Oxidative Geminal Functionalization of Organoboron Compounds

Abstract

Excellent tolerance: Stable acylboronates equipped with N-methyliminodiacetyl (MIDA) boryl groups ([B]) were prepared by using a sequence of oxidative manipulations at the boron-bound carbon center (green in scheme). Chemoselective transformations of these acylated organoboron building blocks yielded a range of multifunctionalized boron derivatives and supplied access to valuable borylated heterocycles (see scheme).

Amphoteric α-Boryl Aldehyde Linchpins in the Synthesis of Heterocycles

“…Irradiation of the α-boryl Barton ester with a 250 W tungsten−halogen lamp in the presence of O 2 and tert-butyl thiol afforded the corresponding α-hydroxy MIDA boronates (Scheme 16). 28 In general, arylsubstituted α-boryl Barton esters resulted in the formation of a number of unidentifiable side-products as compared with the alkyl-substituted α-boryl Barton esters. This is attributed to the delocalization of the benzylic α-boryl radical.…”

“…As was the case with α-bromo boryl aldehyde, condensation with thioamides and thioureas in DMF at elevated temperatures affords the trisubstituted 4-boryl thiazoles (Scheme 17). 28 The use of α-bromo-acyl boronates and α-bromo boryl aldehydes as linchpin reagents permits access to both 4-and 5-boryl thiazoles with full control of regiochemistry.…”

A Reagent for the One‐Step Preparation of Potassium Acyltrifluoroborates (KATs) from Aryl‐ and Heteroarylhalides

“…[5] Unfortunately, the reaction conditions and workup (KHF 2 ) precluded the synthesis of many substrates, including those containing basic nitrogen atoms, esters, and even many aryl halides. [7] In this report we document a novel reagent for the onestep synthesis of KATs from aryl halides that is suitable for preparing a broad range of aromatic and heteroaromatic KATs (Scheme 1). [7] In this report we document a novel reagent for the onestep synthesis of KATs from aryl halides that is suitable for preparing a broad range of aromatic and heteroaromatic KATs (Scheme 1).…”

Cyclopropanation of Terminal Alkenes through Sequential Atom‐Transfer Radical Addition/1,3‐Elimination

“…[43][44][45] a-Haloboronic esters have been used in tin-mediated (Scheme 1A) [46][47][48][49] and metal-catalyzed radical processes. Finally,1 -borylated alkyl radicals were involved in the elegant nickel-catalyzed alkylation and arylation of a-haloboronic esters developed by the Fu [54] and Martin [55] groups,respectively.1-Borylated alkyl radicals have also been generated from Barton esters [56] and xanthates [45] as well as through radical addition to vinylboronates. [53] Interestingly,p inacol iodomethylboronic Figure 1.…”