Contra-Thermodynamic, Photocatalytic <i>E</i>
→<i>Z</i>
Isomerization of Styrenyl Boron Species: Vectors to Facilitate Exploration of Two-Dimensional Chemical Space
作者:John J. Molloy、Jan B. Metternich、Constantin G. Daniliuc、Allan J. B. Watson、Ryan Gilmour
DOI:10.1002/anie.201800286
日期:2018.3.12
Designing strategies to access stereodefined olefinic organoboron species is an important synthetic challenge. Despite significant advances, there is a striking paucity of routes to Z‐α‐substituted styrenyl organoborons. Herein, this strategic imbalance is redressed by exploiting the polarity of the C(sp2)−B bond to activate the neighboring π system, thus enabling a mild, traceless photocatalytic isomerization
The carboboration of terminal alkynes was studied with a N‐heterocyclic carbene‐capped α‐cyclodextrin copper(I) complex as catalyst. The intermolecular reaction with CH3I gave linear (L) vinyl boron isomers with high selectivity. The intramolecular reaction with terminal alkynes led to exocyclic vinyl boronates and to an unexpected endocyclic (Z)‐isomer, suggesting an unusual mechanism promoted by
Copper(I)-Catalyzed Formal Carboboration of Alkynes: Synthesis of Tri- and Tetrasubstituted Vinylboronates
作者:Ricardo Alfaro、Alejandro Parra、José Alemán、José Luis García Ruano、Mariola Tortosa
DOI:10.1021/ja307670k
日期:2012.9.19
The first copper-catalyzed formal carboboration of alkynes, in which a C-B bond and a C-C bond are created in a single catalytic cycle, is presented. The reaction proceeds with high regioselectivity and syn-stereoselectivity to form tri- and tetrasubstituted vinylboronic esters from commercially available bis-(pinacolato)diboron. A subsequent cross-coupling reaction gives access to highly substituted alkenes.