Electron deficient borane-mediated hydride abstraction in amines: stoichiometric and catalytic processes

Abstract

Borane mediated hydride abstraction of amines efficiently generates useful iminium salts. This review explores this fascinating reactivity and discusses how the iminium intermediates are utilised in a variety of stoichiometric and catalytic processes.

A Photoredox-Catalyzed Approach for Formal Hydride Abstraction to Enable Csp3–H Functionalization with Nucleophilic Partners

“…Diphenyl and triphenyl C-H positions were also viable substrates that produced excellent yields (9, 10). Aryl-substituted heterocycles were amenable to fluorination at the benzylic position, as both 5-and 6-membered rings were fluorinated in modest yields (11)(12)(13)(14). Excitingly, benzylic sites adjacent to electron-withdrawing groups successfully provided a-fluoro products in one step (14,15).…”

“…1 The abundance of unactivated Csp 3 -H bonds in small molecules makes them the ideal precursors for LSF, but direct C-H functionalization transformations remain a challenging feat. 2 Current well-established mechanistic designs for derivatizing C-H bonds include: 1) deprotonation 3 , 2) oxidative addition into a C-H bond via a metal catalyst [4][5][6] , 3) insertion via a carbene or nitrene species 7-9 , 4) HAT to access nucleophilic carboncentered radicals [10][11][12] , and lastly, 5) hydride abstraction [13][14][15][16][17][18] . While the first four strategies are widespread and fairly general ( Fig.…”

Towards the Development of Frustrated Lewis Pair (FLP) Catalyzed Hydrogenations of Tertiary and Secondary Carboxylic Amides

“…[19][20][21] Amongst recent developments, e.g. C-H bond activations, [22][23][24][25][26][27] acceptorless dehydrogenations, [28][29][30] or metal-free cross-couplings, 22,31,32 the hydrogenation is still the most utilized and intensively investigated reaction of FLPs. [33][34][35] Whereas the hydrogenation of functional groups, e.g.…”

“…[4][5][6][7][8][9] Milestones 1-3 in this chemistry are certainly the development of highly active intramolecular FLPs, [10][11][12] asymmetric hydrogenations, 11,[13][14][15] olefin 16 and alkyne 17,18 hydrogenation, and the hydrogenation of ketones. [19][20][21] Amongst recent developments (e.g., C-H bond activations, [22][23][24][25][26][27] acceptorless dehydrogenations, [28][29][30] or metal-free cross-couplings 22,31,32 ), hydrogenation is still the most utilized and intensively investigated reaction of FLPs. [33][34][35] Whereas the hydrogenation of functional groups (e.g., imines, enamines, oximes, or ketones) leaves the molecules functionalized, the complete reductive removal of a functional group is a more challenging task.…”

A Photoredox-Catalyzed Approach for Formal Hydride Abstraction to Enable Csp3–H Functionalization with Nucleophilic Partners

“…1 The abundance of Csp 3 -H bonds in small molecules makes them the ideal precursors for 'late-stage functionalization' (LSF), and thus, direct C-H functionalization transformations are still a flourishing area of research. 2 Current well-established mechanistic designs for derivatizing C-H bonds include 3 : 1) deprotonation 4 , 2) oxidative addition into a C-H bond via a metal catalyst 5,6 , 3) insertion via a carbene or nitrene species [7][8][9] , 4) HAT to access nucleophilic carbon-centered radicals [10][11][12] , and lastly, 5) hydride abstraction [13][14][15][16][17][18][19] (Fig. 1a).…”