摘要：

Pyrimidines constitute a prominent class of heterocyclic compounds; their derivatives show interesting pharmacological properties. One synthesis approach that has attracted attention is the reaction of alkynones and amidinium salts (1). Alkynones can be prepared by a Sonogashira-type reaction from acid chlorides and terminal alkynes. Recently, a copper-free method was reported (2) in which the formation of undesired 1,3-butadiyne derivatives are avoided. These authors found that cross-coupling reactions could be performed with a palladium(II)-acetate catalyst and no ligand, giving good to excellent yields. These findings encouraged us to try a pyrimidine-synthesis reaction from acid chlorides via in situ-formed olkynones under microwave conditions. For the cross-coupling reaction catalyst, we chose pollodium(II) acetate that was microencapsulated in a polyurea matrix (3), Pd(II)EnCat[TM]. This reagent had certain handling benefits, especially when in microwave conditions: the risk of hot spot overheating due to metal attachment to the gloss viol wall was eliminated. The catalyst-filtering procedure was easier as well. Results and Discussion The cross-coupling reaction between benzoyl chloride and 4-ethynyltoluene was used as a model for the optimization of the alkynone formation, and was performed on a 0.2-mmol scale. The reaction was heated...

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