Reactions of 4-ethoxy-l,l,l-trifluoro-3-buten-2-one with phosphorous nucleophiles: Diethyl phosphite, tributyl phosphine and tris(diethylamino) phosphine

The reaction of (E)-4-ethoxy-l,l,l-trifluoro-3-buten-2-one EtOCHCHCOCF3 1 with diethyl phosphite (EtO)2P(O)H 2 afforded a 1:1 cis- and trans-mixture of diethyl(l-trifluomethyl-3-ethoxy)allyl-phosphate EtO–CHCH–CH(CF3)OP(O)(OEt)2 3 via the 1,2-λ5-oxaphosphol-4-ene intermediate. While tributyl phosphine Bu3P added to 1 giving the double addition product Bu3P+CH2–C−(COCF3)–CHCH–COCF3 5. Its resonance structure was fully identified by spectral methods and single crystal X-ray diffraction analysis. More strong phosphorous nucleophile tris(diethylamino) phosphine (Et2N)3P reacted with 1 to give the known compound (E)-4-(diethylamino)-l,l,l-trifluoro-3-buten-2-one Et2N–CHCH–COCF3 10 in good yield.