(E)-1,1,1-trifluoro-4-phenyl-but-2-ene-4-one and trimethyl phosphite

The interaction of (E)-1,1,1-trifluoro-4-phenyl-but-2-ene-4-one (1) with trimethyl phosphite affords in a [4 + 1] cycloaddition the 1,2λ5-oxaphospholene 2 as a sole product which upon hydrolysis is transformed into the fluoroalkyl containing γ-ketophosphonate 4. When the reaction is carried out in the presence of small mounts of water, in addition to 2 as a main product, the phosphoric acid ester 6 of the enolic dimer of ketone 1 is also formed. The molecular structure of compound 6 (monoclinic P 2(1)/c with a = 2088.60(2), b = 1403.1(3), c = 1613.8(1) pm, α = 90, β = 100.97(1), γ = 90°, Z = 8) was determined, indicating two independent molecules with (RR) and (SS) configuration and disordered CF3 groups.