&Methyl-1, 7-nonadiene fails to cyclize at 440, but does cyclize to an appreciable extent at 490'giving l-methyl-2-isopropenylcyclohexane. The carbomethoxy group facilitates thermal cyclization as shown by the fact that methyl 5, 9-dimethyl-2, Mecadienoate (X) cyclizes rapidly at 400'. The products are three diaetereomeric methyl 8-p-menthene-3-acetates (XI), the major one of which is believed to be the most stable diastereomer, XII. Monocyclic ...
