Stereo- and enantioselective routes to functionalised cyclohexenes via heterodiene cycloadditions of 6-oxocyclohexene-1-carbaldehydes with ketene acetals

Various substituted cyclohexenes related to alpha-cyclocitral have been pre pared using the heterodiene cycloadditions of 2-formyl-4,4-dimethyl-2-cycto hexen-1-one 4 with ketene acetals as tbe pivotal step. The key intermediate s are accessible in homochiral form via an auxiliary-based sequence in whic h 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 on be recovered in op tically pure form. (C) 1999 Elsevier Science Ltd, All rights reserved.