Generation and Reaction of Tungsten-Containing Carbonyl Ylides:  [3 + 2]-Cycloaddition Reaction with Electron-Rich Alkenes

• Published in: Journal of the American Chemical Society 2005-03, Vol.127 (8), p.2709-2716
• Main Authors: Kusama, Hiroyuki, Funami, Hideaki, Shido, Masahide, Hara, Yoshihiro, Takaya, Jun, Iwasawa, Nobuharu
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; Kinetics and mechanisms; Organic chemistry; Reactivity and mechanisms
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja044194k

Novel tungsten-containing carbonyl ylides 7, generated by the reaction of the o-alkynylphenyl carbonyl derivatives 1 with a catalytic amount of W(CO)5(thf), reacted with alkenes to give polycyclic compounds 5 through [3 + 2]-cycloaddition reaction followed by intramolecular C−H insertion of the produced nonstabilized carbene complex intermediates 8. In the presence of triethylsilane, these tungsten-containing carbene intermediates 8 were smoothly trapped intermolecularly by triethylsilane to give silicon-containing cycloadducts 17 with regeneration of the W(CO)5 species. By this procedure, the scope of alkenes employable for this reaction was clarified. The presence of the tungsten-containing carbonyl ylide 7c was confirmed by direct observation of the mixture of o-ethynylphenyl ketone 1c and W(CO)5(thf-d 8). Careful analysis of the intermediate by 2D NMR, along with the observation of the direct coupling with tungsten-183 employing the 13C-labeled substrate, confirmed the structure of the ylide 7c. Examination using (E)- or (Z)- vinyl ether revealed that the [3 + 2]-cycloaddition reaction proceeded in a concerted manner and that the facial selectivity of the reaction differed considerably depending on the presence or absence of triethylsilane. These results clarified the reversible nature of this [3 + 2]-cycloaddition reaction.