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Efficient synthesis of pyrimido[5,4‐ c ]pyridazines and of thiino[2,3‐ d ]pyrimidines based on an aza‐wittig reaction/heterocyclization strategy
Author(s) -
Barsy Magda A.,
El Rady Eman A.,
Ismael Mostafa A.
Publication year - 2012
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.646
Subject(s) - chemistry , phenylisocyanate , wittig reaction , guanidine , catalysis , sodium ethoxide , oxazines , organic chemistry , medicinal chemistry , combinatorial chemistry , ethanol
A simple one‐pot and efficient method is described for the synthesis of pyrimido[5,4‐ c ]pyridazines 5 and of thiino[2,3‐ 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 pyrimido[5,4‐ c ]pyridazines 5 . Similarly, iminophosphorane 12 reacted with phenylisocyanate and amines to give thiino[2,3‐ d ]pyrimidines 15 in moderate yields. Furthermore, pyridazino[4,3‐ d ]oxazines 10 and thiino[2,3‐ 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).