TRICARBONYLS - REACTIVE MODEL DIENOPHILES FOR ASYMMETRIC DIELS-ALDER REACTIONS

The hetero-Diels-Alder reaction of 2-methyl-1-(1-phenylalkoxy)-butadie nes 5a-d with cyclic triketones proceeds smoothly at room temperature in excellent yield and high diastereoselectivity. The configuration of the cycloadducts 6a and 6b was determined by X-ray single crystal ana lysis. Mild acidic hydrolysis of the cycloadduct 6a using SiO2 as a pr omoter yielded an alpha,beta-unsaturated aldehyde trans-9. The trans-e poxides 10 a-d can be obtained from 6a-d using a freshly prepared solu tion of dimethyldioxirane in acetone.