Benzoyl chloride, transmetallation

As an example of carbometallation, the 1,4-carbosilylation product 218 is obtained by the reaction of dienes, disilanes and acid chlorides of aromatic and a,/i-unsaturatcd acids at 80 °C. The phenylpalladium 216 is formed by the oxidative addition of benzoyl chloride, followed by facile decarbonylation at 80 °C, and reacts with butadiene to generate the benzyl-7i-allylic complex 217. Then, transmetallation with the disilane and reductive elimination afford 4-silyl-2-butenylbenzene 218 [92], Regioselective carbomagnesation of isoprene with allylic magnesium bromide 219 catalysed by Cp2TiCl2 gives 220, which is useful for terpene synthesis [93,94],... 

In his review of 1986, Stille proposed a mechanism based primarily on data obtained from the coupling of benzoyl chloride with tri-n-butyl(phenyl)tin. This proposal already clearly stated four main steps of the catalytic cycle oxidative addition, transmetalation, isomerization, and reductive elimination. 

This very active, chemoselective, sterically hindered base was employed to seleaively zincate 3,6-dibromopyridazine (42) in >95% yield (Scheme 19). Subsequent transmetalation with CuCN-2LiCl followed by benzoylation with benzoyl chloride gave (3,6-dibromopyridazin-4-yl)(phenyl)methanone (43) in 86% yield (Scheme 19). Treatment with other electrophiles, such as iodine and allylic bromides, furnished the respective dibromopyridazines in good yields. 

With cyclic iodoacetals such as 307 the zinc-organic intermediate 308 is produced, which via transmetalation as described above gives rise to the bicydic acetal 309 on treatment with benzoyl chloride [97]. 

The preparation of functionalized uracils and purines is of high interest due to the biological properties of these important classes of heterocycles [97]. Starting from various protected 5-iodouracils such as 168, the addition of iPrMgBr (—40 C, 45 min) leads to the formation of the corresponding magnesium compound 169 that can be trapped by various aldehydes, ketones and acid chlorides, leading for instance, after transmetallation to copper and reaction with benzoyl chloride to ketone 170 in 73% yield (Scheme 4.35) [98]. 

The uncatalyzed reaction of acid chlorides with organozincs is sluggish and inefS-cient. It is often complicated by side reactions and leads usually to low yields of the desired acylation products. In contrast, the CuCN 2LiCl-mediated acylation of various zinc reagents affords ketones in excellent yields. The reaction of the zinc-copper reagent 328 obtained by the direct zinc insertion to the iodide 329 followed by a transmetallation with CuCN 2LiCl reacts with benzoyl chloride at 25 °C leading to the ketone 330 in 85% yield [52b]. The functionalized benzylic bromide 331... 

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