Asymmetric syntheses of 1,6-dialkyl-1,4-cyclohexadiene derivatives

Article abstract of DOI:10.1021/ja00013a032

Ortho-lithiation-alkylation of tertiary benzamide 3 provides a series of 2-substituted chiral benzatnides 3a-g (Scheme I). Birch reduction of 3a-j followed by alkylation of the resulting chiral amide enolate with Mel at -78 °C gives 1,6-di-alkyl-1,4-cyclohexadiene derivatives 4a-j with excellent diastereoselectivities (Table I). Applications of this asymmetric synthesis are illustrated by conversions of 4g to enantiomerically pure bicyclic lactone 9 and octalone 11 (Scheme III) and 4j to hexahydro-9-anthracenone 14 (Scheme IV).