Lead(IV) Acetate-Copper(II) Acetate1


[546-67-8]  · C8H12O8Pb  · Lead(IV) Acetate-Copper(II) Acetate  · (MW 443.40) (Cu(OAc)2.H2O)

[142-71-2]  · C4H8CuO5  · Lead(IV) Acetate-Copper(II) Acetate  · (MW 199.67)

(oxidative decarboxylation of acids to alkenes1a)

Physical Data: see Lead(IV) Acetate and Copper(II) Acetate.

Oxidative decarboxylation of aliphatic and alicyclic carboxylic acids by lead tetraacetate (LTA) usually affords a mixture of saturated hydrocarbons, alkenes, acetate esters, and other products, whose distribution depends upon the structure of the starting acid.1a,b However, when LTA is used in the presence of catalytic amounts of copper(II) acetate, the rates of decarboxylation are greatly enhanced and the yields of alkenes are increased so that the reactions become of synthetic value (eq 1).2 This effect of copper(II) acetate is attributed to the rapid scavenging of the intermediately formed alkyl radicals by copper(II) ions (eq 2).1a,3,5-7 A catalytic amount of Cu(OAc)2 is sufficient, since it is regenerated in the course of the reaction (eq 3).3,6 The reactions are usually carried out in an inert atmosphere in benzene solution, under thermal or photolytic conditions, using a minimal concentration of Cu(OAc)2 (about 0.005 M).1a,3

The LTA-Cu(OAc)2 reagent is particularly applicable for the oxidative decarboxylation of primary and secondary acids, whereby primary carboxylic acids afford terminal alkenes in high yields (eqs 4 and 5).2-4,8-10 In the case of secondary acids, if unsymmetrical, oxidative elimination can take place in two directions, and frequently both possible alkenes are obtained (eqs 6 and 7).2,11-14 Oxidative decarboxylation of secondary acids by the LTA-Cu(OAc)2 reagent is approximately 20 times faster than that of primary acids.1a,15

Decarboxylation of tertiary carboxylic acids by LTA-Cu(OAc)2 proceeds about 100 times faster than that of primary acids, and usually affords alkenes as main products (eqs 8 and 9).6,16-19 However, with tertiary carboxylic acids, in contrast to the behavior of primary and secondary acids, LTA alone reacts in the same way, so that addition of the CuII catalyst is not necessary.1a

In the oxidative decarboxylation of acids by LTA-Cu(OAc)2 the solvent can play an important role, because the relative rates of oxidative elimination with alkene formation and competitive oxidative substitution leading to acetate ester formation may be considerably influenced by the solvent. Thus decarboxylation of cyclobutanecarboxylic acid by LTA-Cu(OAc)2 in benzene affords cyclobutene as the main reaction product; in acetonitrile-acetic acid, cyclobutene is formed in low yield, the major products being a mixture of isomeric acetates (eq 10).1a,2,7 A portionwise addition of LTA to a refluxing solution of carboxylic acid in benzene in the presence of pyridine and Cu(OAc)2, in the absence of air, has been suggested as an improved procedure for oxidative decarboxylation to alkenes.11

1. (a) Sheldon, R. A.; Kochi, J. K. OR 1975, 19, 279. (b) Mihailović, M. Lj.; &CCacute;eković, &ZZbreve;.; Lorenc, Lj. In Organic Synthesis by Oxidation with Metal Compounds; Mijs, W. J.; de Jonge, C. R. H. I., Eds.; Plenum: New York, 1986, pp 741-816. (c) Butler, R. N. In Synthetic Reagents, Pizey, J. S., Ed.; Ellis Horwood: Chichester, 1977; vol. 3, pp 277-419.
2. Bacha, J. D.; Kochi, J. K. T 1968, 24, 2215.
3. Kochi, J. K.; Bemis, A.; Jenkins, C. L. JACS 1968, 90, 4616.
4. Bacha, J. D.; Kochi, J. K. JOC 1968, 33, 83.
5. (a) Kochi, J. K.; Subramanian, R. V. JACS 1965, 87, 4855. (b) Jenkins, C. L.; Kochi, J. K. JACS 1972, 94, 843.
6. Beckwith, A. L. J.; Cross, R. T.; Gream, G. E. AJC 1974, 27, 1673, 1693.
7. Kochi, J. K.; Bacha, J. D. JOC 1968, 33, 2746.
8. (a) Herz, W.; Mirrington, R. N.; Young, H. TL 1968, 405. (b) Kochi, J. K. JACS 1965, 87, 1811, 3609.
9. Beckwith, A. L. J.; Gream, G. E.; Struble, D. L. AJC 1972, 25, 1081.
10. Vaidya, A. S.; Dixit, S. M.; Rao, A. S. TL 1968, 5173.
11. Ogibian, Y. N.; Katsin, M. I.; Nikishin, G. I. IZV 1972, 1228; 1973, 587.
12. (a) Struble, D. L.; Beckwith, A. L. J.; Gream, G. E. TL 1970, 4795. (b) Shono, T.; Nishiguchi, I.; Oda, R. TL 1970, 373.
13. Torssell, K. AK 1970, 31, 401.
14. Barton, D. H. R.; Giacopello, D.; Manitto, P.; Struble, D. L. JCS(C) 1969, 1047.
15. Kochi, J. K.; Sheldon, R. A.; Lande, S. S. T 1969, 25, 1197.
16. Jensen, N. P.; Johnson, W. S. JOC 1967, 32, 2045.
17. Bruck, P. R.; Clark, R. D.; Davidson, R. S.; Günther, W. H. H.; Littlewood, P. S.; Lythgoe, B. JCS(C) 1967, 2529.
18. Kochi, J. K.; Bacha, J. D.; Bethea, T. W., III JACS 1967, 89, 6538.
19. Canonica, L.; Danieli, B.; Manitto, P.; Russo, G. G 1968, 98, 696.

&ZZbreve;ivorad &CCbreve;eković & Mihailo Lj. Mihailović

University of Belgrade, Yugoslavia

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