Efficient preparation of 3-substituted-furan-2(5H)-ones and their direct vinylogous aldol addition

The deprotonation of 3-substituted-furan-2(5H)-ones 1, obtained via the hydrolysis of 3-substituted-2,5-dihydro-2,5-dimethoxyfurans, affords in the reaction with both aromatic and aliphatic aldehydes regioselectively the unsaturated 3-substituted 5-(1′-hydroxy)-γ-butyrolactones, such as 4, 5, 6, 7, 8, 9 and 10. The use of Lewis acids allows modulation of the diastereoisomeric ratios. The subsequent reduction, carried out with nickel boride, gives rise to the formation of the corresponding saturated 5-(1′-hydroxy)-γ-butyrolactones, such as 11, 12 and 13.