Malonate Anion Induced Favorskii-Type Rearrangement. 3. Reaction of Methyl-Substituted α-Chlorocyclohexanones with Sodiomalonates

Article abstract of DOI:10.1021/jo00172a035

The regioselectivity and the stereoselectivity of the ring-opening reaction of bicyclic cyclopropanols such as 6--3-methylbicyclo<3.1.0>hexan-6-ol (8) and 6--endo-2-methylbicyclo<3.1.0>hexan-6-ol (endo-9) and its exo-2-methyl isomer (exo-9) have been studied.Reaction of 2-chloro-4-methylcyclohexanone (2) with diethyl sodiomalonate (4b) gave 8 in 59percent yield.The similar reaction of 2-chloro-5-methylcyclohexanone (3) with 4b afforded a 44:56 mixture of endo-9 and exo-9 in 49percent yield.This mixture was separated to each component by means of HPLC.Reaction of 2-chloro-2-methylcyclohexanone (1) with 4b afforded only the substitution products.The alkaline hydrolysis (2 N NaOH) of 8 followed by pyrolysis gave trans-1-(3-methylcyclopentyl)ethanone (trans-11) selectively, while the acidic (6 N HCl) hydrolysis of 8 afforded a 1:1 mixture of cis- and trans-11 as a result of decarboxylation.The alkaline hydrolysis of endo-9 followed by pyrolysis gave a 50:34 mixture of cis- and trans-11 predominantly, whereas the acidid (35percent HCl) hydrolysis of endo-9 afforded trans-13 regio- and stereoselectively.The similar treatment of exo-9 never displayed such regioselectivity in the ring-opening reaction.