SYNTHESIS AND PROPERTIES OF A 5,6-DIHYDRO-1,3-AZAPHOSPHOLO[5,1-b]OXAZOLE

Abstract

2-Ethyl-3-phenacyl-4,5-dihydrooxazolium bromide 1 enolizes spontaneously in dimethyl sulfoxide solution. Condensation with phosphorus trichloride nevertheless involves both the methylene groups in 2-and 3-position and thus yields a five-membered ring. Hydrolysis of the resulting 1-methyl-3-benzoyl-5,6-dihydro-1,3-azaphospholo[5,1-b]oxazole 2 selectively opens the P[sbnd]C3 bond of the azaphosphole ring to give the zwitterionic 4,5-dihydrooxazolio phosphinate 3.

Key Words:

• Anellated 1,3-azaphospholes
• 3-alkyl-4,5-dihydrooxazolium bromides
• keto/enol equilibrium
• cyclocondensation with PC₃; ³¹P-, ¹H-, ¹³C-NMR spectra
• mass spectral fragmentation