Experiments towards the synthesis of corrins. Part XIII. A new synthesis of 2-cyano-Δ1-pyrroline 1-oxides and their behaviour towards a Grignard reagent

Abstract

2-Alkyl-Δ¹-pyrroline 1-oxides are readily nitrosated by isopentyl nitrite, giving the oximes of the corresponding pyrroline-2-carbonyl compounds. The pyrroline-2-carbaldehyde oximes can be deydrated to 2-cyano-derivatives by treatment with thionyl chloride in pyridine. Attack of methylmagnesium iodide on the sterically hindered 2-cyano-3,3,5,5-tetramethyl-Δ¹-pyrroline 1-oxide occurred at the cyano-group, to yield the corresponding 2-acetyl compound. In less hindered analogues preferential attack on the nitrone carbon atom was observed; the cyano-hydroxylamine derivatives so formed can undergo elimination of MglCN, yielding the parent Δ¹-pyrroline 1-oxide.