Synthesis, characterization, and crystal structures of novel intramolecularly base-stabilized borane derivatives with six- and seven-membered chelate rings

The reaction of (2-dimethylaminophenyl)alcohols 1-HOX-2-NMe2C6H4 [X = CPh2 (1), X = CCy2 (2), X = CPh2CH2 (4)] and 1-phenylaminoalkyl-2-dimethylaminobenzene 1-HN(Ph)X-2-NMe2C6H4 [X = C(H)Ph (3), C(H)PhCH2 (5)] with BH3(THF) yielded the BH2 derivatives 1-H2BOX-2-NMe2C6H4 [X = CPh2 (6), CCy2 (7), CPh2CH2 (9)] and 1-H2BN(Ph)X-2-NMe2C6H4 [X = C(H)Ph (8), C(H)PhCH2 (10)]. Treatment of 1-H2BOCPh2-2-NMe2C6H4 (6) with acetic acid gave 1-(CH3COO)HBOCPh2-2-NMe2C6H4 (11). Compounds 6-11 were characterized spectroscopically (NMR, IR, MS). Crystal structure determinations were carried out on 6-11, which are novel examples of structurally characterized BH2 derivatives containing six- or seven-membered chelate rings. For the chiral compounds 8, 10, and 11, both enantiomers are present in the unit cell.