The reaction of lead tetraacetate with hydrocarbons

The free radical reaction of lead tetraacetate with hydrocarbons has been investigated. The products of these reactions are the acetate esters. The hydrogen abstracting species from lead tetraacetate is found to have a primary to secondary to tertiary selectivity of 1:27:123 based upon relative reactivities.     

The lead tetraacetate oxidation of Δ6-unsaturated tertiary alcohols. Eight-membered cyclic ether formation

In the lead tetraacetate oxidation of the unsaturated tertiary cyclic alcohols 1a and 1b, and the acyclic alcohol 15a, all possessing a Δ⁶-olefinic bond (with respect to the hydroxyl group), the α-acetoxylated eight-membered cyclic ethers 6a, 6b and 16a, respectively, were obtained. With these substrates lead tetraaeetate reacts at the double bond and, if at all, only by weak association with the hydroxyl group, so that fragmentation products derived from alkoxy radical intermediates (such as 2) were not formed. The mechanism of this cyclisation reaction is discussed.     

The conversion of primary alcohols to the corresponding aldehydes by a modified lead tetraacetate oxidation

A novel metod for obtaining aldehydes in good yield from primary alcohols has been devised, using the combination lead tetraacetate—manganous diacetate as the oxidizing agent.     

4H-1,4-benzothiazine derivatives via a novel lead tetraacetate induced ring contraction.

8-Chloro-3,4-dihydro-5-(2-thienyl)-2H-1,6-benzothiazocine underwent a facile lead tetraacetate induced ring contraction forming several 3-(2-thienyl)-4H-1,4-benzothiazine derivatives.     

The stereochemistry of fragmentation products formed in the lead tetraacetate and related oxidations of alcohols. Part. I. β-fragmentation of cis-and trans-4-t-Butylcyclohexanemethanol

The stereochemistry of β-fragmentation products formed in the oxidation of cis-and trans-4-t-butylcyclohexaanemethanol with lead tetraacetate and with lead tetraacetate-metal chloride combinations, under various reaction conditions, has been investigated, and the results compared with those obtained, under similar conditions, in the oxidative decarboxylation of cis-and trans-4-t-butylcyclohexanecarboxylic acid with the same reagents. It was found that all four substrates afford, under comparable conditions, identical cis-trans proportions of the respective fragmentation products, and that, therefore, so far as steric course is concerned, both the initial homolytic and subsequent heterolytic processes involved in the lead tetraacetate fragmentation reaction are independent of the nature and configuration of the starting material.     

Intramolecular cyclic ether formation versus β-fragmentation in the reaction of saturated aliphatic alcohols with lead tetraacetate

In the reaction of lead tetraacetate with saturated aliphatic alcohols containing an alkyl chain long enough to participate in the cyclization process, it was found that intramolecular tetrahydrofuran formation decreases and β-fragmentation increases in the order: primary alcohol---secondary alcohol---tertiary alcohol, and also in the order: β-unsubstituted alcohol---β-monomethyl substituted alcohol---β,β-dimethyl substituted alcohol. These results are discussed in terms of structural factors (steric and polar effects) which control the rate of the two competing homolytic processes in the intermediate alkoxy radicals, i.e. 1,5-hydrogen transfer from the δ-carbon to the hydroxyl oxygen leading to cyclic ether products and cleavage of the C---βC bond leading to fragmentation products.     

Oxidation of aliphatic alcohols with the lead tetraacetate—metal halide system under mechanical activation

The mechanochemical oxidation ofn-pentanol,n-hexanol, andn-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. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1870–1873, November, 2000.     

Oxidation of perfluoronaphthols by lead tetraacetate and lead dioxide

Depending on the reaction conditions, oxidation of perfluoronaphthols by Pb(OAc)₄ proceeds by two routes. Under mild conditions (20°C) oxidation leads to the products of dimerisation of perfluoronaphthoxy radicals. At a higher temperature (80°C) the reaction leads to acetoxydienones. The mechanistic aspects of oxidation of perfluoronaphthols by Pb(OAc)₄ are discussed.     

Photochemical reaction of alcohols—II : Irradiation of aromatic alcohols

The UV irradiation of aromatic alcohols leads to the formation of several products: carbonyl compounds, ethers, α-glycols and tetra-aryl-1,4-dioxanes.The photoformation of α-glycols is qualitatively and quantitatively compared to the photoreduction of the carbonyl compounds. It is noteworthy that the glycols are formed with a stereochemistry very different depending upon whether the substrate is an alcohol or a carbonyl compound.The structure, configuration and conformation of the 1-4-dixoanes obtained are studies as well as their origin.Other aspects of the photochemistry of the alcohols are analyzed using hydroperoxides as model substrates.     

The oxidative-rearrangement of nitrogen heterocycles with lead tetraacetate and t-butyl hypochlorite

Mechanisms for the lead tetraacetate and t-butyl hypochlorite oxidation of 1,4-dihydro-3(2H)-cinnolinones and 1-amino-2-indolinones are discussed. Evidence for the lack of a nitrene intermediate is given.     

Spectra and structure of small ring compounds: Part XXXVIII. Cyclobutanol

The Raman spectrum of gaseous cyclobutanol has been recorded and the far infrared spectrum of the gas has been obtained at a resolution of 0.5 cm^?1. At least six Q-branches arising from the low frequency ring-puckering motion have been observed and assigned on the basis of a potential of the form V(X) = (6.32 ± 0.21) × 10⁵X⁴?(4.18 ± 0.04) × 10⁴X²+ (8.81 ± 1.20) × 10³X³ with a reduced mass of 170 amu. An energy difference between the equatorial and axial forms was found to be 50–150 cm^?1 with the equatorial being more stable and a barrier of 700–900 cm^?1 was found for the interconversion. Three O-H stretching modes were observed in the Raman spectrum. It is concluded that the O-H moiety has both the gauche and trans conformations present in the equatorial form but only the gauche conformer is present in the axial form of the ring. Three O-H torsional modes were observed at 244 (trans conformer), 226.5 and 181.5 cm^?1 (gauche conformer) for the equatorial form and one O-H torsion at 237.5 cm^?1 (gauche conformer) for the axial form. The potential function governing the O-H torsional motion for the equatorial form was found to be V₁ = 280 ± 7 cm^?1 (800 cal mole^?1) and V₃ = 425 ± 3 cm^? (121.5 cal mole^?1) with the trans conformer being more stable than the gauche by approximately 206 cm^?1 (589 cal mole^?). The barriers to trans-gauche and gauche-gauche interconversion have essentially the same values, 500 cm^?1 (1430 cal mole^?1).     

Synthesis of 1,4-diketones by the coupling reaction of trimethylsilyl enol ethers with lead tetraacetate

Synthesis of 1,4-diketones in good yields was achieved by the coupling reaction of the trimethylsilyl enol ethers of acetophenone, thiophene or furan with lead tetraacetate in dry dichloromethane and tetrahydrofuran at −78°C.