2,2,6,6-Tetramethylpiperidine hydrochloride

Peroxides may be used to oxidize alcohols, but additional activation is usually necessary for successful reaction to take place. An early example of this was the use of catalytic amounts of 2,2,6,6-tetramethylpiperidine hydrochloride... 

Oxidation of hydroxyl groups (6, 110-1II). Celia has extended this reaction of peracids catalyzed by 2,2,6,6-tetramethylpiperidine hydrochloride (TMP-HCl) to an efficient preparation of epoxy ketones. Thus unsaturated alcohols can be oxidized in one step to a,j3-, 8,y-, and other epoxy ketones (yield 60-90%). 

A soln. of 85%-m-chloroperoxybenzoic acid in methylene diloride added to a stirred ice-cooled soln. of 5-norbornen-2-ol in the same solvent, after 2 hrs. treated with a soln. of 2,2,6,6-tetramethylpiperidine hydrochloride in methylene chloride followed by additional m-chloroperoxybenzoic acid soln., and the product isolated after 1.5 hrs. exo-5,6-epoxy-2-norbornanone. Y 86%. J. A. Celia, J. A. Celia, J. A. Kelley, and E. F. Kenehan, J. Org. Chem. 40, 1860 (1975) oxidation of alcohols with N-oxide radicals cf. B. Ganem, ibid. 40, 1998 ketones from sec. alcohols with m-chloroperoxybenzoic acid/HCl cf. J. A. Celia, J. P. McGrath, and S. L. Regen, Tetrah. Let. 1975, 4115 review of N-oxide radicals s. H. G. Aurich and W. Weiss, Topics Curr. Chem. 59, 65 (1975). 

The rates of epoxidation of 5,6-disubstituted norborn-2-enes by perbenzoic acid to give 2,3-exo-cis-epoxides are found to increase in the order 5,6-exo-ds < 5,6-trans < 5,6-endo-cis isomer. Substituent electronic effects on reaction rate are discussed. " An interesting report records the use of nitroxide catalysis in the oxidation of alcohols in m-chloroperbenzoic acid. For example, attempted preparation of (515) by direct epoxidation of norbome-2-one gives instead a rearranged Baeyer-Villiger product. Treatment of norborn-5-en-2-ol with one equivalent of the peracid in CHjClj, followed by the addition of a second equivalent and a catalytic amount of 2,2,6,6-tetramethylpiperidine hydrochloride (TMP-HCl) affords (515) in 86 % yield. Likewise... 

The ganglionic blocking action of several methylpiperi-dines as their hydrochlorides or quaternary methosalts has been studied. The most potent compound was the secondary 2,2,6,6-tetramethylpiperidine. The ganglionic blockade produced by secondary and tertiary amines was found to be of long duration. The quaternary compounds were more active in equimolar doses but their effects were of shorter duration. 

---