Reactions of trifluoropyruvic acid methyl ester and 2-alkoxy-4-H-1,3,2-benzodioxaphosphorin-4-ones

Abstract The result of the reactions between trifluoropyruvic acid methyl ester ( I ) and 2-RO-4-H-1,3,2-benzodioxaphosphorin-4-ones ( II ) was found to depend on the conditions (temperature, the order of mixing the reagents) and the nature of the R group. Spirocyclic phosphorane ( III ) is the only product if the reaction proceeds at low temperature (−40 °C) and ( I ) is in excess in solvent. Cyclic expansion products ( IV ) are obtained under higher temperatures. Yields of phosphepanes ( IV ) rise up to 90% at 80–120 °C. Thermal decomposition of compounds ( III ) leads to phospholanes ( V ). The structures of compounds ( III–V ) have been confirmed by a combination of 1 H, 13 C, and 31 P NMR, and IR spectroscopy.