Ring-expansion of a dihalogenocarbene adduct of a cycloheptene derivative and the corresponding retro-reaction

Tetrahedron Printed in

Letters,Vol.28,No.l6,pp Great Britain

RING-EXPANSION

OF A DIHALOGENOCARBENE

DERIVATIVE

oo40-4039/87 $3.00 + .OO peroamon Journals Ltd.

1827-1830,1987

ADDUCT

AND THE CORRESPONDING

OF A CYCLOHEPTENE

RETRO-REACTION

a?: Dashyant aDepartment b

Department

Dhanaka,

of Chemistry,

of Biophysics,

Reiko Kurodab,

King's College

King's

College

and Colin B. Reese

London,

London,

Strand,

London WCZR ZLS, England

26-29 Drury Lane, London WC2B 5RL, England

Summary :

The dihalogenocyclopropane derivative (&) was obtained in 41% isolated yield when (&, was treated with an excess of methanesulphonyl chloride and triethylamine in dichloromethane solution; this transformation may be regarded as the retro-reaction corresponding to the silver(I) perchlorate promoted ring-expansion of (ai to give (&).

It was established servation

of orbital

the presence 2-en-l-01

water

reaction joining

carbonate

in boiling aqueous

and that the same transformation

(la) with a concentrated

(9:l v/v).

silver(I)

of years ago that, in accordance

, exo-8-bromobicyclo[5.l.Oloctane

of sodium hydrogen

(&I,

by treating

a number 1

symmetry

undergoes

dioxane

can be effected3

(>l.O g) solution

with the principle

(&j

at room temperature

perchlorate

In the same way, 8,8-dibromobicyclo[5.l.O]octane (2) readily undergoes 3 hydrolysis to give (31, and it is reasonable to conclude that this

also proceeds

by a concerted substituent

mechanism

involving

heterolytic

cleavage

(7

H

G,,

OH X

X

(1)

a;

X = H

(2) 2;

solely to trans-cycle-octene stereoisomeric

reactions

of (2)

and (2) cations,

systems,

b; X = Br

are stereospecific

derivatives

is obtained.

of (la), and no (2)

trans-allylic octane

alcohols

(3) a; X = H

X = H

b; X = Br

&; X = Br

The above ring-expansion

and, secondly,

Thus no (2)

in two respects:

into (la) and (a).

solvolysis

first, they lead

only one of the two possible dia2-4 in the solvolysis

can be detected

can be detected 3 in the solvolysis

formed by the outward

should undergo

of the bond

to c-8.

H

version

in acetone-

ions promoted

the exe-bromo

products

in

to give2 trans-cyclo-oct-

rapidly

of silver(I)

of con-

solvolysis

respectively, disrotatory

products

requires5 ring-opening

of (lb).

The con-

that the putative

tram,

of the bicyclo[5.1.01-

on the same side as that from which the exe-bromo

group departs.

1827

1828

053 Cl

=I;

(2,

(8) -

X

5;

Y

=

(6)

Br

=

(2,

R = H b; R = MS

2;

&; x = Y = Cl 2; X = Br, Y = Cl

We found' that when (4) was treated with silver(I) lutidine

in anhydrous

(5) was obtained prepare

carbene

(4.28 mmol)

(&)

is allowed

2,4,6-collidine

to react with silver(I)

(13.0 mmol)

in anhydrous

characterized evidence, carbene

compound,

adduct

Where

structure

(h)

(1.25 mmol)

is allowed

(12.4 mm011

as the main product.

Presumably,

(7).

(El,

which

(sj

chloride

The latter compound

is derived

from a tertiary

(see above),

then undergoes

disrotatory

ring closure,

accompanied

mediate

mesylate

(El.

bromide

ions and there

of (&)

by chloride anion departs

Apart from the fact that chloride is no involvement

of silver(I)

with authentic

to give tri-

The latter compound substituent

readily

by analogy with the conversion

in the conversion

and

indole derivative

chloride

system with an a-nitrogen

the same side5 as that from which methanesulphonate

(12.9 mmol)

Calc. for

and by comparison

(3).

dichloro-

in 41% yield,

to the protected

derivative

cation presumed,

to be involved

was isolated

and methanesulphonyl

mesylate

allylic

ionizes to give the trans,trans-allylic (lb) into (2)

(&)

spectra8,

reacts with triethylamine

was

for 20 min, (&I

[M+ at m/z = 411.0597.

of bromochlorocarbene

and the corresponding

chloride

(10 ml) at room temperature

'H and 13C n.m.r.

(&)

spectroscopic

under the above conditions.

: 411.0600],

ethylammonium

The latter compound

for

and isolated

perchlorate

C,, 73Br35C1H,,N0,

by the addition

is obtained

of

The corresponding

on the basis of its mass spectrum

prepared'

When (&I

(Fig. 1).

was characterized

material

yield.

in the presence

(iH, 13C) and mass

to react with methanesulphonyl

in dichloromethane

indole

(12 ml) at room temperature

in 84% yield.

analysis

to

ether gives the dibromo-

(26.0 mmol)

and light, (G)

n.m.r.

derivative

of the protected

in petroleum

perchlorate

of 2,6-

in an attempt

131"C, in 83% isolated

(8b) does not react with silver(I) -

and triethylamine is obtained

crystal

[5] metacyclophane

Treatment

tetrahydrofuran

on the basis of microanalytical,

and an X-ray

(6).

both moisture

m.p. 118-12O"C,

in the presence

study originated

t-butoxide

solid, m.p.

4 hr, with care being taken to exclude as a crystalline

system

and potassium

as a crystalline

perchlorate

the strained

The present

[5] (2,4)quinolinophane

(1) with bromoform

adduct

solution,

in 55% isolated yield.

the related

derivative'

tetrahydrofuran

into (s).

ion solvolysis

occurring

from the putative

ions are involved

ions, the conversion

of

This cation on

inter-

instead of

of (g)

[via

(%)I

1829

Figure 1 Computer-drawn plot of molecular structure of (*)

into (C)

is the reverse of the conversion of (&)

into (s).

We are unaware of other

examples in the literature in which the transformationof a cyclopropyl into an allylic Presumably, the mild conditions

system and the retro-reactionhave both been observed. required for the conversion of (s)

into a very strained allylic cation, the presence of a

suitable nucleophile [i.e. chloride ions] and the particular stability [as evidenced by its resistance to silver(I) perchlorate promoted solvolysis]' of the product all contribute to making this retro-ring-expansionreaction particularly favourable.

Acknowledgement.

We thank the S.E.R.C. for the award of a Research Studentship.

REFERENCES AND FOOTNOTES R.B. Woodward and R. Hoffmann, 'The Conservation of Orbital Symmetry', Verlag Chemie, Weinheim, 1970, pp.55 et seq. G.H. Whitham and M. Wright, J. Chem. Sot., Chem. Commun. 294 (1967); J. Chem. Sot. (Cl 883 (1971). C.B. Reese and A. Shaw, J. Am. Chem. Sot. 92, 2566 (1970); J. Chem. Sot., Perkin Trans. 1 2422 (1975). G.H. Whitham and M. Wright, J. Chem. Sot. CC) 886 (1971). C.B. Reese and A. Shaw, J. Chem. SOC., Chem. Commun.

1365 (1970).

P. Grice and C.B. Reese, J. Chem. SOC., Chem. Commun. 424 (1980). D. Dhanak and C.B. Reese, J. Chem. SW., The 13C n.m.r. spectrum of (&)

Perkin

Trans.

[6c(CDC1,, 62.89 MHz):

1 2181 (1986).

26.39, 27.03, 28.21, 30.92, 31.53,

46.53, 61.3, 62.77, 82.10, 115.60, 122.89, 123.77, 128.81, 130.46, 153.051 is closely similar to the corresponding spectra of (&)

r26.50, 27.19, 28.28, 30.66, 31.53, 46.51,

50.79, 61.0, 82.18, 115.61, 122.81, 123.45, 128.90, 132.04, 146.86, 152.721 and @)

r26.38,