Thallium nitrate oxidation with

In a new reaction of the pyrano[2,3-c]azepines 40 with hydrazine hydrate, the first derivatives of the pyridazino[4,3-c]azepine system 42 (for example R1 = R2 = Me) have been described (Scheme 10). The rearrangement probably involves initial ring opening to the intermediate 41. Aromatisation of this system was achieved by further oxidation with thallium (III) nitrate or copper(II) acetate . 

Oxidative phenolic coupling.1 The vancomycin antibiotics are polypeptides with bridging diphenyl ether groups. Evans et al. have shown in model systems such as 1 that cyclization to o-halophenolic peptides (2) can be accomplished by oxidation with thallium(III) nitrate in THF-methanol or CH2Cl2-methanol followed by CrCl2 reduction of a para-quinol intermediate (a). In three cases the yield of cyclic products was 40-48%. 

Farkas et al., [123] synthesised different natural isoflavanones (255) and isoflavans (256) by oxidative rearrangement of 2-hydroxy chalcones (254) with thallium nitrate in methanol followed by acid-catalyzed cyclization as shown in Fig. (11). 

Thus it has been used as the first stage to obtain the starting material for the microbiological method with CSD-10 and simplified in more recent work leading to a synthesis of estrone in four steps from 3p-acetoxy-19-hydroxyandrost-5-en-17-one (ref. 116). Cholesteryl acetate was transformed by standard methods to the required androstane compound shown in the following scheme, which with hypobromous acid followed by lead tetraacetate and zinc reduction (cf. ref. 115) afforded the 19-hydroxy derivative. This with thallium nitrate in dioxan underwent loss of formaldehyde and hydration with water to afford the 19-nor-10p-alcohol in 70% yield. The diol obtained by saponification was converted by Oppenauer oxidation with N-methylpiperid-4-one as hydride aceptor (ref. 117) and afforded a 78% yield of the enone which was transformed almost quantitatively into... 

Chiral y-amino-acids (e.g. 180) have been prepared from the corresponding optically active /8-amino-acids by the addition of one carbon atom using the Arndt-Eistert reaction.w-Amino-acids are available from cyclic anhydrides by treatment with stannyl azide (to give an w-isocyanatocarboxylic acid) followed by addition of an alcohol. In contrast to simple enamines, oxidation of N-acyl-a-aminocrotonates with thallium nitrate leads to the corresponding a/8-dimethoxy derivatives. 

A simple synthesis of allenic esters uses the oxidation with thallium(iii) nitrate of pyrazolones (284), formed in situ from a-alkyl-jS-keto-esters and hydrazine. ... 

Thallic oxide can be prepared by reaction of thallium with oxygen or hydrogen peroxide and an alkaline thallium(I) solution. However, it is more easily made from the oxidation of thaHous nitrate by chlorine ia aqueous potassium hydroxide solution. It is insoluble in water but dissolves in carboxyUc acids to give carboxylates. 

The mechanism of oxidation probably involves in most cases the initial formation of a glycol (15-35) or cyclic ester,and then further oxidation as in 19-7. In line with the electrophilic attack on the alkene, triple-bonds are more resistant to oxidation than double bonds. Terminal triple-bond compounds can be cleaved to carboxylic acids (RC=CHRCOOH) with thallium(III) nitrate or with [bis(trifluoroacetoxy)iodo]pentafluorobenzene, that is, C6F5l(OCOCF3)2, among other reagents. 

Thallium nitrate is prepared by reacting thallium metal, thaUous oxide, TbO or thaUous hydroxide, TlOH, with nitric acid followed by crystallization ... 

Flavylium salts are oxidized to flavones on treatment with thallium(III) nitrate in methanol. The reaction is considered to involve initial attack at C-2 by methanol. The resulting chromene (484) undergoes reaction with the thallium salt at C-3 and nucleophilic attack at C-4 by methanol to give an unstable adduct (485), which decomposes to the flavone... 

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... 

Chalcones - BenzHs. Oxidation of chalcones with thallium(lll) nitrate in an aqueous acid/glyme medium results in formation of benzils in about 50% yield. Three... 

The action of n-butyllithium in THF at low temperature leads to the anion. After reaction with an electrophilic compound, e hydrolysis can generally be carried out in polar solvents (acetone, alcohols, acetonitrile) in the presence of mercury(II) chloride or oxide and water.In other cases, NBS, - chloramine T, cerium(IV) ammonium nitrate, n-tributyltin hydride, trialkyloxonium tetrafluorobor-ate, thallium nitrate or photochemistry can be used. Desulfurization by Raney nickel gives hydro-carbons. ... 

---