General, Regiodefined Access to α-Substituted Butenolides through Metal−Halogen Exchange of 3-Bromo-2-silyloxyfurans. Efficient Synthesis of an Anti-inflammatory Gorgonian Lipid
摘要:
A variety of alpha-substituted butenolides were efficiently prepared from 3-bromo-2-triisopropylsilyloxyfuran via lithium-bromine exchange and in situ quench with carbon or heteroatom electrophiles. The inherent flexibility of this methodology is illustrated by a short and efficient synthesis of an anti-inflammatory marine natural product.
Preparation and palladium-catalysed cross-coupling reactions of 3- and 4-tributylstannylfuran-2(5H)-ones
作者:Gregory J. Hollingworth、Gemma Perkins、Joseph Sweeney
DOI:10.1039/p19960001913
日期:——
Stannylfuranones 1 and 2 were prepared by ipso radical desulfurative stannylation of phenylsulfanylfuranones 3 and 16. Compounds 1 and 2 underwent Stille coupling reactions with aryl iodides to give 3- and 4-arylfuran-2(5H)-ones.
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
Deprotonation of N-benzyl-3-phenylselenylpyrrol-2(5H)-one 3 and furan-2(5H)-one 4 and reaction with aldehydes affords regioselectively 5-(1'-hydroxy)-gamma-butyrolactones and the aza-analogous butyrolactams with good diastereoisomeric excesses. The presence of Lewis acids enhances the diastereoisomeric ratios.This methodology is an alternative to Lewis acid mediated silyloxydiene condensation. (C) 2000 Elsevier Science Ltd. All rights reserved.