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A new method portraying the utility of lead tetraacetate as an oxidizing agent in the synthesis of α-sulfonyloxyketones from aryl ketones and sulfonic acids has been described. This methodology offers a new alternative for the synthesis of a series of α-sulfonyloxyketones with broad substrate scope, easy availability of reactants as well as the use of simple oxidant. [ABSTRACT FROM AUTHOR]

This article presents a novel approach for synthesizing a new 5,8-dimethoxy derivative of esculetin via the selective cleavage of the methylene bridge in sabandin—naturally occurring and easily synthetically accessible methoxylated coumarin. A high selectivity is achieved by using acetoxylation of methylenedioxy group with lead tetraacetate. Natural coumarin sabandin as a starting compound was prepared in a few simple steps from 5-allyl-4,7-dimethoxybenzo[d][1,3]dioxole (apiol), which is readily available from parsley and dill seed extracts. The developed method enables an efficient and straightforward synthesis of a new derivative of esculetin with potential medicinal and therapeutic applications. [ABSTRACT FROM AUTHOR]

A series of 2-arylbenzoxazole compounds possessing a cytotoxic activity as potential anticancer agents has been synthesised. Oxidative coupling of benzaldehyde with o-aminophenol utilizing lead tetraacetate approach has been used to realize the synthesis of compounds 1-11. The cytotoxicity of 1-11 have been screened against breast cancer cell line MCF-7 and human colon cancer cell line HCT-116 utilizing doxorubicin as reference drug. Among these compounds, 2-(3-benzyloxyphenyl)benzoxazole-5-acetic acid 5 and 2-(4-methoxyphenyl)benzoxazol-5-acetic acid 10, are found to be promising cytotoxic compounds against MCF-7 cell line. In addition, this study shows that the presence of acetic acid group at position 5 of benzoxazole nucleus enhances the activity. Moreover, it is noticed that the presence of oxygen atom directly linked to the phenyl substituent improves activity. The results offer a new benzoxazole based template to design and develop novel antineoplastic agents. [ABSTRACT FROM AUTHOR]

The synthesis of a series of 2-arylbenzoxazole compounds possessing a cytotoxic activity as potential anticancer agents was achieved. Oxidative coupling of benzaldehyde with o-aminophenol utilizing lead tetraacetate approach was used to realize the synthesis of compounds 1-11. The cytotoxicity of 1-11 was screened against breast cancer cell line MCF-7 and human colon cancer cell line HCT-116 utilizing doxorubicin as a reference drug. Among these compounds, 2-(3-benzyloxyphenyl)benzoxazole-5-acetic acid (5) and 2-(4-methoxyphenyl)benzoxazol-5-acetic acid (10), were found to be promising cytotoxic compounds against the MCF-7 cell line. In addition, this study showed that the presence of an acetic acid group at position 5 of the benzoxazole nucleus enhances the activity. Moreover, we noticed that the presence of an oxygen atom directly linked to the phenyl substituent improves activity as well. These results offer a new benzoxazole based template to design and develop novel antineoplastic agents. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The efforts directed towards the stereoselective synthesis of (+)‐lochnerine, a sarpagine alkaloid is disclosed. The synthesis was designed utilizing an intramolecular catalytic hydroamination of an alkene by an oxazolidine, derived in situ from an unsaturated aldehyde, as the key step. The other key steps of the sequence include substrate‐controlled, Lewis acid promoted C3 allylation to secure the C3/C5 syn‐disubstituted product, Kulinkovich and ring‐closing metathesis reactions. [ABSTRACT FROM AUTHOR]

A short five steps synthesis of the title compound from vanillin is described. The racemic spiroether 7 was obtained in 61% yield and in >99% diastereomeric excess (by 1H-NMR) from the corresponding phenolic derivative 3 by oxidation with lead (IV) acetate.

Spiro-OMeTAD represents the benchmark hole transport material (HTM) in the state-of-the-art perovskite solar cells (PSCs). However, restricted by the low conductivity of pristine spiro-OMeTAD, dopants and a long oxidation process are required to improve the conductivity and hole mobility. The long oxidation in air not only prolongs the device fabrication period, but also leads to the decomposition of perovskite layer. Even worse, dopants such as tBP and Li-TFSI will be severely affected and cause irreversible damage during the long oxidation process, which will greatly affect the device performances. In this regard, a strong oxidant lead tetraacetate (LTA) is introduced into spiro-OMeTAD to significantly accelerate the oxidation process. Excitingly, the Pb2+ ions generate as a result of the reduction of LTA could strongly coordinate with tBP, thus hindering the evaporation of tBP, as well as the agglomeration of Li-TFSI. As a result, the PSCs based on LTA-doped spiro-OMeTAD show a high photo-to-electric conversion efficiency of 22.08% with excellent long-term stability and thermal stability. Overall speaking, LTA is commercially available and low-cost, more importantly, the accelerate oxidation process as well as the effect to stabilize the dopants in spiro-OMeTAD, makes it potential as a p-dopant for highly efficient and stable PSCs. [Display omitted] • Lead tetraacetate (LTA) could rapidly oxidize spiro-OMeTAD and thus improve conductivity and hole mobility. • The Pb2+ ions generated from the reduction of LTA could coordinate with tBP to slow down its evaporation. • PSCs based on LTA-doped spiro-OMeTAD showed a high photo-to-electric conversion efficiency (PCE) of 22.08 %. • The efficiency of LTA-doped device maintained 81 % of the initial value after the device was heated at 65 ℃ for 450 h. [ABSTRACT FROM AUTHOR]

A simple and efficient method has been developed for the synthesis of fused pyrano biscoumarins using lead tetraacetate as an oxidizing agent by the condensation of one equivalent of 1,2-diols and four equivalent of 4-hydroxy coumarin in acetonitrile as solvent at 80°C with good to excellent yields. [ABSTRACT FROM AUTHOR]

Treatment of acridine with 1-aminobenzotriazole and lead tetraacetate gives N-phenylacridone by a non-concerted benzyne reaction. A mechanism is proposed by which an initial adduct is converted into this product. [ABSTRACT FROM AUTHOR]

The divergent synthesis of calothrixins and ellipticines has been accomplished by utilising the one-pot formation of o-diacylarenes as a key intermediate through rearrangement of o-hydroxy ketone monoacyl hydrazones by lead tetraacetate mediated oxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] R-Carvone on heating with Pb(OAc) 4 in benzene gives (2 RS)-2-hydroxy-2-[(1 S)-4-methyl-5-oxocyclohex-3-en-1-yl)]-prop-1-yl bis(acetoxy)acetate. Alkaline hydrolysis of this compound affords the corresponding diol which under acidic catalysis is transformed into bis-hydroxy ether and 1,4-dioxane derivatives. [ABSTRACT FROM AUTHOR]

An improved synthetic strategy for 1-substituted 4-H phthalazines using a convenient, three-step reaction sequence under mild conditions is described. The protocol involves condensation of hydrazine hydrate with o -ketobenzaldehydes derived through the Pb(OAc) 4 oxidation of the N -acylhydrazones of salicylaldehydes. This pathway is of high practical value since a wide variety of substituted acylhydrazides and salicylaldehydes, the substrates for N -acylhydrazones, are commercially available. In addition, the three-step sequence could be scaled up without the need for intermediate purification affording a broad range of products in high yield. 1-Phenyl 4-H phthalazine was a versatile compound providing ready access to multiple phthalazine analogs, including the vasodilating agent MY5445. [Display omitted] [ABSTRACT FROM AUTHOR]

The partial synthesis of derivatives of the antimicrobial diterpenoid rosmic acid from the abundant diterpenoid carnosol is described. The key step involved the cleavage of ring C of rosmanol with lead tetraacetate or 7-O-methylrosmanol with mCPBA. Three analogues of rosmic acid, 11,12-seco-8,13-abietadien-12,7:20,6β-dilacton-11-oic acid methyl ester, 7α-O-methyl-11,12-seco-11,12-epoxy-11,12-dioxo-8,13-abietadien-20,6β-olide, its dimethyl ester, and the known methylgaldosol and rosmaquinone were obtained. [ABSTRACT FROM AUTHOR]

A short five steps synthesis of the title compound from vanillin is described. The racemic spiroether 7 was obtained in 61% yield and in >99% diastereomeric excess (by 1H-NMR) from the corresponding phenolic derivative 3 by oxidation with lead (IV) acetate. [ABSTRACT FROM AUTHOR]

Abstract: The transformation of a hydroxyl into an acyl group, a transformation which has been extensively investigated on the benzene nucleus of several substrates, is now applied successfully for the first time to a heterocyclic ring and specifically to the pyrone ring of coumarin to yield novel 3,4-diacylcoumarins in good yields. The reaction involves formation of a new C–C bond. [Copyright &y& Elsevier]

Abstract: α-Acetoxy aldehydes or α-acetoxy ketones can be efficiently synthesized by treating 2,3-epoxy primary alcohols with lead tetraacetate. The reaction, which proceeds with complete regio- and stereoselectivity facilitates the enantioselective synthesis of α-acetoxy carbonyl compounds from allyl alcohols, via Sharpless epoxidation. Cyclic β-hydroxy ethers, with an oxygenated five-, six- or seven-membered ring, are transformed into α-acetoxy ethers. [Copyright &y& Elsevier]

6-Hydroxy derivatives of R-(−)-carvone and 7,8-epoxycarvone were synthesized and subjected to oxidative ring cleavage by the action of lead tetraacetate. These reactions followed different patterns, depending on the substrate structure. [ABSTRACT FROM AUTHOR]

Abstract: The treatment of 2,3-epoxy primary alcohols with lead(IV) acetate (LTA) leads to α-acetoxy aldehydes or α-acetoxy ketones, through the nucleophilic ring-opening of an intermediate oxonium and the subsequent carbon–carbon bond cleavage. This reaction represents a new route to optically active α-hydroxy carbonyl compounds. [Copyright &y& Elsevier]

The two-step synthesis of 3,4-diacyl-2 H -pyran-2-ones was achieved in good yields from dehydroacetic acid via transformation of the hydroxyl group into an acyl group (TROHIA). This transformation which was earlier explored using the benzene nucleus of several substrates as well as the benzene and pyrone ring of coumarins has now been applied successfully to the pyrone heterocyclic ring. The reaction involves the formation of a new C C bond. [ABSTRACT FROM AUTHOR]

A series of seven cyclopent-3-en-1 -ylmethylamines bearing one, two, or three methyl substituents at the C2, 03, C4, or Cα positions, including the unsubstituted parent, was accessed by ring-closing metatheses of α,α-diallylacetonitrile (or methallyl variants) and α,α-diallylacetone followed by hydride reductions or reductive amination, or by Curtius degradationsof α,α-dimethyl- and 2,2,3-trimethylcyclopent- 3-enylacetic acids. Oxidation of the primary amines with Pb(OAc)4 in CH2Cl2, CHCl3 or benzene in the presence of K2CO3 effected efficient intramolecular aziridinations, in all cases except the α-methyl analogue (16), to form the corresponding 1 -azatricyclo[2.2.1 .02,6]heptanes, including the novel monoterpene analogues, 1 -azatricyclene and the 2-azatricyclene enantiomers. The cumulative rate increases of aziridination reactions observed by 1H NMR spectroscopy in CDCl3 resulting from the presence of one or two methyl groups on the cyclopentene double bond, in comparison to the rate of the unsubstituted parent amine (1 :17.5:>280), indicate a highly electrophilic intermediate as the nitrene donor and a symmetrical aziridine-like transition state. A mechanism is outlined in which the amine displaces an acetate ligand from Pb(OAc)4 to form a lead(lV) amide intermediate RNHPb(OAc)3 proposed as the actual aziridinating species. [ABSTRACT FROM AUTHOR]

The reactions between phthalimide N-oxyl (PINO) radical and cyclohexene, cyclooctene, and trans-3-hexene were carried out. The PINO radical has been in situ generated from its hydroxylimide parent, N-hydroxyphthalimide (NHPI), applying two approaches: using metallic salts, such as lead tetraacetate and cerium (IV) ammonium nitrate (CAN), and a “metal free” system in which the role of metallic species has been undertaken by antraquinone. In the former case, the strong influence of lead tetraacetate (or CAN) on the NHPI's reactivity, induce two different channels for the reaction pathway, radical and non-radical, a complex mixture of both saturated and unsaturated diadducts together with the corresponding monoadduct being formed. This behavior will not occur in the case of PINO generation in non-metallic systems, in this case the reaction pathway proceed exclusively via radical mechanism, with the formation of monoadducts as sole products. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The synthesis of 6,7-diacylcoumarins is reported via the oxidation of 6-acetyl-7-hydroxycoumarin N-acylhydrazones with lead tetraacetate. The procedure involves transformation of hydroxy into an acyl group and formation of a new C-C bond. [ABSTRACT FROM AUTHOR]

Abstract: The treatment of a range of N- and O-enones derived from various camphor-based chiral auxiliaries A–D with N-aminophthalimide in the presence of lead tetraacetate is described. In general, N-phthalimidoaziridines were obtained with high diastereoselectivities (up to 98% de) and chemical yields (up to 95%) when 10,10-diphenyl-2,10-camphanediol A derived O-enones with a range of substituents were used under the same reaction conditions. Excellent stereoselectivity was obtained when the N-tosyl camphorpyrazolidinone E derived acrylate was used. The absolute configuration of the new stereogenic center(s) of the major diastereomer was established by X-ray crystallographic analysis. Chiral auxiliary cleavage was achieved under mild reaction conditions. A model to explain the stereochemical induction is also proposed. [Copyright &y& Elsevier]

Abstract: The synthesis of new potential adjuvant saponin aglycons was investigated by selective palladium mediated C–H functionalisation of appropriately functionalised derivatives of lanosterol, cholesterol, and friedelin. The desired equatorial aldehyde functionality was successfully introduced into the lanosterol skeleton as expected. Cyclopalladation of a cholesterol derivative proceeded as expected, but during oxidation of the organopalladium intermediate, participation of the adjacent alkene functionality led to stereoselective formation of a cyclopropane and introduction of an acetate group into the steroid backbone at C-6. Further investigation of this unusual cyclopropane formation on a model decalin system confirmed the result, but C–H activation on a related open chain system was prevented by complexation of the alkene functionality to the palladium. [Copyright &y& Elsevier]

Abstract: The reaction of derivatives on C3 of 6-hydroxy-2,7-dimethyl-11-oxatricyclo[6.2.1.02,6]undecan-4-one with lead tetraacetate and iodine, gave, in a good yield, 1,7-epoxycyclononanes. These compounds are the result of a β-fragmentation at the level of C2–C6 respect to the tertiary hydroxyl group on C6, with an unexpected contraction from a ten to a nine-membered ring system, via a radical addition to the carbonyl group on C4. The treatment of precursors (non-functionalized on C3) with LTA and iodine produced again a β-fragmentation without any structural rearrangement, affording a typical 1,8-epoxycyclodecane system. The transformation of the carbonyl group on C4 into acetate avoided radical additions and rearrangements affording, in high yield, the corresponding cyclodecanes. By this methodology, either 1,7-epoxy-cyclononane or 1,8-epoxycyclodecane could be synthesized, in a good yield, from the same versatile precursor. [Copyright &y& Elsevier]

Zinc bromide and lead tetraacetate is a practical and safe source of bromine. The combined reagents are used to brominate a variety of alkenes to vicinal dibromoalkanes. Similarly, alkynes can be converted into dibromoalkenes in high yields. The reagents are also capable of tetrabromination of alkynes. [ABSTRACT FROM AUTHOR]

Reactions of 23R- and 23S-23-spirostanols in the 25R and 25S series with lead tetraacetate–iodine were studied. The reactions carried out at low temperature afforded d-seco-iododialdehydes and C22 lactones, while similar reactions performed in refluxing tetrachloromethane yielded 20-chlorolactones and their 21-acetoxy derivatives irrespective of the hydroxyl group configuration at C-23. The reaction mechanisms are discussed. [Copyright &y& Elsevier]

A new procedure was developed for the introduction of the oxoalkyl fragment into N-heteroaromatic compounds of the pyridine and quinoline series. The procedure is based on the solid-phase reactions of lead tetraacetate with aromatic N-heterocycles and tertiary cycloalkanols. [ABSTRACT FROM AUTHOR]

We report the oxidative cleavage of unsaturated diols 6 and 7 derived from monocyclic precursors, used as substrates to determine the limits of the olefin as a source of diversity. [Copyright &y& Elsevier]

The mechanochemical oxidation of n-pentanol, n-hexanol, and n-octanol with the Pb(OAc)4-MHal system (M=Li, K; Hal=Cl, Br) in the absence of a solvent affords esters. and secondary alcohols with the composition C8H17OH and C9H19OH give ketones. [ABSTRACT FROM AUTHOR]

The oxoalkylation of pyridine, 2-methyl-, 4-methyl-, 2,4-dimethyl-, 2,6-dimethylpyridines, quinoline, 4-methylquinoline, isoquinoline, and pyrazine with oxoalkyl radicals generated from 1-methylcyclobutanol or 1-methylcyclopentanol under the action of Pb(OAc) or Mn(OAc) has been carried out. The reaction products are isomers with 2-(6)- and 4-positions of the oxoalkyl group in the N-heteroaromatic ring. The isomer ratios have been determined as a function of the structure of the N-heteroaromatic compound and the reaction conditions. [ABSTRACT FROM AUTHOR]

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The main product of the reaction of 1-methylcyclobutanol with Pb(OAc) in benzene is 1-phenyl-4-pentanone; the use of Mn(OAc) in acetic acid gives a mixture of 2,9-decanedione and methyl propyl ketone; 1-(chloro-, bromo-, thiocyano-, or cyano)-4-pentanone is formed in the presence of the systems Pb(OAc)-metal halide or Mn(OAc)-metal halide. [ABSTRACT FROM AUTHOR]

Abstract: Oxidation of N-carbonylhydrazones of 7-hydroxy-8-acetylcoumarin with lead tetraacetate results in the synthesis of 7,8-diacylcoumarins in good yields. The reaction proceeds via the transformation of a hydroxy into an acyl group reported for the first time in heterocyclic chemistry. [Copyright &y& Elsevier]

Abstract: The reaction of 3-acetoxyaminoquinazolinone (QNHOAc) with various sulfoxides in the presence of HMDS as an acetic acid scavenger, afforded the corresponding sulfoximides in good yields. Sulfoximidation of phenyl methyl sulfoxide using a Q*NHOAc having a stereogenic centre on its 2-position gave the products in 1.3:1 ratio of diastereomers. [Copyright &y& Elsevier]