Lithio siloles

Intramolecular Reaction Pattern Formation of a-Lithio Siloles from Silyl-Substituted Di-lithio Reagents via E/Z Isomerization Followed by Nucleopbilic Attack... 

Scheme 4 Intramolecular cyclization of silyl-substituted 1,4-dilithio-1,3-butadienes to afford a-lithio siloles via E/Z isomerization and nucleophilic attack...

Besides, the types of nitrile used in the abovementioned reaction have also strong impact on the reaction patterns. When 1,2,3,4-tetra-substituted di-lithio reagents were treated with MesSiCN, a tandem silylation-intramolecular substitution process readily occurred to yield siloles 45, while the reaction of 2,3-di-substituted di-lithio reagents with MesSiCN gave rise to the first synthesis of (Z, Z)-dienylsilanes 46 with high stereoselectivity (Scheme 23) [63]. In this reaction, the normal reaction pattern that nitriles are attacked at C=N triple bond by mono-Li reagents was not found. Instead, cleavage of Si-C bond in Si-CN moiety was observed. 

All these results revealed that the substitution patterns of di-lithio reagents and the nature of nitriles played key roles in the formation of pyridines, cyclopentadie-nylamine, tricyclic A -bipyrrolines, siloles, and (Z,Z)-dienylsilanes. 

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