Efficient Synthesis of Furan-2-ylacetates, 7-(Alkoxycarbonyl)benzofurans, and 7-(Alkoxycarbonyl)-2,3-dihydrobenzofurans Based on Cyclization Reactions of Free and Masked Dianions: A “Cyclization/Dehydrogenation” Strategy
摘要:
A variety of furan-2-ylacetates have been prepared by dehydrogenation of monocyclic 2-alkylidene-tetrahydrofurans, which are readily available by cyclizations of open-chained 1,3-dicarbonyl dianions with 1-bromo-2-chloroethane. 5'H-[2,3']Bifuranyl-2'-ones are available based on sequential "cyclization/dehydrogenation" reactions of alpha-acetyl-gamma-butyrolactones. A variety of 7-(alkoxycarbonyl)-benzofarans and 7-(alkoxycarbonyl)-2,3-dihydrobenzofurans were prepared by a cyclization/ dehydrogenation strategy. These reactions rely on cyclizations of 2-oxocycloalkane-1-carboxylate/derived 1,3-dicarbonyl dianions ("free dianions") or 1,3-bis-silyl enol ethers ("masked dianions") with various 1,2-dielectrophiles.
Synthesis of Substituted Pyrazoles via Tandem Cross-Coupling/Electrocyclization of Enol Triflates and Diazoacetates
作者:David J. Babinski、Hector R. Aguilar、Raymond Still、Doug E. Frantz
DOI:10.1021/jo201042c
日期:2011.8.5
The synthesis of 3,4,5-trisubstituted pyrazoles via a tandem catalytic cross-coupling/electrocyclization of enoltriflates and diazoacetates is presented. The initial scope of this methodology is demonstrated on a range of differentially substituted acyclic and cyclic enoltriflates as well as an elaborated set of diazoacetates to provide the corresponding pyrazoles with a high degree of structural