10.1021/jo981533h
The research focuses on the development of a convenient one-pot synthesis method for 1,4-dihalobutadienes from alkynes via titanacyclopentadienes, which are significant as precursors for various metalloles containing main group elements. The study aims to overcome the limitations of existing synthetic routes, particularly in the preparation of exocyclic and 2,3-unsubstituted-1,4-dihalobutadienes, which are crucial for the synthesis of bicyclic and 3,4-unsubstituted metalloles. The researchers successfully developed a method that involves the preparation and halogenolysis of titanacyclopentadienes derived from alkynes with a divalent titanium complex, (η2propene)Ti(O-i-Pr)2, which is prepared in situ from Ti(O-i-Pr)4 and i-PrMgCl. The process yields 1,4-dihalobutadienes in good to excellent yields without the need for additives like CuCl, and is more cost-effective compared to the zirconacyclopentadiene route. The synthesized 1,4-dihalobutadienes were further transformed into a series of silole derivatives, demonstrating the synthetic utility of the developed methodology. Key chemicals used in the process include alkynes, Ti(O-i-Pr)4, i-PrMgCl, iodine, bromine, and Si(OMe)4.
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