SYNTHESIS OF 1,4-DIOXA-2-LAMBDA(5)-PHOSPHORINANES BY INSERTION OF TRIPHENYLALKYLIDENEPHOSPHORANES INTO THE PEROXIDE BOND OF 1,2-DIOXETANES - THERMOLYSIS, HYDROLYSIS, AND WITTIG OLEFINATION

The reaction of the methyl-substituted 1,2-dioxetanes 1-3 with triphen ylalkylidenephosphoranes 4-7 was investigated. By nucleophilic attack of the negatively charged phosphorane carbon atom at the peroxide bond of the 1,2-dioxetanes, the dipolar phosphonium alkoxides 8-13 were fo rmed, which were in equilibrium with the ring-closed 2,2,2-triphenyl-1 ,4-dioxa-2 lambda(5)-phosphorinanes 14-19. Hydrolysis of the phosphoni um alkoxides 8-12 afforded the phosphine oxides 21-25 by benzene elimi nation. For the phenyl-substituted phosphonium alkoxide 13, hydrolysis led to the benzyl ether 26, while deprotonation at the cu carbon atom resulted in the corresponding ylide, which on air oxidation led to be nzoate 27 and triphenylphosphine oxide. In the presence of benzaldehyd e, the ylide derived from phosphonium alkoxide 8 was trapped in the fo rm of the novel 3-hydroxy enol ether 28 through stereoselective Wittig olefination, which establishes the phosphonium alkoxides 8-13 as pote ntially useful in situ building blocks.