Stereo- and Enantioselective Routes to Functionalised Cyclohexenes via Heterodiene Cycloadditions of 6-Oxocyclohexene-1-carbaldehydes with Ketene Acetals

摘要

Various substituted cyclohexenes related to #alpha#-cyclocitral have been prepared using the heterodiene cycloadditions of 2-formyl-4,4-dimethyl-2-cyclohexen-1-one 4 with ketene acetals as the pivotal step. The key intermediates are accessible in homochiral form via an auxiliary-based sequence in which a C_2-symmetric ketene acetal derived from 1,2-bis(2-methylphenyl)ethane-1,2-diol 2a serves as the 2#pi# component. The diol 2a can be recovered in optically pure form.