MEISENHEIMER N-Oxide rearrangement

MEISENHEIMER N-Oxide Rearrangement Chlormalion at pyridlnes via rearrangemeirt ol N-oxides. 

MEISENHEIMER N-Oxide Rearrangement Rearrangement of tertiary amine oxides to trisubstituted hydroxylamines via a [2,3] sigmatropic shift. Also chlorination of pyridines via N-oxides (see 1st edition). 

Scheme 14.21 Enantio- and diastereoselective synthesis of homoallylic fragments. CHAPTER 15 [2,3]-REARRANGEMENTS OF AMMONIUM ZWITTERIONS Scheme 15.1 Sigmatrnpic 12.31-rearrangements of reactive ammonium zwitterioas. Scheme 15.2 Meisenheimer s original report of an amine N-oxide rearrangement. Scheme 15.3 12.31- and ri.21-Meisenheimer rearrangements of amine jV-oxides.

Scheme 15.2 Meisenheimer s original report of an amine N-oxide rearrangement.

Epoxyhexahydroazocino[5,4- 7]indole 56 (in the original paper mistakenly related to azocino[5,6- 7]indoles) has been obtained in 60% yield by a Meisenheimer rearrangement of the N-oxide of azetopyrido[3,4-fc] indole 55 (91CL1781 Scheme 17). 

Oxidation of organonitrogen compounds is an important process from both industrial and synthetic viewpoints . N-oxides are obtained by oxidation of tertiary amines (equation 52), which in some cases may undergo further reactions like Cope elimination and Meisenheimer rearrangement . The oxygenation products of secondary amines are generally hydroxylamines, nitroxides and nitrones (equation 53), while oxidation of primary amines usually afforded oxime, nitro, nitroso derivatives and azo and azoxy compounds through coupling, as shown in Scheme 17. Product composition depends on the oxidant, catalyst and reaction conditions employed. 

The Meisenheimer rearrangement of tertiary amine N- oxides has been applied to the synthesis of both monocyclic 1,2-oxazepines, e.g. (309) (65JOC3135, 65JCS1653, 82H(19)173), and those fused to benzene (80AJC833) and a variety of heterocyclic rings (80AJC1335). 

Allylthiols376 and unsaturated lithio sulfones377 have been found to react as nucleophiles with nitrones to yield intermediate hydroxylamines which undergo reverse-Cope cyclization to provide 1,3-thiazolidine N-oxides and pyrrolidine A-oxides, respectively. In the case of derivatives of C-phenyl nitrone (321 R2 = Ph), thermolysis was found to result in smooth Meisenheimer rearrangement leading to 1,5,2-oxathiazinane (322) (see Scheme 76). 

Experimental and computational studies of the pericyclic Meisenheimer rearrangement and a competitive rearrangement of A-propargyl morphol i nc N-oxide revealed a novel inverse secondary kinetic isotope effect (kn/kD 0.8) for the rate-determining cyclization step, probably occurring because of a C(sp) to C(sp2) change in hybridization at the reaction center (Scheme 3).5... 

MEISENHEIMER NOxideRearrangement CMonnalion of pyridlnes via rearrangement of N-oxides. 

Bergbreiter, D. E., Waichuk, B. Meisenheimer Rearrangement of Aiiyi N-Oxides as a Route to Initiators for Nitroxide-Mediated "Living" Free Radical Polymerizations. Macromolecules 1998, 31, 6380-6382. 

Kurihara, T., Doi, M., Hamaura, K., Ohishi, H., Harusawa, S., Yoneda, R. Meisenheimer rearrangement of 2-ethenyl-1,4,5,10b-tetrahydro-2H-azetopyrido[3,4-b]indole N-oxides new route to the 12(S)carba-eudistomin skeleton. Chem. Pharm. Bull. 1991, 39, 811-813. 

MEISENHEIMER N-OxideRearrangement Chlorination of pyridines via rearrangement o< N-oxides. 

N-Allylhydroxylamines can be prepared from nitrone hydrochlorides, which are produced by the reaction of nitroso compounds with alkenes, in an ene-type mechanism (Scheme 188). Analogues of potent dopaminomimetic ergot derivatives have been prepared, in which of a (5R,8S,10R)-6-allylergoline N -oxide was converted into a substituted hydroxylamine function. The key step is a Meisenheimer [3,2] sigmatropic rearrangement of the N6-oxide (Scheme 189). 413... 

The peracid oxidation of a methylene group attached to the 1-nitrogen of a -triazole leads to the interesting 1-alkoxy ethers (8.1-4) probably formed by a Meisenheimer rearrangement of the N-oxide (Eq. 10). Once again the yields are highly variable. 

Without additional reagents Meisenheimer rearrangement 2- thylenealkoxylamines from 2-ethyleneamine N-oxides... 

Figure 8 Meisenheimer s [2, 3]-sigmatropic rearrangement of 6-allylergoline-6-N-oxides...

Isoprene (2-methyl-1,3-butadiene) can be telomerized in diethylamine with / -butyUithium as the catalyst to a mixture of A/,N-diethylneryl- and geranylamines. Oxidation of the amines with hydrogen peroxide gives the amine oxides, which, by the Meisenheimer rearrangement and subsequent pyrolysis, produce linalool in an overall yield of about 70% (127—129). 

In 1950, Cope and coworkers48 unsuccessfully attempted to use the well-known Meisenheimer rearrangement of N-allylamine oxides to 0-allylhydroxylamines49 in performing the formally analogous rearrangements of allyl aryl sulfoxides to allyl arenesulfenates and of allyl aryl sulfones to allyl arenesulfinates (equations 11-13). 

In 1919, Meisenheimer reported a detailed account of an unusual transformation of methyl-allyl-aniline 3 in the presence of benzoic peracid 4, which yielded the N,N,0-trisubstituted hydroxylamine product 6 through amine iV-oxide 5 tScheme IS.21. Although the mechanism of the process was not fully appreciated at the time, this discovery was one of the earliest examples of a [2,3]-sigmatropic rearrangement, and it served as the foundation for the discovery and development of many [2,3]-rearrangements of reactive zwitterionic substrates. 

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