Reactions of Al-N Based Active Lewis Pairs with Ketones and 1,2-Diketones: Insertion into Al-N Bonds, C-C and C-N Bond Formation and a Tricyclic Saturated Tetraaza Compound

Abstract

The monomeric aluminum hydrazide iBu2Al-N(C10H15)(NC5H10) (1) features a strained AlN2 ring and is an efficient active Lewis pair. It reacted with 2,3-diphenyl-2-cyclopropen-1-one by insertion of the C=O group into an Al-N bond, cleavage of the C3 ring and formation of an AlOC3 heterocycle (2). Diacetyl, Me(O)C–C(O)Me, and 1 afforded by insertion of keto groups into both Al-N bonds a heterocyclic α-keto-hemihydrazinal coordinated to aluminum (3). 3 contains fused AlO2C2 and C2N2 heterocycles. In an unexpected reaction, benzil, PhC(O)-C(O)Ph, afforded by C–C and C–N bond formation a unique tricyclic dimer (4) of the hydrazone H10C5N–N=C10H14, which is the starting material for the synthesis of 1. This reaction may involve a radical process, and benzil radical anions coordinated to Al were detected as by-products. In contrast, 1 reacted with simple ketones to yield alcoholates [iBu2AlOR]2 [R = OC(H)(Ph)-C≡C-Ph (5), OCHPh2 (6)] by retrohydroalumination and reaction of resulting iBu2Al-H with C=O groups.