Reinvestigation of reaction of (2-ethoxyvinyl)stannanes with acetyl bromide

Four analogous (2-ethoxyvinyl)stannanes (E/Z)-Bu3SnC(R)=CHOEt (R = Bu, H) were prepared and characterised using H-1, C-13, Sn-119, H-1-C-13 HMQC, H-1-C-13 HMBC, and H-1-Sn-119 HMQC NMR spectroscopy. The course of their reactions with acetyl bromide was studied by NMR spectroscopy. Although tributyltin bromide, ethyl acetate and the coresponding alkyne were identified as reaction products, this present reinvestigation showed unambiguously that heterolytic fragementation reactions, as stated previously, did not take place. Acetyl bromide cleaves the Sn-C= bond yielding tributyltin bromide and vinyl ethers. Subsequent decomposition of vinyl ethers and impurities in the starting stannane is the source of ethyl acetate and the alkyne, respectively.