REACTION OF EPOXIDES WITH METAPHOSPHORIC ACID-DERIVATIVES

Ethyl metaphosphate (EtOPO2), eliminated in the thermolysis of the bridged cyclic phosphonate endo-3-ethoxy-6-methyl-N-phenyl-2,3-oxaphosphabicyclo[2.2.2]oct-5-ene-8,9-dicarboximide 3-oxide, has been found to cause ring opening of epoxides, resulting in formation of 2-ethoxy-4-substituted 1,3,2-dioxaphospholane 2-oxides as major products. N,N-Diethyl metaphosphoramidate (Et2NPO2) reacted similarly. With ethyl metathiophosphate (EtOP(S)O), the 1,3,2-oxathiaphospholane 2-oxide ring was formed. Products of these reactions were characterized by P-31 NMR spectroscopy and by GC-MS. These reactions are presumed to be initiated by electrophilic attack of the metaphosphate on the epoxide oxygen to form a cyclic oxonium ion.