ALKYLATIVE 1,2-CARBONYL TRANSPOSITION OF 2-METHOXY-2-CYCLOHEXENONES

A new alkylative 1, 2-carbonyl transposition sequence is described for the conversion of a number of substituted 2-methoxy-2-cyclohexenones (3) to substituted 2-methyl-2-cyclohexenones (6). The sequence involves reaction of 3 with methylmagnesium iodide to yield alcohol 4 which is then converted to 6 by either of two possible dehydration-hydrolysis procedures. The monoterpene carvotanacetone (6c) is one of the compounds prepared by this method. When this sequence was performed on the bicyclic substrate 9a, enone 11 was the major product formed. Attempts to induce a related 1, 2-methyl shift upon acid treatment of alcohol 10b were not successful but simply led to the “normal” enone 12b. A simpler and more effective procedure for the preparation of the starting methoxy enones 3 and 9 is also described. © 1979, American Chemical Society. All rights reserved. © 1979, American Chemical Society. All rights reserved.