CATALYSIS BY LEWIS-ACIDS AT HIGH-PRESSURE AS A METHOD OF INVOLVING HINDERED STEROID DIENOPHILES IN THE DIELS-ALDER REACTION

The joint action of Lewis acids and high pressure permits the Diels-Al der reaction to be conducted with high yields with greatly sterically hindered steroid dienophiles, which are virtually unreactive under nor mal conditions. The [2 + 4]-cycloadditions of dienes to DELTA16-20-, D ELTA1-3-, DELTA1,4-3-, and DELTA4,6-3-ketones proceed stereospecifical ly with the formation of one stereoisomer for each cycloadduct. The re actions of the steroid dienes studied give mixtures of two monocycload ducts at both double bonds of the steroid, with predominance of the ad duct at the sterically less-hindered double bond (DELTA1- and DELTA6-) . The method developed is a new method of producing various modified s teroids with possible hormonal or antihormonal activity.