PHOTOCHEMICAL CYCLOADDUCTS .4. PHOTOCHEMICAL ADDITION OF OLEFINS AND ACETYLENE TO 3BETA-ACETOXYPREGNA-5,16-DIEN-20-ONE

The photochemical reaction of 3β-acetoxypregna-5,16-dien-20-one (I) with ethylene, aliene, cis- and trans-dichloroethylene, tetrafluoroethylene, hexafluoroacetone, and acetylene is described. The major products isolated from photolyses with ethylene and substituted ethylenes are the 16α,17α-fused cyclobutane adducts. Small amounts of 16β,17β-fused cyclobutane adducts and several rearrangement products are also isolated from the experiments with ethylene and tetrafluoroethylene. Acetylene adds to 1 under the same conditions to give the 16α,17α-cyclobutene (IS), whereas hexafluoroacetone adds to 1 to give the oxetane 21. The stereochemistry and orientation of the cyclobutane adducts are deduced mainly by spectroscopic (nmr and CD) methods. © 1969, American Chemical Society. All rights reserved.