A NEW CLASS OF OXAZABOROLIDINE DERIVATIVES DISCOVERED - KETONES AND ALDEHYDES AS BIDENTATE LIGANDS

Novel adducts (5'a-f) of H2CO/Me(2)CO and H(2)BOR (R = H, Me) to aminoborane (1'a), aminohydroxy-borane (1'b) and 1,3,2-oxazaborolidine (1'c) were studied by means of ab initio MO (RHF) methods. Energies of the formation of the adducts were clearly exothermic [e.g. -140 and -134 kJ mol(-1) (MP2/6-31G*//MP2/6-31G*) in the case of H2(C)O - H2BOH adduct of 1'a and 1'c]. All the Me(2)CO adducts were found to be slightly less stable than the corresponding H2CO adducts. In all the adducts (5'a-f) studied the carbonyl system was found to behave as a bidentate ligand. All the bidentate adducts were found to be significantly more stable than the related monodentate adducts (4'a-c). Activation of the carbonyl moiety of the bidentate adducts resembles that of the related adducts of N-sulfonylated oxazaborolidines (7).