Enantioselective Syntheses of (<i>Z</i>)-6′-Boryl-<i>anti</i>-1,2-oxaborinan-3-enes via a Dienylboronate Protoboration and Asymmetric Allylation Reaction Sequence
作者:Jichao Chen、Ming Chen
DOI:10.1021/acs.orglett.0c02657
日期:2020.9.18
reported. A Cu-catalyzed highly stereoselective 1,4-protoboration of 1,1-bisboryl-1,3-butadiene is developed to generate (E)-α,δ-bisboryl-crotylboronate. The chiral phosphoric-acid-catalyzed asymmetric allylboration of aldehydes with the boron reagent produces 6′-boryl-anti-1,2-oxaborinan-3-enes with excellent Z-selectivities and enantioselectivities. The product contains a vinyl and alkyl boronate unit
Treatment of 1,1-[bis(pinacolato)boryl]alkenes with excess of 1-bromo-1-lithioethene was found to give 2,3-bis[(pinacolato)boryl]-1,3-dienes in moderate to good yields. Synthetic applications of 2,3-[bis(pinacolato)boryl]-1,3-butadiene were also demonstrated.
Highly Diastereo‐ and Enantioselective Synthesis of 3,6′‐Bisboryl‐
<i>anti</i>
‐1,2‐oxaborinan‐3‐enes: An Entry to Enantioenriched Homoallylic Alcohols with A Stereodefined Trisubstituted Alkene
作者:Jichao Chen、Evangelos Miliordos、Ming Chen
DOI:10.1002/anie.202006420
日期:2021.1.11
The three boryl groups in the products are properly differentiated and can undergo a variety of chemoselective transformations to produce enantioenriched homoallylic alcohols with a stereodefinedtrisubstitutedalkene.
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.