Structural studies of organoboron compounds XXIII: preparation and crystal and molecular structures of 2,2-diphenyl-1,3-dioxa-4a- azonia-2-borata-1,2,3,4-tetrahydronaphthalene and 4,4-diphenyl-3-oxa-1-aza-4a-azonia-4-borata-1,2,3,4-tetrahydronaphthalene

Abstract

Details of the synthesis, physical properties, and the crystal molecular structures of 2,2-diphenyl-1,3-dioxa-4a-azonia-2-borata-1,2,3,4-tetrahydronaphthalene, 5, and 4,4-diphenyl-3-oxa-1-aza-4a-azonia-4-borata-1,2,3,4-tetrahydronaphthalene, 9, are reported. Crystals of 5 are monoclinic, a = 9.972(1), b = 11.848(1), c = 13.561(2) Å, β = 106.231(5)°, Z = 4, space group P21/c and those of 9 are orthorhombic, a = 20.676(1), b = 15.4199(9), c = 9.7533(4) Å, Z = 8, space group Pbca. Both structures were solved by direct methods and were refined by full-matrix least-squares procedures to R values of 0.036 and 0.045 for 1060 and 1700 reflections with I ≥ 3σ(I) respectively. Compound 5 has the expected cyclic B,N-betaine structure, resulting from N-aklylation of 2(1H)-pyridone with formaldehyde followed by reaction with (Ph2B)2O. The aza analog, however, does not have the analogous structure. The alkylation of 2-aminopyridine with formaldehyde in the presence of (Ph2B)2O yields 9, derived from alkylation of the amine rather than the pyridine ring nitrogen atom.