Conformational behavior of 3-borabicyclo[3.3.1]nonanes. Intramolecular p-s and p-p interactions in 3,7-endo-disubstituted 3-borabicyclo[3.3.1]nonanes.
Intramol. interactions between the unoccupied p-orbital of the B atom and the s- (Me) or p-orbital (Ph) of the 7-endo-substituent lead to an unusual stability of the chair-chair conformation in 3-borabicyclo[3.3.1]nonanes. X-ray anal. of 3,7a-dimethyl-3-borabicyclo[3.3.1]nonane (7) and 3-methyl-7a-phenyl-3-borabicyclo[3.3.1]nonane (8), and single point ab initio calcn. (B3LYP/6-31G*) of 8 confirmed the existence of this specific attractive interaction.
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