The synthesis of halogenated and trifluoromethylated α-boryl ketones via a one-pot oxidative difunctionalization of alkenyl MIDA boronates is reported. These novel densely functionalized organoborons bearing synthetically and functionally valuable carbonyl, halogen/CF3 and boronate moieties within the same molecule are synthetically challenging for the chemist, but have great synthetic potential, as demonstrated by their applications in a straightforward synthesis of borylated furans. The generality of this reaction was extensively investigated. This reaction is attractive since the starting materials, alkenyl MIDA boronates, are easily accessible.
The copper-catalyzed stereoselective defluorinative borylation and silylation of gem-difluoroalkenes was developed. The protocol led to the exclusive formation of Z type monofluoroalkenyl borons and silanes in generally good efficiency with broad substrate scope. The products formed could be readily transformed to other Fcontaining molecules by taking advantage of the versatile reactivities of CÀB and CÀSi bonds. Experimental and theoretical mechanistic studies were conducted which support an olefin insertion/ syn-planar b-F elimination pathway.
A novel synthesis of α-CF3 and α-CF2H amines via the aminofluorination of gem-difluoroalkenes and mono-fluoroalkenes, respectively, is reported. The method employs Selectfluor as an electrophilic fluorine source and acetonitrile as a nitrogen source. Mechanistic studies revealed a single-electron oxidation/fluorine-abstraction/Ritter-type amination pathway. The protocol allowed the synthesis of a broad range of fluorinated amines including those bearing quaternary carbon centers with good efficiency and functional group tolerance.
α‐Haloboronates are useful organic synthons that can be converted to a diverse array of α‐substituted alkyl borons. Methods to α‐haloboronates are limiting and often suffer from harsh reaction conditions. Reported herein is a photochemical radical C‐H halogenation of benzyl N‐methyliminodiacetyl (MIDA) boronates. Fluorination, chlorination, and bromination reactions were effective by using this protocol. Upon reaction with different nucleophiles, the C−Br bond in the brominated product could be readily transformed to a series of C−C, C−O, C−N, C−S, C−P, and C−I bonds, some of which are difficult to forge with α‐halo sp2‐B boronate esters. An activation effect of B(MIDA) moiety was found.
A rhodium(III)-catalyzed C-H direct allylation reaction with 4-vinyl-1,3-dioxolan-2-ones has been developed. The reaction provides a facile and stereoselective access to substituted-(E)-allylic alcohols under mild and redox-neutral reaction conditions. Olefinic C-H activation is applicable, giving multifunctionalized skipped dienes in good yields. Minimal double-bond migration was observed.
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