Silylcuprates from Allene and Their Reaction with α,β-Unsaturatedd Nitriles and Imines. Synthesis of Silylated Oxo Compounds Leading to Cyclopentane and Cycloheptane Ring Formation

The silylcupration of allenes and the subsequent capture of the intermediate cuprate with α,β-unsaturated nitriles is reported. The influence of the substitution of the nitrile, the nature of the
silylcopper species, and the temperature on the selectivity of the reaction is studied. An interesting
diaddition process was observed (1,2-addition and 1,4-addition), leading to oxo compounds which
simultaneously have an allylsilane and a vinylsilane group. The different reactivity of these two
units has been employed in the intramolecular allylsilane-terminated cyclization of these adducts,
where the vinylsilane moiety remains unchanged. To shed some light on the reaction pathway, the
behavior of α,β-unsaturatedd imines was also checked and a new and convenient way for
cycloheptane annulation presented. In light of the former results a feasible mechanism is proposed.