2- Stannylpyrimidines, reaction with acid

Stannylpyrimidines also react with acid chlorides to form ketones (214) without a catalyst (Scheme 46). The reaction with furoyl chloride is almost instantaneous at -78°C the yield of ketone is 52%. 2-Thienylcarbonyl chloride provides the ketone in 62% yield. On the other... 

Pyrimidines stannylated in the 4-position are highly active in coupling reactions at low temperature and will couple with an acid chloride to form ketones such as (233) in the absence of catalyst (Scheme 38). 2-Stannylpyrimidines also react rapidly with acid chlorides to form the ketones (234) in the absence of catalyst <94T275>. 

Thermal decarboxylation of pyrimidylcarboxylic organotin esters is another means to prepare the corresponding stannylpyrimidines [33]. This method obviates the intermediacy of lithiated pyrimidine species that would undergo undesired reactions at higher temperatures. The decarboxylation occurs at the activated positions. Therefore, thermal decarboxylation of tributyltin carboxylate 62, derived from refluxing carboxylic acid 61 with bis(tributyltin) oxide, provided 4-stannylpyrimidine 63. Addition of certain Pd(II) complexes such as bis(acetonitrile)palladium(II) dichloride improved the yields, whereas AIBN and illumination failed to significantly affect the yield. 

Pyrimidines stannylated in the 4-position are active in coupling reactions. 5-Chloro-4-stannylpyrimidines, either as 2-sulfide or 2-one, are coupled with alkenyl or aryl halides to form 208, 210, and 212. With an acid chloride, ketone 213 is formed in the absence of catalyst, which has an otherwise deleterious effect on the reaction. The reaction between thiophene-2-carbonyl chloride and the 4-stannylpyrimidine is run at -78°C (94T275). 

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