Copper thiophene carboxylate

Since its introduction by Allred and Liebsekind in 1996 [114], copper thiophene-2-carboxylate (CuTC) has emerged as a mild and useful reagent for mediating the cross-coupling of organostannanes with vinyl iodides at room temperature. CuTC is especially effective for substrates that are not stable at high temperature. In Paterson s total synthesis of elaiolide, he enlisted a CuTC-promoted Stille cyclodimerization of vinyl iodide 131 to afford the 16-membered macrocycle 132 under very mild conditions [115]. 

It is remarkable that a biphenyl unit in combination with a chiral amine 11 plays a role of an alternate binaphthol, inducing atropisomerism and giving ethylcyclohexanone in 96% ee [13]. Alexakis also succeeded in his search for efficient copper salts and solvents and reported the combination of CuTC (copper thiophene-2-carboxylate) and ether as a suitable choice. It is also noteworthy that trapping of the resulting zinc enolate with TMSOTf gave a TMS enolate 26, which is a useful intermediate for further synthetic manipulation [26]. Tandem... 

The method of Liebeskind <1996JA2748> was adapted for the coupling of 6-iodopterins 203 with the stannylated l,3-dithiol-2-one 204 in the presence of copper thiophene-2-carboxylate to produce pteridine derivatives 205 and 206 containing the l,3-dithiol-2-one unit (Equation 10) <1998T9559, 2001J(P1)3239>. 

Coupling promoted by copper thiophene-2-carboxylate (CuTC) I. Paterson, H.-G. Lombart, and C. Allerton, Org. Lett., 1, 19 (1999). 

The 2-indolinone system has been found in a large number of pharmaceutically active compounds. This framework could be constructed by a tandem Heck-Suzuki reaction sequence [137]. Intramolecular Heck reaction of 390 afforded a cyclized intermediate that, in situ, reacted with boronic acid 187 to produce 391 in a single pot sequence. The reaction made use of copper thiophene-2-carboxylic acid (CuTC) to generate base-free conditions for the Suzuki reaction. 

In another case, the Stille reaction of the simple 2-iodoquinoxaline 199 and 1,3-dithiole-2-thione stannanes 200 gave the adduct 201 only 0-10% yield, although the use of copper thiophene-2-carboxylate (CuTC) gave 80% yield of 201 [97]. 

Transition metals are also useful catalysts for the title cycloaddition, and copper catalysts have proven especially effective. In an example from Furstner s lab, unactivated alkyne 17 undergoes an intramolecular Diels-Alder reaction catalyzed by copper thiophene 2-carboxylate (CuTC) to provide bicycle 18 in 95% yield. ... 

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