Studies on conformation and reactivity. Part IX. Stereochemical aspects of the Diels–Alder reaction of diethyl azodicarboxylate with steroid dienes

Abstract

Diethyl azodicarboxylate (I) reacts readily with 3β-benzoyloxy-20-acetoxypregna-5,16,20-triene (V) affording in high yield two isomeric Diels–Alder adducts differing only in their stereochemistry at C(16), 16α-(VIa)(major product) and 16β-(VIb)(minor product). Formation of any Alder-ene type products is not observed. The epimeric adducts (VIa) and (VIb) are hydrolysed to diastereoisomeric 20-keto-16α,17α-(VIIa) and 20-keto-16β,17β-(VIIb) respectively. Lithium aluminium hydride reduction of (VIIa) and (VIIb) affords new steroid amines (VIIIa) and (VIIIb) with the N¹N²-dimethylhydrazo-function. O.r.d. and c.d. analysis of (VII) illustrates the successful application of the Octant Rule to the conformational analysis of the dissymmetric 4-oxoperhydropyridazine system (IV). Similar results are obtained with other steroid 16,20-dienes as substrates and also with azodicarboxamide (II) as dienophile.