Silylcuprates from allene and their reaction with alpha,beta-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 alpha,beta-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 alpha,beta-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.
Barbero
Asunción
A
Departamento de Química Orgánica, Universidad de Valladolid, 47011 Valladolid, Spain. barbero@qo.uva.es
Blanco
Yolanda
Y
Pulido
Francisco J
FJ