Allylboronates are highly attractive reagents for allyl additions. Enantiomericallypure, stable reagents with a stereogenic centre in alpha-position to boron are especially versatile, albeit often difficult to synthesize. Starting from boron-containing allyl alcohols 6 and 7, which are discussed in detail herein, a set of reagents were obtained via [3,3]-sigmatropic rearrangements and consecutive
A Novel Enantioselective (2<i>Z</i>)-Alk-2-enylation of Aldehydes via an Allyl-Transfer Reaction from Chiral Allyl Donors Prepared from (+)-Isomenthone
作者:Junzo Nokami、Kenta Nomiyama、Siddiqi M. Shafi、Kazuhide Kataoka
DOI:10.1021/ol0400140
日期:2004.4.1
A highlyenantioselective (2Z)-alk-2-enylation of aldehydes was successfully achieved by an allyl-transferreaction from a chiral allyl donor, which was easily obtained by separation of a diastereomeric mixture of the corresponding homoallylic alcohol gamma-adducts derived from (+)-isomenthone with alk-2-enylmagnesium chloride. [reaction: see text]
use of a convenient protecting group for boronates allows a selective, catalyzed SN2′ reaction to generate allylboronates which are applied for the synthesis of enantiomerically purehomoallylicalcohols. Depending on the configuration of both catalyst and the protecting group any of the four possible stereoisomers can be formed. The rationale behind the selective addition is supported by density functional
对硼酸酯使用方便的保护基可以选择性地催化S N 2'反应生成烯丙基硼酸酯,该烯丙基硼酸酯可用于合成对映体纯的均烯丙基醇。取决于催化剂和保护基的构型,可以形成四种可能的立体异构体中的任何一种。选择性加法背后的基本原理得到密度泛函理论计算的支持。
Stereoselective Synthesis of Secondary and Tertiary Boronic Esters via Matteson Homologation
作者:Markus Tost、Uli Kazmaier
DOI:10.1021/acs.orglett.3c02360
日期:2023.9.22
esters with lithium dichlorocarbenoids and various nucleophiles proved to be a useful method for the synthesis of functionalized polyketides in a highlystereoselective fashion. Via repeated homologation steps, only 1,2-anti- and 1,3-syn-configured products were obtained. Homologation with substituted carbenoids followed by reaction with carbon nucleophiles resulted in configurationally inverted products