Geminal dimetalation of alkylidene-type carbenoids with silylboranes and diborons
摘要:
A novel and efficient method for gem-dimetalation of carbenoids has been demonstrated. Treatment of alkylidene-type lithium carbenoids with such an interelement compound as silylborane or diboron to generate the corresponding borate complex, followed by warming to room temperature, induced migration of the silyl or boryl group from a negatively charged boron atom to the carbenoid carbon to afford 1-boryl-1-silyl-1-alkenes or 1,1-diboryl-1-alkenes in good yields. Carbon-carbon bond forming transformations of the gem-dimetalated compounds mediated by boron or silicon is also described. (C) 2002 Elsevier Science Ltd. All rights reserved.
Geminal dimetalation of alkylidene-type carbenoids with silylboranes and diborons
摘要:
A novel and efficient method for gem-dimetalation of carbenoids has been demonstrated. Treatment of alkylidene-type lithium carbenoids with such an interelement compound as silylborane or diboron to generate the corresponding borate complex, followed by warming to room temperature, induced migration of the silyl or boryl group from a negatively charged boron atom to the carbenoid carbon to afford 1-boryl-1-silyl-1-alkenes or 1,1-diboryl-1-alkenes in good yields. Carbon-carbon bond forming transformations of the gem-dimetalated compounds mediated by boron or silicon is also described. (C) 2002 Elsevier Science Ltd. All rights reserved.
Silaborations of 1,3-cyclohexadiene and 1,3-cycloheptadiene were achieved using catalysts prepared from different combinations of phosphorus ligands and group10metal compounds. For the six-membered compound, 1,4-adducts with up to 82% ee were obtained employing Pt(0) and phosphoramidite ligands. For the seven-membered diene optimal conditions were found using catalysts based on Ni(0), but the highest
Enantioenriched beta-borylallylsilanes were synthesized by palladium-catalyzed enantioface-selective addition of the silicon-boron bond to terminal allenes using a palladium catalyst possessing a chiral monodentate phosphine ligand. Use of a silylborane bearing a chiral auxiliary on the boron atom was beneficial to gain enantioface selectivities as high as 96% de.
Asymmetric Silaboration of Terminal Allenes Bearing α-Stereogenic Centers: Stereoselection Based on “Reagent Control”
作者:Toshimichi Ohmura、Michinori Suginome
DOI:10.1021/ol060666j
日期:2006.6.1
A highly enantioface-selective silaboration of allenes having stereogenic centers at the alpha-positions of the double bonds has been achieved using a combination of a chiral silylborane(-)-2 and a chiral Pd/(R)-3 catalyst. The chiral reagent system efficiently controlled the stereochemistry of the new stereogenic centers even in the reactions of mismatched combinations.
Geminal dimetalation of alkylidene-type carbenoids with silylboranes and diborons
A novel and efficient method for gem-dimetalation of carbenoids has been demonstrated. Treatment of alkylidene-type lithium carbenoids with such an interelement compound as silylborane or diboron to generate the corresponding borate complex, followed by warming to room temperature, induced migration of the silyl or boryl group from a negatively charged boron atom to the carbenoid carbon to afford 1-boryl-1-silyl-1-alkenes or 1,1-diboryl-1-alkenes in good yields. Carbon-carbon bond forming transformations of the gem-dimetalated compounds mediated by boron or silicon is also described. (C) 2002 Elsevier Science Ltd. All rights reserved.