Synthesis, Properties and Stereochemistry of 2-Halo-1,2λ(5)-oxaphosphetanes

Results of research into four-membered 2-halo-1,2λ(5)-oxaphosphetane phosphorus(V)-heterocycles are presented. The preparation of 2-halo-1,2λ(5)-oxaphosphetanes by reaction of P-haloylides with carbonyl compounds is described. The mechanism of asynchronous [2+2]-сycloaddition of ylides to aldehydes was proposed on the base of low-temperature NMR investigations. 2-Halo-1,2λ(5)-oxaphosphetanes were isolated as individual compounds and their structures were confirmed by (1)Н-, (13)C-, (19)F- and (31)Р-NMR spectra. These compounds are convenient reagents for preparing of various organic and organophosphorus compounds hardly available by other methods. Chemical and physical properties of the 2-halo-1,2λ(5)-oxaphosphetanes are reviewed. The 2-chloro-1,2λ(5)-oxaphosphetanes, rearrange with formation of 2-chloroalkyl-phosphonates or convert into trans-phosphorylated alkenes depending on the substituents at the α-carbon atom. Prospective synthetic applications of 2-halo-1,2λ(5)-oxaphosphetanes are analyzed. The 2-halo-1,2λ(5)-oxaphosphetanes may be easily converted to various alkenylphosphonates: allyl- or vinylphosphonates, phosphorus ketenes, thioketenes, ketenimines.