Highly diastereoselective Diels-Alder reactions with (R)-ethoxy p-tolyl vinyl sulfonium tetrafluoroborate
作者:B. Ronan、H.B. Kagan
DOI:10.1016/s0957-4166(00)82159-x
日期:——
p-Tolyl vinyl sulfoxide has been efficiently activated for Diels-Alder reactions by transformation into a sulfonium salt 3a or by addition of TMSOTf. Very high diastereomeric excesses have been achieved (> 98%) at -20-degrees-C in many cases. Best results have been obtained with cyclopentadiene, furan and 2,3-dimethyl-1,3-butadiene. In this way enantiomerically pure oxanorbornenone 19a has been prepared. The reaction mechanism is briefly discussed.