Copper(I) t-Butoxide

t-BuOCu

[35342-67-7]  · C4H9CuO  · Copper(I) t-Butoxide  · (MW 136.66)

(metalation agent for active hydrogen compounds;1 cross-coupling agent of 1,3-dinitrobenzenes and aryl iodides;2 nontransferable group of mixed organocuprates;3 volatile copper precursor for MOCVD4)

Physical Data: sublimation temp 160 °C (0.1 mmHg), 110 °C (10-4 mmHg); mp 260 °C (dec).

Solubility: slightly sol THF, benzene, cyclohexane, and hexane.

Preparative Methods: CuI t-butoxide prepared in situ by the metathesis reaction between Copper(I) Chloride and alkali metal t-butoxide in appropriate organic solvents can be used for synthetic purposes. CuI t-butoxide can be isolated by sublimation under vacuum.

Handling, Storage, and Precautions: extremely oxygen- and moisture-sensitive. Preparation and reaction should be conducted under rigorously oxygen-free and anhydrous conditions.

Metalation.

CuI t-butoxide metalates a variety of active hydrogen compounds under mild conditions, with concomitant quantitative liberation of t-butyl alcohol, in the presence or absence of added ligands to generate corresponding organic CuI compounds, which generally can be easily isolated by evaporation or filtration of t-butyl alcohol and the solvent (eqs 1 -11).1,5 -11 This preparative method is characterized by the absence of alkali metal salts that usually accompany CuI compounds prepared by the metathesis reaction between CuI halides and organoalkali metal compounds. Acylation of (Trimethylsilyl)ethynylcopper(I) (eq 2) with acid chlorides gives trimethylsilylethynyl ketones.5 The CuI bicarbonate complex (eq 6) acts as a reversible CO2 carrier to transfer its CO2 moiety to cyclohexanone.8 CuI carbamate (eq 7) reacts with MeI in the presence of a t-butyl isocyanide ligand to produce methyl carbamate.9 CuI cyclohexanone-2-carboxylate (eq 8) undergoes a specific two-step decarboxylation in DMF to afford CuI enolate.10 Hydrogenolysis of CuI t-butoxide occurs in the presence of Triphenylphosphine to afford hexameric HCuPPh3 (eq 11), which is a useful reducing agent.11 For the synthetic use of CuI acetylides, Copper(I) Phenoxide, and Copper(I) Cyanoacetate, see the corresponding entries.

Cross-Coupling of 1,3-Dinitrobenzenes and Aryl Iodides to 2,6-Dinitrobiphenyls.

CuI t-butoxide with Pyridine mediates cross-coupling of 1,3-dinitrobenzenes with aryl iodides to give 2,6-dinitrobiphenyls under mild conditions (eq 12).2 This 2,6-dinitrobiphenyl synthesis is superior to the Ullmann condensation of aryl iodides with 2,6-dinitrochlorobenzene or Copper(I) Oxide-promoted reaction of 1,3-dinitrobenzenes with aryl iodides in quinoline. Aryl iodides with Me, MeO, Cl, Br, CO2Me, and NO2 substituents and with at least one free ortho position can be used to give substituted 2,6-dinitrobiphenyls in 30-95% yield. Aryl iodides substituted in both ortho positions react sluggishly and without positional preference. Aryl bromides react less effectively. (E)-b-Iodostyrene reacts but alkyl iodides and allyl bromide fail to give arylated products. The incorporation of extra substituents such as Me, CO2Bu-t, and CN in the dinitrobenzene unit is successful. The presence of two nitro groups is an essential requirement, the alternative use of electron-withdrawing substituents such as CO2Me and CN instead of one nitro group of 1,3-dinitrobenzene proving ineffective.

1,3-Dinitrobenzene reacts with 4- and 2-iodophenols in the presence of CuI t-butoxide, Potassium t-Butoxide, and pyridine to give 2,6-dinitrobiphenyl-4-ol (eq 13) and 1-nitrodibenzofuran (eq 14), respectively.12 A similar reaction occurs by using iodomethyl phenyl sulfone and sulfoxide (eq 15). The reaction mechanism of copper-mediated vicarious nucleophilic substitution has been proposed.

In a similar fashion, CuI t-butoxide effects one-pot formation of isocoumestans in the presence of pyridine by cross-coupling of 2-iodophenols with ethyl acetylenecarboxylate via alkenylcopper intermediates (eq 16).13

Nontransferable Group of Mixed Organocuprates.

A nontransferable group of mixed organocuprates has been developed for stabilizing organocuprate reagents and for saving one organic group of diorganocuprates. CuI t-butoxide can be used for a nontransferable group of mixed organocuprates (eq 17).3 The nontransferable thiophenoxy group from CuI thiophenoxide has been reported to be the most useful compared to t-BuO, PhO, t-BuS, and Et2N in the reaction of lithium mixed organocuprates, but CuI t-butoxide has the advantage of easier handling. A variety of reactions of lithium and magnesium organocuprates utilizing CuI t-butoxide for the nontransferable group have been reported: syn carbocupration ((t-BuOCuR)Li/HC&tbond;CH, HC&tbond;CCH(OEt)2, and MeC&tbond;CCH(OEt)2);14,15 acylation with acid chlorides ((t-BuOCuCH2OBu-t)Li);16 and asymmetric conjugate addition of (t-BuOCuBu-n)MgCl to 3-alkyl- and aryl-substituted cyclopentenone 2-sulfoxide enantiomers.17

t-BuOCuL (L = CO, t-BuNC, and PEt3) Complexes.

CuI t-butoxide forms sublimable copper complexes t-BuOCuL (L = CO,18 t-BuNC,18 and PEt31). These complexes metalate cyclopentadiene to afford h5-C5H5CuL complexes.1,18 t-BuOCu(t-BuNC) effects metalation of, and subsequent ligand insertion with, fluorene (eq 18).18 CuI t-butoxide-trialkylphosphine complexes effect hydride transfer to a carbonyl group (Tishchenko reaction and Meerwein-Ponndorf reduction)19 and cyclopropane formation from methyl a-chloropropionate and methacrylonitrile.20 t-BuOCu(t-BuNC) absorbs CO2 reversibly (eq 19).21 At an elevated reaction temperature, t-BuOCu(t-BuNC) effects deoxygenation of CO2 to produce CO and t-butyl isocyanate, which is converted to carbamate by addition of alcohol (eq 20).22

Volatile Copper Precursor for Metallic Copper and CuI Oxide Films by MOCVD.

Metal-organic chemical vapor deposition with CuI t-butoxide results in the deposition of pure CuI oxide whiskers at 237 °C and of metallic copper films at 397 °C (eq 21).4a An elimination mechanism has been proposed for the formation of CuI oxide: elimination of isobutene from t-butoxide groups yields CuI hydroxide intermediates, which subsequently engage in proton transfer processes to produce CuI oxide, t-butyl alcohol, and water. h5-C5H5CuPEt31 and t-BuOCuCO18 also act as the volatile copper precursor for MOCVD.4b


1. Tsuda, T.; Hashimoto, T.; Saegusa, T. JACS 1972, 94, 658.
2. (a) Cornforth, J.; Sierakowski, A. F.; Wallace, T. W. CC 1979, 294. (b) Cornforth, J.; Sierakowski, A. F.; Wallace, T. W. JCS(P1) 1982, 2299. (c) Carter, S. D.; Wallace, T. W. JCR(S) 1985, 136.
3. (a) Posner, G. H.; Whitten, C. E. TL 1973, 1815. (b) Posner, G. H.; Whitten, C. E.; Sterling, J. J. JACS 1973, 95, 7788.
4. (a) Jeffries, P. M.; Dubois, L. H.; Girolami, G. S. Chem. Mater. 1992, 4, 1169. (b) Gross, M. E. J. Electrochem. Soc. 1991, 138, 2422.
5. Logue, M. W.; Moore, G. L. JOC 1975, 40, 131.
6. Lemmen, T. H.; Goeden, G. V.; Huffman, J. C.; Geerts, R. L.; Caulton, K. G. IC 1990, 29, 3680.
7. Rogić, M. M.; Demmin, T. R. JACS 1978, 100, 5472.
8. Tsuda, T.; Chujo, Y.; Saegusa, T. JACS 1980, 102, 431.
9. Tsuda, T.; Washita, H.; Watanabe, K.; Miwa, M.; Saegusa, T. CC 1978, 815.
10. Tsuda, T.; Chujo, Y.; Takahashi, S.; Saegusa, T. JOC 1981, 46, 4980.
11. (a) Goeden, G. V.; Caulton, K. G. JACS 1981, 103, 7354. (b) Brestensky, D. M.; Huseland, D. E.; McGettigan, C.; Stryker, J. M. TL 1988, 29, 3749.
12. Haglund, O.; Hai, A. A. K. M.; Nilsson, M. S 1990, 942.
13. Haglund, O.; Nilsson, M. SL 1991, 723.
14. Alexakis, A.; Cahiez, G.; Normant, J. F. JOM 1979, 177, 293.
15. Alexakis, A.; Commerçon, A.; Villiéras, J.; Normant, J. F. TL 1976, 2313.
16. Corey, E. J.; Eckrich, T. M. TL 1983, 24, 3165.
17. Posner, G. H.; Kogan, T. P.; Hulce, M. TL 1984, 25, 383.
18. Tsuda, T.; Habu, H.; Horiguchi, S.; Saegusa, T. JACS 1974, 96, 5930.
19. Tsuda, T.; Habu, H.; Saegusa, T. CC 1974, 620.
20. Tsuda, T.; Ohoi, F.; Ito, S.; Saegusa, T. CC 1975, 327.
21. Tsuda, T.; Sanada, S.; Ueda, K.; Saegusa, T. IC 1976, 15, 2329.
22. Tsuda, T.; Sanada, S.; Saegusa, T. JOM 1976, 116, C10.

Tetsuo Tsuda

Kyoto University, Japan



Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.