Formation of pyridine from acetylenes and nitriles catalyzed by RuCpCl, CoCp, and RhCp derivatives – A computational mechanistic study

Synthesis of Group 9 Metal‐Olefin Complexes with Identical Ligand Frameworks and Comparison of their Catalytic Activity in [2+2+2] Cycloaddition and other Addition Reactions

“…The computational method and model are given in the Supporting Information. Several computational mechanistic studies on the general mechanisms of cycloaddition reactions have been published, [4] and also investigations comparing CpCo and CpRh fragments specifically in the formation of pyridines have been released by Kirchner et al [29] It can be assumed that the remarkable differences in reactivity of complexes 1-3 during the [2 + 2 + 2] cycloaddition are a consequence of the bonding nature of the metal core and the coordinating olefins. We calculated the energies of some initial steps of the cycloaddition process for evaluating the observed differences in reactivity.…”

“…[29,30] However, the exergonic order of the oxidative cyclization of the alkynes again favours cobalt over rhodium and iridium.…”

Rhodium(I)‐Catalysed Intramolecular [2+2+2] Cyclotrimerisations of 15‐, 20‐ and 25‐Membered Azamacrocycles: Experimental and Theoretical Mechanistic Studies

“…The reaction mechanism for the alkyne cyclotrimerisation reaction catalysed by [CoCp(L) 2 ] (Cp= cyclopentadiene; L = CO, PR 3 , THF and olefin), [10][11][12][13] [RuCpCl] [14][15][16][17] complexes and the {RhCp} [18] and {RhInd} (Ind = indene) [18] fragments has been analysed in these DFT studies. The generally accepted reaction mechanism is drawn in Scheme 3.…”

“…[13] On the other hand, the cyclotrimerisation of nitriles and acetylenes to afford pyridine rings has been also discussed in a series of theoretical studies. [17,18,20,21] The rate-determining step of the overall catalytic cycle changes to become the addition of the nitrile molecule to the metallacyclopentadiene or metallacyclopentatriene intermediate. [17,18] One of the key aspects in the cyclotrimerisation of nitriles and acetylenes is the competition between arene and pyridine formation.…”

Expedient nonclassical reaction of acetylenes with ketones: controlling the switch between bicyclic ketals and cyclopentenols formation

“…Over many years, fundamental organic synthesis has revealed a diversity of reactions of alkynes, which provide new C-C, C-N, and C-O bond formation, e.g. in important biomolecules as pyrroles, 6,7 pyridines, 2,[8][9][10] vitamins A and E, 1,11 β-carotene, 11 linalool, 11 citral, 12 steroids, 13,14 etc. In this area of organic synthesis, the application of superbasic media such as alkaline metal hydroxide or alkoxide/DMSO 15 to promote the reactions of alkynes with nucleophiles is a comparatively underestimated approach.…”