Iron catalyzed highly regioselective dimerization of terminal aryl alkynes

Abstract

Iron can catalyze head-to-head dimerization of terminal aryl alkynes to give the corresponding (E) selective conjugated enynes in high yields. A variety of substituted aryl acetylenes underwent smooth dimerization using catalytic FeCl(3) and DMEDA in the presence of KO(t)Bu.

N‐Substituted Iminopyridine Arene–Ruthenium Complexes for the Regioselective Catalytic Hydration of Terminal Alkynes

“…However, no traces of Markovnikov or anti‐Markovnikov hydration products were detected from these reactions, but surprisingly we observed the dimerization of 1 a to form the homocoupled product 1 aa . We obtained a mixture of E and Z isomers of 1,4‐diphenylbut‐1‐ene‐3‐yne ( 1 aa) with E / Z ratios of 67:33 and 53:47 in t BuOK and KOH, respectively, generated by the head‐to‐head homocoupling of 1 a (Table S8, entries 11–12, and Table S9, entries 1 and 2) . These results suggest the crucial role of H 2 SO 4 in the Markovnikov hydration of terminal alkynes, which is in good agreement with earlier reports suggesting that the presence of H 2 SO 4 enhances the yield of the methyl ketone products …”

Iron‐Catalyzed gem‐Specific Dimerization of Terminal Alkynes

“…In contrast, only a few examples of iron‐based catalysts have been reported . The first reported iron‐catalyzed alkyne dimerization uses FeCl 3 as the catalyst in the presence of a ligand and large excess of KO t Bu; this reaction requires an extremely high catalyst loading (30 mol %) and high temperatures, and gives E enyne products . Recently, Milstein and co‐workers reported a well‐defined iron(II)‐pincer catalyst that can achieve Z ‐selective alkyne dimerization of arylalkynes under mild conditions at 1–3 mol % catalyst loadings in the absence of any additive .…”

Regio- and Stereoselective Homodimerization of Monosubstituted Acetylenes in the Presence of the Second Generation Grubbs Catalyst

“…Many examples of effective run of the process in the presence of transition metal complexes have been described. Catalytic activity in the process has been reported to be shown by complexes of such metals as palladium [4,[7][8][9][10][11][12][13], rhodium [14][15][16][17][18][19], ruthenium [20][21][22][23][24][25][26][27][28][29], nickel [30], iridium [31][32][33], osmium [34,35], iron [36] and the f-block metals [37][38][39]. However, a highly selective synthesis of conjugated enynes by dimerization is still a challenging process.…”