1,5-Dimethyl-2,3,3,4-Tetrachloro-1,5-Diaza-2,4-Diphosphorinan-6-One and some derivatives

A synthesis of C-chlorinated analogues of 1,5-diaza-2,4-diphosphorinan-6-ones is described. The P-chlorophosphine 3 , a key compound for all reported substitution reactions, reacts in an unusual way with N,N′-dimethyl-N,N′-bis(trimethylsilyl)urea to give the unsymmetrical product 5 , the formation of which is accounted for by a silatropy of the intermediate compound 4 . Compound 5 is stable in solution but rearranges quantitatively into isomer 6 without solvent at room temperature. Compound 3 , its fluoro derivative 9 , and the alkoxy derivatives 10a–d exist as cis-and trans-isomers. Some stereochemical aspects, as well as the possibility of 1,2-chlorotropy, are discussed.