Thermal or Lewis acid-promoted electrocyclisation and hetero Diels-Alder cycloaddition of α,β-unsaturated (conjugated) carbodiimides: A facile synthesis of nitrogen-containing heterocycles

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Thermal or Lewis acid-promoted electrocyclisation and hetero

Diels–Alder cycloaddition of á,â-unsaturated (conjugated)

carbodiimides: a facile synthesis of nitrogen-containing

heterocycles

Takao Saito,*^aTakahiro Ohkubo,^aHideki Kuboki,^aMasayuki Maeda,^aKensaku Tsuda,^a

Takayuki Karakasa^band Sadayoshi Satsumabayashi^b

^aDepartment of Chemistry, Faculty of Science, Science University of Tokyo, Kagurazaka,

Shinjuku-ku, Tokyo 162, Japan

^bChemistry Laboratory, The Nippon Dental University, Fujimi, Chiyoda-ku, Tokyo 102, Japan

Received (in Cambridge) 17th July 1998, Accepted 17th July 1998

α,β-Diarylvinyl- and α-styryl-carbodiimides, prepared by the aza-Wittig reaction of iminophosphoranes with

isocyanates, underwent either 6π-electrocyclisation upon heating or a Diels–Alder reaction under thermal or Lewis

acid-promoted conditions with appropriate dienophiles such as tetracyanoethylene, dimethyl acetylenedicarboxylate,

maleimide, ethyl propiolate and tosyl isocyanate, to give isoquinolines, pyridines, oxazines, pyrimidines and

pyrrolopyridines. In contrast, β-styrylcarbodiimide was entirely unreactive toward either the electrocyclisation

or the Diels–Alder reaction even under severe reaction conditions. 4-Coumarylcarbodiimide underwent an inverse

electron-demand Diels–Alder reaction with an enamine either thermally or in the presence of a Lewis acid catalyst

to aﬀord chromenopyridines. Thus experimentally observed reactivity diﬀerences of the substituted vinylcarbodi-

imides toward the pericyclic reactions were rationalised by considering not only the heats of formation but also

the probability of the existence of reactive conformers that were estimated by semi-empirical (AM1) and

molecular mechanics calculations.

For many years carbodiimides have occupied a position as an

Nu

important class of heterocumulene compounds in synthetic

organic chemistry.¹Of particular signiﬁcance is their use as

condensing agents in peptide and nucleotide synthesis and as

oxidation agents combined with dimethyl sulfoxide (Pﬁtner–

Moﬀatt oxidation). Other versatile uses of carbodiimides are

as building blocks in heterocycle synthesis.²In this regard, the

incorporation of unsaturated-conjugated units into reactive

cumulenic systems is expected to provide useful and eﬃcient

systems as potent building blocks capable of taking part in

ring-forming reactions such as electrocyclisation, cumulene-

addition annulation and [4ϩ2]cycloaddition reactions for

heterocycle synthesis. In recent years powerful and useful syn-

thetic routes to a wide range of heterocycles utilising function-

alised carbodiimides have been developed.³The methods

include, in particular, cycloaddition–heteroannulation of highly

reactive carbodiimides containing one or more potentially

available functionalities such as carbon–carbon double bond(s)

N

C

NR

N

C

NR

N

C

NR

Nitrogen

Heterocycles

(1)

of two approaches as shown in Scheme 1. The carbodiimides

3–5 could be isolated in good yields as oils (except for 3d, which

is solid) by means of short-column chromatography, and used

in the cycloaddition without further puriﬁcation.‡

in conjugation with the cumulene N᎐C bond or a remote nucleo-

᎐

philic centre (e.g. an OH or NH group) linked to the cumulene

terminal nitrogen [eqn. (1)].³In earlier preliminary work we

have reported the eﬃciency of these functionalised hetero-

cumulenic species in the construction of a variety of nitrogen-

heterocyclic systems such as pyridines, quinolines, isoquinol-

ines, quinazolines, pyridoindoles, indoloquinolines, oxazines,

pyridazines, pyrrolopyridines and chromenopyridines.^4–7This

paper gives a detailed account of this work.†

Cycloadditions of the carbodiimides 3–5

Upon heating at 140 ЊC in xylene the carbodiimides 3 readily

underwent 6π-electrocyclisation involving the β-aryl ring, the

oleﬁnic bond and one of the cumulene N᎐C bonds to form the

᎐

intermediates 6, which rearomatised by way of H-migration

to aﬀord the 1-aminoisoquinolines 7 in fair to good yields

1

(Scheme 2). The H NMR spectra of 7 gave evidence for the

exocyclic R¹NH group, particularly in the cases of 7e,f,k,l; the

NH signal for 7e,k was observed as a doublet (J = 4 Hz),

Results and discussion

The synthesis of the carbodiimides 3–5 utilised an aza-Wittig

reaction of iminophosphoranes 1 with isocyanates 2 consisting

‡ Prolonged column chromatography decreases the yields of carbodi-

imides probably due to their deterioration or polymerisation on silica

gel. The carbodiimide 4a was not prepared and was subjected only to

the computational calculations (vide infra).

† Part of this work has been reported as preliminary communications.^6,7

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

3065

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Ph₃P

N

R¹

N

C

N

i

CH R³

+

R¹

N

C O

CH R³

+

Ph₃PO

R²

R¹= Ph

2a

R¹= p-Tol

R¹= p-MeOC₆H₄

R¹= p-ClC₆H₄

b

c

1a R²= Ph, R³= Ph

b R²= Ph, R³= p-Tol

3, 4, 5

d

e

R¹= c-Hex

R¹= Me

3

a

R¹

R²

R³

f

Ph

p-Tol

Ph

ii

Ph₃P

N

Tol-p

+

b

c

N

C O

1c

p-MeOC₆H₄

p-ClC₆H₄

c-Hex

Ph

for 4b

2g

d

e

5

R¹

Ph

R²R³

4

R¹

R²R³

f

Me

Ph

a

b

c

g

p-Tol

Ph

H

Ph

a

b

H

Ph

p-Tol

Ph

h

i

p-Tol

c-Hex

Ph

H

p-MeOC₆H₄

p-ClC₆H₄

c-Hex

p-Tol

d

e

j

k

l

p-Tol

c-Hex

f

Me

Scheme 1 Conditions: i, room temp., 1–2 h for 2a–d (R¹= aryl), 1–2 d for 2e,f (R¹= c-Hex or Me), in benzene; ii, room temp., 2 h, in benzene.

and ethoxyethene. Instead, the electrocyclisation preferentially

took place over the expected cycloaddition only to result in

NR¹

H

R¹

N

C

N

R⁴

i

the exclusive formation of 7. A strong dienophile, tetracyano-

ethylene (TCNE), was found to produce the [4ϩ2]cyclo-

adducts 8 when the reaction was performed at room temper-

ature in acetonitrile. During the puriﬁcation operation 1,5-H

migrated isomers 9a,k were incidentally formed from com-

pounds 8a,k.

R⁴

N

CH

Ph

3a–l

6

The carbodiimides 3 also reacted as 2-azadienes (4π com-

ponent) with p-tosyl isocyanate on the C᎐O bond (2π compon-

᎐

ent) in reﬂuxing benzene for 15–30 h to form the intermediary

cycloadducts which, by way of H-migration, gave 2-amino-1,3-

oxazin-6-imines 10, while in acetonitrile at room temperature

NHR¹

N

R⁴

the reaction took place on the C᎐N bond to ﬁnally produce the

᎐

2-iminopyrimidin-4-ones 11 via the Dimroth-like rearrange-

ment¹²of the initial cycloadducts (Scheme 3). Although the

yields of products 10 and 11 were moderate, no other cyclo-

adduct was found from the reaction mixture. The structures 10

and 11 were determined on the basis of spectroscopic studies

(MS, IR, ¹H and ¹³C NMR).¶

The reactions of β-styrylcarbodiimide 4b were next

attempted. Under similar reaction conditions the carbodiimide

4b did not undergo either the electrocyclisation or the [4ϩ2]-

cycloaddition even with some strong dienophiles such as

tetracyanoethylene (TCNE), dimethyl acetylenedicarboxylate

Ph

7

6a–f, 7a–f R⁴= H

6g–l, 7g–l R⁴= Me

NHR¹

NR¹

R¹

N

C

N

(NC)₂

N

(NC)₂

N

ii

CH R³

Ph

§ The intermolecular^8,9and intramolecular^4,10hetero Diels–Alder

reactions of α,β-unsaturated (conjugated) carbodiimides have been

reported. Also, the three-component reaction with the heterocycle-

conjugated carbodiimides as the key intermediates has been docu-

mented.¹¹These [4ϩ2]cycloadditions can possibly involve ionic, step-

wise mechanisms.

R³

9a,k

H

3a–l

8a–l

Scheme 2 Reagents and conditions: i, 140 ЊC, in xylene, 2 h for R¹=

aryl, 7–10 h for R¹= alkyl; ii, TCNE, room temp., in MeCN, 1–11 d.

¶ The mass spectra of compounds 10 and 11 showed intense molecular

ion peaks assigned as 1:1-cycloadducts. In the IR spectra of compounds

10, a ν_NHabsorption band was observed at 3380–3450 cm^Ϫ1and the

peak observed at 1520–1560 cm^Ϫ1was reasonably assigned to that of

ν_{C NTs}rather than ν_{C O}. The ¹H NMR spectra of 10e,k exhibited a char-

coupled with the cyclohexyl (R¹= c-Hex) methine proton, and

the methyl signal for 7f,l appears as a doublet, being split due

to coupling with the NH proton.

Since there are several possible sites for pericyclic reactions

of such conjugated carbodiimides, we tried cycloaddition with

some cycloaddends (dienophiles).⁶§ Unfortunately, the carbo-

diimides 3 did not react at all upon heating with the con-

ventional dienophiles such as dimethyl acetylenedicarboxylate

(DMAD), acrylonitrile, methyl acrylate, dimethyl fumarate

᎐

ac^᎐teristic NH resonance as a doublet coupled with the cyclohexyl (R¹)

methine proton, the ¹³C NMR spectra of 10 displaying resonances of

C-2 at 168–169 ppm and of C-6 at 158–163 ppm or vice versa. The IR

spectra of compounds 11 showed a ν_NHabsorption at 3340–3400 cm^Ϫ1

,

a ν_{C NTs}at 1530–1555 cm^Ϫ1, and a ν_{C O}at 1670–1690 cm^Ϫ1. Resonances

᎐

of C-2 and C-4 were observed at 15^᎐8–159 and 161–163 ppm, respect-

ively, in the ¹³C NMR spectra.

3066

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

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(DMAD), tosyl isocyanate and N-phenylmaleimide (NPMI)

R¹

N

C

N

and gave none of the expected products.|| At elevated temper-

atures no identiﬁable products were obtained.

CH R³

Ph

The α-styrylcarbodiimides 5 smoothly underwent the [4ϩ2]-

cycloaddition with tetracyanoethylene, tosyl isocyanate and N-

(p-methoxyphenyl)maleimide to produce compounds 12–14 as

the sole cycloadducts, respectively (Scheme 4). Since it is struc-

turally impossible for the carbodiimides 5 to undergo 6π-

electrocyclisation, [4ϩ2]cycloaddition with the maleimide

could be eﬀected by heating (Table 1). In all of these cases a

trace amount of diarylcarbodiimide (RЈ = aryl) was formed

as a by-product which would arise from the disproportional

dimerisation–fragmentation of 5 at a high temperature. The

reaction in the presence of MnO₂as a dehydrogenation agent

gave a somewhat better yield of product 14a than the other

cases.

3

ii

i

NR¹

NTs

N

O

H

N

Ph

R³

NTs

Ph

O

H

R³

Dimethyl acetylenedicarboxylate (DMAD) reacted with the

carbodiimides 5 in reﬂuxing toluene to aﬀord the 2-amino-

pyridines 15 in moderate yields (Scheme 5, Table 2). Nitta et al.

also reported the thermal [4ϩ2]cycloaddition reaction of 5a

with acetylenic dienophiles such as DMAD, methyl propiolate,

phenyl acetylene and benzoylacetylene to give 2-amino-

pyridines in moderate yields.⁸In the presence of a Lewis acid

catalyst (AlCl₃, 2 equiv.), the reaction proceeded smoothly at

room temperature in dichloromethane to furnish good yields of

the products 15. The reaction of 5 with ethyl propiolate was

also eﬀected by the Lewis acid catalyst to aﬀord the pyridine

derivatives 16 in 43–51% yields (Scheme 5), whereas the thermal

reaction gave only 9% yield of 16a after heating a toluene

solution of 5a for 17 h. The reactions of 5a,b,d,e with methyl

fumarate and with methyl maleate under the same Lewis acid

promoted conditions also gave 15 via dehydrogenation of the

initially formed cycloadducts, albeit in poor (6–8%) yields.

Coumarin-4-carbodiimides 18, which were prepared in a

similar way by the aza-Wittig reaction of 17, were very

moisture-sensitive and therefore the reaction with enamine was

conducted in one-pot without isolation to result in the exclus-

HNR¹

N

NTs

HN

N-R¹

O

Ph

NTs

R³

11

10

11 R¹

R³

10 R¹

R³

a

b

c

Ph

p-Tol

Ph

a

b

c

Ph

p-Tol

Ph

p-MeOC₆H₄

c-Hex

Ph

p-MeOC₆H₄

c-Hex

d

e

f

e

f

p-Tol

Ph

p-Tol

c-Hex

g

p-MeOC₆H₄

p-Tol

c-Hex

h

|| We found that the carbodiimide 4b is suﬃciently reactive to undergo

an addition reaction with a carboxylic acid (acetic acid, benzoic acid

in acetonitrile at room temperature) to aﬀord both N- and NЈ-

acylureas.^1a,b

Scheme 3 Reagents and conditions: i, TsNCO, reﬂux in benzene, 15–30

h; ii, TsNCO, room temp. in MeCN, 5 d for R¹= c-Hex, 10–17 d for

R¹= aryl.

NR¹

NTs

N-R¹

R¹

N

C

N

ii

N

HN

R²

13 R¹

CH₂

R²

O

Ph

O

5

R²

i

Ph

a

b

c

Ph

p-Tol

Ph

p-Tol

Ph

NR¹

HNR¹

NR¹

O

(NC)₂

N

O

iii

–2H

R²

N

NAr

R²

12 R¹

R²

O

a

Ph

p-Tol

Ph

14 R¹

R²

b

c

Ph

p-Tol

a

p-Tol

Ph

Ar = p-MeOC₆H₄

b

c

p-Tol

d

c-Hex

Ph

d

e

Ph

p-Tol

c-Hex

f

Scheme 4 Reagents and conditions: i, TCNE, room temp. in MeCN, 5–10 d; ii, TsNCO, room temp. in MeCN, 2–3 d; iii, N-(p-methoxy-

phenyl)maleimide, in reﬂuxing solvent.

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

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Table

1

Diels–Alder reaction of

5

with N-(p-methoxyphenyl)-

Table 3 Diels–Alder reaction of 18 with enamine

maleimide

Time/h

AlCl₃

Yield

Carbodiimide Solvent

Time/h Additive

Product (%)^a

Carbodiimide

(equiv.)

17→18

18→19

Product (%)^a

5a

5b

5c

5d

5e

5f

Benzene

Xylene

Mesitylene 10

50

7

14a

10

41

27

51

21

26

5

32

36

32

34

30

18a

18b

18c

18d

18e

b

0.5

4

0.5

4

2

4

20

4

20

4

19a

19b

19c

19d

19e

34

20

45

31

30

23

38

17

47

57

0.2^c

0.5^c

1.0^c

b

Xylene

Benzene

Xylene

7

6

8

20

5

2

6

7

MnO₂

S₈

Nitrobenzene 14a

DDQ

b

14a

14b

14c

14d

14e

14f

0.5^c

b

5

3

1.0^c

2

^aIsolated yield, not optimised. ^bThermal reaction under conditions

i→ii. ^cUnder conditions i→iii.

^aIsolated yield, not optimised.

NR

C

PPh₃

Table 2 Diels–Alder reaction of 5 with DMAD

N

O

N

i

DMAD Lewis acid

Yield

Carbodiimide (equiv.) (equiv.)

Time/h Product (%)^a

O

5a

5b

5c

5d

5e

5f

1.1

2.0

1.1

2.0

EtAlCl₂(1.1)

EtAlCl₂(2.0) 25

3

15a

15b

15c

15d

15e

15f

14

38

26

41

77 (22)

72 (22)

70 (53)

74 (28)

70 (26)

71 (45)

17

18

AlCl₃(1.1)

AlCl₃(1.5)

AlCl₃(2.0)

2

1

0.5

0.25

1

0.5

0.25

ii or iii

NR

HNR

^aIsolated yield, not optimised. The yield from the thermal reaction in

reﬂuxing toluene is given in parentheses.

N

O

N

O

R¹N

O

R¹

N

C

N

CO₂R⁴

R³

i or ii

19

N

CH₂

R²

5

18, 19

R

a

Ph

b

c

d

e

p-Tol

5, 15, 16 R¹

R²

Ph

p-NO₂C₆H₄

p-ClC₆H₄

Ts

a

Ph

p-Tol

HNR¹

b

c

Ph

CO₂R⁴

R³

Scheme 6 Reagents and conditions: i, RNCO, 110 ЊC (room temp. for

e, R = Ts), toluene or tetrachloroethylene, 0.5–5 h; ii, N-(cyclohex-

1-enyl)morpholine, 110 ЊC, toluene, 4–5 h; iii, N-(cyclohex-1-enyl)-

morpholine, Lewis acid, Ϫ 15 ЊC→room temp., tetrachloroethylene,

3–20 h.

c-Hex

Ph

N

p-Tol

d

e

R²

p-Tol

c-Hex

f

15 R³= CO₂Me, R⁴= Me

16 R³= H, R⁴= Et

owing to lower steric hindrance with a dienophile than with

(1,2-diarylvinyl)carbodiimides 3 in the course of the cycloaddi-

tion. In fact, the carbodiimides 5 and 3 did undergo the Diels–

Alder reaction but the carbodiimide 4b did not, and the electro-

cyclisation occurred with 3 but did not with 4b. If there are no

signiﬁcant diﬀerences in the electronic eﬀects of the substitu-

ent(s) on their reactivity, their conformational populations can

be envisaged as an important factor on the reactivity diﬀerences

in these diene-s-cis-requiring Diels–Alder reactions as well

as electrocyclisations to allow eﬀective p-orbitals overlapping

(Scheme 7).¹³

As for the carbodiimides 3 there is steric repulsion between

the cumulene moiety and R², and R³in both s-trans- and s-

cis-conformations, respectively, each being counter-balanced.

Therefore, non-planar populations of 3 would increase, though

the π-conjugation is lacking, giving intermediate reactivity of

the three for the Diels–Alder reaction, and higher reactivity

Scheme 5 Reagents and conditions: i, DMAD, reﬂux in toluene, 3–9 h

or ethyl propiolate, reﬂux in toluene, 17 h; ii, DMAD, Lewis acid, room

temp. in CH₂Cl₂or ethyl propiolate (2 equiv.), AlCl₃(2 equiv.),

Ϫ10 ЊC → room temp., 1 h, CH₂Cl₂.

ive formation of chromenopyridines 19, albeit in moderate

yields (Scheme 6, Table 3). The reaction probably involved a

morpholine-elimination and an H-migration of the initially

formed [4ϩ2]cycloadducts.^8,9Lewis acid also worked as a pro-

moter in this inverse electron-demand [4ϩ2]cycloaddition.

Comparisons of reactivities of carbodiimides 3–5

These Diels–Alder reactivity diﬀerences observed among

carbodiimides 3–5 seemed to be somewhat unexpected at ﬁrst

sight since the β-styrylcarbodiimides 4 should react readily

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J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

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Table 4 Heats of formation for Diels–Alder reaction and electrocyclis-

s-trans

s-cis

ation of 3a, 4a (4b) and 5a^a

R¹

N

C

N

R³

H

∆H_f/kcal mol^Ϫ1

R¹

N

C

N

R²

3

R²

R³

S

TS

P

TS–S TS–P

38.7 54.6

S–P

15.9

H

3a [DA] 303.3 342.0 287.4

3a [El]

150.5 181.9 152.3 (116.1)^b31.4 29.6 Ϫ1.8 (34.4)^b

4a [DA] ^c270.4 307.4 253.4

5a [DA] 277.3 305.7 251.4

37.0 54.6

28.4 54.3

17.0

25.9

R¹

C

H

N

^aTransition states were calculated by AM1 method. DA: Diels–Alder,

El: Electrocyclisation, S: Starting reactant(s) system, TS: Transition

state, P: Product system. ^bIn parentheses, heat of formation for the

ﬁnal, re-aromatised H-migration product (7a). ^cFor 4b [DA] heat of

formation: S, 263.4; TS, 299.4; P, 247.2; TS–S, 36.0; TS–P, 52.2 and

R¹

N

C

N

H

4

H

R³

S–P, 16.2 kcal mol^Ϫ1

.

R¹

C

H

N

H

R¹

N

C

N

R²

Table 5 Probability of existence of reactive conformers in Diels–Alder

reaction and electrocyclisation of 3a, 4a (4b) and 5a at 20 ЊC

R²

H

5

Probability (%)

Diels–Alder reaction

Electrocyclisation

R¹HC

N

R¹

N

C

N

3a

4a

5a

72 (62)^a

29 (29)^b

36

8 (9)^a

—

R²

(Ar, Hetaryl)

R²

(CO₂Et)

X

H

^aAt 80 ЊC. ^bFor 4b.

Molina's case¹⁴

Palacios's case¹⁵

It is known that conformational properties of reactant(s) are

essential factors, as well as the activation energies, for eval-

uation of reactivities. It is true particularly in such a case that

the former entropic factor is crucial for complete understanding

of the real reactivities.¹⁶For example, rate acceleration induced

by substituents in the connecting chain that inﬂuence the prop-

erly disposed conformer’s population for cyclisation are often

explained by the so-called geminal di-substituents eﬀect or

the Thorpe–Ingold eﬀect.¹⁷Even for a bimolecular (inter-

molecular) reaction, rate enhancement, or reduction, is often

observed when it is easy, or diﬃcult, for a conjugated diene to

adopt the s-cis conformation necessary to undergo a Diels–

Alder reaction in a concerted mode. In this context, both the

heats of formations and the probabilities of existence of the

dienes in the demanding cisoid conformations necessary for

reaction, were calculated for the Diels–Alder reactions of carbo-

diimides 3a, 4a and 5a with TCNE, and for electrocyclisation of

3a. The structures of the reactants and the products were evalu-

ated using the intrinsic reaction coordinate (IRC) algorithm

in connection with the transition states. The probabilities were

assessed by applying steric energy values calculated by the

MM2 force ﬁeld,¹⁸to the Boltzmann distribution equation.¹⁹

Sixteen, two and three conformers were generated for carbo-

diimides 3a, 4a and 5a, respectively. Among them, the con-

former(s) having dihedral angle(s) within 0 90Њ was (were)

taken into account for each Diels–Alder reaction. Fortunately,

however, it was found that the conformers of θ = ca. 90Њ

having high energies, other than the cisoids (50Њ у θ у Ϫ50Њ for

3a, 2Њ у θ у Ϫ2Њ for 4a and 5a) make virtually no contribution

to the DA reactivity because of their very small Boltzmann

distribution. The results are shown in Tables 4 and 5 and Figs.

1–6.

Scheme 7

for the electrocyclisation than with 4 for which the geometrical

isomerisation (trans→cis) of R³with respect to the C᎐C bond is

᎐

necessary. The inert dienes 4 in cycloaddition reactions would

most preferentially adopt an s-trans form in which there is no

appreciable steric repulsion, although it exists in the s-cis form.

According to the same argument, the azadienes 5 preferably

adopt an s-cis conformation and hence readily undergo the

[4ϩ2]cycloaddition. Molina et al.¹⁴showed experimentally that

certain carbodiimides of the type 3 which bear an R²substitu-

ent (R²= CO₂Et, R¹= aryl or alkyl, R³= aryl or heteroaryl)

readily underwent, on heating, electrocyclisation in a mechan-

ism involving the conjugated system in R³, although the E, Z-

geometry was not speciﬁed, to give a variety of substituted

nitrogen heterocycles. Palacios et al.¹⁵demonstrated that the

6π electrocyclisation of 4-phenyl-2-azadienes (R³= Ph), which

were prepared by the aza-Wittig reaction of iminophosphor-

anes with aromatic (or heteroaromatic) aldehydes (R¹= aryl or

heteroaryl group), took place in reﬂuxing xylene to aﬀord

1,3-disubstituted isoquinolines. In these cases, all the cyclised

2-azadienes bore R²substituents of aryl or heteroaryl groups

such as phenyl, furyl and thienyl groups, and they have

Z-conﬁguration with respect to the C᎐C bond, and E- or

Z-geometry around the C᎐N bond, the latter geometry being

varied by substituents. These results are consistent with the

above argument.

᎐

Computational calculations

In order to support the above argument and precisely but

qualitatively to understand the reactivity diﬀerences of these

conjugated carbodiimides 3–5 for the pericyclic reactions, semi-

empirical (AM1) and molecular mechanics calculations were

performed. The frontier molecular orbital treatment clearly

did not reﬂect the observed reactivities since it was diﬃcult to

specify their HOMO’s and LUMO’s which largely depended

upon conformational rotations, whereas with a simple vinyl-

carbodiimide a FMO approach gave some information on the

reactivity.⁸

Comparison of the reactivity of carbodiimide 3 in the

electrocyclisation versus the Diels–Alder reaction

From the data in Tables 4 and 5 the following inferences can be

made: (1) As far as the activation energies (∆E_TS-S) are con-

El

cerned, the activation energy (∆E

= 31.4 kcal mol^Ϫ1) of the

TS-S

DA

electrocyclisation is smaller than that (∆E

= 38.7 kcal mol^Ϫ1

)

TS-S

of the Diels–Alder reaction by 7.3 kcal mol^Ϫ1, suggesting that

the electrocyclisation is likely to take place faster than the

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

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Fig. 1 Transition state of 1,6-electrocyclisation of 3a.

Diels–Alder reaction (kinetic control). (2) In the Diels–

Alder reaction the heat of formation of the product system

DA

(∆E

= 54.6kcalmol^Ϫ1)issmallerthanthat(∆E

= 38.7kcal

TS-P

TS-S

mol^Ϫ1) of the starting reactants system by 15.9 kcal mol^Ϫ1, by

which the product system is stabilised. On the contrary, the

product system for the electrocyclisation is more destabilised

than the reactant by 1.8 kcal mol^Ϫ1(thermodynamic control).

(3) Furthermore, the Diels–Alder reaction has advantages over

electrocyclisation because of the contribution of the probability

of the existence of reactive conformers (72% for the former

and 8–9% for the latter). (4) If the formation of the ﬁnal,

El

S-Pf

re-aromatised H-migration product (7a) stabilised by ∆E

=

34.4 kcal mol^Ϫ1is taken into account, electrocyclisation can

predominate. (5) Figs. 4–6 show that the C1–C2 bond distance

becomes constant, immediately followed by the C3–C4 bond

distance becoming constant just after the transition state. This

suggests that the cycloaddition proceeds asynchronously.

In any event, the reaction in the presence of a suﬃciently

reactive dienophile at a low temperature (room temp.), such

that the H-migration does not occur, would give the Diels–

Alder product (kinetic control), while at a higher temperature

the electrocyclisation product would be formed predominantly

following H-migration (thermodynamic control). This rational-

isation is qualitatively in agreement with the experimental

observation.

Fig. 2 Transition states of Diels–Alder reactions of 3a, 4a and 5a with

tetracyanoethylene.

Comparison of the reactivity of carbodiimide 3, 4 and 5 in the

Diels–Alder reaction

Experimental

The activation energies of 3a, 4a (4b) and 5a for the Diels–

Alder reaction are 38.7, 37.0 (36.0) and 28.4 kcal mol^Ϫ1, res-

pectively, suggesting increasing reactivity in the order of

5a ӷ 4a(b) у 3a if the reaction is kinetically controlled. On the

other hand, the calculated probability of the carbodiimide

dienes being in the s-cis conformations at 20 ЊC, are 72% for 3a,

29% for 4a(b), and 36% for 5a (Table 5). These data imply that

the Diels–Alder reactivity should be observed in the order of

3a ӷ 5a > 4a(b) at the given temperature (20 ЊC). By taking

both factors (probability and heat of formation) into account,

it leads to the order of 5a > 3a > 4a(b). This prediction is in

accord with the experimental observation.

In conclusion, we have demonstrated that the heteroannul-

ation of conjugated carbodiimides oﬀers a new entry to useful

synthetic methods of a variety of nitrogen-containing hetero-

cyclic systems and that a Lewis acid catalyst eﬀects the Diels–

Alder cycloaddition. The methodology can be applied to other

suitable types of functionalised carbodiimides. Furthermore,

the computational treatment rationalises the reactivity diﬀer-

ences of conjugated carbodiimides in the cycloadditions.

Melting points were determined on a Yanaco melting point

apparatus and are uncorrected. IR spectra were recorded on a

1

Hitachi Model 270-30 spectrometer. H and ¹³C NMR spectra

were measured on JEOL JNM-PMX60SI (60 MHz), JEOL

JNM-FX-100 (100 MHz, 25 MHz) and/or JEOL JNM-EX 270

(270 MHz, 67.8 MHz) spectrometers in deuteriochloroform

using tetramethylsilane as an internal standard unless otherwise

speciﬁed. The same NMR instrument was used as stated ini-

tially, until a new citation appears. J Values are given in Hz.

Mass spectra were obtained with a Hitachi Model RMU-7M

double focusing mass spectrometer at an ionising potential of

70 eV and/or with a Hitachi Model M-80 spectrometer with

a data processing system M-003. Elemental analyses were

performed on a Yanaco MT-3 CHN recorder. Column chrom-

atography and preparative and analytical TLC were performed

on silica gel, Wakogel C-200, and B-5F and Merck Kieselgel 60

F₂₅₄plates, respectively. Solvents were puriﬁed by the usual

method before use. Reactions were carried out under an argon

atmosphere.

3070

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Fig. 3 Intrinsic reaction coordinate plots for the electrocyclisation of 3a. The reaction proceeds from left to right with the transition state at zero.

The solid line represents energy and the dotted line represents the C1–C2 distance (see Fig. 1).

Fig. 4 Intrinsic reaction coordinate plots for the Diels–Alder reaction of 3a with tetracyanoethylene. The reaction proceeds from left to right with

the transition state at zero. The solid line represents energy, the dotted line represents the C1–C2 distance (see Fig. 2), and the dot-dashed line

represents the C3–C4 distance.

Materials

Preparation of [N-(2-oxo-2H-chromen-4-yl)imino]triphenyl-

phosphorane 17

The N-vinyliminophosphoranes 1a,b were prepared by the

Staudinger reaction²⁰of vinyl azides with triphenylphosphine

and/or by Ciganek’s method²¹via the reaction of phosphonium

methylides with aryl nitriles. The iminophosphorane 1c was

prepared by the Kirsanov method from p-toluidine and

triphenylphosphine.²²

4-p-Tolylsulfonyloxy-2H-chromen-2-one. To a solution con-

taining 4-hydroxycoumarin (9.96 g, 61 mmol) and triethylamine

(10.3 cm³, 73 mmol) in dry tetrahydrofuran (THF) (100 cm³)

was added dropwise a THF solution (100 cm³) of tosyl chloride

(12.9 g, 67 mmol) with stirring at 0 ЊC for 1.5 h. After 0.5 h, the

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

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Fig. 5 Intrinsic reaction coordinate plots for the Diels–Alder reaction of 4a with tetracyanoethylene. The reaction proceeds from left to right with

the transition state at zero. The solid line represents energy, the dotted line represents the C1–C2 distance (see Fig. 2), and the dot-dashed line

represents the C3–C4 distance.

Fig. 6 Intrinsic reaction coordinate plots for the Diels–Alder reaction of 5a with tetracyanoethylene. The reaction proceeds from left to right with

the transition state at zero. The solid line represents energy, the dotted line represents the C1–C2 distance (see Fig. 2), and the dot-dashed line

represents the C3–C4 distance.

reaction mixture was warmed to room temperature and then

the precipitate was ﬁltered and washed with ethyl acetate

(EtOAc). Removal of the solvent from the ﬁltrate and recrystal-

lisation of the residue from diethyl ether aﬀorded 18.7 g (97%)

of the tosyl ester as colourless crystals, which was used without

further puriﬁcation (analytical) in the next reaction. δ_H(270

MHz) 2.47 (3H, s, Me), 6.32 (1H, s, 3-H), 7.26 (1H, d, J 7.26,

8-H), 7.31 (1H, dd, J 8.58, 7.92, 6-H), 7.40 (2H, d, J 8.58, Ts),

7.58 (1H, ddd, J 8.58, 7.26, 1.32, 7-H), 7.64 (1H, dd, J 7.92,

1.32, 5-H) and 7.90 (2H, d, J 8.58, Ts).

of the tosyl ester (15.4 g, 48.8 mmol) was added dropwise an

aqueous solution (30 cm³) of sodium azide (3.50 g, 53.7 mmol)

with stirring at 0 ЊC. Being stirred at room temperature for 1.5

h, the reaction mixture was extracted with CH₂Cl₂(50 cm³× 3),

washed with brine, and dried (MgSO₄). The solvent was evap-

orated and the residue was column-chromatographed on silica

gel using hexane–EtOAc (5:1–1:1) to give 8.77 g (96%) of the

azide as a colourless solid, which was used without further

puriﬁcation (analytical) in the next reaction. ν_max(KBr)/cm^Ϫ1

2172 (N ) and 1730 (C᎐O); δ (270 MHz) 6.13 (s, 3-H), 7.29

᎐

3

H

4-Azido-2H-chromen-2-one. To a methanol solution (75 cm³)

(1H, ddd, J 7.92, 7.26 and 0.99, 6-H), 7.35 (1H, dd, J 8.25 and

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0.99, 8-H), 7.60 (1H, ddd, J 8.25, 7.26 and 1.65, 7-H) and 7.72

(1H, dd, J 7.92 and 1.65, 5-H).

(N᎐C᎐N); δ 2.30 (3H, s, CH ), 6.37 (1H, s, ᎐CH) and 6.73–7.79

᎐ ᎐

(13H, m, ArH).

᎐

H

3

[N-(2-Oxo-2H-chromen-4-yl)imino]triphenylphosphorane 17.

To a CH₂Cl₂solution (50 cm³) of the azide (2.88 g, 15.4 mmol)

was added dropwise a CH₂Cl₂solution (40 cm³) of triphenyl-

phosphine (4.01 g, 15.4 mmol) at room temperature. The

reaction mixture was stirred for 4 h at room temperature. Evap-

oration of the solvent and recrystallisation of the residue from

CH₂Cl₂–hexane gave a quantitative yield of the iminophos-

phorane 17 (6.43 g, 99%) together with a crop from the mother

liquor through chromatographic puriﬁcation [silica gel, hexane–

EtOAc–CH₂Cl₂(4:2:1)]. Colourless solids; mp 239.2–240.5 ЊC

(Found: M^ϩ, 421.1226. C₂₇H₂₀NO₂P requires M, 421.1229);

ν_max(KBr)/cm^Ϫ11692 (C᎐O), 1532 and 1382; δ (270 MHz) 5.09

N-Cyclohexyl-NЈ-[1-phenyl-2-(p-tolyl)vinyl]carbodiimide 3k.

Colourless oil (94% yield); ν_max(NaCl)/cm^Ϫ12130 (N᎐C᎐N); δ

᎐ ᎐

H

0.9–2.0 [10H, m, (CH₂)₅], 2.35 (3H, s, CH₃), 3.30 (1H, br s,

CH), 6.07 (1H, s, ᎐CH) and 6.93–7.80 (9H, m, ArH).

᎐

N-Methyl-NЈ-[1-phenyl-2-(p-tolyl)vinyl]carbodiimide 3l. Col-

ourless oil (70% yield); ν_max(NaCl)/cm^Ϫ12130 (N᎐C᎐N); δ 2.27

᎐ ᎐

H

(3H, s, CH ), 2.91 (3H, s, NCH ), 6.12 (1H, s, ᎐CH) and 6.97–

᎐

3

7.79 (9H, m, ArH).

N-(p-Tolyl)-NЈ-(2-phenylvinyl)carbodiimide 4b. Colourless oil

(65% yield); ν_max(NaCl)/cm^Ϫ12140 (N᎐C᎐N) and 1650 (C᎐C);

᎐ ᎐

᎐

δ_H2.27 (3H, s, CH ), 6.43 (1H, d, J 13.4, ᎐CH), 6.92 (1H, d,

᎐

3

J 13.4, ᎐CH), 7.03 (4H, br s, TolH) and 7.20 (5H, br s, PhH);

᎐

H

(1H, s, 3-H), 7.25 (1H, d, J 7.59, 8-H), 7.28 (1H, ddd, J 8.91,

7.59 and 1.32, 7-H), 7.43–7.85 (16H, m, Ph-H, 6-H) and 8.40

(1H, dd, J 7.91 and 1.32, 5-H); m/z 421 (M^ϩ, 74%), 393 (10,

M^ϩϪ CO), 302 (16), 277 (10) and 185 (100, Ph₂P^ϩ).

m/z 234 (M^ϩ, 53%) and 233 (M^ϩϪ 1, 100).

N-Phenyl-NЈ-(1-phenylvinyl)carbodiimide 5a.⁸Colourless oil

(87% yield); ν_max(NaCl)/cm^Ϫ12148 (N᎐C᎐N); δ 5.10 (1H, d,

᎐ ᎐

H

J 3.0, ᎐CH ), 5.27 (1H, d, J 3.0, ᎐CH ) and 6.95–7.65 (10H, m,

᎐

2

PhH).

N-(1-Phenylvinyl)-NЈ-(p-tolyl)carbodiimide 5b. Colourless oil

Preparation of N-vinylcarbodiimides 3–5. General procedure

(77% yield); ν_max(NaCl)/cm^Ϫ12140 (N᎐C᎐N); δ 2.40 (3H, s,

᎐ ᎐

H

To a dry benzene solution (50 cm³) of iminophosphoranes 1

(5.27 mmol) was added dropwise a benzene solution (50 cm³) of

isocyanates 2 (5.83 mmol). The reaction mixture was stirred at

room temperature for 1–2 h (R¹= aryl, β-styryl) or for 1–2 d

(R¹= alkyl). Evaporation of the solvent and trituration of the

residue with hexane aﬀorded triphenylphosphine as colourless

crystals. Removal of the solvent from the ﬁltrate and short

column chromatography of the residue [silica gel, benzene–

hexane (1:5) as an eluent] gave the carbodiimides 3–5 as viscous

oils or a solid (for 3d) in good yields, which were immediately

used in the next reaction. Further puriﬁcation by distillation

under reduced pressure failed.

Me), 5.10 (1H, d, J 2.2, ᎐CH ), 5.26 (1H, d, J 2.0, ᎐CH ) and

6.80–7.70 (9H, m, ArH).

᎐

2

N-Cyclohexyl-NЈ-(1-phenylvinyl)carbodiimide 5c. Colourless

oil (68% yield); ν_max(NaCl)/cm^Ϫ12936 (CH₂) and 2136

(N᎐C᎐N); δ 1.00–3.70 (11H, m, c-Hex-H), 5.00 (1H, br s,

᎐ ᎐

H

᎐CH ), 5.20 (1H, br s, ᎐CH ) and 7.2–7.8 (5H, m, PhH).

᎐

2

N-Phenyl-NЈ-[1-(p-tolyl)vinyl]carbodiimide 5d. Colourless oil

(78% yield); ν_max(NaCl)/cm^Ϫ12140 (N᎐C᎐N); δ 2.3 (3H, s,

᎐ ᎐

Me), 5.1 (1H, d, J 2.0, ᎐CH ), 5.3 (1H, d, J 2.0, ᎐CH ) and 7.0–

H

᎐

2

7.6 (9H, m, ArH).

N-p-Tolyl-NЈ-[1-(p-tolyl)vinyl]carbodiimide 5e. Colourless oil

(81% yield); ν_max(NaCl)/cm^Ϫ12140 (N᎐C᎐N); δ 2.3 (3H, s,

᎐ ᎐

H

N-Phenyl-NЈ-(1,2-diphenylvinyl)carbodiimide 3a. Colourless

Me), 2.4 (3H, s, Me), 5.1 (1H, d, J 2.0, ᎐CH ), 5.3 (1H, d, J 2.0,

᎐

2

oil (80% yield); ν_max(NaCl)/cm^Ϫ12130 (N᎐C᎐N); δ (60 MHz)

᎐CH ) and 6.7–7.6 (8H, m, ArH).

᎐ ᎐

᎐

H

2

6.37 (1H, s, ᎐CH) and 6.96–7.87 (15H, m, ArH); m/z 296 (M^ϩ,

N-Cyclohexyl-NЈ-(1-p-tolylvinyl)carbodiimide 5f. Colourless

᎐

72%), 295 (88, M^ϩϪ 1), 219 (8, M^ϩϪ Ph) and 178 (100).

N-(1,2-Diphenylvinyl)-NЈ-(p-tolyl)carbodiimide 3b. Colour-

less oil (97% yield); ν_max(NaCl)/cm^Ϫ12130 (N᎐C᎐N); δ 2.27

oil (68% yield); ν_max(NaCl)/cm^Ϫ12936 (CH₂) and 2136

(N᎐C᎐N); δ 0.9–3.7 (11H, m, c-Hex-H), 2.3 (3H, s, Me), 5.0

᎐ ᎐

H

(1H, br s, ᎐CH ), 5.2 (1H, br s, ᎐CH ) and 6.9–7.8 (4H, m,

᎐ ᎐

᎐

H

2

(3H, s, CH ), 6.33 (1H, s, ᎐CH) and 6.95–7.87 (14H, m, ArH);

ArH).

᎐

3

m/z 310 (M^ϩ, 71%), 309 (75, M^ϩϪ 1) and 178 (100).

N-(p-Methoxyphenyl)-NЈ-(1,2-diphenylvinyl)carbodiimide 3c.

Electrocyclisation of N-vinylcarbodiimides 3 leading to

isoquinolines 7. General procedure

Colourless oil (70% yield); ν_max(NaCl)/cm^Ϫ12130 (N᎐C᎐N); δ

᎐ ᎐

H

3.76 (3H, s, OCH ), 6.36 (1H, s, ᎐CH) and 6.63–7.96 (14H, m,

᎐

3

ArH).

A solution of carbodiimide 3 (2.0 mmol) in xylene (20 cm³)

was heated under reﬂux for 2 h (for R¹= aryl) or 7–10 h (for

R¹= alkyl) until 3 had been consumed (monitored by TLC).

After being cooled, the solvent was evaporated and the residue

was column-chromatographed on silica gel using benzene–

hexane as an eluent to give isoquinoline 7, which was recrystal-

lised from benzene–hexane.

N-(p-Chlorophenyl)-NЈ-(1,2-diphenylvinyl)carbodiimide 3d.

Colourless solid (75% yield), mp 103 ЊC; ν_max(NaCl)/cm^Ϫ1

2130 (N᎐C᎐N); δ 6.33 (1H, s, ᎐CH) and 6.65–7.87 (14H, m,

᎐ ᎐

ArH).

᎐

H

N-Cyclohexyl-NЈ-(1,2-diphenylvinyl)carbodiimide 3e. Colour-

less oil (86% yield); ν_max(NaCl)/cm^Ϫ12140 (N᎐C᎐N); δ 0.90–

᎐ ᎐

H

1.93 [10H, m, (CH ) ], 3.33 (1H, br s, CH), 6.12 (1H, s, ᎐CH)

3-Phenyl-1-(phenylamino)isoquinoline 7a. Colourless crystals

(81% yield); mp 104–105 ЊC (Found: C, 85.41; H, 5.59; N,

9.45%. C₂₁H₁₆N₂requires C, 85.11; H, 5.44; N, 9.45%);

ν_max(KBr)/cm^Ϫ13450 (NH) and 1630; δ_H(100 MHz) 6.92–7.92

(14H, m, ArH and NH) and 7.92–8.16 (2H, m, ArH); δ_C(25

MHz) 109.16, 117.83, 119.78, 121.14, 122.26, 126.21, 126.65,

127.92, 128.20, 128.50, 128.74, 129.87, 138.25, 139.66, 140.48,

148.73 and 151.40; m/z 296 (M^ϩ, 69%), 295 (100, M^ϩϪ 1) and

203 (79, M^ϩϪ PhNH₂).

᎐

2

5

and 7.10–7.83 (10H, m, ArH); m/z 302 (M^ϩ, 30%), 220 (10,

M^ϩϪ c-Hex ϩ 1) and 178 (100).

N-Methyl-NЈ-(1,2-diphenylvinyl)carbodiimide 3f. Colourless

oil (51% yield); ν_max(NaCl)/cm^Ϫ12130 (N᎐C᎐N); δ 2.68 (3H, s,

᎐ ᎐

H

NCH ), 6.15 (1H, s, ᎐CH) and 7.0–7.9 (10H, m, ArH).

᎐

3

N-Phenyl-NЈ-[1-phenyl-2-(p-tolyl)vinyl]carbodiimide 3g. Col-

ourless oil (90% yield); ν_max(NaCl)/cm^Ϫ12130 (N᎐C᎐N); δ 2.33

᎐ ᎐

H

(3H, s, CH ), 6.33 (1H, s, ᎐CH) and 6.69–7.83 (14H, m, ArH).

᎐

3

N-[1-Phenyl-2-(p-tolyl)vinyl]-NЈ-(p-tolyl)carbodiimide

᎐ ᎐

3h.

H

3-Phenyl-1-(p-tolylamino)isoquinoline 7b. Colourless needles

(80% yield); mp 112–115 ЊC (Found: C, 84.93; H, 5.82; N,

9.01%. C₂₂H₁₈N₂requires C, 85.13; H, 5.85; N, 9.02%);

ν_max(KBr)/cm^Ϫ13460 (NH) and 1630; δ_H2.29 (3H, s, CH₃), 6.94

(1H, s, NH), 6.98–7.68 (12H, m, ArH) and 7.95–8.12 (2H, m,

ArH); δ_C20.76 (CH₃), 108.72 (C-4), 117.68 (C-8a), 119.97 (C-

2Ј), 121.09, 125.92, 126.60, 122.72, 128.06, 128.40, 129.18,

129.62, 131.58, 137.86, 138.10, 139.76 (C-1Ј), 148.58 (C-3) and

151.45 (C-1); m/z 310 (M^ϩ, 100%), 233 (3, M^ϩϪ Ph) and 204

(79, M^ϩϪ TolNH).

Colourless oil (94% yield); ν_max(NaCl)/cm^Ϫ12120 (N᎐C᎐N); δ

2.17 and 2.27 (3H, s, CH ), 6.27 (1H, s, ᎐CH) and 6.80–7.80

᎐

3

(13H, m, ArH).

N-(p-Methoxyphenyl)-NЈ-[1-phenyl-2-(p-tolyl)vinyl]carbodi-

imide 3i. Colourless oil (75% yield); ν_max(NaCl)/cm^Ϫ12130

(N᎐C᎐N); δ 2.26 (3H, s, CH ), 3.59 (3H, s, OCH ), 6.25 (1H, s,

᎐ ᎐

H

3

᎐CH) and 6.46–7.86 (13H, m, ArH).

᎐

N-(p-Chlorophenyl)-NЈ-[1-phenyl-2-(p-tolyl)vinyl]carbodi-

imide 3j. Colourless oil (70% yield); ν_max(NaCl)/cm^Ϫ12140

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

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3-Phenyl-1-(p-methoxyphenylamino)isoquinoline 7c. Colour-

less needles (75% yield); mp 152 ЊC (Found: C, 80.99; H, 5.50;

N, 9.00%. C₂₂H₁₈N₂O requires C, 80.95; H, 5.56; N, 8.58%);

ν_max(KBr)/cm^Ϫ13420 (NH) and 1630; δ_H3.81 (3H, s, OCH₃),

6.92 (2H, d, J 8.1, ArH), 7.00–7.91 (12H, m, ArH and NH) and

8.07 (1H, dd, J 8.1 and 1.0); δ_C55.55 (OCH₃), 108.57 (C-4),

114.03 (C-2Ј), 117.64 (C-8a), 121.24 (C-5), 122.02 (C-2Љ), 126.06

(C-4Љ), 126.65 (C-7), 127.87 (C-8), 128.16 (C-3Љ), 128.45 (C-3Ј),

129.82 (C-6), 133.72 (C-4a), 138.29 (C-1Љ), 139.76 (C-1Ј), 148.77

(C-3), 151.89 (C-4Ј) and 155.30 (C-1); m/z 326 (M^ϩ, 100%), 325

(47, M^ϩϪ 1) and 311 (77, M^ϩϪ CH₃).

7-Methyl-3-phenyl-1-(cyclohexylamino)isoquinoline 7k. Col-

ourless needles (67% yield); mp 120–123 ЊC (Found: C, 83.55;

H, 7.71; N, 8.88%. C₂₂H₂₄N₂requires C, 83.50; H, 7.65; N,

8.85%); ν_max(KBr)/cm^Ϫ13460 (NH) and 1630; δ_H1.00–2.40

[10H, m, (CH₂)₅], 2.44 (3H, s, CH₃), 4.30 (1H, br s, CH), 4.98

(1H, d, J 4.0, NH), 7.16–7.55 (7H, m, ArH) and 8.00–8.20 (2H,

m, ArH); δ_C21.78 (CH₃), 25.19 (CH₂), 26.12 (CH₂), 33.33

(CH₂), 49.70 (CH), 106.08, 117.34, 120.41, 126.41, 127.43,

127.67, 128.31, 131.28, 135.02 (C-7), 136.00 (C-4a), 140.39 (C-

1Љ), 147.99 (C-3) and 153.35 (C-1); m/z 316 (M^ϩ, 23%), 234

(100, M^ϩϪ C₆H₁₁) and 218 (10, M^ϩϪ C₆H₁₁NH).

3-Phenyl-1-(p-chlorophenylamino)isoquinoline 7d. Colourless

needles (86% yield); mp 153 ЊC (Found: C, 76.13; H, 4.61; N,

8.55%. C₂₁H₁₅N₂Cl requires C, 76.24; H, 4.57; N, 8.47%);

ν_max(KBr)/cm^Ϫ13460 (NH) and 1630; δ_H7.04 (1H, br s, NH),

7.15–7.76 (12H, m, ArH) and 7.86–8.16 (2H, m, ArH); δ_C109.45

(C-4), 117.68 (C-8a), 121.00, 126.31, 126.60, 126.84, 127.92,

128.31, 128.55, 128.65, 129.96, 138.20 (C-1Љ), 139.03 (C-1Ј),

139.51 (C-4Ј), 148.53 (C-3) and 151.01 (C-1); m/z 330 (³⁵Cl)

(M^ϩ, 82%), 329 (100, M^ϩϪ 1) and 294 (12).

7-Methyl-3-phenyl-1-(methylamino)isoquinoline 7l. Colour-

less crystals (64% yield); mp 70–71 ЊC (Found: C, 82.28; H,

6.45; N, 11.21%. C₁₇H₁₆N₂requires C, 82.22; H, 6.49; N,

11.28%); ν_max(KBr)/cm^Ϫ13430 (NH) and 1625; δ_H2.36 (3H, s,

CH₃), 3.14 (3H, d, J 4.0, NCH₃), 5.04 (1H, br s, NH), 7.15–7.55

(7H, m, ArH) and 8.04–8.20 (2H, m, ArH); δ_C21.64 (CH₃),

28.60 (NCH₃), 106.33 (C-4), 117.49 (C-8a), 120.51, 126.45,

127.23, 127.72, 128.26, 131.32, 135.13 (C-7), 135.67 (C-4a),

140.24 (C-1Љ), 147.80 (C-3) and 154.71 (C-1); m/z 248 (M^ϩ,

100%), 247 (62, M^ϩϪ 1) and 218 (32, M^ϩϪ CH₃NH).

3-Phenyl-1-(cyclohexylamino)isoquinoline 7e. Colourless

needles (57% yield); mp 116–117 ЊC (Found: C, 83.23; H, 7.30;

N, 9.22%. C₂₁H₂₂N₂requires C, 83.40; H, 7.33; N, 9.26%);

ν_max(KBr)/cm^Ϫ13470 (NH) and 1630; δ_H1.00–2.20 [10H, m,

(CH₂)₅], 4.28 (1H, br s, CH), 5.00 (1H, d, J 4.0, NH), 7.04–7.84

(8H, m, ArH) and 8.02–8.16 (2H, m, ArH); δ_C25.14 (CH₂),

26.02 (CH₂), 33.19 (CH₂), 49.66 (CH), 106.08 (C-4), 117.20,

121.10, 125.24, 126.50, 127.53, 127.87, 128.31, 129.33, 137.95,

140.24, 148.87 (C-3) and 153.74 (C-1); m/z 302 (M^ϩ, 21%), 220

(100, M^ϩϪ C₆H₁₁ϩ 1) and 204 (14, M^ϩϪ C₆H₁₁NH).

3-Phenyl-1-(methylamino)isoquinoline 7f. Colourless crystals

(40% yield); mp 105–106 ЊC (Found: C, 82.30; H, 6.15; N,

12.01%. C₁₆H₁₄N₂requires C, 82.02; H, 6.02; N, 11.96%);

ν_max(KBr)/cm^Ϫ13475 (NH) and 1625; δ_H3.18 (3H, d, J 4.0,

NCH₃), 5.12 (1H, br s, NH), 7.08–7.72 (8H, m, ArH) and

8.00–8.28 (2H, m, ArH); δ_C28.65 (CH₃), 106.47 (C-4), 117.44

(C-8a), 121.24 (C-5), 125.38 (C-2Ј), 126.60 (C-4Ј), 127.53 (C-7),

127.96 (C-8), 128.35 (C-3Ј), 129.48 (C-6), 137.76 (C-3a), 140.20

(C-1Ј), 148.87 (C-3) and 155.21 (C-1); m/z 234 (M^ϩ, 100%), 233

(58, M^ϩϪ 1) and 204 (76, M^ϩϪ CH₃NH).

Cycloaddition of carbodiimide 3 with tetracyanoethylene

(TCNE). General procedure

A solution of carbodiimide 3 (2.0 mmol) and TCNE (2.2

mmol) in acetonitrile (10 cm³) was stirred at room temperature

for 1–11 h. Removal of the solvent in vacuo and column chrom-

atography of the residue on silica gel using CH₂Cl₂–hexane as

an eluent aﬀorded the cycloadduct 8 and/or its isomer 9 as

yellow needles or ﬁne crystals after recrystallization from

CH₂Cl₂–Et₂O–hexane. In the case of carbodiimide 3j, neither

compound 8j nor compound 9j was obtained due to the low

reactivity of 3j under the conditions.

3,3,4,4-Tetracyano-5,6-diphenyl-2-(phenylimino)-2,3,4,5-

tetrahydropyridine 8a. (25% yield) mp 162 ЊC (decomp.)

(Found: C, 76.34; H, 3.91; N, 19.95%. C₂₇H₁₆N₆requires C,

76.40; H, 3.80; N, 19.80%); ν_max(KBr)/cm^Ϫ12240 (CN) and 1585

(C᎐N); δ_H(100 MHz) 4.84 (1H, s, CH) and 7.12–7.88 (15H, m,

᎐

PhH); δ_C(25 MHz) 28.47 (C-5), 84.36, 108.55 (CN), 108.73,

111.49, 114.19, 117.36, 126.70, 129.28, 129.40, 129.69, 130.04,

130.16, 130.51, 130.69, 131.39, 131.92, 132.04, 135.74, 170.03

(C-6) and 180.83 (C-2); m/z 424 (M^ϩ, 2%), 397 (67, M^ϩϪ

HCN) and 77 (100, Ph^ϩ).

7-Methyl-3-phenyl-1-(phenylamino)isoquinoline 7g. Colour-

less needles (73% yield); mp 118 ЊC (Found: C, 85.46; H, 5.77;

N, 9.16%. C₂₂H₁₈N₂requires C, 85.13; H, 5.85; N, 9.02%);

ν_max(KBr)/cm^Ϫ13450 (NH) and 1630; δ_H2.40 (3H, s, CH₃) and

6.90–8.20 (15H, m, ArH and NH); m/z 310 (M^ϩ, 73%), 309

(100, M^ϩϪ 1) and 295 (3, M^ϩϪ CH₃).

3,3,4,4-Tetracyano-5,6-diphenyl-2-(phenylamino)-3,4-

dihydropyridine 9a. (41% yield) mp 183 ЊC (decomp.) ν_max(KBr)/

cm^Ϫ13430 (NH), 2240 (CN) and 1670 (C᎐N); δ 6.65–7.55

᎐

H

7-Methyl-3-phenyl-1-(p-tolylamino)isoquinoline 7h. Colour-

less needles (70% yield); mp 112–114 ЊC (Found: C, 84.99; H,

6.25; N, 8.71%. C₂₃H₂₀N₂requires C, 85.14; H, 6.21; N, 8.64%);

ν_max(KBr)/cm^Ϫ13460 (NH) and 1640; δ_H2.32 (3H, s, CH₃), 2.42

(3H, s, CH₃), 6.92 (1H, br s, NH) and 7.0–8.12 (13H, m, ArH);

δ_C20.76 (CH₃), 21.83 (CH₃), 108.57 (C-4), 117.73 (C-8a),

119.78, 120.22, 126.50, 127.58, 127.87, 128.35, 129.13, 131.32,

131.62, 135.86, 136.15, 138.01, 139.85 (C-1Ј), 147.60 (C-3) and

150.92 (C-1); m/z 324 (M^ϩ, 81%), 323 (100, M^ϩϪ 1) and 218 (5,

M^ϩϪ TolNH).

7-Methyl-3-phenyl-1-(p-methoxyphenylamino)isoquinoline 7i.

Colourless needles (73% yield); mp 107 ЊC (Found: C, 81.40;

H, 5.95; N, 8.33%. C₂₃H₂₀N₂O requires C, 81.14; H, 5.92; N,

8.23%); ν_max(KBr)/cm^Ϫ13450 (NH) and 1635; δ_H2.30 (3H, s,

CH₃), 3.66 (3H, s, OCH₃), 6.70–7.76 (12H, m, ArH and NH)

and 7.89–8.33 (2H, m, ArH); m/z 340 (M^ϩ, 100%), 339 (47,

M^ϩϪ 1), 325(70, M^ϩϪ CH₃) and218 (23, M^ϩϪ CH₃OPhNH).

7-Methyl-3-phenyl-1-(p-chlorophenylamino)isoquinoline 7j.

Colourless crystals (42% yield); mp 150 ЊC (Found: C, 76.74;

H, 4.98; N, 8.16%. C₂₂H₁₇N₂Cl requires C, 76.62; H, 4.97; N,

8.13%); ν_max(KBr)/cm^Ϫ13460 (NH) and 1630; δ_H2.50 (3H, s,

CH₃), 7.00 (1H, br s, NH), 7.16–7.80 (11H, m, ArH) and 7.90–

8.08 (2H, m, ArH); m/z 344 (³⁵Cl) (M^ϩ, 90%), 343 (100, M^ϩϪ 1)

and 307 (12).

(16H, m, PhH, NH); δ_C88.12, 92.82, 109.55, 113.13, 115.25,

116.48, 122.06, 123.58, 124.11, 127.22, 128.34, 129.16, 129.52,

129.92, 130.69, 132.33, 133.63, 135.39, 137.27, 144.60, 152.41

and 164.50; m/z 424 (M^ϩ, 1%), 396 (76, M^ϩϪ HCN Ϫ 1) and 77

(100, Ph^ϩ).

3,3,4,4-Tetracyano-5,6-diphenyl-2-(p-tolylimino)-2,3,4,5-

tetrahydropyridine 8b. (71% yield) mp 198 ЊC (decomp.) (Found:

C, 76.43; H, 4.18; N, 19.54%. C₂₈H₁₈N₆requires C, 76.69; H,

4.14; N, 19.17%); ν_max(KBr)/cm^Ϫ12235 (CN) and 1585; δ_H2.36

(3H, s, CH₃), 4.76 (1H, s, CH) and 7.12–7.88 (14H, m, PhH);

δ_C21.44 (CH₃), 28.41 (C-5), 84.25, 108.52 (CN), 108.77 (CN),

126.67, 127.33, 127.87, 129.23, 130.15, 130.45, 130.84, 130.93,

131.42, 131.81, 135.61, 142.63, 170.08 (C-6) and 180.69 (C-2);

m/z 438 (M^ϩ, vw), 411 (50%, M^ϩϪ HCN) and 77 (100, Ph^ϩ).

3,3,4,4-Tetracyano-5,6-diphenyl-2-(p-methoxyphenylimino)-

2,3,4,5-tetrahydropyridine 8c. (63% yield) mp 202 ЊC (decomp.)

(Found: C, 74.03; H, 4.00; N, 18.55%. C₂₈H₁₈N₆O requires C,

73.99; H, 3.99; N, 18.49%); ν_max(KBr)/cm^Ϫ12230 (CN) and 1590

(C᎐N); δ_H3.78 (3H, s, OCH₃), 4.87 (1H, s, 5-H) and 6.88–7.92

᎐

(14H, m, ArH); δ_C28.41 (C-5), 55.60 (OCH₃), 84.30, 108.67,

108.86, 111.74, 114.42 (CN), 115.10, 115.64, 122.70, 126.70,

127.38, 129.23, 130.06, 130.45, 130.69, 130.89, 131.38, 131.81,

135.67, 161.98, 170.46 (C-6) and 180.93 (C-2); m/z 454 (M^ϩ, vw)

and 427 (100%, M^ϩϪ HCN).

3074

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

View Article Online

3,3,4,4-Tetracyano-5,6-diphenyl-2-(p-chlorophenylimino)-

2,3,4,5-tetrahydropyridine 8d. (60% yield) mp 190 ЊC (decomp.)

(Found: C, 70.55; H, 3.41; N, 18.44%. C₂₇H₁₅N₆Cl requires C,

70.65; H, 3.30; N, 18.32%); ν_max(KBr)/cm^Ϫ12230 (CN) and 1580

3,3,4,4-Tetracyano-6-phenyl-5-(p-tolyl)-2-(methylimino)-

2,3,4,5-tetrahydropyridine 8l. (67% yield) mp 174–176 ЊC

(decomp.) (Found: C, 72.98; H, 4.31; N, 22.51%. C₂₃H₁₆N₆

requires C, 73.39; H, 4.28; N, 22.33%); ν_max(KBr)/cm^Ϫ12240

(C᎐N); δ 4.96 (1H, s, 5-H) and 7.00–7.88 (14H, m, ArH); δ_C

(CN) and 1590 (C᎐N); δ 2.37 (3H, s, CH ), 3.16 (3H, s, NCH ),

᎐

H 3 3

᎐

H

28.60 (C-5), 84.40, 108.57, 108.67, 111.59, 114.08, 126.65,

127.04, 129.18, 129.33, 129.76, 130.45, 130.60, 131.08, 131.38,

132.06, 135.86, 138.29, 170.07 (C-6) and 181.03 (C-2); m/z

458 (³⁵Cl) (M^ϩ, vw), 431 (97%, M^ϩϪ HCN) and 430 (100,

M^ϩϪ HCN Ϫ 1).

4.38 (1H, s, 5-H) and 7.2–7.85 (9H, m, ArH); δ_C20.71 (CH₃),

29.73 (NCH_3,C-5), 84.99, 95.41, 115.00, 115.44, 126.55, 127.04,

127.23, 129.09, 130.06, 130.54, 135.03, 140.87, 169.53 (C-6) and

183.45 (C-2); m/z 376 (M^ϩ, 3%), 349 (76, M^ϩϪ HCN) and 348

(100, M^ϩϪ HCN Ϫ 1).

3,3,4,4-Tetracyano-5,6-diphenyl-2-(cyclohexylimino)-2,3,4,5-

tetrahydropyridine 8e. (60% yield) mp 200 ЊC (decomp.)

(Found: C, 75.30; H, 5.22; N, 19.61%. C₂₇H₂₂N₆requires C,

75.33; H, 5.15; N, 19.52%); ν_max(KBr)/cm^Ϫ12230 (CN) and 1580

Cycloaddition of carbodiimides 3 with tosyl isocyanate. General

procedure

Method A. A benzene solution (20 cm³) of 3 (2.0 mmol) and

tosyl isocyanate (3.0 mmol) was heated under reﬂux for 15–30

h. Evaporation of the solvent and column chromatography of

the residue on silica gel using benzene–CH₂Cl₂(10:1–2:1) as an

eluent, followed by recrystallization from benzene–hexane gave

oxazine 10.

(C᎐N); δ 0.88–2.00 [10H, m, (CH ) ], 3.36 (1H, br s, CH), 5.18

᎐

H

2 5

(1H, s, 5-H) and 7.24–7.60 (10H, m, ArH); δ_C23.20, 25.49,

28.99, 31.09, 56.58, 85.10, 108.42, 109.20, 115.73, 117.44,

168.61 and 179.86 (C-2); m/z 430 (M^ϩ, 2%), 403 (33, M^ϩϪ

HCN) and 321 (100, M^ϩϪ CN Ϫ C₆H₁₁).

3,3,4,4-Tetracyano-5,6-diphenyl-2-(methylimino)-2,3,4,5-

tetrahydropyridine 8f. (69% yield) mp 187 ЊC (decomp.)

(Found: C, 72.50; H, 3.98; N, 23.55%. C₂₂H₁₄N₆requires C,

72.91; H, 3.89; N, 23.19%); ν_max(KBr)/cm^Ϫ12225 (CN) and 1600

Method B. A mixture of 3 (2.0 mmol) and tosyl isocyanate

(3.0 mmol) in dry acetonitrile (20 cm³) was stirred at room

temperature for 5 d (for R¹= cyclohexyl) or 10–17 d (for

R¹= aryl). The solvent was removed in vacuo and the residue

was column-chromatographed [silica gel, benzene–CH₂Cl₂as

eluent] gave crude pyrimidine 11, which was recrystallised from

benzene–hexane.

4,5-Diphenyl-2-(phenylamino)-6-(tosylimino)-6H-1,3-oxazine

10a. Colourless crystals (12% yield); mp 204–206 ЊC (Found: C,

70.65; H, 4.72; N, 8.51%. C₂₉H₂₃N₃O₃S requires C, 70.58; H,

4.70; N, 8.52%); ν_max(KBr)/cm^Ϫ13380 (NH) 1600 and

(C᎐N); δ_H(DMSO-d₆–CDCl₃) 3.24 (3H, s, NCH₃), 4.54 (1H, s,

᎐

5-H) and 7.28–7.84 10H, m, PhH); δ_C(DMSO-d₆–CDCl₃) 30.53

(NCH_3,C-5), 84.07, 126.70, 127.17, 128.81, 129.05, 130.39,

130.69, 130.92, 131.33, 135.15 and 182.06 (C-2); m/z 362 (M^ϩ,

1%), 335 (73, M^ϩϪ HCN) and 334 (100, M^ϩϪ HCN Ϫ 1).

3,3,4,4-Tetracyano-6-phenyl-5-(p-tolyl)-2-(phenylimino)-

2,3,4,5-tetrahydropyridine 8g. (62% yield) mp 135 ЊC (decomp.)

(Found: C, 76.86; H, 3.92; N, 19.22%. C₂₈H₁₈N₆requires C,

76.69; H, 4.14; N, 19.17%); ν_max(KBr)/cm^Ϫ12220 (CN) and 1580

1520 (C᎐N); δ (100 MHz) 2.37 (3H, s, CH ), 7.66 (2H, d, J 8.5)

᎐

H

3

and 6.95–7.57 (18H, m, ArH and NH); δ_C(25 MHz) 21.69

(CH₃), 114.39, 119.55, 123.00, 127.50, 127.84, 128.18, 128.42,

128.91, 129.25, 129.50, 129.69, 130.91, 132.57, 134.08, 137.54,

(C᎐N); δ 2.36 (3H, s, CH₃), 5.18 (1H, s, 5-H) and 6.92–7.96

᎐

H

(14H, m, ArH); δ_C21.34 (CH₃), 28.60 (C-5), 84.45, 108.72,

108.86, 111.64, 114.42 (CN), 126.60, 126.70, 129.18, 129.43,

129.67, 131.08, 131.38, 133.86, 135.67, 141.02, 142.53, 144.83,

170.07 (C-6) and 181.22 (C-2); m/z 438 (M^ϩ, vw), 411 (97%,

M^ϩϪ HCN) and 410 (100, M^ϩϪ HCN Ϫ 1).

3,3,4,4-Tetracyano-6-phenyl-5-(p-tolyl)-2-(p-tolylimino)-

2,3,4,5-tetrahydropyridine 8h. (60% yield) mp 163–166 ЊC

(decomp.) (Found: C, 76.96; H, 4.59; N, 18.88%. C₂₉H₂₀N₆

requires C, 76.97; H, 4.46; N, 18.57%); ν_max(KBr)/cm^Ϫ12230

138.80, 145.04, 157.81, 162.44 (C᎐N) and 168.63 (C᎐N);

᎐

m/z 493 (M^ϩ, 100%), 428 (43, M^ϩϪ SO₂H) and 338 (79,

M^ϩϪ Ts).

4,5-Diphenyl-2-(p-tolylamino)-6-(tosylimino)-6H-1,3-oxazine

10b. Colourless crystals (18% yield); mp 240–242 ЊC (Found: C,

71.11; H, 5.01; N, 8.22%. C₃₀H₂₅N₃O₃S requires C, 70.99; H,

4.97; N, 8.28%); ν_max(KBr)/cm^Ϫ13400 (NH) 1600 and 1520

(C᎐N); δ 2.34 (3H, s, CH₃), 2.41 (3H, s, CH₃) and 6.99–7.81

᎐

H

(CN) and 1590 (C᎐N); δ_H2.36 (3H, s, CH₃), 2.46 (3H, s, CH₃),

(19H, m, ArH and NH); δ_C20.90 (CH₃), 21.70 (CH₃), 119.80,

125.94, 126.47, 127.45, 127.84, 128.18, 128.42, 129.25, 129.45,

129.64, 129.93, 130.91, 131.20, 132.62, 134.13, 136.22, 137.64,

145.00, 158.00 (C᎐N) and 168.44 (C᎐N); m/z 507 (M^ϩ, 100%),

᎐

4.78 (1H, s, 5-H) and 6.86–7.88 (13H, m, ArH); δ_C21.39 (CH₃),

28.49 (C-5), 84.30, 108.67, 108.86, 111.69, 114.42, 126.60,

126.89, 127.43, 127.96, 128.31, 129.18, 130.84, 131.03, 131.38,

135.56, 142.53, 170.07 (C-6) and 180.98 (C-2); m/z 452 (M^ϩ, vw)

and 425 (100%, M^ϩϪ HCN).

3,3,4,4-Tetracyano-6-phenyl-5-(p-tolyl)-2-(p-methoxyphenyl-

imino)-2,3,4,5-tetrahydropyridine 8i. (60% yield) mp 163 ЊC

(decomp.) (Found: C, 73.92; H, 4.21; N, 18.35%. C₂₉H₂₀N₆O

requires C, 74.34; H, 4.30; N, 17.94%); ν_max(KBr)/cm^Ϫ12220

᎐

442 (28, M^ϩϪ SO₂H) and 352 (92, M^ϩϪ Ts).

2-(p-Methoxyphenylamino)-4,5-diphenyl-6-(tosylimino)-6H-

1,3-oxazine 10c. Pale yellow crystals (20% yield); mp 220–

222 ЊC (Found: C, 68.85; H, 4.82; N, 8.12%. C₃₀H₂₅N₃O₄S

requires C, 68.82; H, 4.81; N, 8.03%); ν_max(KBr)/cm^Ϫ13400

(NH) 1600 and 1510 (C᎐N); δ 2.36 (3H, s, CH₃), 3.80 (3H, s,

᎐

H

(CN) and 1590 (C᎐N); δ 2.46 (3H, s, CH ), 3.78 (3H, s, OCH ),

OCH₃), 6.83 (2H, d, J 8.1), 6.92–7.45 (15H, m, ArH and NH)

and 7.62 (2H, d, J 8.1); δ_C21.68 (CH₃), 55.56 (CH₃), 114.19,

121.84, 127.84, 128.18, 128.47, 128.76, 129.20, 129.45, 129.64,

131.00, 131.93, 132.71, 134.13, 137.68, 144.95, 155.91, 158.20,

162.54 (C᎐N) and 168.63 (C᎐N); m/z 523 (M^ϩ, 22%), 458 (4,

᎐

H

3

4.82 (1H, s, 5-H), 6.88–7.92 (13H, m, ArH); δ_C21.34 (CH₃),

28.41 (C-5), 55.56 (OCH₃), 84.21, 108.72, 108.87, 111.79,

114.47, 114.95 (C-3Ј), 122.75, 126.55, 126.84, 129.13, 130.69,

130.84, 130.99, 131.32, 135.52, 142.39, 161.88, 170.36 (C-6) and

180.98 (C-2); m/z 468 (M^ϩ, vw), 441 (100%, M^ϩϪ HCN) and

(90, M^ϩϪ HCN Ϫ 1).

3,3,4,4-Tetracyano-6-phenyl-5-(p-tolyl)-2-(cyclohexylimino)-

2,3,4,5-tetrahydropyridine 9k. (67% yield) mp 97–99 ЊC

(decomp.) (Found: C, 75.25; H, 5.40; N, 19.05%. C₂₈H₂₄N₆

requires C, 75.65; H, 5.44; N, 18.91%); ν_max(KBr)/cm^Ϫ13250

(NH), 2220 (CN) and 1580; δ_H1.0–2.0 [10H, (CH₂)₅], 2.44 (3H,

s, CH₃), 3.38 (1H, br s, CH), 6.14 (1H, br s, NH) and 7.16–7.76

(9H, m, ArH); δ_C21.83 (CH₃), 24.46 (CH₂), 24.75 (CH₂), 32.94

(CH₂), 53.90 (CH), 111.93, 115.00, 115.20, 128.35, 128.98,

129.33, 129.76, 130.45, 132.45, 134.44, 145.70, 167.77, 168.02

(C-6) and 168.94 (C-2); m/z 444 (M^ϩ, 16), 417 (16, M^ϩϪ HCN),

335 (47) and 55 (100).

᎐

M^ϩϪ SO₂H) and 91 (100, Ph^ϩ).

2-(Cyclohexylamino)-4,5-diphenyl-6-(tosylimino)-6H-1,3-

oxazine 10d. Slightly yellowish crystals (40% yield); mp 176–

178 ЊC (Found: C, 69.47; H, 5.78; N, 8.40%. C₂₉H₂₉N₃O₃S

requires C, 69.72; H, 5.85; N, 8.41%); ν_max(KBr)/cm^Ϫ1

3400 (NH) 1605 and 1550 (C᎐N); δ_H1.0–2.2 [10H, m, (CH₂)₅],

᎐

2.44 (3H, s, CH₃), 3.62 (1H, br s, CH), 5.20 (1H, d, J 8.0, NH),

6.8–7.4 12H, m, ArH) and 7.80 (2H, d, J 8.0, ArH); δ_C21.64

(CH₃), 24.76 (CH₂), 25.64 (CH₂), 32.95 (CH₂), 49.66 (CH),

111.90, 127.11, 127.74, 128.03, 128.23, 128.91, 129.45,

131.06, 131.35, 133.05, 138.03, 144.75, 159.91, 162.78 and

168.58; m/z 499 (M^ϩ, 20), 416 (16, M^ϩϪ c-Hex) and 344 (100,

M^ϩϪ Ts).

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

3075

View Article Online

4-Phenyl-5-(p-tolyl)-2-(p-tolylamino)-6-(tosylimino)-6H-1,3-

oxazine 10e. Colourless crystals (18% yield); mp 202–205 ЊC

(Found: C, 71.45; H, 5.20; N, 8.15%. C₃₁H₂₇N₃O₃S requires C,

71.39; H, 5.22; N, 8.06%) ν_max(KBr)/cm^Ϫ13400 (NH) 1595 and

(Found: C, 71.15; H, 5.05; N, 8.15%. C₃₀H₂₅N₃O₃S requires C,

70.99; H, 4.97; N, 8.28%); ν_max(KBr)/cm^Ϫ13350 (NH) 1680

(CO) and 1540 (C᎐N); δ_H2.25 (3H, s, CH₃), 2.43 (3H, s, CH₃),

᎐

6.90–7.70 (16H, m, ArH), 8.05 (2H, d, J 8.0) and 9.95 (1H, s,

NH); δ_C21.20 (CH₃), 21.74 (CH₃), 116.14, 122.28, 124.77,

127.60, 128.86, 129.11, 129.50, 129.93, 130.57, 130.96, 136.08,

1530 (C᎐N); δ 2.30 (3H, s, CH ), 2.33 (3H, s, CH ), 2.39 (3H, s,

᎐

H

3

CH₃) and 6.86–7.78 (18H, m, ArH and NH); δ_C20.81 (CH₃),

21.25 (CH₃), 21.64 (CH₃), 114.05, 119.80, 126.38, 127.84,

128.42, 128.91, 129.40, 129.59, 130.67, 132.47, 134.08, 136.22,

136.86, 137.49, 137.64, 146.12, 146.26, 158.15 (C᎐N) and

᎐

161.76 (CO); m/z 507 (M^ϩ, 10%), 442 (3, M^ϩϪ SO₂H) and 104

(100).

137.10, 137.59, 143.39, 144.95, 157.81, 162.54 (C᎐N) and

᎐

168.53 (C᎐N); m/z 521 (M^ϩ, 4%), 388 (85, M^ϩϪ TolNCO) and

6-Phenyl-3,5-di-p-tolyl-2-(tosylimino)-2,3-dihydropyrimidin-

4(1H)-one 11f. Colourless crystals (36% yield); mp 182–183 ЊC

(Found: C, 71.44; H, 5.25; N, 8.12%. C₃₁H₂₇N₃O₃S requires C,

71.39; H, 5.22; N, 8.06%) ν_max(KBr)/cm^Ϫ13350 (NH) 1680 (CO)

᎐

323 (100).

2-(Cyclohexylamino)-4-phenyl-5-(p-tolyl)-6-(tosylimino)-6H-

1,3-oxazine 10f. Colourless crystals (48% yield); mp 215–216 ЊC

(Found: C, 70.25; H, 6.09; N, 8.22%. C₃₀H₃₁N₃O₃S requires C,

70.16; H, 6.08; N, 8.18%); ν_max(KBr)/cm^Ϫ13450 (NH) and 1525

and 1540 (C᎐N); δ 2.23 (3H, s, CH₃), 2.35 (3H, s, CH₃), 2.43

᎐

H

(3H, s, CH₃), 6.95–7.67 (15H, m, ArH), 8.05 (2H, d, J 8.0) and

9.84 (1H, s, NH); δ_C20.89 (CH₃), 21.18 (CH₃), 21.70 (CH₃),

119.93, 122.45, 127.59, 128.82, 129.12, 129.47, 130.05, 130.29,

130.46, 131.10, 134.56, 135.14, 136.55, 136.78, 137.95, 146.00,

(C᎐N); δ 1.0–2.2 [10H, m, (CH ) ], 2.23 (3H, s, CH ), 2.46 (3H,

᎐

H

2

5

3

s, CH₃), 3.64 (br s, CH), 5.22 (1H, d, J 8.0, NH), 6.90–7.40

(11H, m, ArH) and 7.83 (2H, d, J 8.0); δ_C21.20 (CH₃), 21.64

(CH₃), 24.76 (CH₂), 25.64 (CH₂), 32.95 (CH₂), 49.66 (CH),

111.90, 126.33, 127.69, 128.23, 128.81, 129.40, 129.50, 129.84,

146.61, 158.31 (C᎐N) and 161.81 (CO); m/z 521 (M^ϩ, 100%),

᎐

456 (24, M^ϩϪ SO₂H) and 366 (83, M^ϩϪ Ts).

130.81, 135.10, 136.71, 138.12, 144.65, 159.81, 162.88 (C᎐N)

3-(p-Methoxyphenyl)-6-phenyl-5-(p-tolyl)-2-(tosylimino)-2,3-

dihydropyrimidin-4(1H)-one 11g. Colourless crystals (35%

yield); mp 175–176 ЊC (Found: C, 69.25; H, 5.10; N, 7.85%.

C₃₁H₂₇N₃O₄S requires C, 69.26; H, 5.06; N, 7.82%) ν_max(KBr)/

cm^Ϫ13350 (NH) 1680 (CO) and 1550 (C᎐N); δ 2.24 (3H, s,

᎐

and 168.58 (C᎐N); m/z 513 (M^ϩ, 100%).

᎐

3,5,6-Triphenyl-2-(tosylimino)-2,3-dihydropyrimidin-4(1H)-

one 11a. Colourless crystals (33% yield); mp 202–204 ЊC

(Found: C, 70.60; H, 4.71; N, 8.55%. C₂₉H₂₃N₃O₃S requires C,

70.58; H, 4.70; N, 8.52%); ν_max(KBr)/cm^Ϫ13340 (NH) 1680

᎐

H

CH₃), 2.42 (3H, s, CH₃), 3.80 (3H, s, OCH₃), 6.85–7.36 (11H, m,

ArH), 6.86 (2H, d, J 8.0), 7.54 (2H, d, J 8.0), 8.01 (2H, d, J 8.0)

and 9.76 (1H, s, NH); δ_C21.23 (CH₃), 21.77 (CH₃), 55.49 (CH₃),

114.02, 124.21, 127.56, 128.85, 129.06, 129.47, 129.94, 130.35,

130.69, 130.97, 136.08, 136.77, 137.72, 146.05, 146.80, 146.00,

(CO) and 1550 (C᎐N); δ (100 MHz) 2.40 (3H, s, CH₃), 6.96–

᎐

H

7.78 (16H, m, ArH), 8.00 (2H, d, J 8.0) and 9.87 (1H, s, NH); δ_C

(25 MHz) 21.82 (CH₃), 116.13, 122.33, 124.85, 127.19, 127.59,

128.06, 128.88, 129.06, 129.53, 129.93, 131.16, 133.68, 136.08,

137.42, 137.54, 146.14, 146.37, 158.48 (C᎐N) and 161.58

156.90, 158.34 (C᎐N) and 161.75 (CO); m/z 537 (M^ϩ, 100%),

᎐

(CO); m/z 493 (M^ϩ, 100%), 428 (37, M^ϩϪ SO₂H) and 338 (43,

472 (7, M^ϩϪ SO₂H) and 382 (62, M^ϩϪ Ts).

M^ϩϪ Ts).

3-Cyclohexyl-6-phenyl-5-(p-tolyl)-2-(tosylimino)-2,3-dihydro-

pyrimidin-4(1H)-one 11h. Colourless crystals (35% yield); mp

190–192 ЊC (Found: C, 70.23; H, 6.15; N, 8.25%. C₃₀H₃₁N₃O₃S

requires C, 70.16; H, 6.08; N, 8.18%) ν_max(KBr)/cm^Ϫ13400

5,6-Diphenyl-3-(p-tolyl)-2-(tosylimino)-2,3-dihydropyrimidin-

4(1H)-one 11b. Colourless crystals (37% yield); mp 241–242 ЊC

(Found: C, 71.05; H, 5.00; N, 8.33%. C₃₀H₂₅N₃O₃S requires C,

70.99; H, 4.97; N, 8.28%); ν_max(KBr)/cm^Ϫ13350 (NH) 1670

(NH) 1690 (CO) and 1555 (C᎐N); δ_H1.2–2.3 [10H, m, (CH₂)₅],

᎐

(CO) and 1540 (C᎐N); δ_H2.35 (3H, s, CH₃), 2.41 (3H, s, CH₃),

2.24 (3H, s, CH₃), 2.42 (3H, s, CH₃), 4.12 (1H, br s, CH), 6.78–

7.78 (11H, m, ArH), 7.94 (2H, d, J 8.1, ArH) and 7.90 (1H, s,

NH); δ_C21.20 (CH₃), 21.73 (CH₃), 24.46 (CH₂), 25.73 (CH₂),

32.36 (CH₂), 50.53 (CH), 113.39, 127.43, 128.26, 128.65,

128.79, 129.33, 129.82, 131.08, 136.34, 136.45, 138.25, 145.61,

᎐

6.90–7.60 (16H, m, ArH) 7.95 (2H, d, J 8.0) and 9.86 (1H, s,

NH); δ_C20.94 (CH₃), 21.96 (CH₃), 115.78, 122.39, 127.13,

127.59, 128.00, 129.06, 129.41, 129.53, 129.99, 131.22, 134.56,

134.79, 136.14, 137.60, 146.08, 146.61, 158.66 (C᎐N) and

᎐

161.64 (CO); m/z 507 (M^ϩ, 83%), 442 (29, M^ϩϪ SO₂H) and 91

148.48, 159.00 (C᎐N) and 161.83 (CO); m/z 513 (M^ϩ, 31) and

᎐

(100, Tol^ϩ).

358 (100, M^ϩϪ Ts).

3-(p-Methoxyphenyl)-5,6-diphenyl-2-(tosylimino)-2,3-

dihydropyrimidin-4(1H)-one 11c. Pale yellow crystals (52%

yield); mp 217–219 ЊC (Found: C, 68.90; H, 4.88; N, 8.13%.

C₃₀H₂₅N₃O₄S requires C, 68.82; H, 4.81; N, 8.03%); ν_max(KBr)/

cm^Ϫ13350 (NH) 1680 (CO) and 1540 (C᎐N); δ 2.40 (3H, s,

CH₃), 3.78 (3H, s, OCH₃), 6.87 (2H, d, J 8.01), 6.85–7.36 (13H,

m, ArH), 7.54 (2H, d, J 8.01), 8.01 (2H, d, J 8.01) and 9.78 (1H,

s, NH); δ_C21.74 (CH₃), 55.46 (CH₃), 114.05, 124.23, 127.06,

127.55, 127.99, 129.01, 129.50, 129.93, 130.28, 131.20, 133.78,

Cycloaddition of carbodiimide 5 with tetracyanoethylene

(TCNE). General procedure

A solution of carbodiimide 5 (2.0 mmol) and TCNE (2.2

mmol) in acetonitrile (20 cm³) was stirred at room temperature

for 5–10 d until 5 had been consumed (monitored by TLC).

Removal of the solvent in vacuo and column chromatography

of the residue on silica gel using EtOAc–CH₂Cl₂–benzene as an

eluent, followed by recrystallization from EtOAc–CH₂Cl₂–

benzene aﬀorded pyridine 12. Compounds 12 are rather labile

and gradually deteriorate in a hot solution.

᎐

H

136.08, 137.59, 146.07, 146.94, 156.94, 158.69 (C᎐N) and

᎐

161.61 (CO); m/z 523 (M^ϩ, 100%), 458 (10, M^ϩϪ SO₂H) and

368 (77, M^ϩϪ Ts).

3-Cyclohexyl-5,6-diphenyl-2-(tosylimino)-2,3-dihydro-

pyrimidin-4(1H)-one 11d. Colourless crystals (45% yield); mp

183–185 ЊC (Found: C, 70.23; H, 6.20; N, 8.15%. C₃₀H₃₁N₃O₃S

requires C, 70.16; H, 6.08; N, 8.18%); ν_max(KBr)/cm^Ϫ13400

3,3,4,4-Tetracyano-6-phenyl-2-(phenylimino)-2,3,4,5-tetra-

hydropyridine 12a. Reddish crystals (45% yield); mp 260 ЊC

(decomp.) (Found: M^ϩ, 348.1124. C₂₁H₁₂N₆requires

M

348.1123; FAB-HRMS Found: M^ϩϩ1, 349.1220. C₂₁H₁₃N₆

requires M ϩ 1 349.1166); ν_max(KBr)/cm^Ϫ12230 and 1570;

δ_H(270 MHz, CDCl₃ϩDMSO-d₆) [NH-isomer] 7.50–7.81

(NH) 1690 (CO) and 1555 (C᎐N); δ_H1.2–2.3 [10H, m, (CH₂)₅],

᎐

2.24 (3H, s, CH₃), 2.42 (3H, s, CH₃), 4.12 (br s, CH), 6.78–7.78

(11H, m, ArH) and 7.94 (2H, d, J 8.1); δ_C21.20 (CH₃), 21.73

(CH₃), 24.46 (CH₂), 25.73 (CH₂), 32.36 (CH₂), 50.53 (CH),

113.39, 127.43, 128.26, 128.65, 128.79, 129.33, 129.82, 131.08,

(10H, m, ArH), 8.28 (1H, s, ᎐CH) and 11.37 (1H, s, NH);

᎐

δ_C(67.8 MHz, DEPT) 91.32 (C-5) , 109.81 (CN), 111.52 (CN),

126.90 (CH), 128.63 (CH), 130.05 (CH), 130.10 (CH), 131.33

(CH), 133.27 (CH), 136.48 (C), 159.89 (C) and 170.71 (C); m/z

348 (M^ϩ, 5%), 346 (96, M^ϩϪ 2) and 320 (100, M^ϩϪ 2 Ϫ CN).

3,3,4,4-Tetracyano-2-(phenylimino)-6-(p-tolyl)-2,3,4,5-tetra-

hydropyridine 12b. Reddish crystals (33% yield); mp 264 ЊC

(decomp.) (Found: C, 72.78; H, 3.81; N, 23.46%. M^ϩ, 362.1278.

136.34, 136.45, 138.25, 145.61, 148.48, 159.00 (C᎐N) and

᎐

161.83 (C᎐N); m/z 499 (M^ϩ, 17%), 416 (M^ϩϪ c-Hex) and 344

᎐

(100, M^ϩϪ Ts).

3,6-Diphenyl-5-(p-tolyl)-2-(tosylimino)-2,3-dihydropyrimidin-

4(1H)-one 11e. Colourless crystals (42% yield); mp 163–164 ЊC

3076

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

View Article Online

C₂₂H₁₄N₆requires C, 72.91; H, 3.89; N, 23.19%. M, 362.1282);

ν_max(KBr)/cm^Ϫ12220 and 1570; δ_H(100 MHz) 1.58 (2H, s, CH₂),

2.49 (3H, s, CH₃) and 7.05–7.85 (9H, m, ArH); m/z 362 (M^ϩ,

6%), 360 (100, M^ϩϪ 2) and 334 (56, M^ϩϪ 2 Ϫ CN).

3,3,4,4-Tetracyano-6-(p-tolyl)-2-(p-tolylimino)-2,3,4,5-tetra-

hydropyridine 12c. Reddish crystals (31% yield); mp 270 ЊC

(decomp.) (Found: C, 73.20; H, 4.22; N, 23.51%. M^ϩ, 376.1446.

C₂₃H₁₆N₆requires C, 73.39; H, 4.28; N, 22.33%. M, 376.1422);

ν_max(KBr)/cm^Ϫ12240 and 1570; δ_H1.56 (2H, s, CH₂), 2.48 (3H,

s, CH₃), 2.51 (3H, s, CH₃), 7.12–7.50 (6H, m, ArH) and 7.76–

7.78 (2H, m, ArH); m/z 376 (M^ϩ, 8%), 374 (100, M^ϩϪ 2) and

348 (58, M^ϩϪ 2 Ϫ CN).

3,3,4,4-Tetracyano-2-(cyclohexylimino)-6-(p-tolyl)-2,3,4,5-

tetrahydropyridine 12d. Reddish crystals (20% yield); mp 195 ЊC

(decomp.) (Found: C, 71.68; H, 5.44; N, 22.95%. M^ϩ, 368.1734.

C₂₂H₂₀N₆requires C, 71.72; H, 5.47; N, 22.81%. M, 368.1777);

ν_max(KBr)/cm^Ϫ12220 and 1560; δ_H1.05–2.8 [12H, m, CH₂,

(CH₂)₅], 2.46 (3H, s, CH₃), 4.62 (1H, br s, CH), 7.12–7.65 (4H,

m, ArH); m/z 368 (M^ϩ, 1%), 366 (6, M^ϩϪ 2) and 83 (100,

c-Hex^ϩ).

benzene as an eluent, followed by recrystallization from

CH₂Cl₂–benzene aﬀorded diazaindanedione 14 (yield in Table

1). Compound 14 is sparingly soluble in CDCl₃for ¹³C NMR

measurement.

2-(p-Methoxyphenyl)-6-phenyl-4-(phenylamino)-2,5-diaza-

indane-1,3-dione 14a. Orange solid; mp 245.3–246.5 ЊC

(decomp.) (Found: C, 74.29; H, 4.56; N, 9.90%. C₂₆H₁₉N₃O₃

requires C, 74.09; H, 4.54; N, 9.97%); ν_max(KBr)/cm^Ϫ13380

(NH) and 1710 (C᎐O); δ (270 MHz) 3.87 (3H, s, OMe), 7.0–

᎐

H

8.2 (14H, m, ArH), 7.70 (1H, s, 7-H) and 8.48 (1H, s, NH);

m/z 421 (M^ϩ, 100%), 299 (4, M^ϩϪ MeOC₆H₄N Ϫ H), 270 (4,

M^ϩϪ MeOC₆H₄NCO Ϫ 2H) and 243 (12, M^ϩϪ MeOC₆H₄-

NCOCO Ϫ H).

2-(p-Methoxyphenyl)-6-phenyl-4-(p-tolylamino)-2,5-diaza-

indane-1,3-dione 14b. Orange solid; mp 197.9–199.8 ЊC

(decomp.) (Found: C, 74.44; H, 4.98; N, 9.60%. C₂₇H₂₁N₃O₃

requires C, 74.47; H, 4.86; N, 9.65%); ν_max(KBr)/cm^Ϫ13388

(NH) and 1698 (C᎐O); δ_H2.36 (3H, s, Me), 3.85 (3H, s, OMe),

᎐

7.00–8.11 (13H, m, ArH), 7.63 (1H, s, 7-H) and 8.37 (1H, s,

NH); m/z 435 (M^ϩ, 100%), 313 (5, M^ϩϪ MeOC₆H₄N Ϫ H), 284

(5, M^ϩϪ MeOC₆H₄NCO Ϫ 2H) and 257 (14, M^ϩϪ MeO Ϫ

C₆H₄Ϫ NCOCO Ϫ H).

4-(Cyclohexylamino)-2-(p-methoxyphenyl)-6-phenyl-2,5-

diazaindane-1,3-dione 14c. Yellow needles; mp 199.5–200.2 ЊC

(decomp.) (Found: C, 73.33; H, 5.98; N, 9.80%. C₂₆H₂₅N₃O₃

requires C, 73.05; H, 5.90; N, 9.83%); ν_max(KBr)/cm^Ϫ13416

Cycloaddition of carbodiimide 5 with tosyl isocyanate. General

procedure

A solution of carbodiimide 5 (2.0 mmol) and tosyl isocyan-

ate (3.0 mmol) in acetonitrile (20 cm³) was stirred at room tem-

perature for 2–3 d until 5 had been consumed. Removal of the

solvent in vacuo, column chromatography of the residue (silica

gel, CH₂Cl₂–benzene as an eluent) and recrystallization

(CH₂Cl₂–benzene) aﬀorded 13.

(NH), 2936 (CH) and 1708 (C᎐O); δ 1.2–2.2 (10H, m,

᎐

H

c-HexH), 3.84 (3H, s, OMe), 4.29 (1H, m, c-HexH), 6.35 (1H,

d, J 7.92, NH), 7.01–8.12 (9H, m, ArH) and 7.48 (1H, s, 7-H);

δ_C(67.8 MHz, DEPT) 24.75 (C-3Љ), 25.70 (C-4Љ), 32.99

(C-2Љ), 49.26 (C-1Љ), 55.47 (MeO), 102.34 (C-7), 103.25

(C-3a), 114.43 (C-3Ј), 124.24 (C-1Ј), 127.49 (C-2Љ), 127.76

(C-2Ј), 128.77 (C-3ٞ), 130.40 (C-4ٞ), 138.47 (C-1ٞ), 142.35

3,6-Diphenyl-2-(tosylimino)-2,3-dihydropyrimidin-4(1H)-one

13a. Colourless crystals (45% yield), mp 161–163 ЊC (Found:

C, 66.29; H, 4.61; N, 10.01%. C₂₃H₁₉N₃O₃S requires C, 66.18;

H, 4.59; N, 10.07%); ν_max(KBr)/cm^Ϫ13350 (NH) 1700 (C᎐O)

᎐

(C-7a), 153.55 (C-4Ј), 159.16 (C-4), 163.83 (C-6), 167.15 (C᎐O)

᎐

and 1540 (C᎐N); m/z 417 (M^ϩ, 72%), 352 (44, M^ϩϪ SO H), 262

᎐

and 169.15 (C᎐O); m/z 427 (M^ϩ, 84%), 398 (6, M^ϩϪ CO Ϫ H),

2

᎐

(100, M^ϩϪ Ts) and 155 (9, Ts^ϩ).

384 (17, M^ϩϪ CO Ϫ Me), 370 (27, M^ϩϪ 2CO Ϫ H), 345 (100,

M^ϩϪ c-Hex ϩ H) and 257 (14, M^ϩϪ MeOC₆H₄).

6-Phenyl-3-(p-tolyl)-2-(tosylimino)-2,3-dihydropyrimidin-

4(1H)-one 13b. Colourless crystals (40% yield); mp 157–159 ЊC

(Found: C, 66.85; H, 4.99; N, 9.80%. C₂₄H₂₁N₃O₃S requires C,

66.81; H, 4.91; N, 9.74%) ν_max(KBr)/cm^Ϫ13350 (NH) 1695

2-(p-Methoxyphenyl)-4-(phenylamino)-6-(p-tolyl)-2,5-diaza-

indane-1,3-dione 14d. Orange solid; mp 288.6–289.7 ЊC

(decomp.) (Found: C, 74.62; H, 4.88; N, 9.65%. C₂₇H₂₁N₃O₃

requires C, 74.47; H, 4.86; N, 9.65%). ν_max(KBr)/cm^Ϫ13384

(C᎐O) and 1550 (C᎐N); δ (100 MHz) 2.37 (3H, s, CH₃), 2.42

᎐

H

(3H, s, CH₃), 6.15 (1H, s, 5-H), 7.1–8.0 (11H, m, ArH), 8.07

(2H, d, J 8.0) and 9.86 (1H, s, NH); δ_C(25 MHz) 20.94 (CH₃),

21.76 (CH₃), 99.86 (C-5), 122.86, 126.42, 127.19, 128.59,

128.82, 129.06, 129.41, 130.93 and 134.67, 134.91, 135.79,

(NH) and 1710 (C᎐O); δ_H2.45 (3H, s, Me), 3.87 (3H, s, OMe),

᎐

7.02–8.06 (13H, m, ArH), 7.68 (1H, s, 7-H) and 8.47 (1H, br s,

NH); m/z 435 (M^ϩ, 100%), 313 (5, M^ϩϪ MeOC₆H₄N Ϫ H), 284

(5, M^ϩϪ MeOC₆H₄NCO Ϫ 2H) and 257 (14, M^ϩϪ MeOC₆H₄-

NCOCO Ϫ H).

2-(p-Methoxyphenyl)-6-(p-tolyl)-4-(p-tolylamino)-2,5-

diazaindane-1,3-dione 14e. Orange solid; mp 226.4–227.2 ЊC

(decomp.) (Found: C, 74.90; H, 5.21; N, 9.40%. C₂₈H₂₃N₃O₃

requires C, 74.81; H, 5.16; N, 9.35%). ν_max(KBr)/cm^Ϫ13384

136.02, 146.26, 148.71, 160.53 (C᎐N) and 161.70 (CO); m/z

᎐

431(M^ϩ, 67%), 366 (44, M^ϩϪ SO₂H), 276 (99, M^ϩϪ Ts) and

155 (12, Ts^ϩ).

3-Phenyl-6-(p-tolyl)-2-(tosylimino)-2,3-dihydropyrimidin-

4(1H)-one 13c. Colourless crystals (40% yield); mp 157–159 ЊC

(Found: C, 66.95; H, 5.01; N, 9.70%. C₂₄H₂₁N₃O₃S requires C,

66.81; H, 4.91; N, 9.74%); ν_max(KBr)/cm^Ϫ13350 (NH) 1700

(NH) and 1704 (C᎐O); δ_H2.37 (3H, s, Me), 2.44 (3H, s, Me),

᎐

3.86 (3H, s, OMe), 7.03–8.02 (12H, m, ArH), 7.63 (1H, s, 7-H)

and 8.37 (1H, br s, NH); m/z 449 (M^ϩ, 100%), 327 (5, M^ϩϪ

MeOC₆H₄N Ϫ H), 298 (5, M^ϩϪ MeOC₆H₄NCO Ϫ 2H) and

271(14, M^ϩϪ MeOC₆H₄NCOCO Ϫ H).

4-(Cyclohexylamino)-2-(p-methoxyphenyl)-6-(p-tolyl)-2,5-

diazaindane-1,3-dione 14f. Yellow needles; mp 214.6–215.8 ЊC

(decomp.) (Found: C, 73.56; H, 6.21; N, 9.48%. C₂₇H₂₇N₃O₃

requires C, 73.45; H, 6.16; N, 9.52%). ν_max(KBr)/cm^Ϫ13420

(C᎐O) and 1550 (C᎐N); δ 2.35 (3H, s, CH ), 2.43 (3H, s, CH ),

᎐

H

3

6.17 (1H, s, 5-H), 7.03–8.23 (13H, m, ArH) and 9.96 (1H, s,

NH); δ_C21.41 (CH₃), 21.76 (CH₃), 99.57 (C-5), 122.80, 125.08,

127.19, 128.88, 129.06, 129.41, 132.98, 136.02 and 137.36,

141.52, 146.26, 148.36, 160.41 (C᎐N) and 161.64 (CO); m/z

᎐

431(M^ϩ, 88%), 367 (44, M^ϩϪ SO₂), 366 (52, M^ϩϪ SO₂H) and

276 (100, M^ϩϪ Ts).

(NH), 2932 (CH) and 1710 (C᎐O); δ 1.20–2.14 (10H, m, c-

᎐

H

Cycloaddition of carbodiimide 5 with N-(p-methoxyphenyl)-

maleimide (NPMI). General procedure

HexH), 2.43 (3H, s, Me), 3.85 (3H, s, OMe), 4.29 (1H, m, c-

HexH), 6.33 (1H, d, J 7.92, NH), 7.01–8.01 (8H, m, ArH) and

7.46 (1H, s, 7-H); m/z 441 (M^ϩ, 86%), 398 (6, M^ϩϪ CO Ϫ H),

398(17, M^ϩϪ CO Ϫ Me), 384 (22, M^ϩϪ 2CO Ϫ H), 359 (100,

M^ϩϪ c-Hex ϩ H) and 334 (10, M^ϩϪ MeOC₆H₄).

A solution of carbodiimide 5 (1.0 mmol) and NPMI (2.0

mmol) in the appropriate solvent (benzene, xylene and mesity-

lene; see Table 1) (20 cm³) was heated under reﬂux for 2–50 h in

the absence or presence of an additive [MnO₂(200 mg), S₈(50

mg) or nitrobenzene (2 cm³); with DDQ, the reaction mixture

was treated after the reaction]. Product 14 partially precipitated

on cooling. Evaporation of the solvent in vacuo and column

chromatography of the residue on silica gel using CH₂Cl₂–

Cycloaddition of carbodiimide 5 with dimethyl

acetylenedicarboxylate (DMAD). General procedure

Thermal reaction. A mixture of carbodiimide 5 (1.50 mmol)

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

3077

View Article Online

and DMAD (277 µl, 2.25 mmol) in toluene (25 cm³) was heated

under reﬂux for 3–9 h until 5 had been consumed. Removal of

the solvent in vacuo, column chromatography of the residue

[silica gel, EtOAc–hexane (20:1) as an eluent] and recrystalliz-

ation (CH₂Cl₂–hexane) aﬀorded pyridine 15 as needles (yields

in Table 2).

3.92 (3H, s, OMe), 7.15 (1H, s, 5-H), 7.16 (2H, d, J 8.25, ArH),

7.24 (2H, d, J 8.25, ArH), 7.61 (2H, d, J 8.25, ArH), 7.93 (2H,

d, J 8.25, ArH) and 9.84 (1H, br s, NH); δ_C20.86 (Me), 21.38

(Me), 52.54 (OMe), 52.76 (OMe), 101.78 (C-3), 108.05 (C-5),

121.11 (C-2Ј), 127.35 (C-2Љ), 129.22 (C-3Љ), 129.49 (C-3Љ),

132.50 (C-4Ј), 134.98 (C-1Љ), 136.94 (C-1Ј), 140.61 (C-4Љ),

Lewis acid-promoted reaction. To a CH₂Cl₂solution (15 cm³)

of DMAD (135–246 µl, 1.10–2.00 mmol) was successively

added a Lewis acid solution (AlCl₃, EtAlCl₂) (1.10–2.20 mmol)

and a CH₂Cl₂solution (15 cm³) of carbodiimide 5 (1.00 mmol)

with stirring at room temperature for 0.25–3 h. The reaction

was quenched with cold saturated aq. NH₄Cl (20 cm³) and the

mixture was extracted with CH₂Cl₂(20 cm₃× 3), washed with

aq. NaHCO₃and brine, and dried (MgSO₄). Work-up for the

puriﬁcation to give pyridine 15 was the same as described above

(yields in Table 2).

145.50 (C-4), 155.27 (C-2), 159.85 (C-6), 167.10 (C᎐O) and

᎐

168.98 (C᎐O); m/z 390 (M^ϩ, 100%), 358 (9, M^ϩϪ OMe Ϫ H)

᎐

and 272 (75, M^ϩϪ 2CO₂Me).

2-(Cyclohexylamino)-3,4-bis(methoxycarbonyl)-6-(p-tolyl)-

pyridine 15f. Yellow needles; mp 114.6–116.2 ЊC (Found: C,

68.96; H, 7.07; N, 7.12%. C₂₂H₂₆N₂O₄requires C, 69.09; H,

6.85; N, 7.33%); ν_max(KBr)/cm^Ϫ13368 (NH), 2928 (CH)

and 1744 (C᎐O); δ 1.23–2.16 (10H, m, c-HexH), 2.40 (3H, s,

᎐

H

Me), 3.83 (3H, s, OMe), 3.90 (3H, s, OMe), 4.23 (1H, m,

c-HexH), 6.94 (1H, s, 5-H), 7.26 (2H, d, J 8.25, p-TolH),

7.83 (1H, d, J 7.25, NH) and 7.94 (2H, d, J 8.25, p-TolH);

δ_C21.38 (Me), 24.82 (C-3Ј), 25.95 (C-4Ј), 32.83 (C-2Ј), 49.33

(C-1Ј), 52.15 (OMe), 52.63 (OMe), 99.84 (C-3), 105.52 (C-5),

127.15 (C-2Љ), 129.38 (C-3Љ), 135.40 (C-1Љ), 140.32 (C-4Љ),

3,4-Bis(methoxycarbonyl)-6-phenyl-2-(phenylamino)pyridine

15a. Yellow needles; mp 109.2–110.3 ЊC (Found: C, 69.82; H,

4.85; N, 7.53%, C₂₁H₁₈N₂O₄requires C, 69.60; H, 5.00; N,

7.73%) ν_max(KBr)/cm^Ϫ13284 (NH) and 1744 (C᎐O); δ (270

᎐

H

MHz) 3.89 (3H, s, OMe), 3.93 (3H, s, OMe), 7.08–8.03 (10H, m,

ArH), 7.21 (1H, s, 5-H) and 9.89 (1H, br s, NH); δ_C(67.8 MHz,

DEPT) 52.60 (OMe), 52.76 (OMe), 102.61 (C-3), 108.70

(C-5), 120.99 (C-2Ј), 123.02 (C-4Ј), 127.39 (C-2Љ), 128.73

(C-3Ј, C-3Љ), 130.28 (C-4Љ), 137.68 (C-1Љ), 139.50 (C-1Ј), 145.53

145.51 (C-4), 157.27 (C-2), 159.94 (C-6), 167.06 (C᎐O) and

᎐

169.52 (C᎐O); m/z 382 (M^ϩ, 30%), 350 (26, M^ϩϪ OMe Ϫ H),

᎐

300 (100, M^ϩϪ c-Hex ϩ H), 293 (26) and 264 (10, M^ϩϪ

2CO₂Me).

(C-4), 155.13 (C-2) 159.80 (C-6), 167.06 (C᎐O) and 168.71

᎐

Cycloaddition of carbodiimides 5 with ethyl propiolate (EP).

General procedure

(C᎐O); m/z 362 (M^ϩ, 100%), 329 (11, M^ϩϪ OMe-2H), 301 (8,

᎐

M^ϩϪ CO₂Me Ϫ 2H) and 244 (97, M^ϩϪ 2CO₂Me).

3,4-Bis(methoxycarbonyl)-6-phenyl-2-(p-tolylamino)pyridine

15b. Yellow needles; mp 125.7–128.5 ЊC (Found: C, 70.27; H,

5.28; N, 7.37%. C₂₂H₂₀N₂O₄requires C, 70.20; H, 5.36; N,

7.44%) ν_max(KBr)/cm^Ϫ13288 (NH) and 1738 (C᎐O); δ 2.34

(3H, s, Me), 3.88 (3H, s, OMe), 3.92 (3H, s, OMe), 7.17–8.03

(9H, m, ArH), 7.18 (1H, s, 5-H) and 9.83 (1H, br s, NH); δ_C

20.88 (Me), 52.60 (OMe), 52.79 (OMe), 102.23 (C-3), 108.35

(C-5), 121.15 (C-2Ј), 127.40 (C-2Љ), 128.75 (C-3Љ), 129.25 (C-3Ј),

130.28 (C-4Љ), 132.59 (C-4Ј), 136.87 (C-1Ј), 137.73 (C-1Љ),

Thermal reaction. A solution of carbodiimide 5a (0.59 mmol)

and EP (120 µl, 1.17 mmol) in toluene (10 cm³) was reﬂuxed for

17 h. The solvent was evaporated in vacuo and the residue was

column-chromatographed on silica gel using EtOAc–hexane

(1:100) as an eluent to give pyridine 16a, which was recrystal-

lised from CH₂Cl₂–hexane (9% yield).

᎐

H

Lewis acid-promoted reaction. To a CH₂Cl₂solution (10 cm³)

of EP (238 µl, 2.32 mmol) was successively added AlCl₃(2.32

mmol) and carbodiimide 5 (1.16 mmol) in CH₂Cl₂(10 cm³) with

stirring at Ϫ 10 ЊC. The reaction mixture was warmed up to

room temperature and stirred for 1 h. The reaction was

quenched with cold saturated aq. NH₄Cl (20 cm³) and the

mixture was extracted with CH₂Cl₂(20 cm³× 3), washed with

aq. NaHCO₃and brine, and dried (MgSO₄). Work-up for the

puriﬁcation to give pyridine 16 was the same as described

above.

145.57 (C-4), 155.27 (C-2), 159.82 (C-6), 167.08 (C᎐O) and

᎐

168.86 (C᎐O); m/z 376 (M^ϩ, 100%), 344 (9, M^ϩϪ OMe Ϫ H)

᎐

and 258 (75, M^ϩϪ 2CO₂Me).

2-(Cyclohexylamino)-3,4-bis(methoxycarbonyl)-6-phenyl-

pyridine 15c. Yellow needles; mp 111.3–112.4 ЊC (Found: C,

68.56; H, 6.62; N, 7.71%. C₂₁H₂₄N₂O₄requires C, 68.46; H,

6.57; N, 7.60%). ν_max(KBr)/cm^Ϫ13364 (NH), 2932 (CH) and

1740 (C᎐O); δ 1.25–2.10 (10H, m, c-HexH), 3.83 (3H, s, OMe),

3-Ethoxycarbonyl-6-phenyl-2-(phenylamino)pyridine

16a.

᎐

H

3.90 (3H, s, OMe), 4.24 (1H, m, c-HexH), 6.97 (1H, s, 5-H),

7.40–8.03 (5H, m, PhH) and 7.81 (1H, d, J 7.26, NH); δ_C24.82

(C-3Ј), 25.98 (C-4Ј), 32.88 (C-2Ј), 49.40 C-1Ј), 52.13 (MeO),

52.60 (MeO), 100.48 (C-3), 105.91 (C-5), 127.24 (C-2Љ), 128.64

(C-3Љ), 130.04 (C-4Љ), 138.24 (C-1Љ), 145.64 (C-4), 157.32 (C-2),

159.93 (C-6), 167.08 (C᎐O) and 169.36 (C᎐O); m/z 368 (M^ϩ,

Yellowish crystals (47% yield); mp 94.8–95.6 ЊC (Found: C,

75.61; H, 5.72; N, 8.95%. C₂₀H₁₈N₂O₂requires C, 75.45; H,

5.70; N, 8.80%); ν_max(KBr)/cm^Ϫ13272 (NH) and 1686 (C᎐O); δ

᎐

H

(270 MHz) 1.41 (3H, t, J 7.26, CH₃), 4.37 (2H, q, J 7.26, CH₂),

7.05 (1H, t, J 7.25, ArH), 7.18 (1H, d, J 8.25, 5-H), 7.37 (2H,

dd, J 7.58 and 7.25, ArH), 7.42–7.50 (3H, m, ArH), 7.84 (2H, d,

J 7.58, ArH), 8.06 (2H, dd, J 7.92 and 1.98, ArH), 8.28 (1H, d,

J 8.25, 4-H) and 10.32 (1H, br s, NH); δ_C(67.8 MHz, DEPT)

14.29 (CH₃), 61.11 (CH₂), 105.64 (C-3), 109.70 (C-5), 120.54

(C-2Ј), 122.39 (C-4Ј), 127.38 (C-2Ј), 128.70 (C-3Ј, C-3Љ), 129.79

(C-4Љ), 138.60 (C-1Љ), 140.02 (C-1Ј), 140.91 (C-4), 155.63 (C-2),

᎐

30%), 336 (26, M^ϩϪ OMe Ϫ H), 286 (100, M^ϩϪ c-Hex ϩH),

279 (33) and 250 (10, M^ϩϪ 2CO₂Me).

3,4-Bis(methoxycarbonyl)-2-phenylamino-6-(p-tolyl)pyridine

15d. Yellow needles; mp 123.3–124.8 ЊC (Found: C, 70.35; H,

5.41; N, 7.45%. C₂₂H₂₀N₂O₄requires C, 70.20; H, 5.36; N,

7.44%) ν_max(KBr)/cm^Ϫ13268 (NH) and 1742 (C᎐O); δ 2.41(3H,

160.00 (C-6) and 167.51 (C᎐O); m/z 318 (M^ϩ, 100%), 289 (3,

᎐

H

s, Me), 3.90 (3H, s, OMe), 3.94 (3H, s, OMe), 7.0–8.0 (9H, m,

ArH), 7.20 (1H, s, 5-H) and 9.93 (1H, br s, NH); δ_C21.37 (Me),

52.58 (OMe), 52.78 (OMe), 102.08 (C-3), 108.37 (C-5), 120.91

(C-2Ј), 122.93 (C-4Ј), 127.33 (C-2Љ), 128.70 (C-3Ј), 129.50

(C-3Љ), 134.89 (C-1Љ), 139.57 (C-1Ј), 140.66 (C-4Љ), 145.48 (C-4),

155.11 (C-2), 159.84 (C-6), 167.08 (C᎐O) and 168.87 (C᎐O);

M^ϩϪ Et), 271 (22, M^ϩϪ OEt Ϫ 2H), 244 (47, M^ϩϪ CO₂Et

Ϫ H) and 167 (3, M^ϩϪ CO₂Et Ϫ Ph Ϫ H).

3-Ethoxycarbonyl-6-phenyl-2-(p-tolylamino)pyridine

16b.

Yellowish crystals (43% yield); mp 108.9–109.8 ЊC (Found: C,

75.93; H, 6.13; N, 8.45%. C₂₁H₂₀N₂O₂requires C, 75.88; H,

6.07; N, 8.43%); ν_max(KBr)/cm^Ϫ13272 (NH) and 1678 (C᎐O); δ

᎐

H

m/z 376 (M^ϩ, 100%), 343 (12, M^ϩϪ OMe Ϫ 2H), 315 (9, M^ϩϪ

1.41 (3H, t, J 7.26, CH₃), 2.34 (3H, s, CH₃), 4.37 (2H, q, J 7.26,

CH₂), 7.16 (1H, d, J 8.25, 5-H), 7.17 (2H, d, J 8.25, ArH), 7.38–

7.49 (3H, m, ArH), 7.71 (2H, d, J 8.25, ArH), 8.07 (2H, dd,

J 8.25 and 1.98, ArH), 8.26 (1H, d, J 8.25, 4-H) and 10.23 (1H,

br s, NH); δ_C14.30 (CH₃, Et), 20.84 (Me), 61.04 (CH₂, Et),

105.41 (C-3), 109.36 (C-5), 120.70 (C-2Ј), 127.38 (C-2Љ),

128.66 (C-3Љ), 129.20 (C-3Ј), 129.76 (C-4Љ), 131.88 (C-4Ј),

CO₂Me Ϫ 2H) and 258 (100, M^ϩϪ 2CO₂Me).

3,4-Bis(methoxycarbonyl)-6-(p-tolyl)-2-(p-tolylamino)-

pyridine 15e. Yellow needles; mp 123.7–125.0 ЊC (Found: C,

70.76; H, 5.50; N, 7.14%. C₂₃H₂₂N₂O₄requires C, 70.75;

H, 5.68; N, 7.18%); ν_max(KBr)/cm^Ϫ13276 (NH) and 1744

(C᎐O); δ 2.34 (3H, s, Me), 2.38 (3H, s, Me), 3.88 (3H, s, OMe),

᎐

H

3078

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

View Article Online

137.41 (C-1Љ), 138.67 (C-1Ј), 140.90 (C-4), 155.74 (C-2),

(30 cm³) was heated under reﬂux for 0.5–5 h. After the enamine

160.00 (C-6) and 167.54 (C᎐O); m/z 332 (M^ϩ, 100%), 286 (33,

(335 mg, 2.00 mmol) was added, heating was continued for

4–5 h. Evaporation of the solvent, column chromatography of

the residue [silica gel, EtOAc–hexane (1:4)] and recrystalliz-

ation (CH₂Cl₂–hexane) gave pure chromenoisoquinolinone 19

(yields in Table 3).

᎐

M^ϩϪ OEt Ϫ H), 258 (30, M^ϩϪ CO₂Et Ϫ H) and 242 (8, M^ϩϪ

p-Tol ϩ H).

2-(Cyclohexylamino)-3-ethoxycarbonyl-6-phenylpyridine 16c.

Pale yellow oil (51% yield); (Found: M^ϩ, 324.1833. C₂₀H₂₄N₂O₂

requires M, 324.1839). ν_max(NaCl)/cm^Ϫ13368 (NH), 2932 (CH)

Lewis acid-promoted reaction. A mixture containing imino-

phosphorane 17 (421 mg, 1.00 mmol) and isocyanate (1.00

mmol) in tetracyanoethylene (30 cm³) was heated at 110 ЊC

for 0.5–2 h. The reaction mixture was cooled to Ϫ 15 ЊC

and then AlCl₃(0.2–1.0 mmol) and the enamine (2.0 mmol)

in tetrachloroethylene (40 cm³) were successively added to

the mixture. The reaction mixture was warmed up to room

temperature with stirring for 3–20 h, quenched with cold

saturated aq. NH₄Cl (20 cm³), extracted with CH₂Cl₂(30

cm³× 3), washed with aq. NaHCO₃and brine, and dried

(MgSO₄). Work-up for the puriﬁcation to give chromeno-

isoquinolinone 19 was the same as described in Method A

(yields in Table 3).

and 1688 (C᎐O); δ_H1.25–2.13 (10H, m, CH₂, c-Hex), 1.38 (3H,

᎐

t, J 7.26, Et), 4.21–4.26 (1H, m, CH, c-Hex), 4.32 (2H, q, J 7.26,

Et), 6.97 (1H, d, J 7.92, 5-H), 7.41–7.49 (3H, m, PhH), 8.00

(1H, br d, J 6.92, NH), 8.06 (2H, dd, J 7.92 and 1.98, Ph-H)

and 8.16 (1H, d, J 8.24, 4-H); δ_C14.38 (CH-3, Et), 24.89

(C-3Ј), 26.04 (C-4Ј), 33.03 (C-2Ј), 48.93 (C-1Ј), 60.48 (CH₂, Et),

104.06 (C-3), 106.88 (C-5), 127.19 (C-2Љ), 128.53 (C-3Љ), 129.52

(C-4Љ), 139.06 (C-1Љ), 140.73 (C-4), 157.70 (C-2), 160.02 (C-6)

and 167.67 (C᎐O); m/z 324 (M^ϩ, 29%), 295 (15, M^ϩϪ Et), 267

᎐

[25, M^ϩϪ (CH₂)₄Ϫ H], 242 (100, M^ϩϪ c-Hex ϩ H) and 170

(32).

3-Ethoxycarbonyl-2-(phenylamino)-6-(p-tolyl)pyridine 16d.

Yellowish crystals (46% yield); mp 93.1–94.1 ЊC (Found: C,

75.93; H, 6.11; N, 8.45%. C₂₁H₂₀N₂O₂requires C, 75.88; H,

6-(Phenylamino)-7,8,9,10-tetrahydro-11H-chromeno[4,3-c]-

isoquinolin-11-one 19a. Colourless plates, mp 230.8–231.9 ЊC

(Found: C, 76.89; H, 5.33; N, 7.96%. C₂₂H₁₈N₂O₂requires C,

77.17; H, 5.30; N, 8.18%); ν_max(KBr)/cm^Ϫ13340 (NH) and 1696

6.07; N, 8.43%); ν_max(KBr)/cm^Ϫ13272 (NH) and 1686 (C᎐O);

᎐

δ_H1.40 (3H, t, J 7.26, CH₃, Et), 2.40 (3H, s, CH₃), 4.37 (2H, q,

J 7.26, CH₂), 7.04 (1H, t, J 7.59, PhH), 7.15 (1H, d, J 8.25,

5-H), 7.26 (2H, d, J 8.58, p-TolH), 7.36 (2H, dd, J 7.91 and 7.59,

Ph-H), 7.84 (2H, d, J 7.91, PhH), 7.97 (2H, d, J 8.58, p-TolH),

8.25 (1H, d, J 8.25, 4-H) and 10.31 (1H, br s, NH); δ_C14.29

(CH₃, Et), 21.35 (Me), 61.04 (CH₂, Et), 105.32 (C-3), 109.40

(C-5), 120.48 (C-2Ј), 122.30 (C-4Ј), 127.31 (C-2Ј), 128.66 (C-3Ј),

129.41 (C-3Ј), 135.85 (C-1Ј), 140.02 (C-1Ј), 140.11 (C-4Ј),

(C᎐O); δ (270 MHz) 1.76–2.00 (4H, m, 8-H, 9-H), 2.56 (2H, m,

᎐

H

7-H), 3.33 (2H, m, 10-H), 6.70 (1H, br s, NH), 7.16 (1H, t,

J 7.92, 4Ј-H), 7.24–7.50 (5H, m, 3Ј-H, 1-H, 2-H, 3-H), 7.74

(2H, d, J 7.92, 2Ј-H) and 8.35 (1H, dd, J 8.25 and 1.65, 4-H); δ_C

(67.8 MHz, DEPT) 21.42 (8-C or 9-C), 21.90 (9-C or 8-C),

24.33 (10-C), 29.18 (7-C), 108.21 (4a-C), 116.30 (1-C), 118.20

(10b-C), 120.00 (6a-C), 121.13 (2Ј-C), 123.63 (4Ј-C), 123.93

(3-C), 125.05 (4-C), 128.88 (3Ј-C), 131.07 (2-C), 139.14 (1Ј-C),

150.78 (10a-C), 150.85 (4b-C), 152.61 (12a-C), 155.92 (6-C) and

160.75 (11-C); m/z 342 (M^ϩ, 100%), 327 (M^ϩ, 20%), 313 (11),

265 (M^ϩϪ Ph, 5) and 251 (15).

140.82 (C-4), 155.63 (C-2), 160.05 (C-6) and 167.54 (C᎐O); m/z

᎐

332 (M^ϩ, 100%), 285 (21, M^ϩϪ OEt Ϫ 2H), 258 (51, M^ϩϪ

O₂Et Ϫ H) and 242 (9, M^ϩϪ p-Tol ϩ H).

3-Ethoxycarbonyl-6-(p-tolyl)-2-(p-tolylamino)pyridine 16e.

Yellowish crystals (46% yield); mp 67.9–68.5 ЊC (Found: C,

76.31; H, 6.51; N, 8.23%. C₂₂H₂₂N₂O₂requires C, 76.27; H, 6.40;

6-(p-Tolylamino)-7,8,9,10-tetrahydro-11H-chromeno[4,3-c]-

isoquinolin-11-one 19b. Colourless plates, mp 230.0–231.1 ЊC;

(Found: C, 77.59; H, 5.76; N, 7.85%. C₂₃H₂₀N₂O₂requires C,

77.50; H, 5.66; N, 7.86%); ν_max(KBr)/cm^Ϫ13360 (NH) and 1698

N, 8.09%); ν_max(KBr)/cm^Ϫ13276 (NH) and 1682 (C᎐O); δ_H1.41

᎐

(3H, t, J 7.26, CH₃, Et), 2.35 (3H, s, CH₃), 2.40 (3H, s, CH₃),

4.37 (2H, q, J 7.26, CH₂), 7.13 (1H, d, J 8.25, 5-H), 7.17 (2H, d,

J 8.25, ArH), 7.27 (2H, d, J 8.25, ArH), 7.71 (2H, d, J 8.25,

ArH), 7.97 (2H, d, J 8.25, ArH), 8.25 (1H, d, J 8.25, 4-H) and

10.22 (1H, br s, NH); δ_C14.32 (CH₃, Et), 20.84 (CH₃), 21.37

(CH₃), 60.99 (CH₂, Et), 105.08 (C-3), 109.07 (C-5), 120.66

(C-2Ј), 127.31 (C-2Љ), 129.16 (C-3Ј), 129.40 (C-3Љ), 131.79 (C-

4Ј), 135.92 (C-1Љ), 137.46 (C-1Ј), 139.96 (C-4Љ), 140.81 (C-4),

(C᎐O); δ_H1.80–1.92 (4H, m, 8-H, 9-H), 2.39 (3H, s, CH₃), 2.55

᎐

(2H, m, 7-H), 3.33 (2H, m, 10-H), 6.65 (1H, br s, NH), 7.21–

7.30 (4H, m, 3Ј-H, 1-H, 3-H), 7.46 (1H, ddd, J 7.92, 7.43 and

1.65, 2-H), 7.61 (2H, d, J 8.58, 2Ј-H) and 8.35 (1H, dd, J 8.09

and 1.65, 4-H); m/z 356 (M^ϩ, 100%), 341 (M^ϩϪ NH, 18), 327

(9), 265 (M^ϩϪ Tol, 4), 251 (15), 178 (5) and 91 (4).

6-(p-Nitrophenylamino)-7,8,9,10-tetrahydro-11H-chromeno-

[4,3-c]isoquinolin-11-one 19c. Yellow needles, mp 333.5–

334.8 ЊC (Found: M^ϩ, 387.1214. C₂₂H₁₇N₃O₄requires M,

387.1220); ν_max(KBr)/cm^Ϫ13456 (NH) and 1724 (C᎐O); δ 1.84–

155.74 (C-2), 160.05 (C-6) and 167.58 (C᎐O); m/z 346 (M^ϩ,

᎐

100%), 317 (3, M^ϩϪ Et), 300 (32, M^ϩϪ OEt Ϫ H), 272 (44,

M^ϩϪ CO₂Et Ϫ H), 256 (9, M^ϩp-Tol ϩ H) and 181 (4,

M^ϩϪ CO₂Et-p-Tol Ϫ H).

᎐

H

2.02 (4H, m, 8-H, 9-H), 2.69 (2H, m, 7-H), 3.42 (2H, m, 10-H),

7.04 (1H, br s, NH), 7.33–7.41 (2H, m, 1-H, 3-H), 7.55 (1H,

ddd, J 7.92, 7.92 and 1.32, 2-H), 7.97 (2H, d, J 9.24, 2Ј-H), 8.34

(2H, d, J 9.24, 3Ј-H) and 8.39 (1H, dd, J 7.92 and 1.32, 4-H);

m/z 387 (M^ϩ, 100%), 372 (M^ϩϪ NH, 12), 340 (M^ϩϪ NO₂H,

8), 312 (6), 265 (M^ϩϪ NO₂Ph, 5) and 251 (19).

6-(p-Chlorophenylamino)-7,8,9,10-tetrahydro-11H-chromeno-

[4,3-c]isoquinolin-11-one 19d. Colourless plates, mp 282.5–

283.9 ЊC (Found: C, 70.17; H, 4.63; N, 7.56%. C₂₂H₁₇N₂O₂Cl

requires C, 70.14; H, 4.55; N, 7.43%); ν_max(KBr)/cm^Ϫ13456

2-(Cyclohexylamino)-3-ethoxycarbonyl-6-(p-tolyl)pyridine

16f. Pale yellow oil (49% yield) (Found: M^ϩ, 338.1993. C₂₀H₂₄-

N₂O₂requires M, 338.1996); ν_max(NaCl)/cm^Ϫ13368 (NH), 2932

(CH) and 1684 (C᎐O); δ 1.25–2.12 (10H, m, CH , c-Hex), 1.37

᎐

H

2

(3H, t, J 6.93, CH₃), 2.39 (3H, s), 4.23–4.30 (1H, m, CH,

c-Hex), 4.31 (2H, q, J 6.93, CH₂), 6.94 (1H, d, J 8.24, 5-H), 7.25

(2H, d, J 8.25, p-TolH), 7.96 (2H, d, J 8.25, p-TolH) 7.98 (1H,

br d, J 6.26, NH) and 8.13 (1H, d, J 8.24, 4-H); δ_C14.38 (CH₃,

Et), 21.35 (CH₃, p-Tol), 24.89 (C-3Ј), 26.04 (C-4Ј), 33.01 (C-2Ј),

48.91 (C-1Ј), 60.39 (CH₂, Et), 103.70 (C-3), 106.59 (C-5), 127.10

(C-2Љ), 129.27 (C-3Љ), 136.31 (C-1Љ), 139.64 (C-4Љ), 140.63 (C-4),

(NH) and 1724 (C᎐O); δ 1.81–1.99 (4H, m, 8-H, 9-H), 2.61

᎐

H

(2H, m, 7-H), 3.38 (2H, m, 10-H), 6.69 (1H, br s, NH), 7.30

(1H, dd, J 6.93 and 1.32, 1-H), 7.34 (1H, ddd, J 7.92, 7.10 and

1.32, 3-H), 7.40 (2H, d, J 8.91, 2Ј-H), 7.50 (1H, ddd, J 7.10, 6.93

and 1.65, 4-H), 7.70 (2H, d, J 8.91, 3Ј-H) and 8.34 (1H, dd,

J 7.92 and 1.65, 4-H); m/z 376 (M^ϩ, 100%), 361 (M^ϩϪ NH, 15),

325 (5), 312 (4), 265 (M^ϩϪ ClPh, 5) and 251 (22).

6-(Tosylamino)-7,8,9,10-tetrahydro-11H-chromeno[4,3-c]-

isoquinolin-11-one 19e. Colourless needles, mp 239.7–240.9 ЊC

(Found: C, 65.75; H, 4.88; N, 6.71%. C₂₃H₂₀N₂O₄S requires C,

65.70; H, 4.80; N, 6.66%); ν_max(KBr)/cm^Ϫ13348 (NH), 1732

157.68 (C-2), 160.05 (C-6) and 167.69 (C᎐O); m/z 338 (M^ϩ,

᎐

26%), 309 (15, M^ϩϪ Et), 281 [25, M^ϩϪ (CH₂)₄Ϫ H], 256 (100,

M^ϩϪ c-Hex ϩ H) and 184 (32).

Aza-Wittig reaction of iminophosphoranes 17 with isocyanates

and cycloaddition of carbodiimides 18 with N-(cyclohexen-1-yl)-

morpholine. General procedure

Thermal reaction. A mixture containing iminophosphorane

17 (421 mg, 1.00 mmol) and isocyanate (1.00 mmol) in toluene

(C᎐O), 1338 and 1164; δ 1.7–1.9 (4H, m, 8-H and 9-H), 2.37

᎐

H

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

3079

View Article Online

9 M. Noguchi, K. Onimura, Y. Isomura and S. Kajigaeshi,

J. Heterocycl. Chem., 1991, 28, 1885; M. Noguchi, K. Onimura,

Y. Isomura and S. Kajigaeshi, Chem. Express, 1989, 4, 593.

10 P. Molina, M. Alajarin, A. Vidal and P. Sanchez Andrada, J. Org.

Chem., 1992, 57, 929; P. Molina, M. Alajarin and A. Vidal, J. Chem.

Soc., Chem. Commun., 1990, 1277.

(3H, s, Me), 2.60 (2H, br s, 1-H), 3.20–3.35 (2H, m, 4-H), 7.2–

8.0 (7H, m, ArH and NH) and 8.10 (2H, d, J 7.82, TsH); m/z

420 (M^ϩ, 9%), 265 (100, M^ϩϪ Ts), 250 (3, M^ϩϪ TsNH) and

91(22).

Computational calculations

11 (a) H. Wamhoﬀ, A. Schmidt and M. Eieger, Tetrahedron Lett., 1991,

32, 4473; (b) H. Wamhoﬀ and A. Schmidt, Heterocycles, 1993, 35,

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6976; (d) H. Wamhoﬀ, C. Bamberg, S. Herrmann and M. Nieger,

J. Org. Chem., 1994, 59, 3985.

Semiempirical calculations were carried out using the AM1

Hamiltonian implemented MOPAC93.²³Transition states

were optimized with TS and NLLSQ algorithms. The force

constant matrix of the transition state revealed the single

negative eigenvalue. The IRC (intrinsic reaction coordinate)

algorithm was applied connecting the transition state with

reactant and product by following the transition vector in

both directions.

12 M. Wahren, Z. Chem., 1969, 9, 241.

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1883.

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18 Chem3D Pro (version 3.5.1), CambridgeSoft Corporation.

19 The JCPE (Japan Chemistry Programme Exchange) programme

(No. P006) was used.

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Paper 8/05574B

3080

J. Chem. Soc., Perkin Trans. 1, 1998, 3065–3080

Article Doi

Thermal or Lewis acid-promoted electrocyclisation and hetero Diels-Alder cycloaddition of α,β-unsaturated (conjugated) carbodiimides: A facile synthesis of nitrogen-containing heterocycles

DOI: 10.1039/a805574b

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Article abstract of DOI:10.1039/a805574b

Full text of DOI:10.1039/a805574b

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