9-borabicyclo -nonyl derivatives

Amides are derivatives of carboxylic acids, so that their coordination behavior to boranes might be similar to that of their parent compounds. B-NMR spectroscopic studies have shown that compounds 31 and 32 are monomeric species in solution, while compounds 33 and 34 with the more Lewis acidic 9-borabicyclo[3.3.1]nonyl unit form aggregates that may be dimeric, oligomeric, or polymeric. The grade of association could not be determined by mass spectrometric analyses, because in all cases only the monomer is liberated into the gas phase [65]. 

BBN = 9-borabicyclo[3.3.1]nonyl cat = Catecholato cod = 1,5-cyclooctadiene coe = Cyclooctene Dur = Duryl = 2,3,5,6-tetramethylphenyl Fc = 1-ferrocenyl fc = l,l -ferrocenediyl Ipc = Isopinocampheyl (derived from (+)-a-pinene) Mes = Mesityl = 2,4,6-trimethylphenyl Np = 2-naphthyl OLED = Organic light-emitting diode Pf = Pentafluorophenyl pin = Pinacolato SCE = Standard calomel electrode thexyl = 2,3-dimethyl-2-butyl TMP = 2,2,6,6-tetramethylpiperidide tripyl = 2,4,6-tri-fro-propyl-phenyl. 

Although (7) reacts with trimethylsilyl chloride (TMS-Cl) at the 7-position because of the steric bulk of the siamyl group, the 9-borabicyclo[3.3.1]nonyl (9-BBN) derivative (equation 1) gives the a-tri-methylsilyl or a-trimethylstannyl allylic-9-BBN upon treatment with TMS-Cl or trimethyltin chloride. ... 

The imine 188, derived from 3-(trimethylsilyl)-2-propynal and (S)-a-methyl-benzylamine, was treated at — 40 °C with the born enolate 187 prepared from S-phenyl butanethioate, 9-borabicyclo[3.3.1]nonyl triflate and DIPEA. After workup, a mixture of the anti p-amino acid 189 and the syn adducts 190 was formed in a 5.2 1 ratio. This mixture was then subjected to cyclization using tert-butylmagnesium chloride in diethylether to give the trans P-lactam 191 in... 

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