Catalytic Nitrile Hydroboration: A Route to N,N‐Diborylamines and Uses Thereof

Abstract

Catalytic reduction of nitriles is considered as an attractive and atom‐economical route to a diversity of synthetically valuable primary amines. Compared to other methods, dihydroboration approach has been developed relatively recently but has already attracted the attention of many research groups due to reasonably mild reaction conditions, selectivity control and the access to N,N‐diborylamines, which emerged as powerful reagents for C−N bond forming reactions. Early developments in catalytic dihydroboration of nitriles implied precious metal catalysts along with harsh conditions and prolonged reaction times, whereas recent advances mostly rely on base and main group metal catalytic systems with significantly improved profiles. This minireview aims to provide an overview of advances and challenges of dihydroboration of nitriles with d‐, f‐ and main group metal catalysts. Mechanistic features of different catalytic systems, functional group tolerance and scope of the methods are also presented. The synthetic utility of N,N‐diborylamies, beyond simple protodeborylation, is discussed in the aspect of N‐arylation, imine and amide synthesis.

Hydroboration of Nitriles, Esters, and Carbonates Catalyzed by Simple Earth‐Abundant Metal Triflate Salts

“…[17a] Akali or alkaline earth, [19] second-row transition metals, [13a,20] actinides, [21] and other metals, [22] have also been reported as catalyst for nitrile hydroboration. [23] The hydroboration of carbonates or esters, on the other hand, has less frequently been explored. Only a few examples have been reported with magnesium-based catalysts, [15a,24] while using other earth-abundant metal based catalysts is scarce.…”

“…Trovitch and co‐workers, for example, have reported a few cobalt [17] and manganese [18] complexes that are active for the dihydroboration of nitriles with TOFs of up to 380 h −1 [17a] . Akali or alkaline earth, [19] second‐row transition metals, [13a,20] actinides, [21] and other metals, [22] have also been reported as catalyst for nitrile hydroboration [23] …”

Iron-catalysed hydroboration of non-activated imines and nitriles: kinetic and mechanistic studies

“…[12][13][14][15] Thus it is unsurprising that catalytic hydroboration of nitriles, [16][17][18][19][20] carbodiimides [21][22][23][24][25] and imines [26][27][28] are common methods used to prepare amines. Many experimental protocols have been studied; 29 catalysts employed in imine hydroboration range from main group elements, [30][31][32] preciousmetals [33][34][35][36] and, rare earth metals. 21,37 The rst report of imine hydroboration catalysed by a transition metal was by Baker and Westcott and used a bidentate phosphine ligated gold(I) complex (5 mol%) and catecholborane in 1995.…”

Recent Advances in Chemical Modifications of Nitriles

“…Nevertheless, harsh reaction conditions were usually required, such as the use of strong acids or bases, high temperature and pressure. [7] To overcome these issues, various catalysts both in homogeneous and heterogeneous systems including transition metal catalysts, [8] ionic liquids, [9][10] metal nanoparticles, [11] metal organic frameworks (MOFs), etc. [12,13] have been developed to activate the carbon-nitrogen triple bond and further facilitated the conversions of nitriles.…”