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-chlorobe n zo)[f]-1,3,2-dioxaphosphepine-5,2'-(3'-trichloromethyl)oxirane} with a high stereoselectivity. Configuration of the four chiral centres (P super(2) sub(S)C super(4) sub(S)C super(5) sub(S)C super(3') sub(S) /P super(2) sub(R)C super(4) sub(R)C super(5) sub(R)C super(3') sub(R)) was determined by a single crystal X-ray diffraction.