Study for New Lewic acid. Prepared from Bf_8・OEt_2 and Trialkylsilyl derwatives.

点击翻译按钮获取中文摘要

1.Boron trifluoride diethyl etherate (BF_3・Oet_2) and trimethylsilyl triflate are the most representative Lewis acids in many kinds of Lewis acids. We found that these two Lewis acids easily and quickly reacted in acetonitrile to give a new Lewis acid (BF_2(OTf)). This new chemical species was identified by ^1H,^<11>B,^<19>FNMR experiments. When 1 equivalent of boron trifluoride etherate was combinated with 1 equivalent of trimethylsilyl triflate in 1 : 1 ratio in CD_3CN,a methyl signal of CH_3OTf at 0.5 ppm (broad singlet) disappered and one set of doublet (J=7.5 Hz) at 0.2 ppm was observed as a methyl signal of trimethylsilyl fluoride in ^1HNMR.Furthermore, decatet signal (J=7.5 Hz) was observed in ^<19>FNMR based on a trimethylsilyl fluoride. It was found that trialkylsilyl derivatives such as trimethylsilyl methanesulfonate, trimethylsilylmethyl ether, triethylsilane and trimethylallylsilane generally reacted with boron trifluoride in acetonitrile.2.It was found that C-allylglycosidation reaction of methylidopyranosyl derivative with free hydroxy groups proceeded efficiently and stereoselectively when this newly develoved BF_2OTf was used.