Organostannanes acylation

Procedures for the synthesis of ketones based on coupling of organostannanes with acyl halides have also been developed.211 The catalytic cycle is similar to that involved in coupling with aryl halides. The scope of compounds to which the reaction is applicable includes tetra-u-butylstannane. This example indicates that the reductive elimination step competes successfully with (3-elimination. 

The acylpalladium is formed by CO insertion as the intermediate of the carbonylation. They can be prepared directly by the oxidative addition of acyl chlorides to Pd(0). Thus ketones can be prepared by the reaction of acyl halides with organozinc reagents and organostannanes. Benzoacetate (490) is obtained by the reaction of benzoyl chloride with the Reformatsky reagent 489 [243], The macrocyclic keto lactone 492 is obtained by intramolecular reaction of the alkenylstannane with acyl chloride in 491 [244]. 

The coupling of an allyl or acyl moiety onto carbon atoms is achieved by anodic oxidation of a-heteroatom substituted organostannanes or Oj -acetals in the presence of allylsilanes or silyl enol ethers. The reaction probably involves carbocations as intermediates that undergo electrophilic addition to the double bond [245c]. 

The acylation of the mildly nucleophilic organostannanes was first reported by Migita in 1977 through the use of palladium catalysis. However, the reported conditions were harsh and of limited... 

Ketones are formed from pyridylzinc halides on acylation with acid chlorides or anhydrides in reactions with benzoyl chloride or benzoic anhydride, pyridyl ketones (307) are formed in moderate yields. Reactions with 3-iodoquinoline gave the 3-benzoyl derivative 308. Organostannanes may be a better choice for ketone formation (see above). 

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