| Popis: |
Results of research into four-membered phosphorus(V)-heterocycles, 2-halogen-1,2λ5-oxaphosphetanes are presented. The preparation of 2-halo-1,2λ5-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-Halogen-1,2λ5-oxaphosphetanes were isolated as individual compounds and their structures were confirmed by 1Н, 13C, 19F and 31Р 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-1,2λ5-oxaphosphetanes are reviewed. The 2-chloro-1,2λ5-oxaphosphetanes depending on substituents at the α-carbon atom rearrange with formation of 2-chloroalkylphosphonates or convert into trans-phosphorylated alkenes. Prospective synthetic applications of 2-halo-1,2λ5-oxaphosphetanes are analyzed. The 2-halo-1,2λ5-oxaphosphetanes may be easily converted to various alkenylphosphonates: allyl- or vinylphosphonates, phosphorus ketenes, thioketenes, ketenimines. |
