The Selective Silylation of <scp>d</scp>‐Mannitol Assisted by Phenylboronic Acid and the Solid State and Solution Structures of the Intermediate 1,6‐bis(silyl) bis(phenylboronates)
作者:Vijaya Bhaskar、Angelo D'Elia、Peter J. Duggan、David G. Humphrey、Guy Y. Krippner、Trang T. Nhan、Edward M. Tyndall
DOI:10.1081/car-120026598
日期:2003.12.31
The influence of phenylboronic acid on the silylation of D-mannitol by TBDMSCI and TBDPSCI has been investigated. Terminal silyation was found to dominate, with PBA significantly enhancing the yield of 1,6 di-TBDMS D-mannitol compared to the control. The intermediate 1,6-disilyl bis(phenylboronates) showed unusually high stability, such that oxidative conditions were required to cleave the boronate esters. X-ray crystal structures of both bis(phenylboronates) were determined, revealing both diboronate esters to exist as two fused six-membered rings. The results of B-11 NMR experiments suggest that these structures also predominate in solution, whereas the bis(phenylboronate) ester of D-mannitol itself exists as a mixture of five-membered and six-membered cyclic boronates.