Thermal wolff rearrangement of 3-diazo-bicyclo(3,1.0) hexan-2-one: A new route to 2-substituted bicyclo(2,1,0) pentanes.

TetrahedronLettersNo.48, pp. 4187-4188,1969. PergamonPress. Printed in Great Britain.

THESLidOLFF

REURANG!&dNT OF

3-DIAEO-BICYCLO(3.1.O)BBXAN-2-oNR: A N8b'

ROUTE TO 2-SUB8TITUTEDBICYCLC(Z,l,O)PENTANE8. By P. R. Brook" and B. V. Brophy (Departmentof Organic Chemistry,Ths University,Leeds IS2 9JT)

Bicyclo(3,l.O)hexan-2-one,with ethyl formate and sodium hydride,gave the hydroxymethylene derivative(I, 74%: m.p. 62-64'); this, treated with diethylamine followedby tosyl azide (l), gave the j-diaeoketone(II, 89:

b.p. 69-72'/0.02mm.+).

BoilingI&methylanilinesmoothlyconvertedthe diaeoketoneto an oily epimericmixture of ring-contracted &aethylcarboxanilides(III and IV, ratiod80:20) which analysed correctlyand had the expected spectralproperties(cyclopropylmethylene: Ymax 3060 cm.-1 . b 0.4-0.9 mult. 2H: amide: vmax 1660 cm.'l: no olefinicsignals in p.m.r.). .

Catalytio

reductionof the epimericanilides led to E-methylcyclopentanecarboxanilide (m.p. 31-34'; 1 mole H2 uptake).

Assigned stereochemistryin the series is baaed on the chemical

shift of the C-(2)& which occurs at higher field when -cis to the cyclopropanering (2). The epimericanilides (III and IV) were equilibratedafter 30 min. at 225' J& planar, 1,ediradical (3). and the mixture contained53% w-isomer(II1).

The high

proportionof (III) in the originalmixture is thereforethe result of kinetically controlledaddition to the intermediateketene (VII).

b

X

b

Ihc

c’/O

X

Y

0

+

I

X = CHOH

II

X = N2

VII

The oil-bathtemperaturewas kept below 115'.

4187

III

X = CORBePh,Y = H

IV

X = H, Y = CORBePh

V

X = C02H, Y = H

VI

X = H, Y = C02H

the

4188

No.48

Photochemicalconversionof the diasoketone(4) to the ketene in presenceofmetbancl gvs a disappcinting13% of methyl esters. good yields of the &co1

Bouewer, the diazoketone(1 g. scale) gave

half esters in boiling ethyleneglyool containing15;~y/~

collid5.ne (180-la5°,2 z&n.>.

Separationof the bicyclopentanesfrom

ethoxybicyolo(3,1,0) hexan-2-011s (2,4-DNPH,m.p. 148') ua5

best

some

3-2'-hydroxy-

effeotedby basic hydrolysis

and isolationof the eptieriomixture of acids (V and VI: 68& from diascketone; ratio 55:455). The oorrespondizgmethyl esters were separatedby preparativeg.1.o. I.ps. of further derivntivesrhioh have been preparedare fould in the Tablo.

P-substituent

exe

-cONHPh -CONEC6H4Br(p) -Mi.C02Ke -Cot $

endo

1a&5o

120-121°

173O

132’

5537O

34-36'

170ca

141O'

a m-p. of 2,4-Dinitrophellprlhydzone Bciliq ethyleneglyool for Wolff rearrangementof diazoketones,may be of we

in the

eyntheaisof other strainedring eysteaa uhen photoohemioalyields are low.

References 1

1. Rcsenberger,P. Yates, J. B. Hendricksonand W. Wolf, Tet. Lett., 1964, 2285.

2

P. K. Fiwemn,

3

J. P. Chesiok,J. Amer. Chem. Soo., 1962,f&

4

Y. Kirrae. Carbene Chem., Academic Press, N.Y., 1964, p. 120.

H. 9.

Grostlo,and F.

A. Rqmond,

J.

Ora.

Chew, 1965, x.

3250.

771.