1597435-48-7Relevant academic research and scientific papers
Reactions of aromatic S- and O-enynes with two methyl substituents on the olefinic unit assisted by a ruthenium complex: Tandem cyclization and product selectivity
Feng, Yi-Jhen,Lai, Ying-Hsuan,Lin, Ying-Chih,Huang, Shou-Ling,Liu, Yi-Hung
, p. 602 - 611 (2014)
Ruthenium-assisted cyclizations of two enynes, HC≡CCH(OH)(C 6H4)X-CH2CH=CMe2 (X=S (1 a), O (1 b)), each of which contains two terminal methyl substituents on the olefinic parts, are explored. The reaction of 1 a in CH2Cl2 gives the vinylidene complex 2 a from the first cyclization and two side products, 3 a and the carbene complex 4 a with a benzothiophene ligand. The same reaction in the presence of HBF4 affords 4 a exclusively. Air oxidation of 4 a in the presence of Et3N readily gives an aldehyde product. In MeOH, tandem cyclizations of 1 a generate a mixture of the benzothiochromene compound 10 a and the carbene complex 7 a also with a benzothiochromene ligand. First, cyclization of 1 b likewise proceeds in CH2Cl2 to give 2 b. Tandem cyclization of 1 b in MeOH yields comparable products 10 b and 7 b with benzochromene moieties, yet with no other side product. The reaction of [Ru]Cl with HC≡CCH(OH)(C6H4)S-CH2CH= CH2 (1 c), which contains no methyl substituent in the olefinic part, in MeOH gives the carbene complex 15 c with an unsubstituted thiochromene by means of a C-S bond formation. Structures of 3 a and 15 c are confirmed by X-ray diffraction analysis. The presence of methyl groups of enynes 1 a and 1 b promotes sequential cyclization reactions that involve C-C bond formation through carbocationic species. Copyright
