Reactions stereoselectives des alkylmagnesiens secondaires avec les anhydrides et lactones rigides

High stereoselectivity was observed in the reactions of secondary alkylmagnesium compounds with bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride $\text{1}$ and lactone 2 leading respectively to the formation of $\text{trans}$ diastereomeric lactones and $\text{erythro}$ primary-secondary diols.     

Oxydations par le carbonate d'argent sur celite—XIII : Preparation de lactones

Silver carbonate on Celite oxidizes primary 1,4-, 1,5-, and 1,6-diols and primary-tertiary diols into lactones in high yield. Primary—secondary diols lead to mixtures of hydroxy-ketones and lactones. Details are given on the synthesis of (±) mevalonolactone.     

聚合物支载溴酸根的氧化性能研究

利用强碱型离子交换树脂支载溴酸根得到聚合物溴酸根氧化剂,它具有良好的氧化性能,在40%HBr或AlCl~3或NaHSO~3作用下,分别氧化伯醇和简单醚为酯,仲醇为酮,α、ω-二醇和环醚为内酯,硫(或硒)醇为二硫(或硒)化合物,并得到较好的产率。     

A general electron transfer reduction of lactones using SmI2-H2O

Herein we describe a strategy for the selective, electron transfer reduction of lactones of all ring sizes and topologies using SmI(2)-H(2)O and a Lewis base to tune the redox properties of the complex. The current protocol permits instantaneous reduction of lactones to the corresponding diols in excellent yields, under mild reaction conditions and with useful chemoselectivity. We demonstrate the broad utility of this transformation through the reduction of complex lactones and sensitive drug-like molecules. Sequential electron transfer reactions and syntheses of deuterated diols are also described.     

Preparation and Pyrolysis of Cyclooctyl Phenyl Sulfoxide

We recently reported a facile synthesis for bicyclo-[n.2.0]alkanediols of the general structure 1. ¹ The recent demonstration² that cis-bicyclo[3.2.0]heptane-1,7-diol(3) can be converted to the novel, highly-strained trans-bicyclo[4.1.0]heptane system increases the interest in this class of compounds. Comparison of our diols with materials used by Paukstelis and Kao in the rearrangement studies² and further work in our laboratory has shown that the diols reported in our initial communication are trans-diols and should be assigned structures 4 and 5.     

Direct Lithiation. I

In the previous paper,² we described the reaction of lithiated ethynyl compounds using butyllithium at -70° with lactones and sugar lactones such as 2,3 : 5, 6-di-o-isopropyl-idene-L-gulonolactone (I) or 2,3-o-isopropylidene-D-ribonolactone (II) to obtain ethynyl lactols.     

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.     

Structure of the sequiterpene lactones fromCyclachaena xanthifolia

Conclusions The racemes ofCyclachaena xanthifolia Fresen. have yielded four sesquiterpene lactones, two of which are new, not having been described in the literature previously, and these have been called ivoxanthin and 1,2-anhydrocoronopilin. Structures II and IV have been proposed for these.The plant also contains the sesquiterpene lactones coronopilin and ambrosin.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 6, pp. 487–490, 1969     

Convenient Synthesis of Bicyclic Lactones Related to the Trichothecenes

Short and convenient synthesis of bicyclic lactones (1) and (2), important intermediates in trichothecene synthesis is described.     

Facile organocatalytic domino oxidation of diols to lactones by in situ-generated TetMe-IBX

The domino oxidation of diols to lactones is an important transformation, and catalytic protocols that allow this conversion smoothly are scarce. Capitalizing on the established reactivity of tetramethyl-IBX (TetMe-IBX) and its in situ generation in the presence of a co-oxidant, such as oxone, we have shown that a variety of diols can be converted to the corresponding lactones in respectable yields by employing the precursor of TetMe-IBX, namely, tetramethyl-o-iodobenzoic acid (TetMe-IA), as a catalyst in 5 mol % in the presence of 2 equiv of oxone.     

Synthetic approach to natural products by Claisen rearrangement of glyceraldehyde derivatives

For the purpose of organic syntheses of some corynanthe-type indole alkaloids, sesquiterpenes, and steroids, optically active intermediates cyclopentanone 3-allylalcohol, α-methylene-γ-butylo lactones andtrans-hydrindanone-propionic acid, were synthesized from (R)- and (S)-isopropylideneglyceraldehyde derived fromD-mannitol andLascorbic acid, respectively, utilizing Claisen rearrangement as a key reaction. Actually total syntheses of natural alkaloids, (-)-antirhine, (+)-dihydroantirhine and (-) dihydrocorynantheol were accomplished.     

Asymmetric electrochemical lactonization of diols on a chiral 1-azaspiro[5.5]undecane N-oxyl radical mediator-modified graphite felt electrode

A graphite felt electrode modified with (6S,7R,10R)-4-amino-2,2,7-trimethyl-10-isopropyl-1-azaspiro[5.5]undecane N-oxyl was prepared for electrocatalytic oxidation of diols; electrolysis of diols on the modified electrode yielded optically active lactones (92.0-96.4%), with an enantiopurity of 82-99% ee.     

New anisatin-like sesquitepene lactones from pericarps of illicium majus

Two new sesquiterpene lactones, isolated from the pericarps of Illicium majus together with anisatin, have been assigned structures with an anisatin skeleton on the basis of detailed spectroscopic analysis and established by an X-ray diffraction method.     

Etude de l'action des alkylmagnesiens primaires et arylmagnesiens sur les anhydrides tricycliques pontes

The reaction of primary alkyl and aromatic Grignard reagents with bridged tricyclic di-carboxylic anhydrides gives the corresponding dialkylated tricyclic lactones via di-addition process. The lactones were transformed by retro-Diels-Alder reactions into 4,4-dialkylated butenolides.     

Investigation of the lignin isolated fromPhragmites communis by the method of mechanical milling

Summary Two isomeric dihydrofurocoumarins — zosimin and deltoin — have been isolated from the roots ofZosimia absinthifolia, which contain 3.2% of lactones.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 3, pp. 220–223, 1965     

Selective homogeneous hydrogenation of biogenic carboxylic acids with [Ru(TriPhos)H]+: a mechanistic study

Selective hydrogenation of biogenic carboxylic acids is an important transformation for biorefinery concepts based on platform chemicals. We herein report a mechanistic study on the homogeneously ruthenium/phosphine catalyzed transformations of levulinic acid (LA) and itaconic acid (IA) to the corresponding lactones, diols, and cyclic ethers. A density functional theory (DFT) study was performed and corroborated with experimental data from catalytic processes and NMR investigations. For [Ru(TriPhos)H](+) as the catalytically active unit, a common mechanistic pathway for the reduction of the C═O functionality in aldehydes, ketones, lactones, and even free carboxylic acids could be identified. Hydride transfer from the Ru-H group to the carbonyl or carboxyl carbon is followed by protonation of the resulting Ru-O unit via σ-bond metathesis from a coordinated dihydrogen molecule. The energetic spans for the reduction of the different functional groups increase in the order aldehyde < ketone < lactone ≈ carboxylic acid. This reactivity pattern as well as the absolute values are in full agreement with experimentally observed activities and selectivities, forming a rational basis for further catalyst development.     

Ring‐opening polycondensations

Ring‐opening polycondensation is a novel synthetic strategy using heterocycles of any ring size having two reactive bonds as bifunctional monomers in step‐growth polymerizations. The first part of this article reviews previous publications. The previous studies mainly dealt with syntheses of polyesters from tin‐containing macrocycles including cyclic polylactones. These tin‐containing cyclic oligomers or polymers were easily obtained in two ways, either by ring‐closing polycondensation of dibutyltin compounds with preformed diols or by ring‐expansion polymerizations of lactones by means of cyclic tin‐initiators. The second part of this article presents new results which deal with ring‐opening polycondensations of silicon containing macrocycles derived from oligo(ethylene glycol)s. In these cases the chain growth proceeds by elimination of dimethyl dichlorosilane. In addition to syntheses of homopolyesters, copolycondensations with silylated or stanylenated monomers were studied. Finally, the thermodynamical aspects of ring‐opening polycondensations will be discussed.     

Silenes as novel synthetic reagents: synthesis of diols and lactones from simple alkyldienes

Aryl substituted silenes can be generated by a modified Peterson olefination reaction and trapped in situ to afford silacycles with high diastereoselectivity. These silacycles can be elaborated by ‘Fleming-Tamao’ type oxidation to provide access to functionalized diols and lactones.     

Synthesis of Dibenzocyclooctadienes by Anodic Oxidation

the use of electrochemical oxidation was applied to the synthesis of dibenzocyclooctadiene lactones related to steganacin skeleton. This reaction, performed with compounds 1 and 2, led to results comparable with the oxidation with RuTFA, TTFA and VOF₃.     

The Oxidation of Primary Alcohols to Methyl Esters and Diols to Lactones Using Trichloroisocyanuric Acid

Abstract

Primary alcohols and diols are easily oxidized to methyl esters by a solution of trichloroisocyanuric acid with methyl alcohol in dichloromethane. In addition, α,ω-diols are also readily oxidized into lactones by refluxing with trichloroisocyanuric acid and pyridine in dichloromethane.