The reaction of cyclic and open-chain diastereomerically pure secondary organoboranes with diisopropylzinc allows the preparation of secondary dialkylzinc reagents with good to excellent retention of configuration as shown by deuterolysis and CuI- and Pd0-mediated reactions with electrophiles. The importance of a high boron-zinc exchange rate to obtain high diastereoselectivity has been shown. Improvement
Mixed acyclic dialkylzincs are stereoselectively prepared from E- and Z-trisubstituted alkenes.
混合无环二烷基锌是从E-和Z-三取代烯烃立体选择性地制备的。
Steric Parameters in the Ir-Catalyzed Regio- and Diastereoselective Isomerization of Primary Allylic Alcohols
作者:Houhua Li、Clément Mazet
DOI:10.1021/ol403023x
日期:2013.12.20
The iridium-catalyzed diastereo- and regioselective isomerization of primary allylic alcohols using Crabtree's catalyst or sterically modified analogs is reported. The importance of the size of the substituents on either the substrates or the catalysts has been rationalized by linear free energy relationships.
731. Epimeric dihydroaromatic hydrocarbons: stereospecific syntheses of cis- and trans-1,2-dihydro-1,2-dimethylnaphthalenes and 9,10-dihydro-9,10-dimethylanthracenes
作者:L. M. Jackman、J. W. Lown
DOI:10.1039/jr9620003776
日期:——
[1,2]- and [1,4]-Wittig rearrangements of α-alkoxysilanes: effect of substitutions at both the migrating benzylic carbon and the terminal sp2 carbon of the allyl moiety
作者:Edith N. Onyeozili、Luis M. Mori-Quiroz、Robert E. Maleczka
DOI:10.1016/j.tet.2012.10.091
日期:2013.1
Substituted alpha-alkoxysilanes can be deprotonated by alkyllithium bases and made to undergo Wittig rearrangements to afford the [1,4]- and [1,2]-rearranged products in varying ratios. Substitution at the benzylic migrating carbon and/or at the allylic carbon of the allyl moiety impacts the rearrangement reaction, influencing the reactivity as well as the [1,4]-/[1,2]-selectivity. Diastereomeric alpha-alkoxysilanes show different reactivities with the syn diastereomer being the more reactive isomer. (c) 2012 Elsevier Ltd. All rights reserved.