Photocatalytic C–F Bond Borylation of Polyfluoroarenes with NHC-boranes

Abstract

The first photoredox-catalyzed defluoroborylation of polyfluoroarenes with NHC-BH3 has been facilely achieved at room temperature via a single-electron-transfer (SET)/radical addition pathway. This new strategy makes full use of the advantage of photoredox catalysis to generate the key boryl radical via direct activation of a B–H bond. Good functional group tolerance and high regioselectivity offer this protocol incomparable advantages in preparing a wide array of valuable polyfluoroarylboron compounds. Moreover, both computational and experimental studies were performed to illustrate the reaction mechanism.

Palladium-catalysed C–F alumination of fluorobenzenes: mechanistic diversity and origin of selectivity

“…The reactions of the monomeric aluminium(I) complex 1 40,41 with FB, diFBs and triFBs catalysed by 3 mol% [Pd(PCy 3 ) 2 ] in benzene or toluene solutions proceed extremely rapidly at 25 C. Facile C-F bond alumination to form 2a-h was observed. In all cases the reactions were complete within the acquisition of the rst time point (<5 min) as evidenced by 19 F NMR spectroscopy (Fig. 2).…”

“…7a). Monitoring this reaction as a function of time by 19 F NMR spectroscopy, revealed slow consumption of 4c at longer time points, suggesting this species may be a kinetic product which can equilibrate to the thermodynamic product 5c 0 . While independently prepared samples of 4c did not convert to 5c 0 under thermal conditions, addition of catalytic quantities of [Pd(PCy 3 ) 2 ] exposed an unprecedented and 100% atom efficient isomerisation reaction which interconverts the C-H functionalisation aluminium hydride to a C-F functionalised aluminium uoride (Fig.…”

“…12 An alternative method to prepare uorinated building blocks from uorobenzenes is C-F bond functionalisation. A number of non-catalysed, photo-catalysed and transition metal catalysed methods for the borylation, [13][14][15][16][17][18][19][20] magnesiation, [21][22][23][24] alumination [25][26][27][28] and silylation [29][30][31][32][33] of uorobenzenes have emerged in recent years. The advantage of these approaches is that they form new C-B, C-Mg, C-Al and C-Si bonds respectively, allowing access to main group intermediates that can be used in onwards reactions.…”

C-F bond activation under transition-metal-free conditions

“…In 2016, Hosoya's group [91] reported a single C-F bond cleavage of trifluoromethylarenes with an ortho-silyl group (Scheme 32). The activation of the hydrosilyl group with a trityl cation in the presence of nucleophiles allowed for selective C-F bond functionalization (183)(184)(185)(186)(187)(188)(189). The authors proposed that the reaction was triggered by hydride abstraction or underwent a concerted pathway involving hydride abstraction and C-F bond cleavage.…”

Synthesis of Polycyclic Furan and Chromene Derivatives via Cascade Reactions Enabled by Cleavage of Multiple C(sp3)−F Bonds

“…bond formation and precise retention of partially fluorinated scaffold, although most of the advances focus on the manipulation of single CÀ F bond. Compared with more activated aromatic [21][22][23][24][25] or vinylic analogues, [26][27][28][29][30][31][32][33] selective aliphatic C(sp 3 )À F functionalization of unreactive perfluoroalkyl substance with multiple CÀ F bonds attached remote to π-system is relatively uncommon. [34][35][36][37][38][39][40][41][42][43][44][45][46][47] The successful realization of this challenging issue is complicated by several apparent factors (Scheme 1A).…”