Boranes

Vedejs, E.; Chapman, R. W.; Fields, S. C.; Lin, F.; Schrimpf, M. R. "Conversion of Arylboronic Acids into Potassium Aryltrifluoroborates: Convenient Precursors of Arylboron difluoride Lewis Acids", J. Org. Chem., 1995, 60, 3020.

Abstract:  Reaction of ArB(OH)2 (Ar = Ph, 1-naphthyl, 4-F3CC6H4, etc.) with KHF2 affords cryst. salts KArBF3 (I). In the presence of TMSCl in acetonitrile, I (R = Ph) reacts to give NMR signals typical of PhBF2 in acetonitrile soln. When the reaction of I + TMSCl is performed in the presence of potential Lewis bases, the trivalent borane is intercepted, resulting in organoboron complexes. Thus, the oxazaborolidinones, e.g. II, have been prepd. from amino acid-derived amidine carboxylates NaO2CCH(R)N:CHNMe2 (R = H or phenyl). Complexes, e.g. III, derived from 1,3-diketones are also easily prepd.

Vedejs, E.; Fields, S. C.; Schrimpf, M. R. "Asymmetric Transformation in Boron Ate Complexes of Amino Acids", J. Org. Chem., 1995, 60, 3028.

Abstract:  Amidine-protected oxazaborolidinones I were prepd. from Me2NCH:NCH(R'')CO2Na (R'' = CHMe2, CH2Ph) and KPhBF3/TMSCl. The diastereomers undergo equilibration and asym. transformation under conditions of crystn., resulting in the formation of one diastereomer high selectivity. Treatment of phenylalanine with ArB(CH3)OCHMe2 (Ar = Ph, 4-F3CC6H4) affords a 1:1 diastereomer mixt. of the oxazaborolidinones II. Crystn. affords a single diastereomer in high yield. These are all examples of asym. transformation of the second kind or second order, abbreviated as AT. Crystn. of the less sol. diastereomers

Fields, Stephen Craig "Synthesis of optically active α-alkyl-α-amino acids via boroxazolidinones. (1990), 285 pp. CAN 115:115053 AN 1991:515053

Abstract:  Ph.D. thesis at the University of Wisconsin-Madison, 1990.