Transmetallation carbonylation pathways

Lewis acids, particularly the boron trifluroride diethyl ether complex, are used to promote the reaction between allyl(trialkyl)- and allyl(triaryl)stannanes and aldehydes and ketones52-54. The mechanism of these Lewis acid promoted reactions may involve coordination of the Lewis acid to the carbonyl compound so increasing its reactivity towards nucleophilic attack, or in situ transmetalation of the allyl(trialkyl)stannane by the Lewis acid to generate a more reactive allylmetal reagent. Which pathway operates in any particular case depends on the order of mixing of the reagents, the Lewis acid, temperature, solvent etc.55- 58. 

TMRC) pathway accounted for the high efficiency of this transformation. The key step is the ring-opening reaction of the cyclopropene in the presence of copper catalyst and subsequent transmetalation to palladium generating the key C-Pd bonds, which could undergo the carbonylative steps providing the desired products. 

Through the use of Inis, Baba et al. had managed to dispense with TMSCI to regenerate the catalyst [30]. Only 10 to 20 mol% of Inis was required for the allylation of aldehydes and aromatic ketones with allyltributyltin, and stoichiometric amounts of Inis was found to inhibit the reaction. Reaction was expected to proceed via an entirely transmetallation pathway owing to the lower Lewis acidity of Inis. Thus, for y-substituted allylic tin compounds, typical anti preference for the addition product was observed. A chelation-controlled addition was used to explain the rate acceleration and higher yields of carbonyl compounds with vicinal alkoxy group, and the predominance of the syn addition product for such compounds (Figure 8.12). 

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