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

Lithium (N-methoxycarbonyl)phosphazenes add C-regioselectively to DMAD, dim ethyl malonate, fumarate, and butyl idenmalonate in a [1,4] manner. Only on e diastereoisomer is observed with the olefinic electrophiles. With DMAD th e 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 degreesC affords beta -hydroxyphosphazenes diastereoselectively. For lithi um oc,bi-dimethyl(N-methoxycarbonyl)phospha the intermediate all;oxides cyc locondense at room temperature to 5,6-dihydro-1,3,4-oxazaphosphinin-2-ones. (C) 2001 Elsevier Science Ltd. All rights reserved.