Potier—Polonovski

Sundberg, R. J., Gadamasetti, K. G., Hunt, P. J. Mechanistic aspects of the formation of anhydrovinblastine by Potier-Polonovski oxidative coupling of catharanthine and vindoline. Spectroscopic observation and chemical reactions of intermediates. Tetrahedron 1992,48, 277-296. 

The modified Polonovski reaction first used in [19] and later called the Potier-Polonovski reaction, resulted in the formation of an iminium dimer which, after reduction with NaBELt, yielded a-3 ,4 -anhydrovinblastine, Fig. (2). Thus, this was the first dimeric Vinca alkaloid with the natural configuration to be synthesized. This method allowed, subsequently, the development of approaches to the synthesis of other natural dimerics like vinblastine, vincristine, leurosidine and leurosine [110-114], and more recently, to the semisynthetic vinorelbine and vinflunine [16, 22]. 

Vinylogous trifluoromethyl amides. The Potier-Polonovski rearrangement of tertiary amine A(-oxides induced by (CFjCOjjO is frequently followed by trifluoroacetylation. This method is most suitable for the synthesis of (-)-altemicidin. ... 

Ponzio Reaction Potier-Polonovski Reaction Prevost Reaction... 

The reaction proceeds via an iminium ion intermediate which becomes the stable reaction product when trifluoroacetic anhydride is employed. This modified procedure is commonly referred to as the Potier-Polonovski reaction A. Cave et al, Tetrahedron 23, 4681 (1967) T. Tamminen etal, ibid. 45,2683 (1989) R. J. Sundberg, etal, ibid. 48, 277 (1992). 

Applying the Potier-Polonovski reaction, vobasine-type indole alkaloids such as vobasine, dregamine, and tabernaemontanine could be transformed into dehydroervatamine, 20-epiervatamine, and ervatamine, respectively (70). 

Laboratory transformations took advantage of fragmentation of dregamine (30), tabemaemontanine (31), and vobasine (32) as N4 oxide induced by treatment with trifluoroacetic anhydride (Polonovski-Potier reaction) (192) and reductive capture of the intermediate iminium ion (Scheme 1). 

A modification of the Polonovski reaction where trifluoroacetic anhydride is used in place of acetic anhydride. Because the reaction conditions for the Polonovski-Potier reaction are mild, it has largely replaced the Polonovski reaction. 

In another search for an alternative to Potier s modified Polonovski reaction of catharanthine A-oxide (45), it has now been found that anhy-drovinblastine (42) can be generated directly, in 77% yield, from a reaction of catharanthine and vindoline in 0.01 N acid, promoted by ionized ferric salts, followed by reduction with sodium borohydride (Scheme 30) (Wl). Remarkably, the cation radical 106 generated by Fe(III), in accord with other simple amine oxidations by Lindsay Smith and Mead (102), resulted in isoquinuclidine fragmentation and coupling to vindoline at 0°C, without the conformational inversion observed in the modified Polonovski reaction at that temperature (see Scheme 15). Other metal oxidants or ligand-bound Fe(lll) did not promote the coupling reaction. It will be of interest to see if the overwhelming competition of C-5-C-6 bond... 

The iminium salts of 2,3-dihydropyridines are far more stable than the free bases and have been used extensively in the synthesis of alkaloids. N-Benzyl iminium salt 26, formed from the Polonovski-Potier reaction of V-oxide 25, was transformed into enol ether 27, which is a synthon for the unstable AT-benzvl-l, 2-dihvdropyridine 28 (Scheme 5) <2004LOC168>. The same transformation on a similar iminium salt has been used in the formation of macrocyclic marine alkaloids <1995TL2059>. Carbon nucleophiles, such as the silylenol ethers of esters, have been shown to undergo 1,2-addition rather than 1,4-addition to 2,3-dihydropyridinium salts <1999T14995>. 

The pioneering application of the Polonovski reaction to the synthesis of anhy-drovinblastine by Potier s group22" has been described in detail 159 the work of Kutney s group in this same area has also been published in extenso.160... 

The Polonovski reaction (see Volume 6, Chapter 4.7) — the action of an acid anhydride on an V-oxide — can give rise both to elimination or fragmentation reactions. Potier has modified the fragmentation by use of TFAA rather than AC2O and has applied this version to a useful synthesis of compounds related to antitumor alkaloids of Catharanthus roseus, e.g. vinblastine and vincristine. 

In the laboratory of J. Kobayashi, the biomimetic one-pot transformation of serratinine into serratezomine A was accomplished using the Polonovski-Potier reaction Serratinine was first treated with m-chloroperbenzoic acid to obtain the A/-oxide, and then excess TFAA was added. The iminium ion was formed in the following fashion the C13 hydroxyl group formed a hemiacetal with the C5 carbonyl group and simultaneously with the formation of the C5-C13 lactone the C4-C5 bond was broken. The iminium ion was then reduced with sodium cyanoborohydride to afford the tertiary amine functionality. Besides serratezomine A, another lactone (between the C8 hydroxyl and C5 carbonyl) was formed in 27% yield. 

The naturally occurring sulfonamide (-)-altemicidin is the first 6-azaindene monoterpene alkaloid isolated as a metabolite of microorganisms. A.S. Kende utilized the Polonovski-Potier reaction in the key step to introduce the carbamoyl enamine functionality. The tertiary amine was oxidized to the A/-oxide by H2O2 followed by treatment with excess TFAA to afford the desired vinylogous trifluoromethyl amide. 

Potier, P. Is the modified Polonovski reaction biomimetic Annu. Proc. Phytochem. Soc. Eur. 1980, 17, 159-169. 

Cave, A., Kan-Fan, C., Potier, P., Le Men, J. Modification of the Polonovski reaction. Reaction of trifluoroacetic anhydride with an amine oxide. Tetrahedron 1967, 23, 4681-4689. 

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