o-,
m-Carom.), 139.43 (d, Jˆ8.9 Hz, C3), 139.72 (d,
Jˆ20.4 Hz, i-Carom.), 141.70 (d, Jˆ175.2 Hz, C2), 147.88
(s, p-Carom.), 225.96 (d, Jˆ9.5 Hz, CˆS); Anal. Calcd for
C15H20NO5PS2: C, 46.26; H, 5.18; N, 3.60; S 16.47. Found:
C, 46.27; H, 5.11; N, 3.65; S 16.28.
Ethyl (E)-2-diethoxyphosphoryl-3-(4-tri¯uoromethyl-
phenyl)propendithioate (E)-2c. dP 12.10; dH 1.18±1.35
(9H, m, CH3CH2S and CH3CH2OP), 3.25 (2H, q,
Jˆ7.7 Hz, CH3CH2S), 4.10 (4H, qui, Jˆ7.1 Hz,
CH3CH2OP), 7.44 (1H, d, Jˆ24.5 Hz, H-C3), 7.48 and
7.58 (4H, 2d, Jˆ8.2 Hz, Harom.); dC 11.62 (s, CH3CH2S),
16.00 (d, Jˆ7.1 Hz, CH3CH2OP), 30.88 (s, CH3CH2S),
63.79 (d, Jˆ5.4 Hz, CH3CH2OP), 123.38 (q, Jˆ272.5 Hz,
F3CAr), 125.10 (q, Jˆ3.6 Hz, m-Carom.), 131.33 (s, o-Carom.),
131.80 (q, Jˆ32.7 Hz, CCF3), 136.68 (d, Jˆ20.3 Hz,
i-Carom.), 139.93 (d, Jˆ177.3 Hz, C2), 140.50 (d,
Jˆ9.4 Hz, C3), 226.26 (d, Jˆ9.4 Hz, CˆS); Anal. Calcd
for C16H20F3O3PS2: C, 46.60; H, 4.89, S, 15.55. Found: C,
46.72; H, 5.02; S 15.14.
General procedure for the synthesis of phosphono-
dithioesters 2
To a solution of phosphonate 1 (10 mmol) and chloroacetic
acid (1.85 g, 20 mmol) in toluene (15 cm3) was added the
appropriate bis(morpholino) aminal 4 (10 mmol). The
³³
mixture was stirred under nitrogen atmosphere at 208C for
48 h, the reaction being monitored by 31P NMR spectro-
scopy. The reaction mixture was then hydrolysed by water
(20 cm3) and the residue obtained after the usual work-up
was puri®ed as indicated in Table 1, leading to pure
thiadiene 2, isolated as a deep orange liquid.
Ethyl (E)-2-diethoxyphosphoryl-3-(4-methyoxyphenyl)-
propendithioate (E)-2d. dP 13.80; dH 1.22±1.30 (9H, m,
CH3CH2S and CH3CH2OP), 3.25 (2H, q, Jˆ7.4 Hz,
CH3CH2S), 3.78 (s, CH3O-Ar), 4.10 (4H, qui, Jˆ7.1 Hz,
CH3CH2OP), 6.76 (2H, d Jˆ8.8 Hz, Harom.), 7.32 (1H, d,
Jˆ24.1 Hz, H-C3), 7.42 (2H, d, Jˆ8.8 Hz, Harom.); dC
11.66 (s, CH3CH2S), 16.07 (d, Jˆ7.2 Hz, CH3CH2OP),
30.78 (s, CH3CH2S), 55.20 (s, CH3O-Ar), 62.70 (d,
Ethyl (E)-2-diethoxyphosphoryl-3-phenylpropendithio-
ate (E)-2a. dP 13.10; dH 1.17±1.34 (9H, m, CH3CH2S and
³³
The required aminals were prepared from the corresponding aldehyde
according to Ref. 21.

H. Al-Badri et al. / Tetrahedron 56 (2000) 3909±3919
3915
Jˆ5.1 Hz, CH3CH2OP), 113.84 and 132.34 (2s, o-,
m-Carom.), 125.86 (d, Jˆ20.5 Hz, i-Carom.), 134.55 (d,
Jˆ178.9 Hz, C2), 142.33 (d, Jˆ8.9 Hz, C3), 160.92 (s,
p-Carom.), 228.60 (d, Jˆ9.8 Hz, CvS); Anal. Calcd for
C16H23O4PS2: C, 51.32; H, 6.19; S, 17.12. Found: C,
51.03; H, 6.28; S, 17.18.
t-3aÐdP 16.60; dH 1.00 (3H, t, Jˆ7.1 Hz, CH3CH2S),
1.02±1.36 (9H, m, CH3CH2O and CH3CH2OP), 2.00±2.20
and 2.25±2.35 (2H, m, H-C3), 2.95±3.10 (2H, m,
CH3CH2S), 3.25±3.68 and 3.75±3.90 (6H, 2m, CH3CH2O
and CH3CH2OP), 4.10±4.25 (1H, m, H-C4), 4.64 (1H, dd,
Jˆ3.6, 10.1 Hz, H-C2), 7.05±7.30 (5H, m, Harom.); dC 14.60
(s, CH3CH2S), 14.97 (s, CH3CH2O), 16.00±16.17 (m,
CH3CH2OP), 28.85 (s, CH3CH2S), 37.42 (d, Jˆ8.1 Hz,
C3), 43.44 (d, Jˆ10.4 Hz, C4), 61.55 and 61.90 (2d,
Jˆ6.0, 5.8 Hz, CH3CH2OP), 65.35 (s, CH3CH2O), 80.33
(s, C2), 124.00 (d, Jˆ189.0 Hz, C5), 126.60, 127.90
and 128.40 (3s, o-, m-, p-Carom.), 142.10 (d, Jˆ1.3 Hz,
i-Carom.), 147.09 (d, Jˆ12.3 Hz, C6).
Ethyl (E)-2-diethoxyphosphoryl-3-(3-pyridyl)propendithio-
ate (E)-2e. dP 11.90; dH 1.20±1.32 (9H, m, CH3CH2S and
CH3CH2OP), 3.23 (2H, q, Jˆ7.2 Hz, CH3CH2S), 4.03±4.20
(4H, m, CH3CH2OP), 7.17 (1H, dd, Jˆ4.9, 8.3 Hz, Harom.),
7.35 (1H, d, Jˆ23.7 Hz, H-C3), 7.75 (1H, d, Jˆ8.3 Hz,
Harom.), 8.46 (1H, d, Jˆ4.9 Hz, Harom.), 8.64 (1H, bs,
Harom.); dC 11.59 (s, CH3CH2S), 16.02 (d, Jˆ6.9 Hz,
CH3CH2OP), 29.90 (s, CH3CH2S), 63.00 (d, Jˆ5.2 Hz,
CH3CH2OP), 123.03 135.68, 150.21 and 150.88 (4s, o-,
m-, p-Carom.), 129.39 (d, Jˆ20.2 Hz, i-Carom.), 138.61 (d,
Jˆ9.1 Hz, C3), 140.27 (d, Jˆ176.5 Hz, C2), 226.25 (d,
Jˆ9.2 Hz, CvS); Anal. Calcd for C14H20NO3PS2: C,
48.68; H, 5.84; N, 4.06; S, 18.56. Found: C, 48.54; H,
5.98; N, 4.46; S, 18.06.
c-3aÐdP 16.30; dH 0.75 (3H, t, Jˆ7.0 Hz, CH3CH2S),
1.06±1.36 (9H, m, CH3CH2O and CH3CH2OP), 2.10±2.20
and 2.47±2.57 (2H, m, H-C3), 2.95±3.10 (2H, m,
CH3CH2S), 3.25±3.68 and 3.75±3.90 (6H, 2m, CH3CH2O
and CH3CH2OP), 4.10±4.25 (1H, m, H-C4), 4.85 (1H, bs,
H-C2), 7.05±7.30 (5H, m, Harom.); dC 14.34 (s, CH3CH2S),
14.54 (s, CH3CH2O), 16.00±16.17 (m, CH3CH2OP), 29.13
(s, CH3CH2S), 36.45 (d, Jˆ8.4 Hz, C3), 42.10 (d, Jˆ9.6 Hz,
C4), 61.52 and 61.95 (2d, Jˆ6.0, 5.7 Hz, CH3CH2OP), 64.62
(s, CH3CH2O), 81.46 (s, C2), 126.46 (d, Jˆ192.1 Hz, C5),
125.80, 127.45 and 128.42 (3s, o-, m-, p-Carom.), 142.73 (s,
i-Carom.), 145.07 (d, Jˆ11.3 Hz, C6).
Ethyl (E)-2-diethoxyphosphoryl-3-(4-pyridyl)propen-
dithioate (E)-2f. dP 11.40; dH 1.20±1.32 (9H, m,
CH3CH2S and CH3CH2OP), 3.20 (2H, q, Jˆ7.4 Hz,
CH3CH2S), 4.15 (4H, qui, Jˆ7.2 Hz, CH3CH2OP), 7.30
(2H, d, Jˆ6.1 Hz, Harom.), 7.34 (1H, d, Jˆ23.1 Hz, H-C3),
8.33 (2H, d, Jˆ5.9 Hz, Harom.); dC 11.45 (s, CH3CH2S),
15.96 (d, Jˆ7.0 Hz, CH3CH2OP), 30.68 (s, CH3CH2S),
63.08 (d, Jˆ6.2 Hz, CH3CH2OP), 123.36 and 149.82 (2s,
o-, m-Carom.), 139.02 (d, Jˆ8.7 Hz, C3), 140.70 (d,
Jˆ20.2 Hz, i-Carom.), 142.54 (d, Jˆ174.9 Hz, C2), 225.38
(d, Jˆ8.8 Hz, CvS); Anal. Calcd for C14H20NO3PS2: C,
48.68; H, 5.84; N, 4.06; S, 18.56. Found: C, 48.30; H,
5.87; N, 4.25; S, 18.19.
5-Diethoxyphosphoryl-3,4-dihydro-2-ethoxy-6-ethylthio-
4-(4-nitrophenyl)-2H-thiopyran 3b. Anal. Calcd for
C19H28NO6PS2: C, 49.45; H, 6.11; N, 3.03; S, 13.89.
Found: C, 49.21; H, 6.12; N, 3.01; S, 13.76.
t-3bÐdP 16.10; dH 1.00±1.40 (12H, m, CH3CH2S,
CH3CH2O and CH3CH2OP), 2.21±2.30 (2H, m, H-C3),
2.90±3.15 (2H, m, CH3CH2S), 3.20±4.00 (6H, 2m,
CH3CH2O and CH3CH2OP), 4.20±4.35 (1H, m, H-C4),
4.63 (1H, dd, Jˆ4.6, 8.0 Hz, H-C2), 7.25 and 8.10 (4H,
2d, Jˆ8.2 Hz, Harom.); dC 14.55 (s, CH3CH2S), 14.85 (s,
CH3CH2O), 15.60±15.70 (m, CH3CH2OP), 28.62 (s,
CH3CH2S), 37.81 (d, Jˆ7.7 Hz, C3), 43.02 (d, Jˆ10.3 Hz,
C4), 61.50±62.00 (m, CH3CH2OP), 65.41 (s, CH3CH2O),
79.86 (s, C2), 122.50 (d, Jˆ189.3 Hz, C5), 123.65 and
128.58 (2s, o-, m-Carom.), 146.57 (s, i-Carom.), 148.26 (d,
Jˆ11.8 Hz, C6), 150.65 (s, p-Carom.).
General procedure for the synthesis of phosphono-
thiopyrans 3 in a sealed tube (method A)
A solution of thiadiene 2 (2 mmol) in an excess of dieno-
phile 5 (10 equiv.) was placed in a sealed tube and heated at
1258C for a time indicated in Table 2, the reaction being
monitored by 31P NMR spectroscopy. The excess of dieno-
phile was then evaporated under reduced pressure and the
residue was puri®ed as indicated in Table 2 to give the pure
cycloadduct 3, isolated as a mixture of diastereomers, which
were not separated.
c-3bÐdP 15.70; dH 0.70 (3H, t, Jˆ7.0 Hz, CH3CH2S),
1.00±1.40 (9H, m, CH3CH2O and CH3CH2OP), 2.16±2.20
and 2.50±2.63 (2H, 2m, H-C3), 2.90±3.15 (2H, m,
CH3CH2S), 3.20±4.00 (6H, 2m, CH3CH2O and
CH3CH2OP), 4.20±4.35 (1H, m, H-C4), 4.85 (1H, bs,
H-C2), 7.23 and 7.90 (4H, 2d, Jˆ8.6 Hz, Harom.); dC 14.25
(s, CH3CH2S), 14.55 (s, CH3CH2O), 15.60±15.7 (m,
CH3CH2OP), 28.96 (s, CH3CH2S), 35.37 (d, Jˆ7.9 Hz,
C3), 41.27 (d, Jˆ9.5 Hz, C4), 61.50±62.00 (m,
CH3CH2OP), 64.65 (s, CH3CH2O), 80.86 (s, C2), 122.57
and 129.22 (2s, o-, m-Carom.), 124.36 (d, Jˆ190.6 Hz,
C5), 146.00 (s, i-Carom.), 146.50 (d, Jˆ11.0 Hz, C6), 151.29
(s, p-Carom.).
General procedure for the synthesis of phosphonothio-
pyrans 3 by the pressure-promoted hetero Diels±Alder
reaction (method B)
A solution of thiadiene 2 (2 mmol) in an excess of dieno-
phile 5 (10 equiv.) was introduced in a pressure vessel, then
put in the high-pressure apparatus, and left under 11 kbar at
208C and for a time indicated in Table 2. Then, after release
of pressure, further work-up and puri®cation were carried
out as above, leading to the pure product 3, isolated as a
viscous liquid.
5-Diethoxyphosphoryl-3,4-dihydro-2-ethoxy-6-ethylthio-
4-(4-tri¯uoromethylphenyl)-2H-thiopyran 3c. Anal.
Calcd for C20H28F3O4PS2: C, 49.58; H, 5.82; S, 13.23.
Found: C, 49.89; H, 5.84; S, 13.42.
5-Diethoxyphosphoryl-3,4-dihydro-2-ethoxy-6-ethylthio-
4-phenyl-2H-thiopyran 3a. HRMS required for
C19H29O4PS2 (M): 416.1244. Found: M1: 416.1244.

3916
H. Al-Badri et al. / Tetrahedron 56 (2000) 3909±3919
t-3cÐdP 16.30; dH 0.75 (3H, t, Jˆ7.0 Hz, CH3CH2S),
1.02±1.18 (6H, m, CH3CH2O and CH3CH2OP), 1.32 (3H,
t, Jˆ7.3 Hz, CH3CH2OP), 2.18±2.34 (2H, m, H-C3), 2.90±
3.10 (2H, m, CH3CH2S), 3.40±3.95 (6H, 2m, CH3CH2O and
CH3CH2OP), 4.20±4.30 (1H, m, H-C4), 4.65 (1H, dd,
Jˆ3.8, 9.4 Hz, H-C2), 7.18 and 7.50 (4H, 2d, Jˆ7.8 Hz,
Harom.); dC 14.60 (s, CH3CH2S), 15.10 (s, CH3CH2O),
16.01±16.21 (m, CH3CH2OP), 28.80 (s, CH3CH2S), 37.62
(d, Jˆ8.0 Hz, C3), 43.18 (d, Jˆ10.3 Hz, C4), 61.60±62.00
(m, CH3CH2OP), 65.48 (s, CH3CH2O), 80.13 (s, C2), 123.10
(d, Jˆ189.4 Hz, C5), 124.10 (q, Jˆ271.8 Hz, F3CAr),
125.50 (q, Jˆ4.0 Hz, m-Carom.), 127.80 (s, o-Carom.),
128.80 (q, Jˆ32.5 Hz, CCF3), 146.70 (s, i-Carom.), 147.92
(d, Jˆ12.0 Hz, C6).
5-Diethoxyphosphoryl-3,4-dihydro-2-ethoxy-6-ethylthio-
4-(3-pyridyl)-2H-thiopyran 3e. Anal. Calcd for
C18H28NO4PS2: C, 51.78; H, 6.76; N, 3.35; S, 15.36.
Found: C, 51.72; H, 6.64; N, 3.42; S, 15.51.
t-3eÐdP 16.20; dH 0.74 (3H, t, Jˆ6.9 Hz, CH3CH2S),
1.01±1.20 (6H, m, CH3CH2O and CH3CH2OP), 1.28 (3H,
t, Jˆ7.2 Hz, CH3CH2OP), 2.25±2.40 (2H, m, H-C3), 2.90±
3.15 (2H, m, CH3CH2S), 2.30±4.00 (6H, m, CH3CH2O and
CH3CH2OP), 4.15±4.28 (1H, m, H-C4), 4.65 (1H, dd,
Jˆ4.2, 9.4 Hz, H-C2), 7.20 (1H, dd, Jˆ3.0, 7.8 Hz,
Harom.), 7.42 (1H, d, Jˆ7.2 Hz, Harom.), 7.42 (1H, d,
Jˆ4.8 Hz, Harom.), 8.40 (1H, bs, Harom.); dC 14.03 (s,
CH3CH2S), 14.77 (s, CH3CH2O), 15.90±16.00 (m,
CH3CH2OP), 28.36 (s, CH3CH2S), 37.50 (d, Jˆ7.2 Hz,
C3), 40.80 (d, Jˆ10.1 Hz, C4), 61.53 and 61.76 (2d,
Jˆ6.3, 6.0 Hz, CH3CH2OP), 65.30 (s, CH3CH2O), 79.86
(s, C2), 123.17, 135.00, 147.10 and 149.28 (4s, o-, m-,
p-Carom.), 124.10 (d, Jˆ190.0 Hz, C5), 138.33 (s, i-Carom.),
145.80 (d, Jˆ11.2 Hz, C6).
c-3cÐdP 15.90; dH 0.70 (3H, t, Jˆ7.0 Hz, CH3CH2S),
1.02±1.18 (6H, m, CH3CH2O and CH3CH2OP), 1.34 (3H,
t, Jˆ7.4 Hz, CH3CH2OP), 2.15±2.26 and 2.50±2.60 (2H,
2m, H-C3), 2.90±3.10 (2H, m, CH3CH2S), 3.40±3.95 (6H,
2m, CH3CH2O and CH3CH2OP), 4.20±4.30 (1H, m, H-C4),
4.84 (1H, t, Jˆ2.5 Hz, H-C2), 7.28 and 7.40 (4H, 2d,
Jˆ8.0 Hz, Harom.); dC 14.20 (s, CH3CH2S), 14.58 (s,
CH3CH2O), 16.01±16.21 (m, CH3CH2OP), 29.12 (s,
CH3CH2S), 35.77 (d, Jˆ7.5 Hz, C3), 41.48 (d, Jˆ9.8 Hz,
C4), 61.60±62.00 (m, CH3CH2OP), 64.66 (s, CH3CH2O),
81.17 (s, C2), 123.05 (q, Jˆ271.9 Hz, F3CAr), 124.40 (q,
Jˆ3.0 Hz, m-Carom.), 125.40 (d, Jˆ190.0 Hz, C5), 128.10 (q,
Jˆ32.3 Hz, CCF3), 128.30 (s, o-Carom.), 146.10 (d,
Jˆ10.9 Hz, C6), 147.20 (s, i-Carom.).
c-3eÐdP 15.80; dH 0.74 (3H, t, Jˆ6.9 Hz, CH3CH2S),
1.01±1.20 (6H, m, CH3CH2O and CH3CH2OP), 1.28 (3H,
t, Jˆ7.2 Hz, CH3CH2OP), 1.31 (3H, t, Jˆ7.2 Hz,
CH3CH2OP), 2.21 (1H, ddd, Jˆ2.6, 6.7, 14.3 Hz, H-C3),
2.54 (1H, dq, Jˆ2.6, 14.3 Hz, H-C3), 2.90±3.15 (2H, m,
CH3CH2S), 2.30±4.00 (6H, m, CH3CH2O and CH3CH2OP),
4.15±4.28 (1H, m, H-C4), 4.86 (1H, bs, H-C2), 7.05 (1H, dd,
Jˆ4.8, 7.5 Hz, Harom.), 7.45 (1H, d, Jˆ7.5 Hz, Harom.), 8.25
(1H, d, Jˆ4.8 Hz, Harom.), 8.40 (1H, bs, Harom.); dC 14.03 (s,
CH3CH2S), 14.42 (s, CH3CH2O), 15.90±16.00 (m,
CH3CH2OP), 29.02 (s, CH3CH2S), 35.30 (d, Jˆ7.9 Hz,
C3), 39.16 (d, Jˆ9.5 Hz, C4), 61.4 and 61.76 (2d, Jˆ6.3,
6.0 Hz, CH3CH2OP), 65.58 (s, CH3CH2O), 81.05 (s, C2),
122.13, 135.10, 146.77 and 149.76 (4s, o-, m-, p-Carom.),
124.83 (d, Jˆ189.9 Hz, C5), 138.33 (s, i-Carom.), 145.80 (d,
Jˆ11.2 Hz, C6).
5-Diethoxyphosphoryl-3,4-dihydro-2-ethoxy-6-ethylthio-
4-(4-methoxyphenyl)-2H-thiopyran 3d. HRMS required
for C20H31O5PS2 (M): 446.1350. Found: M1: 446.1348.
t-3dÐdP 16.70; dH 1.00±1.38 (12H, m, CH3CH2S,
CH3CH2O and CH3CH2OP), 2.05±2.25 (2H, m, H-C3),
3.00 (2H, q, Jˆ7.1 Hz, CH3CH2S), 3.05±3.60 (4H, m,
CH3CH2O and CH3CH2OP), 3.70 (3H, s, CH3O-Ar),
3.88±3.95 (2H, m, CH3CH2OP), 4.05±4.20 (1H, m, H-C4),
4.65 (1H, dd, Jˆ3.6, 10.3 Hz, H-C2), 6.75 and 7.05 (4H, 2d,
Jˆ8.5 Hz, Harom.); dC 14.64 (s, CH3CH2S), 15.05 (s,
CH3CH2O), 16.10±16.26 (m, CH3CH2OP), 28.90 (s,
CH3CH2S), 37.45 (d, Jˆ8.6 Hz, C3), 42.74 (d, Jˆ10.2 Hz,
C4), 55.14 (s, CH3O-Ar), 61.50 and 61.60 (2d, Jˆ5.8,
5.6 Hz, CH3CH2OP), 65.41 (s, CH3CH2O), 80.48 (s, C2),
113.80 and 128.71 (2s, o-, m-Carom.), 124.54 (d,
Jˆ188.3 Hz, C5), 134.06 (d, Jˆ1.7 Hz, i-Carom.), 146.53
(d, Jˆ12.7 Hz, C6), 158.26 (s, p-Carom.).
5-Diethoxyphosphoryl-3,4-dihydro-2-ethoxy-6-ethylthio-
4-(4-pyridyl)-2H-thiopyran 3f. Anal. Calcd for
C18H28NO4PS2: C, 51.78; H, 6.76; N, 3.35; S, 15.36.
Found: C, 52.02; H, 6.82; N, 3.14; S, 15.02.
t-3f±dP 16.00; dH 0.72 (3H, t, Jˆ7.2 Hz, CH3CH2S), 1.08
(3H, t, Jˆ7.0 Hz, CH3CH2O), 1.15 and 1.32 (6H, 2t, Jˆ7.4,
7.1 Hz, CH3CH2OP), 2.28±2.35 (2H, m, H-C3), 2.90±3.10
and 3.30±3.97 (6H, m, CH3CH2S and CH3CH2OP), 4.12±
4.26 (1H, m, H-C4), 4.62 (1H, dd, Jˆ3.9, 9.2 Hz, H-C2),
7.12 and 8.36 (4H, 2d, Jˆ6.0 Hz, Harom.); dC 14.53 (s,
CH3CH2S), 14.59 (s, CH3CH2O), 16.06±16.14 (m,
CH3CH2OP), 28.73 (s, CH3CH2S), 37.20 (d, Jˆ7.8 Hz,
C3), 42.70 (d, Jˆ10.1 Hz, C4), 61.67 and 61.75 (2d,
Jˆ5.8 Hz, CH3CH2OP), 65.46 (s, CH3CH2O), 80.01 (s,
C2), 122.32 (d, Jˆ190.2 Hz, C5), 123.00 and 149.82 (2s,
o-, m-Carom.), 146.54 (d, Jˆ10.9 Hz, C6), 151.80 (d,
Jˆ1.7 Hz, i-Carom.).
c-3dÐdP 16.40; dH 0.80 (3H, t, Jˆ7.0 Hz, CH3CH2S),
1.00±1.38 (9H, m, CH3CH2O and CH3CH2OP), 2.10±2.20
and 2.40±2.50 (2H, 2m, H-C3), 3.00 (2H, q, Jˆ7.1 Hz,
CH3CH2S), 3.05±3.60 (4H, m, CH3CH2O and CH3CH2OP),
3.62 (3H, s, CH3O-Ar), 3.88±3.95 (2H, m, CH3CH2OP),
4.05±4.20 (1H, m, H-C4), 4.82 (1H, bs, H-C2), 6.62 and
6.97 (4H, 2d, Jˆ8.5 Hz, Harom.); dC 14.45 (s, CH3CH2S),
14.60 (s, CH3CH2O), 16.10±16.26 (m, CH3CH2OP), 29.17
(s, CH3CH2S), 36.60 (d, Jˆ8.2 Hz, C3), 41.48 (d, Jˆ9.8 Hz,
C4), 55.14 (s, CH3O-Ar), 61.40 and 61.80 (2d, Jˆ5.9,
5.8 Hz, CH3CH2OP), 64.70 (s, CH3CH2O), 81.58 (s, C2),
112.89 and 129.51 (2s, o-, m-Carom.), 127.04 (d,
Jˆ190.1 Hz, C5), 134.88 (s, i-Carom.), 144.40 (d,
Jˆ11.0 Hz, C6), 157.81 (s, p-Carom.).
c-3fÐdP 15.60; dH 0.72 (3H, t, Jˆ7.2 Hz, CH3CH2S), 1.05
(3H, t, Jˆ7.1 Hz, CH3CH2O), 1.14 and 1.34 (6H, 2t,
Jˆ7.2 Hz, CH3CH2OP), 2.20 (1H, ddd, Jˆ3.0, 6.0,
14.2 Hz, H-C3), 2.57 (1H, dq, Jˆ3.0, 14.2 Hz, H-C3),
2.90±3.10 and 3.30±3.97 (6H, m, CH3CH2S and
CH3CH2OP), 4.12±4.26 (1H, m, H-C4), 4.85 (1H, bs,

H. Al-Badri et al. / Tetrahedron 56 (2000) 3909±3919
3917
H-C2), 7.08 and 8.48 (4H, 2d, Jˆ5.8 Hz, Harom.); dC 14.01 (s,
CH3CH2S), 14.43 (s, CH3CH2O), 16.06±16.14 (m,
CH3CH2OP), 29.58 (s, CH3CH2S), 35.03 (d, Jˆ7.8 Hz,
C3), 40.85 (d, Jˆ9.2 Hz, C4), 61.65 and 61.98 (2d, Jˆ6.9,
6.6 Hz, CH3CH2OP), 64.67 (s, CH3CH2O), 80.87 (s, C2),
124.24 (d, Jˆ190.8 Hz, C5), 123.89 and 148.46 (2s, o-,
m-Carom.), 146.32 (d, Jˆ10.8 Hz, C6), 153.0 (bs, i-Carom.).
42.03 (d, Jˆ9.5 Hz, C4), 61.60±61.92 (m, CH3CH2OP),
74.31 (s, C2), 75.43 [s, C(CH3)3], 122.64, 129.21 (2s, o-,
m-Carom.), 123.40 (d, Jˆ191.1 Hz, C5), 145.97 (s, i-Carom.),
147.86 (d, Jˆ10.9 Hz, C6), 151.67 (s, p-Carom.).
2-tert-Butoxy-5-diethoxyphosphonyl-3,4-dihydro-6-ethyl-
thio-4-(4-tri¯uoromethylphenyl)-2H-thiopyran 3i. HRMS
required for C22H32F3O4PS2 (M): 512.1431. Found: M1:
512.1432.
2-tert-Butoxy-5-diethoxyphosphonyl-3,4-dihydro-6-ethyl-
thio-4-phenyl-2H-thiopyran 3g. HRMS required for
C21H33O4PS2 (M): 444.1557. Found: M1: 444.1557.
t-3iÐdP 16.70; dH 1.00 [9H, s, C(CH3)3], 1.07 (3H, t,
Jˆ7.0 Hz, CH3CH2S), 1.16 and 1.33 (6H, 2t, Jˆ7.0 Hz,
CH3CH2OP), 2.05±2.20 (2H, m, H-C3), 2.95±3.10 (2H, m,
CH3CH2S), 3.88 (4H, qui, Jˆ7.0 Hz, CH3CH2OP), 4.20±
4.32 (1H, m, H-C4), 4.68 (1H, dd, Jˆ4.4, 10.3 Hz, H-C2),
7.27 and 7.55 (4H, 2d, Jˆ7.8 Hz, Harom.); dC 15.20 (s,
CH3CH2S), 16.06±16.37 (m, CH3CH2OP), 27.90 [s,
C(CH3)3], 31.19 (s, CH3CH2S), 38.10 (d, Jˆ7.8 Hz, C3),
43.85 (d, Jˆ10.6 Hz, C4), 61.68±61.90 (m, CH3CH2OP),
73.06 (s, C2), 75.70 [s, C(CH3)3], 121.30 (d, Jˆ190.4 Hz,
C5), 123.56 (q, Jˆ272.2 Hz, F3CAr), 125.50 (q, Jˆ3.7 Hz,
m-Carom.), 128.10 (s, o-Carom.), 129.20 (q, Jˆ32.9 Hz, CCF3),
146.60 (s, i-Carom.), 149.70 (d, Jˆ12.2 Hz, C6).
t-3gÐdP 17.00; dH 1.00 [9H, s, C(CH3)3], 1.05±1.32 (9H,
m, CH3CH2S and CH3CH2OP), 2.10±2.40 (2H, m, H-C3),
2.95±3.10 (2H, m, CH3CH2S), 3.70±3.95 (4H, m,
CH3CH2OP), 4.10±4.25 (1H, m, H-C4), 4.74 (1H, dd,
Jˆ3.8, 10.8 Hz, H-C2), 7.05±7.20 (5H, 2d, Jˆ8.6 Hz,
Harom.); dC 14.97 (s, CH3CH2S), 16.00±16.18 (m,
CH3CH2OP), 27.90 [s, C(CH3)3], 28.63 (s, CH3CH2S),
38.09 (d, Jˆ7.8 Hz, C3), 43.81 (d, Jˆ10.5 Hz, C4), 61.71±
61.90 (m, CH3CH2OP), 73.30 (s, C2), 75.61 [s, C(CH3)3],
120.35 (d, Jˆ189.9 Hz, C5), 126.70, 128.05 and 128.53 (3s,
o-, m-, p-Carom.), 142.20 (s, i-Carom.), 148.40 (d, Jˆ12.0 Hz,
C6).
c-3iÐdP 16.40; dH 0.88 [9H, s, C(CH3)3], 1.05 (3H, t,
Jˆ7.0 Hz, CH3CH2S), 1.18 and 1.34 (6H, 2t, Jˆ7.0 Hz,
CH3CH2OP), 2.10±2.08 and 2.20±2.30 (2H, m, H-C3),
2.95±3.10 (2H, m, CH3CH2S), 3.65±3.10 (4H, m,
CH3CH2OP), 4.20±4.32 (1H, m, H-C4), 5.05 (1H, bs,
H-C2), 7.40 and 7.48 (4H, 2d, Jˆ8.0 Hz, Harom.); dC 14.60
(s, CH3CH2S), 16.06±16.37 (m, CH3CH2OP), 28.91 [s,
C(CH3)3], 30.55 (s, CH3CH2S), 39.00 (d, Jˆ8.1 Hz, C3),
44.00 (d, Jˆ9.7 Hz, C4), 61.68±61.90 (m, CH3CH2OP),
74.70 (s, C2), 76.40 [s, C(CH3)3], 122.00 (q, Jˆ272.1 Hz,
F3CAr), 123.40 (d, Jˆ190.9 Hz, C5), 125.80 (q, Jˆ3.1 Hz,
m-Carom.), 128.80 (s, o-Carom.), 129.01 (q, Jˆ32.7 Hz, CCF3),
147.70 (d, Jˆ11.0 Hz, C6), 147.90 (s, i-Carom.).
c-3gÐdP 16.80; dH 0.95 [9H, s, C(CH3)3], 1.05±1.32 (9H,
m, CH3CH2S and CH3CH2OP), 2.10±2.40 (2H, m, H-C3),
2.95±3.10 (2H, m, CH3CH2S), 3.70±3.95 (4H, m,
CH3CH2OP), 4.10±4.25 (1H, m, H-C4), 5.03 (1H, bs,
H-C2), 7.05±7.20 (5H, 2d, Jˆ8.6 Hz, Harom.); dC 14.88 (s,
CH3CH2S), 16.00±16.18 (m, CH3CH2OP), 27.78 [s,
C(CH3)3], 29.05 (s, CH3CH2S), 38.20 (d, Jˆ7.9 Hz, C3),
42.10 (d, Jˆ9.6 Hz, C4), 61.71±60.90 (m, CH3CH2OP),
74.41 (s, C2), 75.40 [s, C(CH3)3], 123.14 (d, Jˆ190.2 Hz,
C5), 125.93, 127.55 and 128.60 (3s, o-, m-, p-Carom.), 142.80
(s, i-Carom.), 146.50 (d, Jˆ11.0 Hz, C6).
2-tert-Butoxy-5-diethoxyphosphonyl-3,4-dihydro-6-ethyl-
thio-4-(4-nitrophenyl)-2H-thiopyran 3h. Anal. Calcd for
C21H32NO6PS2: C, 51.52; H, 6.59; N, 2.86; S, 13.10. Found:
C, 51.82; H, 6.89; N, 3.11; S, 12.96.
2-tert-Butoxy-5-diethoxyphosphonyl-3,4-dihydro-6-ethyl-
thio-4-(4-methoxyphenyl)-2H-thiopyran
3j.
HRMS
required for C22H35O5PS2 (M): 474.1663. Found: M1:
474.1668.
t-3hÐdP 16.40; dH 1.05 [9H, s, C(CH3)3], 1.08±1.28 (9H,
m, CH3CH2S and CH3CH2OP), 2.10±2.15 (2H, m, H-C3),
3.00 (2H, q, Jˆ7.6 Hz, CH3CH2S), 3.72±3.89 (4H, m,
CH3CH2OP), 4.28±4.40 (1H, m, H-C4), 4.70 (1H, dd,
Jˆ5.4, 9.3 Hz, H-C2), 7.33 and 8.16 (4H, 2d, Jˆ8.6 Hz,
Harom.); dC 14.56 (s, CH3CH2S), 16.06±16.19 (m,
CH3CH2OP), 27.82 [s, C(CH3)3], 28.54 (s, CH3CH2S),
38.50 (d, Jˆ7.9 Hz, C3), 43.73 (d, Jˆ10.4 Hz, C4), 61.60±
61.92 (m, CH3CH2OP), 72.81 (s, C2), 75.59 [s, C(CH3)3],
120.55 (d, Jˆ190.7 Hz, C5), 123.70 and 128.46 (2s, o-,
m-Carom.), 146.66 (s, i-Carom.), 150.19 (d, Jˆ12.1 Hz, C6),
150.39 (s, p-Carom.).
t-3jÐdP 17.00; dH 1.00 [9H, s, C(CH3)3], 1.05±1.32 (9H,
m, CH3CH2S and CH3CH2OP), 2.09±2.35 (2H, m, H-C3),
2.90±3.10 (2H, m, CH3CH2S), 3.68 (3H, s, CH3O-Ar),
3.75±3.90 (4H, m, CH3CH2OP), 4.08±4.20 (1H, m, H-C4),
4.74 (1H, dd, Jˆ4.1, 11.0 Hz, H-C2), 6.78 and 7.05 (4H, 2d,
Jˆ8.7 Hz, Harom.); dC 14.99 (s, CH3CH2S), 16.02±16.19 (m,
CH3CH2OP), 27.95 [s, C(CH3)3], 28.68 (s, CH3CH2S), 38.12
(d, Jˆ8.3 Hz, C3), 43.13 (d, Jˆ10.2 Hz, C4), 55.28 (s,
CH3O-Ar), 61.56 and 61.70 (2d, Jˆ5.8, 5.7 Hz,
CH3CH2OP), 74.20 (s, C2), 75.65 [s, C(CH3)3], 113.90 and
128.70 (2s, o-, m-Carom.), 120.31 (d, Jˆ189.1 Hz, C5),
134.20 (s, i-Carom.), 146.37 (d, Jˆ12.5 Hz, C6), 158.10 (s,
p-Carom.).
c-3hÐdP 16.10; dH 0.90 [9H, s, C(CH3)3], 1.08±1.22 (9H,
m, CH3CH2S and CH3CH2OP), 1.30 (3H, t, Jˆ7.3 Hz,
CH3CH2OP), 2.16±2.22 and 2.40±2.51 (2H, 2m, H-C3),
3.00 (2H, q, Jˆ7.6 Hz, CH3CH2S), 4.00±3.02 (4H, m,
CH3CH2OP), 4.28±4.40 (1H, m, H-C4), 5.05 (1H, bs,
H-C2), 7.34 and 8.01 (4H, 2d, Jˆ8.6 Hz, Harom.); dC 14.48
(s, CH3CH2S), 16.06±16.19 (m, CH3CH2OP), 27.52 [s,
C(CH3)3], 28.95 (s, CH3CH2S), 38.50 (d, Jˆ7.9 Hz, C3),
c-3jÐdP 16.90; dH 0.97 [9H, s, C(CH3)3], 1.05±1.32 (9H,
m, CH3CH2S and CH3CH2OP), 2.09±2.35 (2H, m, H-C3),
2.90±3.10 (2H, m, CH3CH2S), 3.68 (3H, s, CH3O-Ar),
3.75±3.90 (4H, m, CH3CH2OP), 4.08±4.20 (1H, m, H-C4),
5.01 (1H, bs, H-C2), 6.70 and 7.10 (4H, 2d, Jˆ8.6 Hz,
Harom.); dC 14.91 (s, CH3CH2S), 16.02±16.19 (m,

3918
H. Al-Badri et al. / Tetrahedron 56 (2000) 3909±3919
CH3CH2OP), 27.67 [s, C(CH3)3], 28.98 (s, CH3CH2S), 37.32
(d, Jˆ7.8 Hz, C3), 42.43 (d, Jˆ9.9 Hz, C4), 55.29 (s, CH3O-
Ar), 61.45 and 61.88 (2d, Jˆ5.9, 5.8 Hz, CH3CH2OP),
75.40 (s, C2), 75.43 [s, C(CH3)3], 113.00 and 129.50 (2s,
o-, m-Carom.), 123.10 (d, Jˆ190.3 Hz, C5), 135.00 (s,
i-Carom.), 145.40 (d, Jˆ11.1 Hz, C6), 158.71 (s, p-Carom.).
CH3CH2OP), 4.15±4.24 (1H, m, H-C4), 5.02 (1H, bs,
H-C2), 7.11 and 8.35 (4H, 2d, Jˆ5.6 Hz, Harom.); dC 14.58
(s, CH3CH2S), 16.11±16.30 (m, CH3CH2OP), 27.60 [s,
C(CH3)3], 29.14 (s, CH3CH2S), 38.25 (d, Jˆ7.9 Hz, C3),
41.65 (d, Jˆ9.6 Hz, C4), 61.65±62.03 (m, CH3CH2OP),
74.44 (s, C2), 75.66 [s, C(CH3)3], 123.52 (d, Jˆ191.2 Hz,
C5), 147.00 (d, Jˆ10.1 Hz, C6), 123.88 and 148.84 (2s, o-,
m-Carom.), 152.83 (s, i-Carom.).
2-tert-Butoxy-5-diethoxyphosphonyl-3,4-dihydro-6-ethyl-
thio-4-(3-pyridyl)-2H-thiopyran 3k. Anal. Calcd for
C20H32NO4PS2: C, 53.91; H, 7.24; N, 3.14; S, 14.39.
Found: C, 53.82; H, 7.32; N, 3.29; S, 13.98.
5-Diethoxyphosphonyl-2,6-diethylthio-3,4-dihydro-4-(4-
nitrophenyl)-2H-thiopyran 3m. Anal. Calcd for
C19H28NO5PS3: C, 47.78; H, 5.91; N, 2.93; S, 20.14.
Found: C, 47.82; H, 5.34; N, 2.83; S, 19.69.
t-3kÐdP 16.50; dH 0.95 [9H, s, C(CH3)3], 1.05±1.30 (9H,
m, CH3CH2S and CH3CH2OP), 2.05±2.20 and 2.30±2.38
(2H, 2m, H-C3), 2.92±3.10 (2H, m, CH3CH2S), 3.69±4.00
(4H, m, CH3CH2OP), 4.18±4.30 (1H, m, H-C4), 4.72 (1H,
dd, Jˆ5.7, 9.4 Hz, H-C2), 7.20 (1H, dd, Jˆ4.9, 7.2 Hz,
Harom.), 7.48 (1H, dm, Jˆ7.2 Hz, Harom.), 8.29 (1H, dd,
Jˆ1.9, 4.9 Hz, Harom.), 8.43 (1H, bs, Harom.); dC 14.6 (s,
CH3CH2S), 16.01±16.17 (m, CH3CH2OP), 28.65 [s,
C(CH3)3], 29.04 (s, CH3CH2S), 38.42 (d, Jˆ7.6 Hz, C3),
41.56 (d, Jˆ10.6 Hz, C4), 61.55 and 61.85 (2d, Jˆ6.4 Hz,
CH3CH2OP), 72.84 (s, C2), 76.33 [s, C(CH3)3], 123.24,
135.18, 148.00 and 149.56 (4s, o-, m-, p-Carom.), 123.81
(d, Jˆ190.9 Hz, C5), 137.92 (s, i-Carom.), 147.34 (d,
Jˆ11.3 Hz, C6).
t-3mÐdP 15.90; dH 1.00±1.40 (12H, m, CH3CH2S and
CH3CH2OP), 2.05±2.18 and 2.25±2.38 (2H, 2m, H-C3),
2.58 (2H, q, Jˆ7.2 Hz, CH3CH2S), 2.95±3.15 (2H, m,
CH3CH2S), 3.65±3.95 (4H, m, CH3CH2OP), 4.25 (1H, t,
Jˆ6.6 Hz, H-C4), 4.38 (1H, dd, Jˆ0.8, 11.0 Hz, H-C2),
7.28 and 8.15 (4H, 2d, Jˆ8.4 Hz, Harom.); dC 14.74 and
14.79 (2s, CH3CH2S), 16.20 and 16.30 (2d, Jˆ4.2 Hz,
CH3CH2OP), 24.10 and 29.02 (2s, CH3CH2S), 36.70 (d,
Jˆ8.0 Hz, C3), 43.03 (s, C2), 44.50 (d, Jˆ10.1 Hz, C4),
61.70 and 62.05 (2d, Jˆ6.2 Hz, CH3CH2OP), 121.50 (d,
Jˆ191.4 Hz, C5), 123.90 and 128.80 (2s, o-, m-Carom.),
146.95 (s, i-Carom.), 149.79 (d, Jˆ11.2 Hz, C6), 150.45 (s,
p-Carom.).
c-3kÐdP 16.10; dH 0.93 [9H, s, C(CH3)3], 1.05±1.30 (9H,
m, CH3CH2S and CH3CH2OP), 2.05±2.20 and 2.30±2.38
(2H, 2m, H-C3), 2.92±3.10 (2H, m, CH3CH2S), 3.69±4.00
(4H, m, CH3CH2OP), 4.18±4.30 (1H, m, H-C4), 5.06 (1H,
bs, H-C2), 7.06 (1H, dd, Jˆ4.9, 7.9 Hz, Harom.), 7.52 (1H,
dm, Jˆ7.9 Hz, Harom.), 8.29 (1H, dd, Jˆ1.9, 4.9 Hz, Harom.),
8.40 (1H, d, Jˆ2.3 Hz, Harom.); dC 14.48 (s, CH3CH2S),
16.01±16.17 (m, CH3CH2OP), 27.81 [s, C(CH3)3], 29.22
(s, CH3CH2S), 38.55 (d, Jˆ7.8 Hz, C3), 39.97 (d,
Jˆ9.2 Hz, C4), 61.55 and 61.85 (2d, Jˆ6.4 Hz,
CH3CH2OP), 74.50 (s, C2), 75.46 [s, C(CH3)3], 122.43,
136.38, 146.49 and 149.50 (4s, o-, m-, p-Carom.), 123.81
(d, Jˆ190.9 Hz, C5), 138.90 (s, i-Carom.), 147.34 (d,
Jˆ11.3 Hz, C6).
c-3mÐdP 16.10; dH 1.00±1.40 (12H, m, CH3CH2S and
CH3CH2OP), 2.01±2.15 (1H, m, H-C3), 2.52±2.68 (3H, m,
CH3CH2S and H-C3), 2.87±2.90 and 3.03±3.17 (2H, 2m,
CH3CH2S), 3.66±3.91 (4H, m, CH3CH2OP), 4.10 (1H, dd,
Jˆ2.6, 8.6 Hz, H-C2), 4.18±4.29 (1H, m, H-C4), 7.36 and
8.08 (4H, 2d, Jˆ8.7 Hz, Harom.); dC 14.60 (s, CH3CH2S),
16.19 (d, Jˆ6.7 Hz, CH3CH2OP), 25.55 and 28.78 (2s,
CH3CH2S), 42.65 (d, Jˆ9.0 Hz, C3), 46.61 (s, C2), 46.68
(d, Jˆ10.1 Hz, C4), 61.62 and 61.85 (2d, Jˆ6.3 Hz,
CH3CH2OP), 123.20 (d, Jˆ189.7 Hz, C5), 123.50 and
128.80 (2s, o-, m-Carom.), 146.50 (s, i-Carom.), 150.40 (d,
Jˆ10.4 Hz, C6), 151.80 (s, p-Carom.).
General procedure for the one-pot synthesis of phos-
phonothiopyrans 3
2-tert-Butoxy-5-diethoxyphosphonyl-3,4-dihydro-6-ethyl-
thio-4-(4-pyridyl)-2H-thiopyran 3l. HRMS required for
C20H32NO4PS2 (M): 445.1510. Found: M1: 445.1500.
To a 100 cm3 ¯ask equipped with a Dean±Stark trap and a
re¯ux condenser were added a mixture of phosphonate 1
(1.28 g, 5 mmol), the appropriate aldehyde 6 (5 mmol)
and the dienophile 5 (50 mmol) in toluene (50 cm3). Then
two drops of piperidine were introduced. The reaction
mixture was re¯uxed for a time indicated in Table 3, then
the toluene was removed by distillation under reduced pres-
sure. Further work-up and puri®cation were carried out as
above, giving the pure product 3 (Table 3).
t-3lÐdP 16.40; dH 1.00 [9H, s, C(CH3)3], 1.12 (3H, t,
Jˆ7.1 Hz, CH3CH2S), 1.16 and 1.32 (6H, 2t, Jˆ7.1 Hz,
CH3CH2OP), 2.10±2.28 (2H, m, H-C3), 2.95±3.10 (2H, m,
CH3CH2S), 3.65±3.98 (4H, m, CH3CH2OP), 4.15±4.24
(1H, m, H-C4), 4.66 (1H, dd, Jˆ4.5, 10.3 Hz, H-C2), 7.07
and 8.46 (4H, 2d, Jˆ5.6 Hz, Harom.); dC 14.66 (s, CH3CH2S),
16.11±16.30 (m, CH3CH2OP), 27.90 [s, C(CH3)3], 28.70 (s,
CH3CH2S), 38.00 (d, Jˆ7.6 Hz, C3), 43.60 (d, Jˆ10.4 Hz,
C4), 61.65±62.03 (m, CH3CH2OP), 73.00 (s, C2), 76.50 [s,
C(CH3)3], 120.30 (d, Jˆ191.1 Hz, C5), 122.87 and 150.03
(2s, o-, m-Carom.), 150.25 (d, Jˆ12.1 Hz, C6), 151.70 (s,
i-Carom.).
Acknowledgements
We warmly thank Dr X. Pannecoucke, who conducted the
c-3lÐdP 16.00; dH 0.85 [9H, s, C(CH3)3], 1.10 (3H, t,
Jˆ7.2 Hz, CH3CH2S), 1.18 and 1.34 (6H, 2t, Jˆ7.0 Hz,
CH3CH2OP), 2.12±2.25 and 2.29±2.40 (2H, 2m, H-C3),
2.95±3.10 (2H, m, CH3CH2S), 3.65±3.98 (4H, m,
Â
NOE experiments. This work was supported by the Reseau
Interregional Normand de Chimie Organique Fine (Contrat
Â
de Plan Etat-Bassin Parisien-Regions Haute-Normandie et
Basse-Normandie), which is gratefully acknowledged.
Â

H. Al-Badri et al. / Tetrahedron 56 (2000) 3909±3919
3919
19. Marvel, C. S.; De Radzitzky, P.; Brader, J. J. J. Am. Chem.
Soc. 1955, 77, 5997±5999.
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