Organophosphate‐accelerated copper‐catalyzed C(sp²)–C(sp) Sonogashira‐type cross couplings

Abstract

A dramatic acceleration in copper-catalyzed Sonogashira-type reactions was observed when an organophosphate was used as additive. The catalyst systems featuring low copper loading (0.5 mol% < Cu < 5 mol%) gave Sonogashira-type products with a broad scope of aromatic and aliphatic terminal alkynes as well as aryl iodides in good to excellent yields. Among the organophosphate/copper catalytic systems, that of 4 mol% Cu(OTf) 2 /10 mol% (R)-(À)-1,1′-binaphthyl-2,2′-diyl hydrogenphosphate exhibited the highest catalytic activity.

Methionine: a green and efficient promoter for copper‐catalyzed Sonogashira cross‐coupling reactions

“…They obtained coupled products using CuI (10 mol%) as catalyst and N , N ‐dimethylglycine hydrochloride salt (30 mol%) as promoter in the presence of K 2 CO 3 and DMF at 100°C in 24–36 h. Xu et al . have recently reported catalytic systems featuring low copper loading (0.5 mol% < Cu < 5 mol%) for copper‐catalyzed Sonogashira‐type reactions accelerated by a catalytic amount of additives such as polycyclic aromatic hydrocarbon or organophosphate as the ligand . They found Cu(OTf) 2 as an effective copper source in this reaction system.…”

A Sustainable, User‐Friendly Protocol for the Pd‐Free Sonogashira Coupling Reaction

“…The most widely used Cu‐based catalytic systems employ ethylenediamine, 1,10‐phenanthroline, 1,4‐diphenyl‐1,4‐diazabuta‐1,3‐diene, 1,4‐diazabicyclo[2.2.2]octane (DABCO) or N , N′ ‐dibenzyl‐BINAM . In most cases, a large excess (up to 30 %) of the multi‐dentate ligand is required . Other synthetic protocols employ multinuclear copper complexes bridged by N‐donor ligands, copper nanoparticles, microwave‐assisted reactions, or Cu‐catalyzed Sonogashira couplings under blue LED light irradiation , …”

Copper-catalyzed Sonogashira reactions: advances and perspectives since 2014

“…Xu et al proposed an efficient catalytic system (Cu(OTf) 2 /L1 (L1 = ( R )-(−)-1,1′-binaphthyl-2,2′-diyl hydrogenphosphate)) towards Sonogashira cross coupling reactions. 35 The system needed a low copper loading of about 4 mol% for the cross-coupling between aromatic or aliphatic terminal alkynes and aryl iodides. The optimised reaction condition for the Sonogashira coupling using this novel catalytic system include 4 mol% of Cu(OTf) 2 and 10 mol% of phosphate ligand at 130 °C for 16 h. Iodobenzenes with electron-donating groups are more efficient in this reaction than electron-withdrawing ones.…”