Unusual reactions of steroidal and non-steroidal 1,5-dioximes. Stereochemistry and mechanism of formation of N-hydroxy-piperidine analogues

Abstract

4,5-Secocholestane-3,5-dioxime on NaBH₄ reduction gave N-hydroxy-3β-methyl-4-aza-5α-cholestane and N-hydroxy-3α-methyl-4-aza-5β-cholestane. The stereochemistry of the products was fully established by converting the N-hydroxy compounds to N-chloro compounds which resulted in ¹H nmr signals separating out from the steroid envelope. The dioxime on reaction with NH₂ OCH₃ underwent a regiospecific replacement of the oxime at C-3 by an oxime ether. In both these reactions this and other 1,5 dioximes exhibit unique behaviour not shown by isolated oximes. Arguments are presented pin-pointing a single mechanism involving a "oxadiaza" intermediate lsomeric with the dioxime.