Reactions of lithiated P-diphenyl(alkyl)(N-methoxycarbonyl)phosphazenes with Michael acceptors and aldehydes. Synthesis of 1H-1,2-azaphosphinin-6-ones, β-hydroxy(N-methoxycarbonyl)phosphazenes and 5,6-dihydro-1,3,4-oxazaphosphinin-2-ones

Lithium (N-methoxycarbonyl)phosphazenes add C-regioselectively to DMAD, dimethyl malonate, fumarate, and butylidenmalonate in a [1,4] manner. Only one diastereoisomer is observed with the olefinic electrophiles. With DMAD the initial adduct evolves through cyclocondensation with the CO2Me group of the phosphazene and 1H-1,2-azaphosphinin-6-ones are obtained. Exceptionally, methyl phenylpropiolate reacted exclusively through the carbonyl yielding a mixture of C- and N-acylated compounds. The addition to aldehydes at −80°C affords β-hydroxyphosphazenes diastereoselectively. For lithium α,α-dimethyl(N-methoxycarbonyl)phosphazenes, the intermediate alkoxides cyclocondense at room temperature to 5,6-dihydro-1,3,4-oxazaphosphinin-2-ones.