Racemic and asymmetric Diels-Alder reactions of 1-(2-oxazolidinon-3-yl)-3-siloxy-1,3-butadienes

Achiral and chiral 1-(2-oxazolidinon-3-yl)-3-siloxy-1,3-butadienes were pre pared from readily available starting materials. Although more stable than the parent 1-amino-3-siloxy dienes, the 1-(2-oxazolidinon-3-yl)-3-siloxy-1, 3-butadienes are still very reactive in Diels-Alder reactions, somewhat mo re than 1,3-dialkoxy-1,3-butadienes (e.g., Danishefsky's diene). The cycloa dditions of the achiral and chiral dienes with several different dienophile s were;examined The reactions proceeded in good yield, with modest to high endo selectivity. The chiral dienes exhibited excellent facial selectivity in cycloadditions with alpha -substituted acroleins, maleic anhydride and N -phenyl-maleimide; Upon; reduction and hydrolysis of the cycloadducts, subs tituted cyclohexenones were obtained with ee's ranging from 22% to >98%.