Iridium-Catalyzed Borylation of Secondary Benzylic C–H Bonds Directed by a Hydrosilane
摘要:
Most functionalizations of C-H bonds by main-group reagents occur at aryl or methyl groups. We describe a highly regioselective borylation of secondary benzylic C-H bonds catalyzed by an iridium precursor and 3,4,7,8-tetramethyl-1,10-phenanthroline as the ligand. The reaction is directed to the benzylic position by a hydrosilyl substituent. This hydrosilyl directing group is readily deprotected or transformed to other functional groups after the borylation reaction, providing access to a diverse set of secondary benzylboronate esters by C-H borylation chemistry.
A palladium(II)-catalyzed hydroboration of aryl alkenes with stable and easy-to-handle (pinacolato)diboron (B2pin2) under mild conditions has been developed. Acetic acid acted as the solvent and the hydrogen source, which has been identified by deuterium experiments. Notably, isomerization–hydroboration of allyl benzene derivatives was observed. As a result, a series of benzyl boronic esters were obtained
Cobalt-Catalyzed Hydroboration of Alkenes, Aldehydes, and Ketones
作者:Sem Raj Tamang、Deepika Bedi、Sara Shafiei-Haghighi、Cecilia R. Smith、Christian Crawford、Michael Findlater
DOI:10.1021/acs.orglett.8b02775
日期:2018.11.2
An operationally convenient and general method for hydroboration of alkenes, aldehydes, and ketones employing Co(acac)3 as a precatalyst is reported. The hydroboration of alkenes in the presence of HBpin, PPh3, and NaOtBu affords good to excellent yields with high Markovnikov selectivity with up to 97:3 branched/linear selectivity. Moreover, Co(acac)3 could be used effectively to hydroborate aldehydes
报道了使用Co(acac)3作为预催化剂对烯烃,醛和酮进行氢硼化的操作方便且通用的方法。在HBpin,PPh 3和NaO t Bu存在下,烯烃进行硼氢化可提供良好的产率,并具有高的马尔可夫尼科夫选择性和高达97:3的支链/线性选择性。而且,在温和的反应条件下,在不存在添加剂的情况下,Co(acac)3可有效地用于硼氢化醛和酮。醛基的分子间和分子内化学选择性还原发生在酮官能团之上。
Selective Benzylic CH‐Borylations by Tandem Cobalt Catalysis
作者:Pradip Ghosh、Roland Schoch、Matthias Bauer、Axel Jacobi von Wangelin
DOI:10.1002/anie.202110821
日期:2022.1.3
An inexpensive cobalt catalyst enables the combination of benzylic CH-borylation and dehydrocoupling to an overall acceptorless dehydrogenative functionalization of hydrocarbons at mild conditions. Mechanisticstudies indicate a tandem catalysis via molecular CoI catalysts.
Alkene Isomerization–Hydroboration Promoted by Phosphine-Ligated Cobalt Catalysts
作者:Margaret L. Scheuermann、Elizabeth J. Johnson、Paul J. Chirik
DOI:10.1021/acs.orglett.5b01135
日期:2015.6.5
Generated in situ from air-stable cobalt precursors or readily synthesized using NaHBEt3, (PPh3)(3)CoH(N-2) was found to be an effective catalyst for the hydroboration of alkenes. Unlike previous base-metal catalysts for alkene isomerizationhydroboration which favor the incorporation of boron at terminal positions, (PPh3)(3)CoH(N-2) promotes boron incorporation adjacent to pi-systems even in substrates where the alkene is at a remote position, enabling a unique route to 1,1-diboron compounds from alpha,omega-dienes.