Synthesis of 2,3-trans disubstituted tetrahydrofurans through sequential xanthate radical addition-substitution reactions

A two-step preparation of 2,3-trans disubstituted tetrahydrofuran derivatives is reported from S-alkyl dithiocarbonates. The study of the group transfer reaction from xanthates and alkenes afforded intermediate S-alkyl dithiocarbonates. From 2,3-dihydrofuran derivatives, the displacement of the resulting anomeric xanthates with various nucleophiles in the presence of Lewis acid allowed the formation of new carbon-carbon and carbon-heteroatom bonds. This strategy was illustrated by a two-step synthesis of a precursor of modified 2'-beta-C-branched nucleoside analogues.     

Palladium(0)-catalyzed allylic alkylation of diketoester-dioxinones with allyl acetates under neutral conditions: synthesis of hexasubstituted benzene derivatives

Intermolecular palladium(0)-catalyzed allylic alkylation of diketoester-dioxinones was performed under neutral conditions with 2-alkenyl and 2-cycloalkenyl acetates. Subsequent aromatization using cesium carbonate gave rise to isopropylidene-protected hexasubstituted resorcylates.     

Functionalized cyclopentanes via radical cyclizations using thiocarbonate derivatives as initiators and terminators

A radical-based cyclization is described that employs xanthates or cyclic thionocarbonates as initiators and allylic dithiocarbonates or allylic thiocarbamates as terminators.     

Regioselective amidation of allylic α-hydroxyphosphonates with Nitriles: A convenient route to (3-acetylamino-1-alkenyl)-phosphonates

Summary Reaction of dialkyl (1-hydroxy-2-alkenyl)- and (1-hydroxy-2-cycloalkenyl)phosphonates (1) with acetonitrile in the presence of trifluoromethane sulfonic acid (TfOH) affords regiospecifically and with high (E)-stereoselectivity the 1,3-transposed acetamides3 in modest to good yields.

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Regioselektive Amidierung von allylischen -Hydroxyphosphonaten mit Nitrilen: Ein einfacher Weg zu (3-Acetylamino-1-alkenyl)phosphonaten

Zusammenfassung (1-Hydroxy-2-alkenyl)- und (1-Hydroxy-2-cycloalkenyl)phosphonate (1) reagieren mit Acetonitril in Gegenwart von Trifluormethansulfonsäure (TfOH) in mäßigen bis guten Ausbeuten regiospezifisch und mit hoher (E)-Stereoselektivität zu den 1,3-umgelagerten Acetamiden3.

     

An unexpected synthesis of ketene monothioacetals

Some dithiocarbonates (xanthates) can be converted into ketene monothioacetals through extrusion of sulfur upon treatment with base and an alkylating agent.     

Solvolysis of 1-Chloro-1-Alkenyl Phenyl Sulfides. Synthesis of α-Bromo Phenyl Thiocarboxylic Esters, α-Bromo Alkyl Carboxylic Esters and α-Phenylthio Methyl Carboxylic Esters

1-chloro-1-alkenyl phenyl sulfides treated with bromine followed by hydrolysis or methanolysis give α-bromo phenyl thiocarboxylic esters and α-phenyl-thio methyl carboxylic esters. Direct oxidative solvolysis with bromine and alcohol give α-bromo alkyl carboxylic esters.     

Generation and intermolecular capture of cyclopropylacyl radicals

[reaction: see text] Cyclopropylacyl radicals derived from S-cyclopropylacyl xanthates (dithiocarbonates) undergo intermolecular additions to olefins without loss of CO or ring opening. In the presence of a phenyl ring on carbon C-1 of the cyclopropane ring, loss can be made to occur in the absence of an olefinic trap. The adducts from the cyclopropylacyl radical additions are easily converted into enones by base-induced beta-elimination of the xanthate group.     

Crown Ether Catalysis in the Synthesis of Xanthates

Xanthates (0,S-dialkyl dithiocarbonates) received much attention in connection with technological¹ and synthetic applications². Pyrolytic elimination of xanthates, called the Chugaev reaction, has been widely used as a method of dehydrating alcohols without rearrangement of carbon skeleton³.     

On triazoles. XXI. Synthesis of 1,2,4-triazolyldithiocarbonates

The reaction of 5-amino-1,2,4-triazoles 1 with carbon disulfide and alkylating agents in basic condition to yield alkyl, aralkyl and aryl (5-amino-3-Q-1,2,4-triazol-1-yl)dithiocarbonates 2 and alkyl (3-Q-1,2,4-triazol-5-yl-amino)dithiocarbonates 3 was studied. The isomeric and tautomeric structure of derivatives obtained was proved with the help of their uv, pmr and cmr spectra using model compounds prepared for this purpose. The results obtained enabled us to correct some confusion in the literature.     

One-pot synthesis of symmetrical and unsymmetrical aryl sulfides by Pd-catalyzed couplings of aryl halides and thioacetates

Aryl sulfides were obtained from the coupling reaction of S-aryl (or S-alkyl) thioacetates and aryl bromides in the presence of palladium catalyst. This reaction method enables the one-pot synthesis of symmetrical and unsymmetrical diaryl sulfides by employing potassium thioacetate with aryl iodides and aryl bromides.     

Effect of Varying Alkyl Chain Length on Thermal Decomposition Temperature of Zinc(II) Xanthates and its Impact on Curing of Epoxy Resin

Linear and branched zinc(II) xanthates with varying alkyl chain length were synthesized and characterized by ¹H NMR, ¹³C NMR, and IR spectroscopy, as well as elemental analysis. Zinc sulfide as the final decomposition product upon thermal annealing of zinc(II) xanthates was confirmed by XRD analysis. Cure time for epoxy resin composite at various temperatures was analyzed employing zinc(II) xanthates (5 % mass) as latent cure catalysts. XRD investigation of the cured epoxy resin including zinc(II) xanthates upon thermal annealing revealed the presence of ZnS in‐situ in the composite matrix, indicating the in‐situ thermal decomposition of zinc(II) xanthates as probable mechanism for curing. Thermogravimetric analysis was performed to investigate the thermal decomposition temperature trend of zinc(II) xanthates. A parallel trend was observed correlating the thermal decomposition temperature trend of zinc(II) xanthates and the order of curing catalytic efficiency utilizing zinc(II) xanthates. In the case of linear alkylzinc(II) xanthates with an increase in the alkyl chain length, both thermal decomposition temperature and the cure time were enhanced. In contrast, in case of branched alkyl chain zinc(II) xanthates with increasing alkyl chain length show decreasing thermal decomposition temperature as well as cure time.     

Innovative reactions mediated by zirconocene

Radical reactions mediated by Schwartz reagent and zirconocene(alkene) complex are firstly described. Schwartz reagent is a promising alternative to tributyltin hydride and the first transition metal hydrido complex used as a radical mediator in organic synthesis. A zirconocene(alkene) complex effects single electron transfer to alkyl halide to generate the corresponding alkyl radical. Secondly, serendipitous allylic C-H bond activation of the coordinating alkene of zirconocene(alkene) complex and its application to organic synthesis are summarized. By utilizing equilibrium between zirconocene(alkene) and zirconocene 2-alkenyl hydride, reaction of acid chloride with zirconocene(alkene) provides the corresponding homoallylic alcohol by sequential attacks of the hydride and 2-alkenyl moieties. A set of hydride and 2-alkenyl attacks on 1,4-diketone yields 6-heptene-1,4-diol derivative in high yield with high stereoselectivity. Selective capture of the hydride with diisopropyl ketone gives zirconocene 2-alkenyl alkoxide, which is a useful reagent for stereoselective allylation of aldehyde and imine. alpha-Halo carbonyl compounds undergo radical allylation with the zirconocene 2-alkenyl alkoxide which serves as a substitute for allyltin.     

On the reaction of acetyl bromide with phenyldi-n-alkylarsine sulfides

Conclusions Reaction of acetyl bromide with phenyldi-n-alkylarsine sulfides in a sealed tube at 80–90° for 14–18 h gave alkyl bromide, the mixed thioanhydride of phenyl-n-alkylarsinic acid and acetic acid, phenyl-n-alkylbromoarsine and the S-alkyl ester of thioacetic acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1878–1880, August, 1968.     

Stereo-recognizing transformation of (E)-alkenyl halides into sulfides catalyzed by nickel(0) triethyl phosphite complex

(E)-Alkenyl halides were transformed into (E)-alkenyl sulfides by the nickel(0) triethyl phosphite complex-catalyzed reaction with thiols, whereas (Z)-alkenyl halides gave alkynes under the same reaction conditions. Aryl halides were also transformed into aryl sulfides using the same reagent system.     

Selective one-pot synthesis of trithiocarbonates, xanthates, and dithiocarbamates for use in RAFT/MADIX living radical polymerizations

[reaction: see text] We report a facile route for the production of chain transfer agents for reversible addition fragmentation chain transfer (RAFT) and macromolecular design via the interchange of xanthates (MADIX) polymerizations, via a one-pot reaction. 1,1'-Thiocarbonyl diimidazole (TCDI) undergoes controlled monosubstitution when reacted with secondary thiols or alcohols. The intermediate S/O-esters of imidazole-N-thionocarboxylic acid react efficiently with a range of primary thiols, alcohols, and amines to form asymmetrical dithiocarbonates, trithiocarbonates, and dithiocarbamates, respectively. The synthesis provides a facile approach to the controlled radical polymerization of vinyl monomers through the reversible addition-fragmentation chain transfer (RAFT) mechanism.     

Research on pyrazolidine

4-Alkyl-4-(1-cycloalkenyl)-1,2-diphenyl-3,5-dioxopyrazolidines were obtained by the reaction of 4-cycloalkylidene-1,2-diphenyl-3,5-dioxopyrazolidines with alkyl halides.See [1] for communication 23.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 254–256, February, 1979.     

Deoxygenation of alcohols employing water as the hydrogen atom source

Trialkylboranes (BMe3, BEt3, and BBu3) have been shown to mediate reductive deoxygenation reactions of O-alkyl-S-methyl dithiocarbonates (methyl xanthates) in which water or deuterium oxide functions as the source of hydrogen or deuterium. This method has proven versatile with regard to substrate scope and is capable of providing protio- or deuterioalkane products in high yields with excellent levels of D-incorporation. Ab initio calculations suggest that the trialkylborane-water complex possesses an unusually low O-H bond dissociation energy (73 kcal/mol) and support a radical chain mechanism for this process. Taken together, this report provides evidence for fundamentally novel and previously overlooked modes of reactivity for water and trialkylboranes of wide ranging importance in both theoretical and applied investigations.     

Formation mechanism of furfuryl sulfides from o-furfuryl dithiocarbonates: density functional theory study for aromatic [3,3]-sigmatropic rearrangement

Density functional theory (DFT) calculations at the B3LYP/6-31G(d) and B3LYP/6-31G+(d) levels demonstrated that O-furfuryl S-alkyl dithiocarbonate (1) undergoes aromatic [3,3]-sigmatropic rearrangement to the energetically unfavorable S-(2-methylene-2,3-dihydrofuran-3-yl) S-alkyl dithiocarbonate (2'), which then rearranges to furfuryl alkyl sulfide (3) with COS extrusion to regain the aromaticity lost in the first step.     

Convenient stereoselective synthesis of 3-hydroxy-2-iodo-2(E)-alkenyl sulfides via iodohydroxylation of 1,2-allenyl sulfoxides in the presence of BnSH

The iodohydroxylation of 1,2-allenyl sulfoxides with I₂ in the presence of BnSH affords 3-hydroxy-2-iodo-2(E)-alkenyl sulfides in good yields and selectivities. The stereochemistry for the products of this transformation is opposite to what was obtained from the iodohydroxylation of 1,2-allenyl sulfides. Based on the results of some control experiment, a mechanism was proposed.     

Synthesis and biosynthesis of alkoxylipids.

Chromatographic methods have shown that lipids with long alkyl or 1-alkenyl chains–called alkoxylipids or ether lipids–are widely distributed in human and animal tissues. These compounds comprise neutral alkoxylipids, i. e. 1-O-alkyl or 1-O-(1-alkenyl)-2,3-di-O-acylglycerols, and alkoxylipids which are linked by a phosphate residue at C-3 to aminoethanol, choline or serine. 1-O-Alkylglycerols, 1-O-(1-alkenyl)glycerols and other natural alkoxylipids can be synthesized in high yields. 2-Alkyl, 1,3-dialkyl and trialkylglycerols which are not found in nature are also accessible by synthesis. The neutral alkoxylipids are employed in biomedical investigations, e.g. as substrates in acyl-hydrolase systems or in fat absorption studies. The principal features of alkoxylipid biosynthesis have been elucidated. The alkyl residue is derived from a saturated or monounsaturated fatty acid via the corresponding alcohol. 1-O-(1-alkenyl)-2-O-acylglycerophosphoryl aminoethanols (“plasmalogens”) are apparently formed from the appropriate 1-alkyl compounds; this is not possible in the case of the choline series. Both “aminoethanol” and “choline” plasmalogens are, nevertheless, present in most tissues.