Substituted Alkyne Synthesis under Nonbasic Conditions:  Copper Carboxylate-Mediated, Palladium-Catalyzed Thioalkyne−Boronic Acid Cross-Coupling

Abstract

[figure: see text] A new methodology for the synthesis of substituted alkynes is described. In the presence of copper(I) thiophene-2-carboxylate (CuTC) or copper (I) 3-methylsalicylate (CuMeSal), the palladium-catalyzed cross-coupling of thioalkyne derivatives with boronic acids affords functionalized alkynes in yields ranging from 39 to 91%. This coupling occurs efficiently under mild, nonbasic conditions with a wide variety of thioalkynes and boronic acids, providing a reaction complementary to the Sonogashira protocol.

Pd‐ and Ni‐Catalyzed Cross‐Coupling Reactions of Functionalized Organozinc Reagents with Unsaturated Thioethers

“…More recently, this Pd-catalyzed reaction has been modified to allow the coupling of organoboronic acids or organostannanes with heteroaromatic or alkynyl thioethers. [5] All of these cross-coupling reactions require stoichiometric amounts of Cu I salts to proceed. Zinc organometallics are very useful reagents for organic synthesis due to their high tolerance to a broad range of functional groups.…”

NHC‐containing chiral bidentate ligands: Synthesis and evaluation in enantioselective copper‐catalyzed conjugate addition

“…Replacement of Cu(OTf) 2 by copper(I) salts such as CuOTf.C 6 H 6 or copper(I) thiophene-2-carboxylate 44 [CuTC; this salt has been shown to be very efficient in the cross-coupling reaction (see Ref. 45 )] led to a decrease of the catalytic activity, while no significant increase of the ee was observed (entries 6 and 7). We believe that ligands associating NHC and phosphine could yield to excellent results, but in the case of 6, the bulky PPh 2 function is located too close to the asymmetric center.…”

A one‐pot synthesis of alkynyl sulfides from terminal alkynes

“…Because of the activity of the alkylthio group to the carbon-carbon triple bonds, alkynyl sulfides have been involved in hydrostannation [3], [ [6], and cross-coupling reactions [7] as well as in the preparation of self-assembled monolayers in the production of composite materials [8].…”