Chromium(II)-Mediated Stereodivergent Additions of Allylic Phosphates and Halides to Aldehydes
作者:Stefan Nowotny、Charles E. Tucker、Carole Jubert、Paul Knochel
DOI:10.1021/jo00114a026
日期:1995.5
The addition of gamma-disubstituted allylchromium(III) reagents to aldehydes proceeds in a stereodivergent manner, in contrast to the case of gamma-monosubstituted allylchromium(III) species. The method allows the preparation of a variety of homoallylic alcohols bearing a quaternary center of defined relative configuration in the alpha-position. The preparation of both stereomeric homoallylic alcohols 13 is possible by using either of the two (E)- or (Z)-allylic precursors. The reaction has been extended to a gamma-monosubstituted beta-(trimethylsilyl)allylic system. The intermediate allylic chromium(III) reagents can be conveniently prepared from the corresponding phosphates (or chlorides) in DMPU or THF in the presence of catalytic amounts of LiI.
A stereoselective synthesis of 3,3-disubstituted allylborane derivatives using haloboration reaction and their application for the diastereospecific synthesis of homoallylic alcohols having quaternary carbon
3,3-Disubstituted allylborane derivatives (1c) can be prepared stereoselectively from the haloboration adducts of 1-alkynes and they afford homoallylic alcohols having quaternary carbon (2c) diastereospecifically by the reaction with aldehydes.
Diastereo-, Enantio-, and <i>anti-</i>Selective Formation of Secondary Alcohol and Quaternary Carbon Stereocenters by Cu-Catalyzed Additions of B-Substituted Allyl Nucleophiles to Carbonyls
作者:Emilie Wheatley、Joseph M. Zanghi、Simon J. Meek
DOI:10.1021/acs.orglett.0c03495
日期:2020.12.4
secondary homoallylic alcohols containing α-quaternary carbon stereogenic centers in high diastereo- and enantioselectivity (up to >20:1 dr and >99:1 er) is disclosed. Transformations employ readily accessible aldehydes, allylic diboronates, and a chiral copper catalyst and proceed by γ-addition of in situ generated enantioenriched boron-stabilized allylic copper nucleophiles. The catalytic protocol