Ruthenium catalyzed transformation of alcohols to esters and lactones

Homogeneous catalytic oxidative condensation of alcohols and diols to their corresponding esters and lactones has been accomplished using RuH₂(PPh₃)₄.     

A novel transformation of 7-membered ring lactones to β-keto ethers

The development of an efficient and regioselective transposition of a 7-membered lactone to a corresponding β-keto ether is reported.     

Reductive alkylation of anhydrides and lactones: direct access to monosubstituted lactones

Reductive alkylation of anhydrides (1 equiv) with a 2:0.25 mixture of Grignard reagent and Zn(BH₄)₂ afforded monosubstituted lactones in moderate yields. The same sequence applied to unsubstituted lactones gave monoalkylated diols, which were further selectively oxidised with tetra-n-propylammonium perruthenate (TPAP) into the expected monoalkylated lactones.     

Thermally induced structural transformation of polytriazoleimide to polyindoleimide

A new kind of polytriazoleimide containing bisphenyl-l,2,3-triazole（BPT） was synthesized by copper-catalyzed 1,3-dipolar cycloaddition of azides and alkynes（CuAAC） and polycondensation.The thermal stability and degradation mechanism of the polytriazoleimide were investigated.The results show that the structure of BPT in polytriazoleimide transforms to phenylindole after thermal treatment,accompanying the release of N₂.     

Carboxymethylglycoside lactones (CMGLs): structural variations on the carbohydrate moiety

New glucose and galactose based bicyclic lactones, with variations in the anomeric configuration, the protecting groups (acetyl or benzyl) and the furanosyl or pyranosyl rings were synthesized from allyl glycosides and used for the preparation of a series of new glycosylated alkyne amides.     

A synthetic approach to seven-membered lactones by the microbial transformation of ynones having a trifluoromethyl group

Studies on the microbial transformations of a number of ynones bearing a trifluoromethyl group prepared by the reaction of ethyl trifluoroacetate with a variety of lithium alkynates, have been undertaken. The major products were the corresponding carbinols but microbial carbon-carbon bond degradation and formation occurred also, which proceeded to novel fluorinated seven-membered lactones as significant products.     

Copper(II)-activated transformation of azomethine to imidate: synthetic and structural studies

The Schiff base 2-pyridine–carboxaldehyde 4-dimethylaminobenzoylhydrazone (HL, 1) was prepared by reacting 2-pyridine–carboxaldehyde and 4-dimethylaminobenzoylhydrazine in a 1:1 molar ratio in methanol. Reaction of HL (1) with Cu(O₂CCH₃)₂·H₂O (in a 1:1 molar ratio) in methanol afforded a dinuclear copper(II) complex, [Cu₂(μ-O₂CCH₃)₂L′₂]·2H₂O (2). The azomethine functionality (---CH=N---) of 1 is converted to imidate (---C(OMe)=N---) in the complexed ligand L′⁻. Molecular structures of both 1 and 2 were determined by X-ray crystallographic studies. The dinuclear molecule of 2 is centrosymmetric and contains two monoatomic bridging acetate groups. Each copper(II) centre is in a square-pyramidal N₂O₃ coordination sphere. The ligand, L′⁻ coordinates the metal ion via the pyridine-N, the imidate-N, and the deprotonated amide-O atoms. One of the acetate oxygen atoms completes the N₂O₂ square-plane. The oxygen of the symmetry-related acetate fills the apical coordination site. Structural parameters are consistent with both copper ions being in a +2 oxidation state. The room temperature magnetic moment is 1.89 μ_B (per Cu). In powder phase the complex displays an axial EPR spectrum at 298 K. The complex is nonconducting in methanol solution. The electronic spectrum shows a ligand field absorption at 680 nm and charge transfer bands in the range 426–215 nm.     

Substituted lactones and their transformations; IV. Hydrogenation of substituted lactones to alkyltetrahydrofurans

To make a comparative study of the connection between odor and structure in the alkyl--butyrolactone and alkyltetrahydrofuran series, -,-, and ,-dialkylbutyrolactones are hydrogenated over copper-chromium catalyst to give the corresponding tetrahydrofurans. Most of the compounds obtained retain a fruity odor, reminiscent of that of the starting lactones.For Part III see [1].     

Conversion of penicillin to cephalosporin lactones.

Penicillin G ( 1 , R ? CH₂Ph) was converted to cephaloram- and 6-epicephaloram lactones 11 and 12 respectively by the initial replacement of thiazolidine part of penicillin by the mercaptan 9 followed by intramolecular cyclization and subsequent introduction of double bond at C(3).     

Fragmentation of sesquiterpene lactones related to leucomisin

The mass spectra of seven sesquiterpene lactones — leucomisin, austricin, parishin B, parishin C, matricarin, artelin, and artelin diacetate — have been studied. It has been shown that the presence of the conjugated bonds C(1)=C(10), C(2)=0, and C(3)=C(4), and also C(5)=C(6), stabilizes M⁺, and the main fragmentation process is that of the splitting out of the lactone ring. The presence of hydroxy substituents at C(3) and C(8) of the guaiane system does not change the stability of M⁺ under electron impact. The directions of fragmentation have been confirmed by an analysis of spectra obtained by the metastable defocussing of daughter ions and by measuring the accurate masses of the main peaks of the fragmentary ions.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 96–101, January–February, 1987.