Selective Double Hydroboration and Dihydroborylsilylation of Organonitriles by an Iron–indium Cooperative Catalytic System

Abstract

Organonitriles (RC≡N) were selectively converted into the corresponding diborylamines (RCHN(Bpin)) in reactions with pinacolborane (pinBH) in the presence of a catalytic amount of the iron-indium complex [Fe(CHCN)][cis-Fe(CO)(InCl)]. The catalytic reaction mechanism was tentatively proposed. In addition, this catalytic system was found to be applicable for the synthesis of borylsilylamine in high yield when organonitrile was treated with hydroborane and hydrosilane simultaneously.

Catalytic Hydroboration of Organic Nitriles Promoted by Aluminum Complex

“…Although several reports in literature [41][42][43][44][45][46][47][48][49] have described the catalytic hydroboration of aryl nitriles with lower conversion to the desired diboryl amine products even after prolonged reaction times, the current protocol demonstrates that we can achieve the target compounds in very good yields under mild conditions and in shorter reaction times. To extend the synthetic scope of this response, we also tested the chemoselective hydroboration of nitriles.…”

“…[36][37][38] On the other hand, while the reduction of aryl and alkyl nitriles can be achieved using stoichiometric quantities of maingroup reducing agents such as LiAlH 4 and NaBH 4 , [39] the combustible nature of these reagents and large quantities of inorganic waste by-products they generate render the process unattractive, and hence reductive hydroboration is preferable in order to provide further functionality to the resultant amine. [40] Recently, Nakazawa et al reported the use of an ironindium complex as a catalyst for the hydroboration of aryl and alkyl nitriles, [41] while Nikonov et al introduced the Mo(IV) complex as a catalyst (5 mol %), which resulted in the hydroboration of acetonitrile and benzonitrile using the only catecholborane. [42][43] The Szymczak working group and Gunanathan et al have also reported that a ruthenium metal-based complex (1 mol %) catalyzed nitrile and imine hydroboration in preparing the corresponding diborylamines.…”

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

“…[19,20] During the last decade, since the discovery of Mo-catalyzed dihydroboration of nitriles, [19,20] a number of research publications concerning other catalytic systems have appeared in the literature, with the vast majority of developments being accomplished in the area of transition metal catalysis. The newly developed methods mostly rely on Ru [22,29,30] and Co [21,23,31,32] catalysts, with a handful of examples using Ti, [33,34] Mn, [35] Fe [36] and Ni. [37] With regards to f-block elements, only two reports on using Er, Y, Dy, Gd [38] and Th [39] systems in dihydroboration of nitriles have been disclosed.…”

“…Moving beyond ruthenium systems, a series of abundant base metal catalysts (Fe, [36] Co, [21,23,31,32] Ni [37] and Mn [35] ) have been reported to facilitate hydroboration of nitriles. Thus, ironcatalyzed reactions were disclosed by Nakazawa et.…”

“…Thus, ironcatalyzed reactions were disclosed by Nakazawa et. al in 2017 using [Fe(CH 3 CN) 6 ][cis-Fe(CO) 4 (InCl 3 ) 2 ] (9), [36] which was previously shown to facilitate hydrosilylation of nitriles. [50] The hydroboration reactions were performed with HBPin and 5 mol% (to HBPin) of 9 under solvent-free conditions (10-fold excess of RCN) at 80°C and required 24 h for completion (Scheme 9).…”