Regioselectivity / 31P-, lH-, 13C-NMR spectraThe [3 + 21 cyclocondensation of 2-amino-1,3-thiazoline, 2-aminopyridines, 2-and 4-aminopyrimidines, 2-aminopyrazine, and 2-aminoquinoline with chloromethyldichlorophos- [',*]. These syntheses often parallel those of azoles: When carboxylic acid derivatives are used for condensation to yield azoles, phosphorus trihalides or trisamides take their part in azaphosphole syntheses. When acetylenes are employed in the synthesis of azoles involving cycloaddition, phosphaalkynes are used instead for azaphospholes. A further route to azaphospholes by a condensation reaction may be understood as a parallel of the Hantzsch thiazole synthesis, with the part of the ahaloketone played by chloromethyldichlorophosphane. Starting from thioamides, we thus obtained 1,3,4-thiazaphospholes and starting from amidines, we obtained 1,4,2-diazaphospholes. Only this route does give access to representatives containing an unsubstituted carbon ring member adjacent to phosphorus (i.e. in the 5-or 3-position)r31. The present paper describes the synthesis of anellated 1,4,2-diazaphospholes starting from heterocycles containing an amidine system, i.e. 2-aminopyridines and 2-amino-l,3-thiazoles, and in one case a 2-aminothiazoline.
SynthesesThe condensation of equimolar amounts of 2-amino-l,3-thiazoline with chloromethyldichlorophosphane in the presence of a threefold molar amount of triethylamine in acetonitrile proceeds regiospecifically to give 5,6-dihydro