Reactions of [2+2+1]-cycloaddition with the participation of cyclopropenes and dicobalt hexacarbonyl complexes of acetylenes

Recent Advances in Cyclopropene Chemistry

“…138 It was demonstrated that this reaction proceeds readily in the presence of sulfide and N-oxide promoters in a highly diastereoselective manner, producing a single isomer of cyclopentenone 131. In contrast to the endo selectivity previously reported by Nefedov, 139 the formation of exo adducts, confirmed unambiguously by X-ray studies, was observed in this case. 138…”

The Intermolecular Pauson–Khand Reaction

“…The CCC angle of cyclopropene is 64.58°,25 and hence a low‐lying LUMO and high reactivity are expected. After two reports on the use of substituted cyclopropenes15f, 24a in the intermolecular Pauson–Khand reaction, in 2001 Pericás, Riera, and co‐workers used cyclopropene itself for the first time in the cobalt‐mediated version of this reaction 24b. In this NMO‐promoted coupling, cyclopropene reacted with bulky terminal alkynes to give synthetically attractive bicyclo[3.1.0]hex‐3‐en‐2‐ones 13 in good to excellent yields (Table 4, entry 1).…”

Recent developments of cyclopropene chemistry

“…123,124 Several examples of cyclopropene involved Pauson-Khand reactions have been previously reported. [125][126][127][128] Recently, Fox et al described general conditions for the utilization of chiral cyclopropenes in intermolecular Pauson-Khand reactions, 129 and the enantioselective synthesis of pentalenene via an intramolecular cyclopropene Pauson-Khand reaction. 130 In 2008, they successfully isolated Co-complexes derived from the putative alkene-insertion intermediates of Pauson-Khand reactions and the X-ray crystallographic as well as spectral properties of Co-complexes that were isolated from two Pauson-Khand reactions of chiral cyclopropenes have been described.…”