improved generation of chiral cationic iridium catalysts for the asymmetricisomerization of primaryallylicalcohols is disclosed. The design of these air‐stable complexes relied on the preliminary mechanistic information available, and on Charton analyses using two preceding generations of iridium catalysts developed for this highly challenging transformation. Sterically unbiased chiral aldehydes
Synthesis of Silicon Substituted Cyclopropylmethyl Alcohols in Optically Active Form<i>via</i>Asymmetric Simmons-Smith Reaction of γ-Silicon Substituted Allylic Alcohols
作者:Yutaka Ukaji、Kazunori Sada、Katsuhiko Inomata
DOI:10.1246/cl.1993.1227
日期:1993.7
Optically active silicon substituted cyclopropylmethyl alcohols were synthesized through asymmetricSimmons-Smithreaction; that is, the reaction of γ-silicon substituted allylic alcohols with diethylzinc and diiodomethane utilizing (+)-diethyl tartrate as a chiral auxiliary was found to afford the corresponding silicon substituted cyclopropylmethyl alcohols with high stereoselectivity up to 92% ee
Copper(I) <i>tert</i>-Butoxide-Promoted 1,4 C<sup>sp</sup><sup><sup>2</sup></sup>-to-O Silyl Migration: Generation of Vinyl Copper Equivalents and Their Stereospecific Cross-Coupling with Allylic, Aryl, and Vinylic Halides
copper(I) tert-butoxide and allylic halides followed by the tetrabutylammonium fluoride-assisted hydrolysis produced the allylation products, 2,5-alkadien-1-ols, with complete retention of configuration. Similar treatment of the organometallic intermediates with aryl and vinylichalides in the presence of palladium(0) catalyst gave the corresponding cross-coupling products in good yields. The stereoselective
Stereoselective synthesis of terminal 1,3-butadienes by the condensation reaction of aldehydes and ketones with .gamma.-trimethylsilyl-substituted allylboranes
作者:Kung K. Wang、Chin Liu、Yu Gui Gu、Friedrich N. Burnett、Prem D. Sattsangi
DOI:10.1021/jo00005a045
日期:1991.3
Allylboranes 7-12, readily prepared from allenylsilanes 1-6 by hydroboration with 9-borabicyclo[3.3.1]nonane, smoothly condense with aldehydes and ketones to afford, after basic or acidic workup to promote the Peterson olefination reaction, a variety of terminal 1,3-butadienes. The dienes derived from aldehydes have high isomeric purity except in the cases with allylborane 12. Apparently, high diastereoselectivity was obtained during the condensation step with 7-11 to form 14. In each case, by simply changing the workup conditions to induce syn or anti elimination of hydroxytrimethylsilane, either the Z or the E isomer of the diene was obtained.
[GRAPHICS]The cyclic silyl ethers, 2,2-dimethyl-1-oxa-2-slia-3-cyclopentenes, were produced by the treatment of (2)-gamma -trimethylsilyl allylic alcohols with a catalytic or stoichiometric amount of lithium tort-butoxide. On the other hand, successive treatment of the alcohols with copper(l) tert-butoxide and allylic halides followed by the tetrabutylammmonium fluoride assisted hydrolysis produced the allylation products, 2,5-alkadien-1-ols, with complete retention of configuration of the double bond.