Al/N-based active Lewis pairs: isocyanate insertion products as efficient nucleophiles employed for the facile generation of highly functional molecules

The previously reported active Lewis pair (ALP) i Bu2Al–N(2-Ad)NC5H10 (1) (2-Ad = 2-adamantyl) is readily accessible by hydroalumination of the hydrazone H10C5N–N=(2-C10H14) with H–Al i Bu2. Treatment of 1 with two equivalents of isocyanates R-N=C=O yields six-membered AlC2N2O heterocycles 2 (2a, R = Ph; 2b, R = p-Tol) by dual insertion into the Al–N bonds. 2a reacts as a nucleophile with carboxylic acid chlorides R-C(O)–Cl [R = CH2 t Bu, p-Tol, H2CCH(Me)C6H4(4-CH2CHMe2) (Ibu-profen acid chloride), 0.5 (1,4-C6H4)] to afford by elimination of i Bu2AlCl and hydrolysis new triuret derivatives R-C(O)[N(Ph)C(O)]2–N(2-Ad)NC5H10 (3a to 3d) as colourless, sparingly soluble solids in moderate (3c) to high (3b) yields. The analogous reaction of 2a with (p-Tol)–C(Cl)=N(p-Tol) leads to the imidoyl derivative (p-Tol)N=C(p-Tol)[N(Ph)C(O)]2–N(2-Ad)NC5H10 (4a), which showed a fast exchange of phenyl and tolyl groups to yield a mixture of isomers. The analogous reaction of 2b affords the corresponding compound 4b for which a single isomer is isolated despite the scrambling of substituents.