efficient heterogeneous catalyst for the selective borylation of benzylicC(sp3)–H bonds of alkylarenes including secondary derivatives, using pinacolborane as the borylating agent. A thorough physicochemical analysis reveals that in situ reduced ultrasmall Ni species on CeO2 during the reaction are the actual active species responsible for the borylation.
Cobalt-Catalyzed Benzylic Borylation: Enabling Polyborylation and Functionalization of Remote, Unactivated C(sp<sup>3</sup>)–H Bonds
作者:W. Neil Palmer、Jennifer V. Obligacion、Iraklis Pappas、Paul J. Chirik
DOI:10.1021/jacs.5b12249
日期:2016.1.27
have been synthesized and demonstrated as active for the C(sp(3))-H borylation of a range of substituted alkyl arenes using B2Pin2 (Pin = pinacolate) as the boron source. At longer reaction times, rare examples of polyborylation were observed, and in the case of toluene, all three benzylic C-H positions were functionalized. Coupling benzylic C-H activation with alkyl isomerization enabled a base-metal-catalyzed
Selective C−C Coupling of Vinyl Epoxides with Diborylmethide Lithium Salts
作者:Riccardo Gava、Elena Fernández
DOI:10.1002/chem.201901406
日期:2019.6.18
Vinyl epoxides and styrene oxide can react with diborylmethide lithiumsalts through an exclusive SN2 borylmethylation/ring opening in a regio‐ and diastereoselective way, depending on the nature of the substrate. The ring‐opening protocol provides homoallylboronates that can be transformed into challenging diastereomeric bishomoallylic alicyclic 1,3‐diols. Unprecedented 3‐borylated 1,2‐oxaborolan‐2‐ol
取决于底物的性质,乙烯基环氧化物和苯乙烯氧化物可以通过排他性和非对映选择性的方式,通过专有的S N 2硼甲基化/开环与甲基二硼化锂盐反应。开环方案提供了高烯丙基硼酸酯,可以将其转化为具有挑战性的非对映体双烯丙基烯丙基脂环式1,3-二醇。通过硼甲基化/ 2-甲基-2-乙烯基环氧乙烷的开环,然后进行分子内环化,制备了史无前例的3-硼化的1,2-氧杂硼烷-2-醇产品。
Ketone Synthesis from Benzyldiboronates and Esters: Leveraging α-Boryl Carbanions for Carbon–Carbon Bond Formation
作者:Boran Lee、Paul J. Chirik
DOI:10.1021/jacs.9b11944
日期:2020.2.5
method for the synthesis of ketones from readily available esters and benzyldiboronates is described. The synthetic method is compatible with a host of sterically differentiated alkyl groups, alkenes, acidic protons, amides and aryl rings having common organic functional groups. With esters bearing α-stereocenters, high enantiomeric excess was maintained during ketoneformation, establishing minimal competing
Palladium-Catalyzed Chemoselective Negishi Cross-Coupling of Bis[(pinacolato)boryl]methylzinc Halides with Aryl (Pseudo)Halides
作者:Hyojae Lee、Yeosan Lee、Seung Hwan Cho
DOI:10.1021/acs.orglett.9b02050
日期:2019.8.2
We describe a palladium-catalyzed chemoselective Negishicross-coupling of a bis[(pinacolato)boryl]methylzinc halide with aryl (pseudo)halides. This reaction affords an array of benzylic 1,1-diboronate esters, which can serve as useful synthetic handles for further transformations. The developed coupling reaction is compatible with various functional groups and can be easily scaled up. The coupling