Addition and Cyclization Reactions in the Thermal Conversion of Hydrocarbons with an Enyne Structure, 5. High-Temperature Ring Closures of 1,3-Hexadien-5-ynes to Naphthalenes – Competing Reactions via Isoaromatics, Alkenylidene Carbenes, and Vinyl-type Radicals
2-ethynylstyrenes 7a–c were subjected to high-temperature pyrolysis. The cycloisomerization products isolated suggest that these are formed by three competing processes: by (i) an electrocyclic or a molecule-induced, (ii) an alkenylidenecarbene controlled, and (iii) a radical-controlled ring-closure process. To estimate the relative importance of these three reactions here mentioned, the substrates have
Dihydrobiphenylenes through Ruthenium-Catalyzed [2+2+2] Cycloadditions of<i>ortho</i>-Alkenylarylacetylenes with Alkynes
作者:Silvia García-Rubín、Carlos González-Rodríguez、Cristina García-Yebra、Jesús A. Varela、Miguel A. Esteruelas、Carlos Saá
DOI:10.1002/anie.201309496
日期:2014.2.10
A new synthetic route to dihydrobiphenylenes has been developed. The process involves a mild RuII‐catalyzed [2+2+2] dimerization of ortho‐alkenylarylacetylenes or its more versatile variant, the Ru‐catalyzed [2+2+2] cycloaddition of ortho‐ethynylstyrenes with alkynes. Mechanistic aspects of this [2+2+2] cycloaddition are discussed.