Research News, July 10th, 2012

 1,3-Butadienylzinctrimer Formed via Transmetallation from 1,4-Dilithio-1,3-butadienes: Synthesis, Structural Characterization and Application in Negishi Cross-Coupling

Yi Zhou, Wen-Xiong Zhang, and Zhenfeng Xi*

 Organometallics 2012, accepted.

  
Fifteen-membered metallacyclic rings composed of three butadienyl units and three zinc atoms are prepared highly efficiently by transmetallation of 1,4-dilithio-1,3-butadienes with 1 equiv of ZnBr2. Their structures are determined by single-crystal X-ray structural analysis. The reaction chemistry is demonstrated by the Pd-catalyzed Negishi cross-coupling with iodobenzenes.

Organozinc compounds are useful synthetic reagents and reactive organometallic intermediates. There are many reports on their reactivities and synthetic applications. In contrast, much less investigation has been carried out on their structures. We have been interested in the reaction chemistry and transmetallation of 1,4-dilithio-1,3-butadienes (Organo-di-Lithio reagents). Our previous results demonstrate that those organo-di-metallic compounds formed via this transmetallation show unique structures and reactivities. Herein we report the synthesis, structural characterization and reaction chemistry of the first well-defined 1,3-butadienylzinctrimers formed from 1,4-dilithio-1,3-butadienes and ZnBr2.