A new stereospecific synthesis of unusual (Z)-β-branched Baylis-Hillman adducts
作者:Guigen Li、Han-Xun Wei、Steven Willis
DOI:10.1016/s0040-4039(98)00850-8
日期:1998.6
A new method has been developed for the stereospecific synthesis of unusual (Z)-β-branched Baylis-Hillman adducts with high selectivity (>99 %) in modest to good yields. The process involves successful formation of anionic β-substituted [α-(alkoxycarbonyl)vinyl]aluminum intermediates and their coupling with aldehydes and ketones catalyzed by n-Bu2BOTf at −78 °C.
Facile Approach to Optically Active α-Alkylidene-β-amino Esters by Thermal Overman Rearrangement
作者:Sung Il Lee、Soon Young Moon、Geum-Sook Hwang、Do Hyun Ryu
DOI:10.1021/ol1011746
日期:2010.7.16
A convenient synthetic method for enantioenriched (E)-α-alkylidene-β-amino esters has been developed through thermal Overman rearrangement. Readily accessible (Z)-β-branched Morita−Baylis−Hillman esters serve as chiral pool precursors. Thermalrearrangement proceeded through a concerted pseudopericyclic transition state to produce (E)-stereoselective products. We expanded the synthetic utilities of
Vinylalumination for the Synthesis of Functionalized Allyl Alcohols, Vinylepoxides, and α-Alkylidene-β-hydroxy-γ-lactones
作者:P. Veeraraghavan Ramachandran、Michael T. Rudd、Thomas E. Burghardt、M. Venkat Ram Reddy
DOI:10.1021/jo034954u
日期:2003.11.1
A modified hydroalumination protocol for the preparation of [alpha-(ethoxycarbonyl)vinyl]diisobutyl-aluminum and its beta-methyl or -phenyl analogues was developed. These vinylaluminum reagents react with aldehydes and ketones to provide the corresponding functionalized allyl alcohols in good to excellent yields. Perfluoroalkyl and -aryl carbonyl compounds, alpha-keto esters, alpha-acyl cyanides, and alpha-acetylenic ketones provide the corresponding alpha-hydroxyalkenes in high yields. The allyl alcohol product ratios from the vinylalumination of unsymmetrical alpha-diketones with [alpha-(ethoxycarbonyl)vinyl] diisobutylaluminum and its beta-methyl or -phenyl analogues depend on the steric and electronic environments of the ketones as well as the reagents. The products from the vinylalumination of alpha-bromoaldehydes and -ketones were cyclized With K2CO3 or KF under nonaqueous conditions to provide functionalized vinylepoxides in high yields. Vinylaluminations of keto-protected pyruvaldehyde provided the products, which were converted to alpha-alkylidene-beta-hydroxy-gamma-lactones.
Novel Functionalized Trisubstituted Allylboronates via Hosomi−Miyaura Borylation of Functionalized Allyl Acetates
A series of novel functionalized achiral and chiral allylboronates have been synthesized via the nucleophilic addition of boronates on allyl acetates derived via vinylalumination or Baylis-Hillman reaction of aldehydes. These reagents, upon allylboration with aldehydes, furnish,beta-substituted-alpha-methylene-gamma-butyrolactones stereoselectively.
Chemistry of substituted (.alpha.-carbethoxyvinyl)cuprates. 2. Stereospecific olefin synthesis