STRAINED RING SYSTEMS .8. AN ALTERNATE SYNTHESIS OF 2-OXY DERIVATIVES OF BICYCLO[2.2.O]HEXANE AND REARRANGEMENT OF ENDO-BICYCLO[2.2.O]HEX-2-YL ACETATE

The synthesis of methyl endo-bicyclo[2.2.0]hexane-2-carboxylate (6) by diimide reduction of methyl bicyclo[2.2.0]hexa-2,5-diene-2-carboxylate (5) is reported. Conversion of 6 via the methylsulfinyl carbanion and reduction of the resulting adduct leads to a 38:62 mixture of endo- (7) and exo-bicyclo[2.2.0]hex-2-yl methyl ketone (8) which on Baeyer-Villiger oxidation yields a mixture of exo-bicyclo[2.2.0]hex-2-yl acetate (9, 91%), cis-bicyclo[3.1.0]hex-2-yl acetate (10, 9%), and 3-cyclohexenyl acetate (11, <1%). Conversion of 6 into its acid chloride and reaction with dimethylcadmium also gives a mixture of 7 and 8 but in a ratio of 65:35. Baeyer-Villiger oxidation produces a mixture of 9 (49%), endo-bicyclo[2.2.0]hex-2-yl acetate (12, 27%), 10 (18%), and 11 (6%). On standing in a nonpolar solvent 12 is observed to rearrange to 10 and 11, thereby establishing them as artifacts of the Baeyer-Villiger reaction. The mechanism of this rearrangement is discussed. © 1969, American Chemical Society. All rights reserved.