Synthesis of allylstannanes and vinylstannanes by the stannyl-cupration of allenes

Stannyl-cupration of allenes followed by electrophilic attack gives allyl-and vinyl-stannanes with a variety of substitution patterns. The regiochemistry of the reaction depends upon the temperature at which the intermediate cuprate is quenched with an electrophile. With allene itself, the allylstannane-vinylcuprate 1-(tributylstannylmethyl)vinylcuprate, 5, is the product of kinetically controlled addition, but the vinylstannane-allylcuprate 2-(tributylstannyl)allylcuprate, 6, is thermo-dynamically lower in energy. The equilibration between these isomers begins to take place between –100 and –78 °C.