Dimethyl cis- and trans-1, 2-dimethyl-cyclohexane-1, 2-dicarboxylate

Abstract

L- Methoxy-3-trimethylsilyloxybuta-l, 3-diene adds readily to dimethylmaleic anhydride, and the product can be converted into dimethyl cis-1, 2-dimethylcyclohex-4-ene-l, 2-dicarboxylate (3). The several steps required mean that this route compares unfavourably with direct addition of butadiene to the anhydride. The best route to the cis-diester (3) is cyclialkylation of the dianion from dimethyl 2, 3-dimethylbutanedioate with (Z)-1, 4-dichlorobut-2-ene. A bismethylation reaction is used to prepare imide (11), which can be converted into the cis-diester (1) only with considerable difficulty, and bismethylation of the dianion formed from dimethyl cis-cyclohex-4-ene-l, 2-dicarboxylate gives mai..