Lead Tetraacetate Oxidation Research Articles

One-Pot Synthesis of 2,4,5-Triphenyl Imidazoles from 1,2-Diols as Key Reagents

A simple one-pot procedure for the preparation of 2,4,5-triphenyl imidazole derivatives is presented. The procedure involves the lead tetraacetate oxidation of 1,2-diols to give aldehydes in situ, which then undergo a three-component reaction with benzil and ammonium acetate to yield the imidazole derivatives.

Rickenyls A–E, antioxidative terphenyls from the fungus Hypoxylon rickii (Xylariaceae, Ascomycota)

Our screening efforts for new natural products with interesting bioactivity have revealed the neotropical ascomycete Hypoxylon rickii as a prolific source. We isolated five secondary metabolites with a p-terphenyl backbone from the mycelial extract of a fermentation of this fungus in 70l scale by using RP-HPLC, which were named rickenyls A–E (1–5). Their structures were elucidated by X-ray crystallography and NMR spectroscopy, complemented by HRESIMS. Two of the compounds contained a quinone core structure in ortho (2) and para-position (5), respectively. We obtained 2 spontaneously and by lead tetraacetate oxidation from 1. All compounds were screened for antimicrobial, antioxidative and cytotoxic activities. Rickenyl A (1) exhibited strong antioxidative effects and moderate cytotoxic activity against various cancer cell lines.

Novel covalently linked pyrene–aryl azide systems: synthesis of 1-(4-azidobenzoyloxy)pyrene

Lead tetraacetate oxidation of pyrene followed by hydrolysis affords 1-hydroxypyrene whose esterification with 4-azidobenzoic acid gives a new bifunctional luminophore characterized by UV and luminescence spectroscopy.

Efficient synthesis of functionalized 1,3-dihydroisobenzofurans from salicylaldehydes: Application to the synthesis of escitalopram

Abstract An efficient synthesis of substituted 1,3-dihydroisobenzofurans is developed. In this novel route, o-aroylbenzaldehydes, as key intermediates, can be obtained by lead tetraacetate oxidation of N-aroylhydrazones of salicylaldehydes. The mild and general strategy enables the synthesis of various substituted 1,3-dihydroisobenzofurans in high yields. Moreover, this method can be applied to efficiently synthesize escitalopram.

ChemInform Abstract: A Study on m-Chloroperbenzoic Acid and Lead Tetraacetate Oxidation of Some 1-Aroyl-4,5-dihydro-4,4-dimethyl-5-methylene-1H-pyrazoles.

1-Aroyl-4,5-dihydro-5-methylene-1H-pyrazoles 1 are converted upon oxidation with m-chloroperbenzoic acid to the pyrazolones 2. The same aroyl enamides 1 are also oxidized with LTA to form the acetoxy derivatives 7 and 8. The reaction mechanisms are discussed.

A Versatile and Regiospecific Synthesis of Functionalized 1,3-Diarylisobenzofurans

A convenient, versatile, and regiospecific synthesis of functionalized 1,3-diarylisobenzofurans has been developed. It involves chemoselective addition of arylmagnesium reagents to the aldehyde function of o-aroylbenzaldehydes, themselves readily obtained by lead tetraacetate oxidation of N-aroylhydrazones of salicylaldehydes. Various functional groups, including nitro, iodo, or ester functionalities, have thus been positioned with complete regiospecificity on the 1,3-diphenylisobenzofuran backbone.

Synthesis and Characterization of Model Ultimate Carcinogens/Metabolites Derived from Lead Tetraacetate Oxidation of Arylnitrones: 2′-Deoxyguanosine Adducts

The synthesis of model reactive metabolites 4a-c by lead tetraacetate (LTA) oxidation of arylnitrones 3a-c is described. Compounds 4a-c react with deoxyguanosine (dG) to give N-benzoylated C8-adducts 5a-c. Following debenzoylation with the heterogeneous system (sodium carbonate/methanol) leads to the corresponding C8-adducts 6a-c.

Synthesis ofN-Acetoxy-N-benzoyl-2-aminofluorene, an Ultimate Carcinogen by LTA Oxidation of α-Phenyl-N-(2-aminofluorenyl)nitrone, andN-(2′-Deoxyguanosin-8-yl)-2-aminofluorene

The rearrangement of a new α-phenyl-N-(2-aminofluorenyl)nitrone (8) to a new ultimate carcinogen, N-acetoxy-N-benzoyl-2-aminofluorene (9) is achieved in a lead tetraacetate (LTA) oxidation reaction. Compound 9 reacts with deoxyguanosine (dG) at pH 7.0 to give N-(benzoyl)-N-(deoxyguanosin-8-yl)-2-aminofluorene (10). Subsequent debenzoylation with the heterogeneous system (sodium carbonate/methanol) leads to the C8-adduct, N-(2′-deoxyguanosin-8-yl)-2-aminofluorene (11).

Syntheses of [1,2,3]selenadiazolo[4,5‐e]benzofuran or benzothiophene, [1,2,3]thiadiazolo[4,5‐e]benzofuran or benzothiophene, and 2‐benzofuranyl‐1,3,4‐oxodiazole derivatives

AbstractDehydrogenation of ethyl 3‐methyl‐4‐oxo‐4,5,6,7‐tetrahydrobenzofuran‐2‐carboxylate 1 with 2,2′‐azobi‐sisobutyronitrile and N‐bromosuccinimide gave ethyl 4‐hydroxy‐3‐methylbenzofuran‐2‐carboxylate 3. Reaction of compounds 3–4 with hydrazine hydrate afforded the corresponding hydrazides 5a‐b. The reaction of 5a‐b with aldehydes yielded substituted hydrazones 6a‐l. Compounds 7a‐d were prepared from compounds 6a‐d and bromine in acetic acid. Lead tetraacetate oxidation of compounds 6e‐l afforded substituted oxadiazoles 8e‐l. Selenium dioxide oxidation of 4‐oxo‐4,5,6,7‐tetrahydrobenzofuran semicarbazones 9, 14a and 4‐oxo‐4,5,6,7‐tetrahydrobenzothiophene 14b gave the tricyclic 1,2,3‐selenadiazoles 10, 15a and 15b respectively. Reaction of semicarbazones 9, 14a and 14b with thionyl chloride afforded the corresponding 1,2,3‐thiadiazoles 12, 16a and 16b respectively.

Synthesis of a Diterpene 1,3,4-Oxadiazolin-2′-one from Dimethylcyclopentenonepimarate

A diterpene 1,3,4-oxadiazolin-2′-one was synthesized by lead-tetraacetate oxidation of 16,17- epoxydimethylcyclpentenonepimarate. The structures of the synthesized compounds were confirmed by IR and NMR spectroscopies.

Formation of an Unusual Dimeric Compound (IV) by Lead Tetraacetate Oxidation of a Corynanthe‐Type Indole Alkaloid, Mitragynine (I).

Formation of an Unusual Dimeric Compound (IV) by Lead Tetraacetate Oxidation of a Corynanthe‐Type Indole Alkaloid, Mitragynine (I).

SYNTHESIS AND CHARACTERIZATION OF NUCLEOSIDE DERIVATIVES, N-(BENZOYL)-N-(DEOXYGUANOSIN-8-YL)-4-AMINOBIPHENYL AND N-(2′-DEOXYGUANOSIN-8-YL)-4-AMINOBIPHENYL VIA α-PHENYL-N-(4-BIPHENYL)NITRONE

ABSTRACT Lead tetraacetate (LTA) oxidation of α-Phenyl-N-(4-biphenyl)nitrone (8) to give a new ultimate carcinogen, N-acetoxy-N-benzoyl-4-aminobiphenyl (9) which was reacted with deoxyguanosine (dG) at pH 6.9 to give nucleoside derivative, N-(benzoyl)-N-(deoxyguanosin-8-yl)-4-aminobiphenyl (10). Following debenzoylation with sodium carbonate-methanol leads to N-(2′-deoxyguanosin-8-yl)-4-aminobiphenyl (11).

Formation of an unusual dimeric compound by lead tetraacetate oxidation of a corynanthe-type indole alkaloid, mitragynine.

Lead tetraacetate oxidation of a Corynanthe-type indole alkaloid, mitragynine, produced mainly 7-acetoxyindolenine derivative (2) together with a dimeric compound (4) as a minor product. The novel structure having a bridge between the C-11' and C-7 positions in the respective indolenine parts and its formation mechanism were studied.

ChemInform Abstract: Synthesis and Characterization of Model Ultimate Carcinogens/Metabolites Derived from Lead Tetraacetate Oxidation of Arylnitrones: 2′‐Deoxyguanosine Adducts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A photometric screening method for dimeric naphthylisoquinoline alkaloids and complete on-line structural elucidation of a dimer in crude plant extracts, by the LC-MS/LC-NMR/LC-CD triad.

An efficient evaluation procedure for the chemical screening and on-line structural elucidation of dimeric naphthylisoquinoline alkaloids has been developed. The method is based on the lead tetraacetate oxidation of the central binaphthalene core of the alkaloids. UV spectra of the extracts after addition of the oxidant show, in the presence of naphthylisoquinoline dimers, the appearance of a characteristic long-wavelength absorption indicative of dinaphthoquinones. The efficiency and relevance of the method has been demonstrated in the discovery of a constitutionally and configurationally new dimeric naphthylisoquinoline alkaloid, named ancistrogriffithine A (4), from the previously uninvestigated Asian liana Ancistrocladus griffithii. After verification of this screening result by LC-ESI-MS/MS, the constitution and the relative configuration of the compound were elucidated on line, by LC-NMR and LC-CD on the extract. Using an LC-NMR-WET-ROESY experiment, itwas possible for the first time to determine the relative axial configuration of a natural biaryl compound on line, by observing long-range ROE interactions. Finally, an oxidative degradation right on the extract delivered the absolute configuration of 4, without isolation of the alkaloid. Ancistrogriffithine A is the as yet only dimeric naphthylisoquinoline from an Asian Ancistrocladaceae plant.

Ring Expansion Reactions of Acronycine to Fused 1,4-Oxazepine and 1,4-Dioxepin Systems

Baeyer-Villiger oxidation of acronycine and 2-nitroacronycine led to 6-methoxy-3,3,13-trimethyl-8,13-dihydro-3 H-chromeno[5,6-b][4,1]benzoxazepin-8-one (4) and 6-methoxy-3,3,13-trimethyl-2-nitro-8,13-dihydro-3H-chromeno[5,6-b][4,1]benzoxazepin-8-one (6), respectively. Lead tetraacetate oxidation of cis-1,2-dihydroxy-1,2-dihydroacronycine followed by treatment with sodium borohydride afforded 3-hydroxy-7-methoxy-4,4,13-trimethyl-3,4,8,13-tetrahydro-1H-[1,4]dioxepino[5,6-c]acridin-8-one (13).

Lead tetraacetate oxidation of the Diels-Alder adduct of 7-dehydrocholestryl acetate with maleic anhydride

The Diels-Alder adduct (3), obtained by cycloaddition of 7-dehydrocholesteryl acetate (1) and maleic anhydride (2), was heated at ca. 90?C with a large excess of lead tetraacetate in pyridine solution for 5h. Under these conditions, compound 3 underwent lactonization with the participation of the olefinic ?6-double bond to give two isomeric monolactone derivatives, 9 and 10 (in a total yield of ca. 6%), and the bislactone product 11 (in 11.5% yield). The starting material was recovered in 36% yield.

The crystal structure of 14-0x0-13,14-seco-5α-cholest-13(18)-en-3β-yl acetate and the assignment of the configuration of its acetoxy derivatives

The crystal structure of 14-oxo-13,14-seco-5?-cholest-13(18)-en-3?-yl acetate (2), obtained (in addition to the (E)-?l2-isomer 3) by oxidative fragmentation of the C(13)-C(14) bond of 14?-hydroxy-5?-cholestan-3?-yl acetate (1), was determined by X-ray analysis. In addition, the configurations of the acetoxy derivatives 4-6, formed by the thermal lead tetraacetate oxidation of 1, were deduced from the relevant 1?-NMR parameters.

13,14-Seco-steroids: A New Type of Modified Steroids Containing a Nine-Membered Ring

Oxidations of 14α-hydroxy-5α-cholestan-3β-yl acetate (5) with lead tetraacetate under thermal or photolytic conditions or in the presence of iodine proceed mainly by fragmentation of the C(13)−C(14) bond to give as the primary products the 13,18-didehydro-13,14-seco derivative 6 and the (E )-Δ12-13,14-seco ketone 11, respectively. Further transformations of these compounds under conditions of their formation afforded, in addition, the acetoxy derivatives 7 – 9 (from 6), and the D-homo-C-nor compound 12 and (12R,13R)-epoxide 13 (from 11). Unexpectedly, the photolytic lead-tetraacetate oxidation of 5 resulted partly (to ca. 20%) in a reversible fragmentation involving scission and recombination of the C(8)−C(14) bond followed by formation of the 14β,22-ether 10. Possible mechanisms for the observed transformations are discussed.

New Strategies in Carbonylation Chemistry: The Synthesis of δ-Lactones from Saturated Alcohols and CO

This paper describes the δ-carbonylation of saturated alcohols which uses a 1,5-hydrogen-transfer reaction of alkoxyl radicals and subsequent carbonylation at the δ-carbon atoms as the key. The carbonylation reactions of five classes of saturated alcohols, namely, primary alcohols having primary δ-carbons, primary alcohols having secondary δ-carbons, primary alcohols having tertiary δ-carbons, secondary alcohols having primary δ-carbons, secondary alcohols having secondary δ-carbons, were carried out, in which lead tetraacetate (LTA) was used as a one-electron oxidant to generate the alkoxyl radicals. Carbonylation of these saturated alcohols, except for primary alcohols having tertiary δ-carbons, took place to afford δ-lactones in moderate to good yields. The mechanism of the remote carbonylation likely involves (1) alkoxyl radical generation via LTA oxidation of a saturated alcohol, (2) conversion of this alkoxyl radical to a δ-hydroxyalkyl radical by a 1,5-hydrogen-transfer reaction, (3) CO trapping of the δ-hydroxyalkyl radical yielding an acyl radical, and (4) oxidation and cyclization of the acyl radical to give a δ-lactone. A metal salt-free system was also tested for a substrate derived from a tertiary alcohol having a secondary δ-carbon; the photolysis of an alkyl 4-nitrobenzenesulfenate under CO pressures gave a δ-lactone in moderate yield.