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Ligand Mediated Iron Catalyzed Dimerization of Terminal Aryl Alkynes: Scope and Limitations by Ganesh Chandra Midya; Bibudha Parasar; Kalyan Dhara; Jyotirmayee Dash is a Chemistry article available to read on EtoBox.

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Regioselective dimerization of terminal aryl alkynes to produce conjugated enynes has been achieved using FeCl3 and KO(t)Bu in the presence of either DMEDA or dppe. The reaction proceeds smoothly in toluene at 145 °C for 2 h to give the corresponding head-to-head dimers in good to excellent yields (54 to 99%) with high E-selectivity (67 : 33 to 83 : 17 E/Z). Both strongly electron-donating and electron-withdrawing groups are compatible with this procedure. The bidentate phosphine (dppe) ligand exhibits better catalytic activity than the bidentate amine (DMEDA). The aliphatic acetylene fails to react under this catalytic system which suggests that potassium tertiary butoxide activates the conjugated system of aryl acetylene through cation-pi interaction and pi-pi interaction. A radical inhibitor (galvinoxyl or TEMPO) completely suppresses the reaction. Employing FeCl2 as a catalyst instead of FeCl3, only phenyl acetylene afforded the corresponding head to head dimer in good yield. Mechanistic pathways for both FeCl3 catalyzed dimerization of aryl alkynes and FeCl2 catalyzed dimerization of phenyl acetylene have been proposed.

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Author

Ganesh Chandra Midya; Bibudha Parasar; Kalyan Dhara; Jyotirmayee Dash

Publisher

Royal Society of Chemistry (RSC)

Published

2014

Language

EN

Field

Chemistry (Physical Sciences)