Silver nitrate, rearrangements with

Rearrangement of the diazo ketone, with loss of nitrogen, in the presence of suitable reagents and a catalyst (colloidal silver, silver oxide, or silver nitrate in the presence of ammonia solution). An acid is formed In the presence of water, an amide results when ammonia or an amine is used, and an ester is produced in the presence of an alcohol ... 

Pyrrolines and pyrroles can be readily prepared from the rearrangement of a-aminoallenes. Optically enriched a-aminoallene 137 is rearranged to pyrroline 138 by catalytic silver nitrate (Eq. 13.45) [53], The yield of the reaction is high and the cyclization occurs with high levels of asymmetry transfer. Annulated 3-pyrroline 140 is the product of rearrangement of allenyl pyrrolidine 139 (Eq. 13.46) [53]. 

The cydization can also be carried out on a-tosylaminoallenes, in which case the choice of reaction conditions determines whether the product is the N-tosyl-3-pyrro-line or whether elimination of toluenesulfonic acid acid gives the pyrrole. For example, in the presence of catalytic silver nitrate, allene 141 (Eq. 13.47) rearranges to N-tosylpyrroline 142 in excellent yield, whereas when 141 is treated with potassium tert-butoxide in DMSO, pyrrole 143 is formed in 71% yield [54]. Warming the lithium salt of 141 in DMSO also leads to 143. The rearrangement of 141 to 143 may be mechanistically related to the conversion of 130 to 131 (Eq. 13.42). 

Af-Nitroamides 368 are produced by the rapid rearrangement of the imidoyl nitrates 367 formed in the reactions of imidoyl chlorides with silver nitrate. The transient nitrate esters were detected by NMR spectroscopy411. 

A nice example of a degenerate rearrangement has been reported for the complex pentacarbonyltungsten(0)-thioaldehyde-l,2-dithiol 177 (R = H) or the thioketone-1,2-dithiol complex 177 (R = CH3). These compounds (obtained by the reaction of silver nitrate with tetraethylammonium pentacar-bonyliodotungstate(O) in the presence of l,6,6 z -trithiapentalenes) appeared to exist as an equilibrium mixture of the two isomers 177/178 (Scheme IV.70) [83JCS(CC)289]. The symmetrically substituted 1,2-dithiol (R = CH3, R = H) displays fluxional behavior as appears by NMR spectroscopy... 

The rearrangement of imidoyl nitrates yields nitramides via an O N migration. This reaction is instantaneous when imidoyl chlorides are treated with silver nitrate in acetonitrile. 

The rearrangement of the 5-cyano-4,5-dihydro-l//-azepine (93) to furo[2,3-6]pyridine (95 Scheme 9) with sodium nitrate in glacial acetic acid or with silver nitrate in aqueous ethanol proceeds by initial protonation at either C-3 or C-6 followed by hydrolysis to the cyanooctanedione ester (94). By carrying out the rearrangement with an acid ion exchange resin it is now possible to isolate the dione ester (77CJC4061). Likewise, the hydrolysis of the tetrahydro-2-benzazepine (96) to an 0 -(anilinoalkyl)benzophenone is an example of proton attack at the /3 -carbon of the enamine system (77JA5045). 

Methyla-arylacetates. These esters have been obtained by oxidative rearrangement of alkyl aryl ketones with thallium(III) nitrate in acidic methanol or trimethyl orthoformate (4,496 5, 656 7, 362). A new method, which avoids the toxic TTN, is based on the Woodward version of the Prevost reaction. Thus, treatment of the ketone with iodine (or bromine) and silver nitrate (2 equiv.) in refluxing methanol containing trimethyl orthoformate results in methyl a-arylacetates in 90% yield from simple substrates. Yields are lowered by electron-withdrawing substituents on the aromatic group and by a-branching in the alkyl group.2... 

Preparation of diazoketones and their rearrangements during hydrolysis (method 271) and alcoholysis (method 295) are discussed elsewhere. Ammonolysis of diazoketones leads to amides of acids containing one more carbon atom than the original acyl halide. Halogen atoms may be present in a remote position on an aliphatic chain. The reaction is carried out by heating the diazoketone in alcohol or dioxane solution with aqueous ammonia in the presence of silver oxide or silver nitrate catalysts. Substituted acetanilides are formed when aniline is used in place of ammonia. ... 

Anthrasteroids have also been formed by ordinary dienone-phenol rearrangements. Treatment of 7-oxo-5,8(9)-diene systems, either in the lojS- [lyo] or loa- [192] series, with sulphuric acid in acetic anhydride gave anthrasteroids with oxygen functions both in ring A and in the aromatic ring B. A similar reaction is reported with zinc and silver nitrate in acetic acid [ 192 J, but the mode of action of this reagent system is not known. 

Wolovsky describes the oxidative coupling of 1,5-hexadiyne, followed by prototropic rearrangement by heating with potassium /-butoxide in f-butanol-benzene at 100°. The resulting mixture of unsaturated hydrocarbons was easily separated by elution chromatography on a column of alumina impregnated with 20% silver nitrate into the tetradehydro[18]annulene (111) and the two isomeric tridehydro[18]annulenes (1) and (11). 

Treatment of bicyclo[4.1.0]heptan-2-ols with perchloric acid in acetic acid caused very clean rearrangement with formation of cyclohept-3-enyl acetates (Table 1). Only in the case of cxo-7-methylbicyclo[4.1.0]heptan-2-ol was the cyclohex-2-enyl acetate the major product probably because the 7-methyl group conferred additional stabilization on the carbocation formed by j0-scission of the outer cyclopropane bond. The same type of reactant could be oxidatively rearranged using pyridinium chlorochromate to afford cyclohepten-4-ones, together with (chloromethyl)cyclohexenes. However, if the chloride in the reagent was replaced with tetrafluoroborate, or if pyridinium chlorochromate was used with silver(I) nitrate, formation of the substituted cyclohexenes was completely suppressed, e.g. formation of 7 from 6, although the reported yields were low. ... 

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