Intramolecular cyclization of N-sulfonyl substituted α-bromoamidines and guanidines

Tetrahedron Letters No. 1, pp 49 - 52. Ltd. 1979. Printed in Great Britain.

%,F’ergamon Press

INTRAMOLECULAR

CYCLIZATION

a-BROMOAMIDINES

Gerrit Department

L'abbe

the reaction a second Thus,

when

yield -2a.

which The

in ether gave

with

-la

spectral

IR spectrum

data

'c-c

strong

t

/

recently

azide.

was

treated

c: R

non-equivalent function. at 6 96.4 peak

(S=O)

absorptions

fragment

(50%, Me2C=C=NBut'+

to afford

158.6

of potassium

was obtained

consistent

at 1685,

with

1650

in 83%

structure

(doublet,

C=N)

\\90 ) CH3./ 1/C\o/SlR3 R

1

=

Me,

R2 = tB~, R3 = Ph

1

R3 = Me

= H, R2 = tBu, R3 = Ph (CDC13)

the two methyl

(at 6 1.52 and 1.7) due to the anisotropic

(C') and

two equiv

R2N+ C-N

BuOK

In the 'H NMR spectrum

The ring carbon

(5%) and

Similarly,

.

from

to report

(mp 67-68')

b: R1 = Me, R2 = p-CH3C6H4,

-1

obtained

2

a: R

1050 cm

been

We now wish

with

analysis

1

and

1

system.

‘\,S02R3

Br

have

and elemental

NHR2

CH3

Belgium

for 2 h, a compound

(KBr) shows

R"l

Heverlee,

(mp 85-86")2

at O'C

of Leuven

methanesulfonyl

to this new ring

a-bromoamidine

tert-butoxide

Verbruggen

University

3-oxathiazol-2-ones

of ketenimines

approach

and Andre

200F, B-3030

4-Imino-4,5-dihydro-1,2A6,

SUBSTITUTED

AND GUANIDINES

of Chemistry,

Celestijnenlaan

OF N-SULFONYL

absorptions (C4).

peaks

in the

The mass

at m/e

222

13

C NMR

spectrum

effect

spectrum

exhibits

(7%, M'+ - Me2CO),

groups

are

of the sulfinyl (CDC13) are found

a weak molecular 141

ion

(90%, PhS02+),

125

) and 77 (lOO%, Ph+).

_lb (mp 128-129O) respectively

-2b

and -lc

(mp 83-84')

(40%, mp 96-97') 49

reacted

and -2c

with

tBuOK

(50%, colourless

in ether oil).

at O'C

Compound

No.

50

-2b was

identical

in all respects

N-tolylketenimine shows

and methanesulfonyl

the presence

4 in steady-state sure and

because

2a,b isomerize --

3a,b on warming. --

(i) a concerted

1

aside.

mixture

smoothly

shift,

equilibrium

1,5-sigmatropic

with

R2N\.H-CH2,/C

and

The mixture

could

of 2

of -2a and -3a during gration order

concerted

A kinetic

activation Since

the reaction

parameters:

the dipole

trend

but

not found. when

in a stepwise

manner

estimated signals.

in benzene),

b

of

CH2=ClCcNR2

I NHS02R3

reproducible.

solvents. from

was

in Table

1.

and AS

*

H NMR

than that of 2

were

giving

by inte-

strictly

The experiments

first-

in ben-

the following

(3.6 and 5.0 D for 2

for the concerted

substituted

spectra

amounts

= -32 e.u.

mechanism

of the solvent

in chloroform

does

we may

increases.

for acetonitrile

If, on the contrary,

via decomposition

1

the

temperatures

observed

The relative

The reactions

as the polarity

benzene

The rate acceleration is indeed

were

in several

of 2 is smaller

in rate constant

sulfoxide.

out

out at different

a small

was

slow

II N 'S02R3

are summarized

determined

however,

study

2

CH3\ Rl/C\C/NR

tB~ proton

-3b respectively, increase

ring clo-

3

Ea = 16.3 kcal/mol

moment

of dipole

CH2=C=C_NHR2 II 7 NS02R=

p

Lx

T-

was carried

also carried

isomerization:

5

and the rate constants

zene-d 6 were

ami-

,l K

2

of the CH3 and/or

the acrylic

undergoes

into the amidines.

4 the thermolysis

at 20'.

formation

4 subsequently

2

R1/C\c&NR

even

for this

-N

”

CH3\+

(CDC13) of C

at 6 1.42 and

into

(ii) the intermediate

shift

from dimethyl-

not be separated

in solution

andquantitatively

Dipole

U//O ,lJ\,,S._3

Lx

two doublets

can be considered

with 2.

hydrogen

prepared

1H NMR spectrum

it decomposed

Two mechanisms

1,7-hydrogen

sample

The

at 6 4.96 and 5.12 ppm.

the two diastereoisomers

The oxathiazolines dines

an authentic

of an erythro-threo

1.6 and two quartets into

with

1

and expect This,

or dimethyl

not fit the general

the isomerization

of 2 in the rate-determining

proceeds

step, we may

No. 1

51

Table 1. Kinetics for the isomerization & Temp, OC

Solventa CgD6

+

3a

lo5 kl (set-'1

55

2.88

61

4.25

69

8.21

74.5

11.7

CDC13

60

11

CD3CN

60

4.95

DMSO-d6 60 -________-____-_-_-

1.45

a The solvents were treated with alumina in order to avoid acid-catalyzed isomerization

expect a similar kinetic behaviour to that reported by Quast (autocatalytic reaction!). 3

This was not found to be the case so that no definite conclusion can

be drawn on the mechanism at the present time. Attempts to synthesize the desired sulfonyl substituted aziridinimines were unsuccessful.

For instance, 2 proved to be unreactive towards tBuOK or

lithium 2,2,6,6_tetramethylpiperidide. of the tosyl

(e.g. 21

4

This contrasts sharply with the isolation

substituted diaziridinimine 8 (mp 80-81°) in 85% yield from the

guanidine l5 as shown below. tBu 1

NHBut / a NS02C6H5

/But

tBU

t tBuNH-C-NHBu1: 'Ts

'N-N \/

1) tBuOCl F 2) tBuOK

N-N

NC '

/" 'Ts

'Ts 9

-8

Compound g possesses an IR spectrum (KBr) with absorptions 1320 and 1160 cm -' (S02), while the 1H NMR spectrum

tert-butyl

\

- (CH3)2C=CH2

I

ce of one broad

tB~

h

tert-butyl

substituents

signal

is also

at 6 1.25 ppm.

apparent

6

at 1750 (broad s, C=N),

(CDC13)

indicates

The presence

from the 13C NMR

the presen-

of two identical

spectrum

(resonances

at

No.

52

6 26.8 and spectrum

The ring carbon

of 8 features

(6%, M'+Thermolysis needles

62.1 ppm).

2 Me2C=CH2),

peaks 168

of 8 in boiling

(mp 176-177')

The tosyl

7

toluene

(2%, M'+),

(348, Ts+)

The formation t

BuN=NH

then rearranges

yielding

is found at 6 157.9 ppm. 267

(20%, M'+-

and 91

for 5 h yielded

of 8 into

isonitrile8

to the azo compound,

323

(60%), 155

in 58% yield.

in terms of fragmentation tene.

at m/e

atom

The mass

Me2C=CH2),

211

(90%, CH3C6H4+).

the hydrazine

-9 as white

of this compound

and TsNC with to the more

1

is interpreted

elimination

stable

of isobu-

nitrile

and adds

2.

ACKNOWLEDGEMENT We thank R. Verbergt for experimental assistance. A. Verbruggen is indebted to the I.W.O.N.L. for a doctoral fellowship. Financial support from the Ministry of National Education and from the F.K.F.O. is gratefully acknowledged. REFERENCES 1.

AND NOTES

G. L'abbe, C-C. Yu, J-P. Declercq, G. Germain, and M. Van Meerssche, Angew. Chem., 90, 394 (1978); Angew. Chem. Int. Ed. Engl., II, 352 (1978).

2. The starting materials -la-c were prepared from the correspondingN-sulfonyl substituted a-bromoamides by treatment with PC15 and then with primary amines, analogous to the procedures described by J. v. Braun and W. Rudolph, Ber., 67, 1762 (1934). 3. H. Quast and P. Schifer, Tetrahedron Lett., 1057 (1977). 4. R. A. Olofson and C. M. Dougherty, J. Am. Chem. Sot., 95, 581 (1973). 5. W. V. Farrar, J. Chem. Sot., 856 (1965). 6. At lower temp. (-6') the tert-butyl groups become magnetically non-equivalent and give rise to two singlets. This is due to restricted isomerization at the C=N double bond, see also ref. 7. 7.

H. Quast and E. Schmitt, Angew. Chem., 81, 428 (1969); Angew. Chem. Int. Ed. Engl., S, 448 (1969).

8. Sulfonyl isonitriles are unknown but N-acyl and N-imidoyl substituted isonitriles have recently been prepared, see G. Hzfle and B. Lange, Angew. Chem., 2, Int. Ed. Engl., 16, 262 and 727 (1977).

(Received in UK

30 October 1978)

272 and 742 (1977);

Angew. Chem.