Lithium 2-thienylcyanocuprate

Lithium metal (8.40 mmol) and naphthalene (9.20 mmol) were mixed in 10 ml THF at ambient temperature 2 hours and then cooled to -108°C. Lithium 2-thienylcyanocuprate (32ml 0.25M) was added via cannula at -50°C and the solution stirred at -108°C 30 minutes. The resulting zerovalent copper species was ready for immediate use. 

A highly reactive zero-valent copper species has been prepared by direct reduction of lithium 2-thienylcyanocuprate in THF with lithium naphthalenide <89SC1833>. 

By zirconium-iodine and then iodine-lithium exchange, the trans-alkenyllithi-um is obtained, which is reacted first with lithium 2-thienylcyanocuprate and then with the tricycle. Attack at the homo vinylogous 7-position produces a bicyclic compound, in which the five-membered ring has the oi-chain already with the correct stereochemistry. 

Substituting lithium 2-thienylcyanocuprate for the CuCN/LiBr complex and omitting boron trifluoride etherate from the reaction of the organozinc halide species with 2-cyclohexenone indeed gave a reasonable yield (76% GC) of the... 

Although the choice of phosphine ligand was found to be crucial for the formation and subsequent reactivity of the organocopper species, the presence of malodorous phosphine ligands was often found to interfere with product isolation. In our search for a more reactive copper that did not require the use of phosphorus ligands, we discovered that the lithium napthalenide reduction of a solution of a commercially available lithium 2-thienylcyanocuprate or CuCN LiCl complex produced a highly reactive zerovalent copper complex. 

Lithium 2-Thienylcyanocuprate-Based Copper 223 Table 5.6 1,4-Conjugate addition reactions with thienyl-based organocopper reagents. 

Li(0) (4.2 mmol) and naphthalene (4.6 mmol) in freshly distilled THF (5 ml) were stirred at room temperature under an argon atmosphere for 2 h. To this dark-green preformed lithium naphthalenide solution (-78 C), lithium 2-thienylcyanocuprate (0.25 M, 16 ml, 4.0 mmol) was added via a syringe. The solution of activated copper was used after it was stirred at -78°C for 0.5 h. For... 

The organocalcium reagent (2.66 mmol) was prepared from 1-chlorooctane (395 mg, 2.66 mmol) and highly reactive calcium (3.10 mmol) as described in the preceding text. Lithium 2-thienylcyanocuprate (0.25 M in THE, 14 ml,... 

Lithium 2-thienylcyanocuprate was purchased from Aldrich Chemical Co. Lipshutz, B.H. Koerner, M. Parker, D.A. Tetrahedron Lett. 1987, 28, 945. 

Its reaction with benzaldehyde provides the desired homoallylic alcohol 4 in 96% yield [8]. An improved procedure allowing the generation of an exceptionally active copper(O) reagent is obtained by the low-temperature reduction of lithium 2-thienylcyanocuprate 5 with lithium naphthalenide [9]. In this case, 1,4-additions to enones in the presence of MejSiCl [10] proceed especially well. 

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