1,2-migration of 2'-oxoalkyl group and concomitant synthesis of 2-C-branched O-, S-glycosides and glycosyl azides via 1,2-cyclopropanated sugars

Treatment of 2'-oxoalkyl 2-O-Ms(Ts)-alpha-C-mannosides (4, 5, and 6) with base resulted in 1,2-cyclopropanation via an intramolecular SN2 reaction due to their 1,2-trans-diaxial configurations. The 1,2-cyclopropanated sugars (10 and 13) were reacted with various alcohols, thiols, and sodium azide to produce 2-C-branched O- and S-glycosides and glycosyl azides (11, 14-28) in good to excellent yields. In contrast, 1,2-cis 2'-oxoalkyl 2-O-Ms(Ts)-alpha-C-glucoside 9 formed an acyclic conjugated aldehyde (31) under basic conditions, which occurred by 1'-enolation followed by beta-elimination. An intramolecular Michael addition from 31 produced 2-O-Ms-beta-C-glucoside 30 as a major product. However, due to the electron-withdrawing effect exerted by 2-O-Ms compound 31 also undergoes a C2 epimerization to form 32. Thereafter, the intramolecular Michael addition led to the formation of both 1,2-trans 2'-oxoalkyl 2-O-Ms-alpha-C-mannoside 4 and its beta-anomer (33). Because beta-elimination/Michael addition and C2 epimerization are reversible reactions, equilibriums among 9, 31, 30, 32, 33, and 4 were established, which included the transformation of 1,2-cis C-glucoside 9 into 1,2-trans C-mannoside 4. The subsequent 1,2-cyclopropanation of 4 was an irreversible reaction yielding 1,2-cyclopropanated 10 and further conversion to 1,2-migration products (11 and 12).     

Recent advances in the stereoselective synthesis of carbohydrate 2-C-analogs

C-branched carbohydrates are of current interest for glycochemistry, are widely found in nature and serve as important subunits in many antibiotics, bacterial polysaccharides and macrolides. Among C-functionalized saccharides, 2-C-branched carbohydrates represent challenging structures for synthetic chemists, since in contrast to C-glycosides they are not easily accessible from glycosyl bromides or other simple precursors. In this perspective we want to summarize recent approaches to 2-C-branched carbohydrates over the past fifteen years. The two main strategies are based on ring-opening of 1,2-cyclopropanated carbohydrates by various reagents, as well as radical additions to glycals and further transformations, developed in our group. Both methods are characterized by high stereoselectivities and good yields and give access to a broad variety of functionalized carbohydrate 2-C-analogs.     

Reactive iron carbonyl reagents via reaction of metal alkoxides with Fe(CO)5 or Fe2(CO)9: synthesis of cyclobutenediones via double carbonylation of alkynes

Alkoxy bases such as t-BuOK react with Fe(CO)(5) to give reactive iron carbonyl intermediates that in turn react with alkynes at 70 °C in THF to give 1,2-cyclobutenediones in 70-93% yields after CuCl(2)·2H(2)O oxidation. A novel 1,2-diacyloxyferrole derivative was isolated in the reaction of diphenylacetylene with Fe(CO)(5)/t-BuOK in the presence of acetyl chloride in contrast to the formation of a 1,4-diacyloxyferrole complex formed in the reaction using Fe(CO)(5)/Me(3)NO. The Fe(2)(CO)(9)/t-BuOK reagent system also converts the alkynes to corresponding cyclobutenediones in 63-90% yields under similar reaction conditions.     

A highly efficient procedure for 3-sulfenylation of indole-2-carboxylates

A highly efficient one-pot procedure for 3-sulfenylation of 2-carboxyindoles is described. Treatment of thiols with N-chlorosuccinimide at -78 degrees C in CH(2)Cl(2) affords sulfenyl chlorides in situ that readily react with 2-carboxyindoles to give 3-thioindoles in high yields. This new method is milder, produces less waste, and is compatible with a wide range of thiol and indole functionality. [reaction: see text]     

Novel [6 + 2] cycloaddition of fulvenes with alkenes: a facile synthesis of the anislactone and hirsutane framework

[reaction: see text] In contrast to the Diels-Alder reaction of fulvenes and various alkenes, 6-aminofulvenes react with maleic anhydride (or maleimide) to give [6 + 2] cycloaddition adducts, constituting an efficient and novel route to pentaleno[1,2-c]furan, pentaleno[1,2-c]pyrrole, and cyclopenta[a]pentalene skeleton.     

Reaction of 3-phenyl-3-chloro-2-oxopropionic acid derivatives with ortho-phenylenediamine

Conclusions The reaction of dialkylamides of 3-phenyl-3-chloro-2-oxopropionic acid with orthophenylenediamine gave 2-(N,N-dialkylcarbamoyl)-1,4-dihydroquinoxalines, while esters of this acid react with ortho-phenylenediamine to give 3-(-chlorobenzyl)-2-oxo-1,2-dihydro-quinoxalines, which react with phosphites to yield the corresponding 3-(O,O-dialkylphos-phonobenzyl)-2-oxo-1,2-dihydroquinoxalines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1412–1414, June, 1989.     

An efficient intermolecular C(aryl)-S bond forming reaction catalyzed by BINAM-copper(II) complex

A wide range of diaryl thioethers and aryl alkyl thioethers are synthesized from the corresponding aryl iodides and aromatic/aliphatic thiols through Ullmann type intermolecular coupling reactions in the presence of a catalytic amount of easily available BINAM-Cu(OTf)₂ complex. Less reactive aryl bromides have also been shown to react with thiols under identical reaction conditions to give good yields of the thioethers without increasing the reaction temperature and time.     

Efficient methodology for the synthesis of 2-C-branched glyco-amino acids by ring opening of 1,2-cyclopropanecarboxylated sugars

An efficient methodology for the synthesis of 2-C-branched glyco-amino acid derivatives by diastereoselective ring opening of 1,2-cyclopropanecarboxylated sugars in good yields is reported. [reaction--see text]     

Novel and efficient one‐pot synthesis of azuleno[1,2‐b]‐benzothiophenic enones from the corresponding 2‐cycloheptatrientyl‐3‐(2‐furyl)benzothiophenes

2‐Cycloheptatrienyl‐3‐(2‐furyl)benzothiophenes, which are prepared by Stille coupling reaction of 2‐cyclo‐heptatrienyl‐3‐bromobenzothiophene with the 5‐substituted 2‐trimethylstannylfurans, react with triphenylmethyl tetrafluoroborate to give the corresponding azuleno[1,2‐b]benzothiophenic enones in excellent yields.     

Divergent sequential reactions of β-(2-aminophenyl)-α,β-ynones with nitrogen nucleophiles

β-(2-Aminophenyl)-α,β-ynones readily react with nitrogen nucleophiles to give three major types of products, depending on reaction conditions and variation in the nucleophiles. The reaction may lead to simple 1,2-nucleophilic adducts or, at higher temperatures, to a divergent sequential cyclisation giving rise to 2-aryl-4-aminoquinolines by reaction with amines, or to substituted 2-aryl or 2-alkyl-4-alkylidene quinazolines by reaction with amidines. The latter could also be synthesised by reaction of β-(2-aminophenyl)-α,β-ynones with iminochlorides.     

Two directions of interaction of 2-aryl-1,2,3,4-tetrahydropyridine-3,3,4,4-tetracarbonitriles with nucleophiles

Depending on the reaction conditions, 2-aryl-1,2,3,4-tetrahydropyridine-3,3,4,4-tetracarbonitriles react with alcohols, thiols and ketoximes to give 3-amino-4-aryl-1,1-di[R-oxy(thio)]-6,7-dialkyl-3a,4,5,7a-tetrahydro-1H-pyrrolo[3,4-c]pyridine-3a, 7a-dicarbonitrles or 2-aryl-5,6-dialkylpyridine-3,4-dicarbonitriles.Chuvash State University, Cheboksary 428015. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 367–375, March, 1997.     

Synthesis of 5-alkyl(aryl)sulfanyl-4-chloro-3-trichloromethyl-1,2-thiazoles and 5-Alkyl(aryl)sulfanyl-4-chloro-1,2-thiazole-3-carboxylic acids

Butane-, phenylmethane-, and benzenethiols reacted with 4,5-dichloro-3-trichloromethyl-1,2-thiazole in the presence of sodium ethoxide to give the corresponding 5-alkyl(aryl)sulfanyl-4-chloro-3-trichloromethyl-1,2-thiazoles. The reaction of 4,5-dichloro-1,2-thiazole-3-carboxylic acid with the same thiols under similar conditions resulted in the formation of sodium 4,5-dichloro-1,2-thiazole-3-carboxylate, while in the presence of pyridine 5-alkyl(aryl)sulfanyl-4-chloro-1,2-thiazole-3-carboxylic acids were obtained.     

Synthese d'une Serie de 2-(F-alkyl) Thioenol Ethers

2-(F-alkyl) enol ethers react easily with thiols. With one equivalent of the thiol, the corresponding 2-(F-alkyl) thioenol ethers were formed via an addition-elimination mechanism. With two equivalents of thiol or with one equivalent of 1,2-ethanedithiol, 2-(F-alkyl) thioacetals or 2-(F-alkyl) dithiolanes were obtained in good yields.     

Reactions of 2-polyfluoroalkylchromones with aliphatic diamines

2-Polyfluoroalkylchromones react with aliphatic 1,2-diamines to give 2,3-dihydro-1H-1,4-diazepines. A similar reaction with 1,3-diaminopropane yieldsN,N′-trimethylenebis(2-hydroxyacetophenomines) as a result of scission of the original chromones. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 817–819, April, 1999.     

Reactions of 1-alkyl-1,2-diphospholes with 1,3-dipoles: diphenyldiazomethane and nitrones

The reaction of 1-alkyl-1,2-diphosphacyclopenta-2,4-dienes (1-alkyl-1,2-diphospholes) (1) with diphenyldiazomethane proceeds at room temperature via unstable [3+2] cycloadducts to form bicyclic phosphiranes (2). However, 1-alkyl-1,2-diphospholes (1) react with N,alpha-diphenylnitrone or N-tert-butyl-alpha-phenylnitrone depending on the temperature to give either dimers of 1-alkyl-1-oxo-1,2-diphospholes (5) or 1-alkyl-1,7-dioxo-6-azo-1,7-diphospha-bicyclo[3.2.0]hept-2-enes (7) - phosphorus analogues of β-lactams.     

Preparations and properties of polymers containing 3,4-bis[(2,4,6-tri-t-butylphenyl)phosphinidene]-1,2-di(2-thienyl)cyclobutene moieties

Reaction of 1,8-bis[5-{(2,4,6-tri-t-butylphenyl)phosphinoethynyl}-2-thienyl]octane with butyllithium followed by treatment with 1,2-dibromoethane afforded a new polymer containing 3,4-bis[(2,4,6-tri-t-butylphenyl)phosphinidene]-1,2-di(2-thienyl)cyclobutene units. The polymer was allowed to react with bis(benzonitrile)dichloropalladium to give the polymer complex. A Sonogashira coupling reaction between ethynyltrimethylsilane and 4-bromonitrobenzene proceeded in DMF at 100 °C to give 4-nitro(trimethylsilylethynyl)benzene in the presence of the polymer complex, CuI, and triethylamine.     

Novel preparation of (−)-4-hydroxycyclohex-2-enone: reaction of 4-hydroxycyclohex-2-enone and 4-hydroxycyclopent-2-enone with some thiols

A new route to (R)-4-hydroxycyclohex-2-enone from cyclohexanedione monoketal (27% yield) commences with reaction of the ketal with nitrosobenzene catalysed by l-proline. 4-Hydroxycyclohex-2-enone and 4-hydroxycyclopent-2-enone react with thiols to afford the corresponding syn-disubstituted cycloalkanones.     

甲基取代的甲酸态的四氢叶酸辅酶模型的合成及其取代碳单元转移反应

以乙二胺和乙酰胺为原料,经4步反应合成了碘化1,2-二甲基-3-间(或对)-硝基苯磺酰基咪唑啉(2a,2b),以2a和2b作为甲基取代的甲酸态四氢叶酸辅酶模型,同单亲核中心的氮亲核体(对甲苯胺,对甲氧基苯胺等)和碳亲核体(丙二腈)反应得到次乙基单元(CH₃-C>)转移的中间体产物;与双亲核中心的亲核体(邻苯二胺,邻氨基酚)反应得到次乙基单元完全转移的产物。     

4-Hydroxyquinol-2-ones. 87. Unusual Synthesis of 1-R-4-Hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylic Acid Pyridylamides

4-Chloro-2-oxo-1,2-dihydroquinoline-3-carboxylic acids and their esters react with aminopyridines in refluxing DMF to give the corresponding 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylic acid pyridylamides. Their structures were proved by ¹H NMR and mass spectroscopy, counter synthesis, and by X-ray analysis. A possible mechanism is proposed for the indicated chemical reaction. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1362–1371, September, 2005.     

Highly Diastereoselective thioglycosylation of functionalized peracetylated glycosides catalyzed by MoO2Cl2

Among 18 oxometallic species, MoO2Cl2 was found to be the most reactive in catalytic thioglycosylation of O-acetylated glycosides with functionalized thiols in CH2Cl2, leading cleanly to 1,2-trans-thioglycosides with exclusive diastereocontrol. The new catalytic protocol is applicable to a monoglycoside building block and beta-(1-->6)-S-linked-thiodisaccharide synthesis. [reaction: see text].