Dilithium Tris(1-pentynyl)cuprate

[58384-88-6]  · C15H21CuLi2  · Dilithium Tris(1-pentynyl)cuprate  · (MW 278.79)

(organometallic alkynylating agent for a,b-unsaturated ketones1 and for displacement of electrophilic amines2)

Solubility: sol ether to -78 °C.

Preparative Method: to purified Copper(I) Iodide (10.5 mmol) suspended in ether at 0 °C is added 1-pentynyllithium (30 mmol; prepared from n-Butyllithium and 1-pentyne).3

Handling, Storage, and Precautions: should be used immediately following preparation.

Addition to a,b-Unsaturated Cyclic Ketones.

Li2Cu(1-pentynyl)3, in ether with HMPA as cosolvent, adds regiospecifically to cyclic enones to produce 1,2-alkylation products in high (85-95%) yield (eq 1).1 Li2Cu(1-pentynyl)3, as well as other dilithium trialkynylcuprates, failed to give 1,2- or 1,4-addition products in ether alone.3,4

Synthesis of 1-Alkynylamines.

1-Pentynylamines are formed by displacement of electrophilic amines with Li2Cu(1-pentynyl)3 in 69-87% yield (eq 2) depending on the amine substrate and the conditions used in the preparation of Li2Cu(1-pentynyl)3.2 For example, formation of Li2Cu(1-pentynyl)3 from 3 equiv of 1-pentynyllithium and 1 equiv of Copper(I) Cyanide resulted in a 69% yield, while forming Li2Cu(1-pentynyl)3 from 3 equiv of 1-pentynyllithium and 1 equiv of CuBr.DMS (see Copper(I) Bromide) gave an 87% yield using the same electrophilic amine.

1. Palmisano, G.; Pellegata, R. CC 1975, 892.
2. Boche, G.; Bernheim, M.; Niessner, M. AG(E) 1983, 22, 53.
3. House, H. O.; Fischer, W. F. JOC 1969, 34, 3615.
4. Whitesides, G. M.; Fischer, W. F.; San Fillippo, J.; Bashe, R. W.; House, H. O. JACS 1969, 91, 4871.

Timothy J. Guzi & Timothy L. Macdonald

University of Virginia, Charlottesville, VA, USA

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