Quantum chemical modeling of chiral catalysis. Part 14. On the coordination of carbonyl compounds to diaza-, oxaza- and dioxaluminolidines of potential use as chiral controllers in organic synthetic chemistry

Conformers of 4-coordinate adducts of carbonyl compounds and diaza-, oxaza- and dioxaluminolidines were investigated by means of ab initio MO methods (RHF). Formaldehyde was used as a model of carbonyl compounds. Relative stabilities of the conformers indicate formation of syn adducts of carbonyl compounds and aluminolidines (C_C=O and aluminolidine ring syn about the Al---O_C=O bond) to be favoured over that of the corresponding anti ones (all syn/anti ratios higher than 99:1, 6–31G//6–31G). The energetic preference for the formation of syn adducts of oxazaaluminolidines was about twice as high as that of diaza- or dioxaluminolidines of which the syn/anti selectivities were found to be practically equal.