FIRST P-TRIFLUOROMETHYLATED YLIDES

Trifluoromethylated phosphines R(2)PCF(2), (R = NEt(2), Me, Pr-1) were methylated by CH3OSO2CF3, yielding the corresponding phosphonium salt s [R(2)P(CF3)CH3](+) [F3CSO3](-). Treatment with LiN(SiMe(3))(2) at -8 0 degrees C furnished the phosphorus ylides R(2)P(CF3)=CH2 that could be trapped by use of hexafluoroacetone with formation of stable 1,2 la mbda(5) sigma(5)-oxaphosphetanes. The single-crystal X-ray structure d etermination of one of these oxaphosphetanes showed a distorted trigon al bipyramid at phosphorus with the P-CF, group in an axial position. (C) 1996 John Wiley & Sons, Inc.