D. Jeremić

Lead tetraacetate oxidation of saturated aliphatic alcohols.—III : Unbranched primary and secondary alcohols

Abstract The action of lead tetraacetate, in benzene solution, on various unbranched primary and secondary aliphatic alcohols containing 4 to 12 carbon atoms has been investigated and the ratio of carbonyl compounds, cyclic ethers and fragmentation products determined. The results obtained are discussed with regard to the number and length of the n-alkyl rests attached to the carbinol carbon atom of the starting alcohol.

Reactions with lead tetraacetate—IV : Oxidation of saturated aliphatic alcohols—II; Alcohols of low molecular weight

Abstract The action of lead tetraacetate on ethanol, 1-propanol, 2-propanol and 2-butanol has been studied under various experimental conditions, and it was found that the tetravalent lead compound reacts with alcohols in ways not so far observed. The possible reaction schemes are discussed in terms of homolytic and heterolytic cleavage of the intermediate alkoxy lead acetate complexes.

Reactions with lead tetraacetate—I : Oxidation of saturated aliphatic alcohols part 1

Abstract When oxidized with lead tetraacetate 1-heptanol and 1-octanol undergo cyclization to give as major products the corresponding 2-alkyltetrahydrofurans, accompanied by a small amount of the isomeric tetrahydropyran derivatives. Secondary aliphatic alcohols, under similar conditions, are converted to a mixture of cis and trans 2,5-dialkyltetrahydrofurans.

The reaction of lead tetraacetate with alicyclic alcohols—I cycloalkanols☆☆☆

Abstract Secondary cycloalkanols, containing 4- to 16-membered rings, have been treated with lead tetraacetate in refluxing benzene. It was found that the ease of oxidation to the corresponding ketones follows the reactivity order of reactions of alicyclic compounds involving an sp3 → sp2 ring carbon hybridization change, and that the amount of β-fragmentation resulting in opening of the ring is in accord with the total strain associated with carbocyclic rings. The yield of intramolecular ether formation appears to depend upon ring size and conformational factors in the transition state; it increases from cyclohexanol to cyclooctanol, drops sharply for cyclododecanol and reaches the highest value with cyclohexadecanol. The major ether obtained in the case of cyclodecanol was trans-1,2-epoxycyclodecane.

Lead tetraacetate oxidation of saturated aliphatic alcohols—IV : The formation of six-membered cyclic ethers☆☆☆★

Abstract The lead tetraacetate oxidation of saturated aliphatic alcohols, with structures which do not permit 1,5-cyclization, gave tetrahydropyran derivatives in yields not exceeding 16%. The formation of a small amount of the rearranged ether, 2-ethyl-2-methyltetrahydrofuran, from 4,4-dimethyl-1-pentanol indicates that the cyclization reaction proceeds via an intermediate with carbonium ion character.

A novel pimara-8(9),15-diene from Lycopus europaeus

Abstract Identification of a novel trioxygenated Δ 8(9),15_ pimaric acid methyl ester from plant species Lycopus europaeus by means of two-dimensional 1 H NMR spectroscopy (COSY and NOESY) is reported.

The reaction of lead tetraacetate with some acyclic alcohols containing phenyl groups

Abstract α-Substituted benzyl alcohols, 2-phenylethanol, 1,1-dimethyl-2-phenylethanol, 3-phenyl-1-propanol, 4-phenyl-1-butanol and 5-phenyl-1-pentanol have been subjected to the action of lead tetraacetate in nonpolar and polar solvents. The products obtained, i.e. carbonyl compounds corresponding to the starting alcohols, cyclic ethers and fragmentation carbonyl compounds and fragmentation acetates, and their relative distribution are discussed in terms of structural factors influencing the oxidation, cyclization and fragmentation processes.

Deuterium-induced 13C NMR isotope shifts for signal assignments and determination of deuteriation site in cyclododecanone

Abstract Deuterium-induced 13 C isotope shifts were measured in the 13 C { 1 H} NMR spectra of monodeuteriated cyclododecanones formed upon oxidation of [1- 2 H 1 ] cyclododecanol with lead tetraacetate. These shifts, when used in conjunction with 13 C NMR data of specifically labelled analogues, [2, 2, 12, 12- 2 H 4 ]- and [2- 2 H 1 ] cyclododecanone, enabled the ketone formed with lead tetraacetate to be identified as a mixture of [5- 2 H 1 ]- and [6- 2 H 1 ] isotopomers.

Simultaneous determination of N-unsubstituted and N-substituted nitroazoles and criteria for their identification—II: Chromatographic separation and polarographic determination of nitropyrazoles

The N-unsubstituted nitropyrazoles have an imino hydrogen atom, in contrast to the N-substituted derivatives, and react with hydroxide to give nitropyrazole anions. The strongly negative shift of E(1 2 ) for these anions makes possible simultaneous polarographic determination of any pair of compounds, one of which is an N-unsubstituted nitropyrazole and the other a corresponding N-substituted derivative. Simultaneous polarographic determination of three compounds [3(5)-, 3- and 5-nitropyrazoles] is also possible with 0.1M sodium hydroxide as supporting electrolyte, but only when DeltaE(1 2 ) between the N-substituted isomers is at least 100 mV. In this case adequate DeltaE(1 2 ) is caused by the different electron densities of the nitro-groups of isomers. In the medium mentioned it is possible to determine simultaneously even four compounds [1-, 3(5)-, 3- and 5-nitropyrazoles], because the E(1 2 ) value of 1-nitropyrazole does not change with pH, contrary to other nitropyrazoles. Developers for the chromatographic separation are proposed. Some criteria are given for the distinction of the N-unsubstituted- and the corresponding N-substituted nitropyrazoles. The structures of two new compounds have been determined. Methods are recommended for the simultaneous identification and determination of the compounds appearing together in the reaction mixtures during the substitution of the imino hydrogen atom, or during the rearrangements of the 1-nitropyrazoles to the N-unsubstituted ones.

1,5-Shift of hydrogen from carbon to carbon in the lead tetraacetate oxidation of 5,5-dimethyl-2-heptanol☆

Abstract By using α-deuteriated substrate, it was established that in the thermal lead tetraacetate reaction (in benzene) of 5,5-dimethyl-2-heptanol ( 1 ) oxidation to the corresponding ketone 4 proceeds not only by way of direct elimination of the carbinol (α) hydrogen, but also, to the extent of 43·-5%, by a route which involves 1,5-transfer of hydrogen from the carbinol (α) carbon atom to the ϵ-C atom.