Tropylium‐BF₄ as Organocatalyst for Efficient Synthesis of Nitriles from Aldoximes; Synthetic Scope and Mechanistic Insights

Abstract

Structurally diverse aldoximes were conveniently transformed within minutes to the corresponding nitriles by using tropylium BF 4 as organocatalyst, in 1-butyl-3-methylimidazolium ionic liquids (BMIM-ILs) as solvent, under microwave irradiation. The scope of this convenient, cyanide free, process for nitrile synthesis was explored, and DFT computations were employed to shed light on the mechanistic steps of this catalytic reaction leading to dehydration.

Tropylium‐BF4as Organocatalyst for Microwave‐assisted Beckmann rearrangement in [TMG][BF4]: One‐pot conversion of Ketones to Amides

“…As a result, it's possible that more hydroxylamine hydrochloride will be required to turn all of the ketones into oximes. Thus, a loading of hydroxylamine hydrochloride was investigated to increase output (Table 1, entries [15][16][17]. By increasing the amount of hydroxylamine hydrochloride to 2.6 mmol, we were able to produce 67 % and 68 % of the yield as well as traces of benzophenone under both heat and MW irradiation (entry 15).…”

“…To begin with, fluorine was introduced on the acetophenone at ortho, meta and para position that led to 79, 69 and 86 % of the respective amides (entries [13][14][15]. Further, chloro group substitution yielded 86, 82 and 87 % of the products (entries [16][17][18]. Inclusion of bromo group on ortho and meta position could end up with 76 and 87 % of the targeted products (entry [19][20].…”

“…Further, amide synthesis was achieved by N ‐arylation of 1‐aryltriazenes in presence of various ionic liquids [4d] . With a keen interest in method development, we have reported the conversion of aldoximes to nitriles by employing tropylium tetrafluoroborate (Tp + BF − 4 ) as an organocatalyst [16] . In line with this, we are reporting the efficiency of Tp + BF − 4 as an organocatalyst in the one‐pot conversion of ketones into amides under microwave irradiation using guanidinium IL as reusable solvent and acid promoter [12p] …”