A convenient approach to dialkyl heteroarylmethylphosphonates and [alkylthio(heteroaryl)methyl]phosphonates: Synthesis of imidazo[1,2-a]pyridine, imidazo[1,2-a]pyrimidine, indolizine and thiazole derivatives

Article abstract of DOI:10.1055/s-1991-26466

The [heteroaryl(hydroxy)methyl]phosphonates 2-5 (indolizines 2, imidazo[1,2-a]pyridines 3, imidazo[1,2-a]pyrimidines 4, and 2-phenylthiazoles 5, are converted readily to the corresponding O,O-thiocarbonates 6-8 and 18 on treatment with p-tolyloxythiocarbonyl chloride in acetonitrile/4-dimethylaminopyridine, while reaction in pyridine/dichloromethane affords the isomeric O,S-thiocarbonates 9-11 and 19, respectively. Homolytic cleavage of both series of compounds proceeds smoothly, using tributyltin hydride/azobisisobutyronitrile (AIBN) in warm toluene to give the new heteroarylmethylphosphonates 12-14 and 20. Conversion of the O,S-thiocarbonates 9-11 and 19 into the synthetically attractive α-methylthio-substituted derivatives 15-17 and 21 is effected efficiently upon saponification with sodium methoxide in methanol and subsequent alkylation with methyl iodide.