Recent advances in transition-metal-catalyzed C–CN bond activations

Abstract

Recent advances in transition-metal-catalyzed C–CN bond activation, leading to a lot of important approaches such as cyanofunctionalization, cross-coupling and cyanation, are reviewed.

Cu‐Catalyzed Cyanation of Arylboronic Acids with Acetonitrile: A Dual Role of TEMPO

“…Therefore, aw ide range of oxidantsw ere examined in the presence of I 2 . [16] To our delight, TEMPO was the best oxidant, which gave the corresponding cyanated product 2a in 50 % yield ( [2][3][4][5][6][7][8][9][10][11][12][13][14]. When iPr 2 NH and H 2 Ow ere used as additives, we considered that they might combine with the boronic compound that is released from substrate 1a,w hich would drive the cyanation reaction forward and result in ah igher yield of the product.…”

“…Consequently,c atalytic activation of the acetonitrile CÀCN bond by transition metals hasr arely been explored. [2] Af ew examples of cyanation by employing the relatively safe acetonitrile as the cyano source have been documented by Cheng, Li, Zhu, Shen, and others. [3,4] Recently,w e disclosedt he Cu-catalyzed cyanation of aromatic CÀHb onds throughC H 3 ÀCN bond cleavage,i nw hich disilanep lays ac rucial role in promoting acetonitrile cleavage.…”

“…[5][6][7][8] However,t ot he besto fo ur knowledge,t here are only af ew examples regardingt he transformation of arylboronic acids into aryl nitriles, whichu se Pd, [9a-b] Rh, [9c] or Cu [10] catalysts or stoichiometric promoters. In these procedures, metal cyanides (e.g.,Z n(CN) 2 ,K 4 [Fe(CN) 6 ], CuCN, CuSCN)o rs pecific organic cyanides (e.g.,T MSCN,B nCN,N CTS, RSCN) were used as the cyanating agent. Identifying ways to generate "CN" in situ from simple and readily availablereagents by acombination process is ah ighly attractive strategy.S ince Chang's pioneering discovery,t here have been notable advances in this area; [8d, 11-14] however,t he main problemw ith these procedures is that superstoichiometric amountso fc oppers pecies were required.…”

“Cut and Sew” Transformations via Transition-Metal-Catalyzed Carbon–Carbon Bond Activation

“…In particular, carbocyanation of an unsaturated π moiety via C–CN bond activation provides a unique approach to prepare nitrile compounds. 92 Since the early work of intermolecular coupling between arylnitriles and internal acetylenes by Hiyama and Nakao in 2004, 93 a variety of nitrile derivatives, such as allylnitriles, 94 carbonocyanidates, 95 carbamoyl cyanides, 96 alkynylnitriles, and alkenylnitriles were demonstrated to be well compatible for such a “cut and sew” transformation. In addition, the carbocyanation reaction also proceeded in an intramolecular fashion, 93b,96a–b,97 where use of chiral ligands provided the cyclization products with high enantioselectivities.…”

“…The resulting alkyl/aryl/acyl–metal bond then undergoes migratory insertion into the unsaturated unit, such as alkenes, alkynes and allenes, 104 followed by subsequent C–CN bond-forming reductive elimination to furnish the “cut and sew” product 114 . Given that this area has recently been extensively reviewed by Nakao 92b–c, 105 , Chatani 106 , and others 92a,d,f,107 , detailed discussions will not be included in this perspective.…”