A General Approach to Deboronative Radical Chain Reactions with Pinacol Alkylboronic Esters. (4th June 2020)

• Record Type: Journal Article
• Authors: André‐Joyaux, Emy; Kuzovlev, Andrey; Tappin, Nicholas D. C.; Renaud, Philippe
• Is Part Of: Angewandte Chemie. Volume 132:Number 33(2020)
• Page Start: 13963
• Page End: 13968
• Publication Date: 2020-06-04
• Subjects: deborylation -- organoboron compounds -- pinacol boronic esters -- radical reactions -- transesterification; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202004012
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: The generation of carbon‐centered radicals from air‐sensitive organoboron compounds through nucleohomolytic substitution at boron is a general method to generate non‐functionalized and functionalized radicals. Due to their reduced Lewis acidity, alkylboronic pinacol esters are not suitable substrates. We report their in situ conversion into alkylboronic catechol esters by boron‐transesterification with a substoichiometric amount of catechol methyl borate combined with an array of radical chain processes. This simple one‐pot radical‐chain deboronative method enables the conversion of pinacol boronic esters into iodides, bromides, chlorides, and thioethers. The process is also suitable the formation of nitriles and allylated compounds through C−C bond formation using sulfonyl radical traps. The power of combining radical and classical boron chemistry is illustrated with a modular 5‐membered ring formation using a combination of three‐component coupling and protodeboronative cyclization. Abstract : Well I'll B : Activation of the radical‐inactive pinacol alkylboronic esters through a simple transesterification process provides access to highly reactive radical precursors that can be involved in a broad range of radical chain reactions involving C−X, C−C and C−H bonds. Merging this process with the unique and rich chemistry of boronic esters holds tremendous potential for synthetic applications.