The Effect of Added Silver Nitrate on the Palladium-Catalyzed Arylation of Allyltrimethylsilanes

Article abstract of DOI:10.1021/jo00220a042

The palladium-catalyzed reaction of iodobenzene with allyltrimethylsilane at 120 deg C (the Heck arylation) ressulted predominantly in arylation at the terminal position giving (E)-1-phenyl-3-(trimethylsilyl)-1-propene (1) as the major product and considerable amounts of 3-phenyl-1-propene (6) and 2-phenyl-1-propene (7) as minor products.At 50 deg C the reaction gave approximately the same product distribution, but 53percent of the iodobenzene remained after 2 days.The addition of silver nitrate at this temperature had a dramatic effect on the reaction.All the starting materi al was consumed after 2 days.The vinylsilane (E)-3-phenyl-1-(trimethylsilyl)-1-propene (2) was then the major component, only 3percent of 1 was formed, and no desilylation was observed.Thus addition of silver nitrate at low temperature (a) enhances the reaction rate, (b) changes the direction of elimination, and (c) supresses the desilylation.Arylation of (E)-1,3-bis(trimethylsilyl)-1-propene in the presence of silver salts gave almost exclusively the stereospecific product (Z)-1,3-bis(trimethylsilyl)-2-phenyl-1-propene (4) at 50 deg C and 2-phenyl-3-(trimethylsilyl)-1-propene (3) at 120 deg C.Compound 3 was also formed in the absence of silver nitrate at 120 deg C, but then the reaction required a considerably longer reaction time.