Synthesis and oxidation of pregna-3,5-dien-20-ols and -20-one and selective reduction of pregna-3,5-dien-20-one

Pregna‐3,5‐dien‐20‐one (4) and (20S)‐ and (20R)‐pregna‐3,5‐dien‐20‐ol (2 and 3) were synthesized from progesterone. Oxidation of a mixture of 2 and 3 with Jones reagent gave 4, while a large excess of Jones reagent afforded besides 4, 6‐oxoprogesterone (5), 6β‐hydroxyprogesterone (6) and 5α‐pregnane‐3,6,20‐trione (7). With L‐selectride as reducing agent, reduction of 4 led to 2 and 3 in a ratio of about 1:1. However, some reducing agents gave a higher ratio of isomer 3.