The reaction of 4-(1,3,2-benzodioxaphosphol-2-yloxy)-3-tert-butylpent-4-en-2-one with hexafluoroacetone

Catalytic (ZnCl₂, Et₃N) phosphorylation of tert-butylacetylacetone with 2-chloro-1,3,2-benzodioxaphosphole unexpectedly occurs with elimination of proton from the methyl group and leads to vinyloxyphosphole derivative, viz., 4-(1,3,2-benzodioxaphosphol-2-yloxy)-3-tert-butylpent-4-en-2-one. Its reaction with hexafluoroacetone gives a cage phosphorane as a result of subsequent chemoselective [4+2]- and [3+2]-cycloadditions with stereoselectivity above 95%.