Synthesis of Octahydropyrano[2,3- d ]Pyrimidine Derivatives via Tetrahydropyrano[3,2- e ][1,3]Thiazolo[3,2- a ]Pyrimidine and 2,6-Dichlorobenzonitrile Oxide

N¹-substituted octahydro-1H-pyrano[2,3-d]pyrimidines derivatives were prepared in moderate yield by the reaction of methyl [(4aRS,5SR,10aRS)-5-aryl-2-oxo-3,4,4a,10a-tetrahydro-2H,5H-pyrano[3,2-e][1,3]thiazolo[3,2-a]pyrimidin-8(9H)-ylidene]acetate and 2,6-dichorobenzonitrile oxide via a domino 1,3-dipolar cycloaddition/ring-opening/dethionation process. The structures of the products were characterised by spectroscopic and X-ray crystallographic analysis.