C-Quaternary alkynyl glycinols via the Ritter reaction of cobalt complexed alkynyl glycols

Abstract

A novel approach to C-quaternary alkynyl glycinols based on the Ritter reaction of acetonitrile with cobalt complexed alkynyl glycols is presented. The reaction is promoted by acids such as H₂SO₄ or BF₃·Et₂O to give oxazolines as the reaction products. These are subjected to cobalt complex cleavage in oxidative conditions and subsequent acidic hydrolysis providing amino alcohols. The substrates for the Ritter reaction can be easily assembled to introduce structural diversity at both variable positions. The Ritter reaction conditions for oxazoline formation is compatible with a range of substituents at the alkyne terminal position providing oxazolines in moderate to good yields. Methyl, hydroxymethyl and silyloxymethyl substituents at the reaction center of glycols are well tolerated, while a phenyl group in this position is detrimental to the reaction.