Synthesis of multifunctionalized phosphonic acid esters via opening of oxiranes and azetidinium salts with phosphoryl-substituted carbanions

Ring-opening of N,N-diethyl-3-benzyloxyazetidinium salt 1b and N,N-dibenzyl-2,3-epoxypropylamine 6 by phosphoryl-substituted carbanions generated from phosphonates 2a-e furnishes the multifunctional phosphonates 3a-e and 7a, 7b, 7e bearing the same carbon skeleton. The reaction of the heterocyclic electrophiles 1b and 6 with the P-allyl anion generated from 2f demonstrates the strong dependence of the alpha/gamma -regioselectivity on the reaction conditions. Depending on the character of the electrophile and/or the reaction medium the regioselective synthesis of both alpha- and gamma -regioisomers is realized.