Frustrated Lewis Pair‐Catalyzed Hydroboration of Nitriles: FLP Versus Borenium Catalysis

Abstract

A frustrated Lewis pair-catalyzed hydroboration of aromatic and aliphatic nitriles was developed. The catalyst provides the primary amines in high yields of 77-99% with catalyst loading as low as 2 mol%. The reaction displays high functional group tolerance towards esters, amides, nitro groups and aliphatic halides. The addition of the diborylated amines to ethyl 3phenylpropiolate proceeds with Z-selectivity with d.r. of > 99:1 in 77-90% yield over two steps. The reaction mechanism was investigated by control and computational experiments.

Au nanoparticle-catalyzed double hydrosilylation of nitriles by diethylsilane

“…There are several reports in the literature concerning the competing chemoselectivity of such reductions. Generally, treatment of cyano and nitro bearing substrates with specific boron hydrides, 34 and primarily in the metal-catalyzed reduction with hydrosilanes, 8 a ,17,19 a the cyano group is selectively reduced. The opposite selectivity, such as under our conditions, occurs performing catalytic hydrogenation, 4 or employing hydrosilanes with Au/Fe 3 O 4 24 or Cu(OTf) 2 35 as catalysts.…”

Structure–Reactivity Relationships in Borane-Based FLP-Catalyzed Hydrogenations, Dehydrogenations, and Cycloisomerizations

“…The adjustment to the weaker Lewis acid B(2,6-F 2 −C 6 H 3 ) 3 (16, 2 mol %) allowed the reaction to be performed at room temperature and produced the primary amines 45a−r in high to excellent yields (isolated as hydrochloride salts, Scheme 11). 59 Key to the mild reaction conditions is that now the hydride is transferred from the transiently generated borohydride [H− 16] − and not from the DABCO•HBpin adduct. The latter mechanism would generate a thermodynamically and kinetically unfavorable borenium ion.…”