Efficient synthesis of pyrimido[5,4‐c]pyridazines and of thiino[2,3‐d]pyrimidines based on an aza‐wittig reaction/heterocyclization strategy |
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Authors: | Magda A Barsy Eman A El Rady Mostafa A Ismael |
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Institution: | Department of Chemistry, Faculty of Science, South Valley University, Aswan 81528, Egypt |
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Abstract: | A simple one‐pot and efficient method is described for the synthesis of pyrimido5,4‐c]pyridazines 5 and of thiino2,3‐d] pyrimidines 15 by a domino process involving an aza‐Wittig reaction/heterocyclization. The iminophosphorane 2 reacted with phenylisocyanate, followed by heterocyclization on addition of amines to give the corresponding guanidine intermediates 4 . The guanidine intermediates were cyclized in the presence of catalytic amount of sodium ethoxide to pyrimido5,4‐c]pyridazines 5 . Similarly, iminophosphorane 12 reacted with phenylisocyanate and amines to give thiino2,3‐d]pyrimidines 15 in moderate yields. Furthermore, pyridazino4,3‐d]oxazines 10 and thiino2,3‐d]oxazines 19 were synthesized by the intremolecular aza‐Wittig reaction of phosphazenes 2 and 12 , respectively, with acid chlorides followed by heterocylization via imidoyl chloride intermediates. J. Heterocyclic Chem., (2012). |
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