TRIFLUOROMETHYLATED 1,2-LAMBDA(5)SIGMA(4)-OXAPHOSPHOLANES VIA LAMBDA(5)SIGMA-P-5 TRICYCLIC PHOSPHORANES FROM 4,4,4-TRIFLUORO-3-HYDROXY-1-PHENYLBUTANE-1-ONE AND DICHLOROPHOSPHINES - MOLECULAR-STRUCTURE OF A TRAPPED PHOSPHONITE

Reacting 4,4,4-trifluoro-3-hydroxy-1-phenylbutane-one (1) with the dic hlorophosphines RPCl2 (2a, R=Me; 2b, R=Ph) gave the phosphonites 3a an d 3b, which, in the case of 3a, was trapped using hexafluoroacetone to furnish the 1,3,2 lambda(5) sigma(5)-dioxaphospholane 4a. In a concer ted mechanism, compounds 3a and 3b rearranged forming the thermally un stable tricyclic diastereoisomeric phosphoranes 5a and 5b. After split ting off 1,1,1-trifluoro-4-phenyl-2-butene-4-one (6) the diastereoisom eric 1,2 lambda(5) sigma(4)-oxaphospholanes 7a and 7b were obtained. T he molecular structure of 4a (triclinic, P (1) over bar, a=1020.3(1) p m, b=1239.0(1) pm, c=1298.7(2) pm, alpha=85.55(1)degrees, beta=70.10(1 )degrees, gamma=79.85(1)degrees) was determined. (C) 1997 Elsevier Sci ence S.A.