Formation of Δ⁴-6-Keto Isomer in the Synthesis of Δ²-6-Keto Steroids Used as Intermediates in the Synthesis of Brassinolide and Analogous Plant Growth Stimulators

Abstract

The α,β-unsaturated Δ⁴-6-keto isomer is also formed in the synthesis of Δ²-6-keto steroids, both by heating the corresponding 3β-tosylates (or chlorides) with lithium salts in dimethylformamide or directly by heating the 3α, 5-cyclo-6-ketosteroids with p-toluenesulphonic acid in sulfolane.