Complexes of (CF3)3B with Sterically Crowded Amines. Unexpected Side Products from the Trifluoromethylation of Cl2BN(t-Bu)(Bz). Crystal and Molecular Structures of (CF3)3BNH(CH2)6, HO(CF3)2BCH(Ph)NH(t-Bu)(Bz) and Ph(CF3)2BCHN(t-Bu)(Bz)

Abstract

Trifluoromethylation of C12BN(CH2)6, Cl2B(tmp), tmp = 2,2,6,6-tetramethylpiperidino, and Cl2BN(t-Bu)(Bz) with three equivalents of CF3Br/P(NEt2)3 yields the amine complexes (CF3)3B · NH(CH2)6 (1), (CF3)3B ·NH2CMe2(CH2)2CHCMe2 (2) and (CF3)3B · NH2(Bz) (3). The preparation of 3 was accompanied by formation of three unexpected trifluoromethylboron derivatives X(CF3)2BCH(Ph)NH(t-Bu)(Bz) (D), X = Br (4), Cl (5), and (Ph)(CF3)2BCHN(t-Bu)(Bz) (6), the latter being formed from 4 by HBr elimination and rearrangement. Reaction of 4 with H2O, EtOH, HCONMe2 and Me3SnH yielded D, X = OH (7), EtO (8), HCOO (9), and (Ph)(CF3)2BCH2NH(t-Bu)(Bz) (10), respectively. The structures of 1, 6 and 7 have been determined by X-ray diffraction analysis.