Base-promoted reactions of β-enaminones with 2-bromo-2-methylpropanamides. Formation of 2-ketonyloxazolidin-4-ones and cyclohexanespiro-oxazolidin-4-ones

Abstract

Representative β-enaminones (1) and (2) react with N-alkyl-2-bromo-2-methylpropanamides (4a), (4b), and (4c) in the presence of NaH, to afford oxazolidin-4-ones (5) and (6) or spiro-oxazolidinone derivatives (7) and (8). The formation of an imidazolidin-4-one derivative (9) from 2-bromo-2-methylpropanilide (4c) is ascribed to the presence of an intermediate α-lactam (15). The behaviour of a spiro-oxazolidinone derivative on hydrolysis, reduction, and thiation is described.