Synthesis and reactions of 1,1-dichloro-2,2,6,6-tetramethyl-4-oxaspiro-[2.3]hexan-5-one

Abstract

The addition of dichlorocarbene to 2,2,4-trimethylpent-3-en-3-olids (I) gave the spirolactone, 1,1-dichloro-2,2,6,6-tetramethyl-4-oxaspiro[2.3]hexan-5-one (II). The spirolactone (II) on pyrolysis gave 4-chloro-2,2,5-tri-methyl-3-oxohex-4-enoyl chloride (III). Aluminium chloride catalysed rearrangement gave 3-dichloromethyl-ene-2,2,4-trimethylpentan-4-olide (VII). Methanolysis occurred with acyl attack to give methyl 4-chloro-2,2,5-trimethyl-3-oxo-hex-4-enoate (IX).