Mechanism of the cyclization of dimethyl diethynyl silane with selenium tetrabromide: Computational and structural studies, and monitoring

• Published in: Journal of organometallic chemistry Vol. 692; no. 16; pp. 3307 - 3315
• Main Authors: Amosova, Svetlana V., Shagun, Vladimir A., Martynov, Alexander V., Makhaeva, Natalia A., Larina, Lyudmila I., Lysenko, Konstantin A., Voronkov, Mikhail G.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.07.2007
• Subjects: Chalcogens; Five-membered unsaturated heterocycles; NMR spectroscopy; Reaction mechanisms; X-ray diffraction; X-ray diffraction; Five-membered unsaturated heterocycles; Chalcogens; Reaction mechanisms; NMR spectroscopy
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/j.jorganchem.2007.01.023

The structure of 2,4-dibromo-2-dibromomethyl-3,3-dimethyl-1-selena-3-silacyclopentene-4, formed by regioselective electrophilic addition of SeBr 4 to dimethyl diethynyl silane, has been determined using X-ray analysis technique. Quantum chemistry methods were used to study elementary stages of the reaction. The formation of only five-membered heterocycle is explained by kinetically preferable ring closure through four-center transition state. The conclusions obtained by calculations were confirmed by monitoring of the reaction using 1H NMR method. The structure of 2,4-dibromo-2-dibromomethyl-3,3-dimethyl-1-selena-3-silacyclopentene-4, formed by regioselective electrophilic addition of SeBr 4 to dimethyl diethynyl silane, has been determined using X-ray analysis technique. Quantum chemistry methods were used to study elementary stages of the reaction. It was found that the first stage consisted of SeBr 4 conversion into bimolecular complex Br 2⋯SeBr 2, initiated by dimethyl diethynyl silane. Possible formation of five-membered and six-membered heterocycles involves different cyclization mechanisms. The formation of only five-membered heterocycle is explained by kinetically preferable ring closure through four-center transition state. The conclusions obtained by calculations were confirmed by monitoring of the reaction using 1H NMR method.