Reaktive EC(p–p)π‐Systeme, XXXII^[1a] Phosphorylide Me₃P = C(X)P(F)CF₃ mit π‐Donor‐Substituenten X = F, OMe, OEt

Abstract

Reactive E = C(p–p)π Systems, XXXII [1] . – Phosphorus Ylides Me 3 P = C(X)P(F)CF 3 with π‐Donor Substituents X = F, OMe, OEt Fluorophosphaalkenes of the type F 3 CP = C(X)F react with tri‐methylphosphane in a 1:1 molar ratio at temperatures below – 20°C to give the novel phosphorus ylides Me 3 P = C(X)P(F)CF 3 in good yields [X = F ( 4 ), 70%; OMe ( 7 ), 62%; OEt ( 8 ), 74%]. Compounds 4, 7 and 8 are stable up to about 10°C, but decompose at higher temperatures yielding in case of 4 Me 3 PF 2 as main product. The 31 P‐NMR spectra indicate a high barrier of rotation for the F 3 C(F)P group around the P III –sp 2 C bond. The new ylides owe their existence to the electron withdrawing effect of the F 3 C(F)P unit which over‐compensates the destabilizing influence of the fluorine or alkoxy substituents on the sp 2 C atom.