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■ Pseudoesters and Derivatives XXXVI. Reactions of Enolates of 5-Ethylthiofuran-2(5H)-ones with Aromatic Aldehydes: A Synthesis of Losigamone

M. Rosario Martín, M. Victoria Martín, Ana Martinez de Guereñu, and J. Luis Ortego

*Inst. de Química Orgánica General, Juan de la Cierva 3, Madrid 28006, Spain

Abstract

The furanones (3a) and (3b), key intermediates in our approach to losigamone (1₂), have been prepared by reaction of 2-chlorobenzaldehyde with the enolates (2A) and (2B) of the corresponding tetronic acid derivatives (2a) and (2b). The reductive conversion of 3b into 1 was carried out with Raney nickel. However, 3a remains unchanged after treatment with Reney nickel or aluminium amalgam. The addition of the enolates (2A) and (2B) to 2-chlorobenzaldehyde led in regioselective manner to the corresponding 5-hydroxyarylfuranones (3a) and (3b). Whereas the addition of 2B to benzaldehyde affords, in a 60:40 ratio, the C-5 and C-3 hydroxybenzylfuranones (7b) and (8b).