An unusual cascade reaction of 4,5-dihydro-4,4-bis(trifluoromethyl)-2-phenyl-6,7-(4-chlorobenzo)[e]-1,3,2-dioxaphosphepin-5-one with chloral

The reaction of 4,5-dihydro-4,4-bis(trifluoromethyl)-2-phenyl-6,7-(4-chlorobenzo)[e]-1,3,2-dioxaphosphepin-5-one with chloral (1:2) proceeds with evolving hexafluoroacetone and gives spiro{2-oxo-4-trichloromethyl-4,5-dihydro-2-phenyl-6,7-(4-chlorobenzo)[f]-1,3,2-dioxaphosphepine-5,2'-(3'-trichloromethyl)oxirane} with a high stereoselectivity. Configuration of the four chiral centres (P²_SC⁴_SC⁵_SC^3'_S/P²_RC⁴_RC⁵_RC^3'_R) was determined by a single crystal X-ray diffraction.