Synthesis of new types of tetracyclo[4.3.0.02,4.03,7]nonane hydrocarbons by cyclocodimerization of norbornadiene and its derivatives with diacetylenes and vinylacetylenes, catalyzed by low-valence cobalt complexes

Abstract

145ChemInform Abstract The ternary system cobalt acetylacetonate-triphenylphosphine-diethylaluminum chloride catalyzes the cycloaddition reaction of the norbornadienes (I) with the acetylenic compounds (II), (V) and (VI), or (XII), producing the tetracyclic ring system mentioned in the title. (Further examples are given in the original paper).

Nickel-Catalyzed Intermolecular [2 + 2] Cycloaddition of Conjugated Enynes with Alkenes

“…In fact, two examples showing that conjugated enynes can facilitate [2 + 2] cycloaddition with alkenes in cobalt-catalyzed reactions can be found in the literature. Tolstikov and co-workers showed that vinylacetylene favors [2 + 2] cycloaddition with norbornadiene over the competing homo-Diels–Alder reaction . Hilt et al reported that (1-cyclohexen-1-ylethynyl)benzene showed complete selectivity for [2 + 2] cycloaddition with cyclopentene while other internal alkynes gave a mixture of [2 + 2] cycloadducts and Alder–ene products.…”

Synthesis of Cyclobutenes and Allenes by Cobalt‐Catalyzed Cross‐Dimerization of Simple Alkenes with 1,3‐Enynes

“…We assumed that, as with nickel catalysis, if the oxidative cyclization of alkenes with 1,3‐enynes at the cobalt center can occur to form a η 3 ‐butadienyl intermediate, then β‐H elimination could be avoided, and cyclobutenes could be provided by means of reductive elimination. In fact, two examples can be found in the literature, showing that 1,3‐enynes facilitate [2+2] cycloaddition with alkenes under cobalt catalysis 7a. 8…”

Harnessing the Polarizability of Conjugated Alkynes toward [2 + 2] Cycloaddition, Alkenylation, and Ring Expansion of Indoles

“…Despite the diversity of alkynes tailored toward [2 + 2] cycloadditions with alkenes (inter- or intramolecular), many of them operate through combinations of precious metal catalysts and supporting ligands . Directed intermolecular cycloadditions using Au, Ni, and Co utilizing the distinct reactivity of conjugated enynes are some examples.…”