Hydroboration of imines: intermolecularvs.intramolecular hydride transfer

Abstract

A crucial step in the formation of mono-aminoboranes (R2N-BH2) from the corresponding imine-BH3 adducts, under mild reaction conditions, is the 1,3-hydride shift. We offer experimental and theoretical insights into this...

Sequential Nitrile Amidination–Reduction as a Straightforward Procedure to Selective Linear Polyamine Preparation

“…Thus, as the most basic center in the cyclic amidines is the nitrogen atom at the C(2)N(3) double bond, the formation of an N(3)-borane adduct, I , promotes hydride transfer to C2 to produce the N(3)-imidazolidine-borane intermediate, II . For this first hydride transfer, a mechanism similar to that of the well-studied imine reductions is expected, which leads to an intermediate ( II ) that possesses an amine–borane bond . Such amino-borane structures are defined by a notable double-bond character, − as represented by the dipolar canonical form IIb in Scheme , that also entails a low basicity at N(3) due to the involvement of the nitrogen lone pair in the partial π-bond with boron.…”

“…For this first hydride transfer, a mechanism similar to that of the well-studied imine reductions is expected, which leads to an intermediate ( II ) that possesses an amine–borane bond. 30 Such amino-borane structures are defined by a notable double-bond character, 31 − 33 as represented by the dipolar canonical form IIb in Scheme 3 , that also entails a low basicity at N(3) due to the involvement of the nitrogen lone pair in the partial π-bond with boron. Intermediate II is crucial to justify the chemoselectivity of the borane reductive opening since the formation of a second amine-boron adduct will now be favored at N(1) position owing to the complete availability of its unshared electron pair which makes of N(1) the most basic center of this intermediate.…”

Density functional theory study of crown ether–magnesium complexes: from a solvated ion to an ion trap

“…Herein we test this assumption and estimate the contribution of quantum effects in magnesium–crown interaction using the interacting quantum atoms (IQA) methodology, 34,35 which has so far been used for analysis of numerous systems with covalent and non-covalent interactions. 36–64…”