Synthesis, crystal structure, and catalytic properties of MgCo6Ge6

The ternary compound MgCo6Ge6 represents a novel member of the RM6X6 phases, which contains a graphite-type Ge network, Kagomé nets of Co atoms, and Ge2 dumbbells with an unexpected short Ge-Ge contact in the range of a localized Ge-Ge single bond. The title compound shows a large variety of chemical bonding, which ranges from metallic to multicenter and covalent bonding. The role of polar intermetallic alloys as promising candidates for the application as catalysts for the selective hydrogenation of alpha,beta-unsaturated aldehydes is discussed. MgCo6Ge6 possesses a remarkable activity and selectivity for the hydrogenation of cis/trans-citral to geraniol and nerol.     

Synthesis of 4, 6-diphenacylpyrimidines

Reaction of 4,6-dimethylpyrimidine with the acyl chlorides of aromatic carboxylic acids gave N-acyl-4-phenacyl-6-acylmethylidynepyrimidines, which undergo alcoholysis to give the corresponding diketones — 4,6-diphenacylpyrimidines.     

Synthesis of 6, 9, 11-Trihydroxy-6a, 12a-dehydrorotenoid

6, 9, 11-Trihydroxy-6a, 12a-dehydrorotenoid 1 (coccineone B) was synthesized from 2-hydroxybenzaldehyde 2 and phloroglucinol.     

Synthesis of New Sialidase Inhibitors, 6-Amino-6-Deoxysialic Acids

The synthesis of the 6-amino-6-deoxysialic-acid analogues 4, 5 , and 6 , is described. Mitsunobu reaction of the 1-C-nitroglycal 8 , (PPh₃, HCOOH, DEAD) gave the formiate 10 with inversion of configuration at C(3) (Scheme 2). Treatment of 10 with aq. NH₃ and subsequent protection of the amino function gave the imines 14 and 15 (Scheme 3), which were transformed into the triflates 17 . Substitution by azide, deprotection, and N-acetylation gave the anormeric 2-acetamido-3-azido-1-deoxy-1-nitro-D -mannoses 16 and the enol ether 18 . Chain elongation of the nitro azides 16 followed by hydroylsis gave the nonulosonates 20/22 , which upon reduction yielded the diols 23 and 24 , respectively (Scheme 4). The diol 23 was transformed into the sialic-acid analogues 5, 6 , and 32 by ozonolysis, transfer hydrogenation, hydorgenolysis, and deprotection (Scheme 5), and the diol 24 into 4 by a similar reaction sequence. The sialic-acid analogues 4 and 6 inhibit bacterial and viral sialidases competitively. The inbibitor constants for this enzyme from Vibrio cholerae are 0.12 mm for 4 and 0.19 mm for 6 , respectively. The activity of fowl plague virus sialidase was reduced by 17% and 36% under the influence of 4 and 6 , respectively, at a concentration of 0.1 mM . Compound 5 was inactive.     

Synthesis of 2',3'-dideoxy-6',6'-difluorocarbocyclic nucleosides

2',3'-Dideoxy-6',6'-difluorouracils, a novel series of gem-difluoromethylenated carbocyclic nucleosides, were synthesized from (Z)-but-2-ene-1,4-diol in 14 steps. A notable step was the construction of the carbocyclic ring via ring-closing metathesis and the incorporation of gem-difluoromethylene group by way of silicon-induced Reformatskii-Claisen reaction of chlorodifluoroacetic ester 3.     

Synthesis of 3, 6-anhydrocellulose by the saponification of 6-O-tosyl-2, 3-di-O-acetylcellulose

Summary 1. Derivatives of cellulose containing 3, 6-anhydro rings have been synthesized by the following route: cellulose 6-O-tritylcellulose 6-O-trityl-2, 3-di-O-acetylcellulose 2, 3-di-O-acetylcellulose 6-O-tosyl-2, 3-di-O-acetylcellulose 3, 6-anhydrocellulose.2. The composition of the 3, 6-anhydrocellulose has been studied by exhaustive acetylation, nitration, and periodate oxidation, and also by IR spectroscopy.Khimiya Prirodnykh Soedinenii, Vol. 2, No. 6, pp. 372–375, 1966     

Synthesis of 6S, 7S-anhydro-serricornine.

Diastereoselective and enantioselective reduction of the β-ketoester $\text{3}$ by yeast to $\text{4}$ provided the chiral starting material for a synthesis of 4RS,6S,7S-serricornine, having the same configuration as the natural product. This material was converted into optically active and diastereomerically pure 6S,7S-anhydro-serricornine ($\text{2}$).     

Synthesis of Stereoisomers of Cryptofolione 6'-Mono- and 4', 6'-Di-O-benzyl Ethers

Synthesis of stereoisomers of 6′‐mono‐ and 4′,6′‐di‐O‐benzyl cryptofolione is described through a key intermediate 6 , which was prepared by coupling of iodobenzene 8 with chiral propargyl alcohol 9 under Cosford protocol conditions. Monobenzyl ether 4 is obtained via epoxide 6 opening with vinyl Grignard, followed by cross‐metathesis reaction with a vinyl lactone 11 . Whereas, dibenzyl ether 5 is prepared by epoxide 6 opening with chiral propargyl alcohol 7 followed by simple transformations and finally cis‐Wittig olefination.     

Synthesis of 6-Styrylheptalenes

4-Methylazulenes 3 , 15 , and 23 were transformed into 4-[(methylthio)methyl]azulene 4 , and azulene-4-carbaldehyde dimethyl dithioacetals 16 and 24 , respectively. Vilsmeier formylation of 4 and 16 , and subsequent reduction led to the 1-methyl derivatives 6 and 18 , respectively. The thermal reaction of azulenes 6 , 18 , and 24 with dimethyl acetylenedicarboxylate (ADM) in toluene afforded heptalenes with a (methylthio)methyl group or a [bis(methylthio)]methyl group at C(6). Chlorination of [(methylthio)methyl]heptalene 7 , followed by treatment with HgO and BF₃⋅OEt₂ in aqueous tetrahydrofuran (THF), led to 6-formylheptalene-dicarboxylate 12 in excellent yield. Similarly, hydrolysis of 18 and 24 by HgO and BF₃⋅OEt₂ in aqueous THF afforded the 6-formyl derivatives 21 and 27 , respectively. Wittig reaction of the 6-formyl-substituted heptalenes and phosphonium salts 13a – e in the two-phase system CH₂Cl₂/2n aqueous NaOH resulted in the formation of 6-styryl-substituted heptalenes.     

Synthesis of novel 6-enaminopurines

Two different approaches have been used for the synthesis of 6-enaminopurines 6 from 5-amino-4-cyanoformimidoyl imidazoles. In the first approach imidazoles 1 were reacted with ethoxymethylenemalononitrile or ethoxymethylenecyanoacetate under mild experimental conditions and this led to 9-substituted-6-(1-amino-2,2-dicyanovinyl) purines 6a-f or 9-substituted-6-(1-amino-2-cyano-2-methoxycarbonylvinyl) purines 6g-k. These reactions are postulated to occur through an imidazo-pyrrolidine intermediate 7, which rapidly rearranges to the 6-enaminopurine 6. In the second approach 6-methoxyformimidoyl purines 3, prepared in two efficient steps from 5-amino-4-cyanoformimidoyl imidazoles 1, were reacted with malononitrile and methylcyanoacetate with a mild acid catalysis (ammonium acetate or piperidinium acetate) to give 6-enaminopurines 6a, 6d, 6f, 6g and 6k in very good yields. Only low yields were obtained for the 6-enaminopurine 6j, as competing nucleophilic attack on C-8 of either 3d or 6jcauses ring opening with formation of pyrimido-pyrimidines 11 and 10a respectively.     

Synthesis of 6-formylpterin

Conclusions A method was developed for the synthesis of 6-formylpterin by the bromination of 2-acetamldo-4-hydroxy-6-methylpteridine in AcOH in the presence of NiC1₂ and subsequent hydrolysis of the intermediate 2-acetamido-4-hydroxy-6-dibromomethylpteridine.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1669–1670, July, 1981.     

Synthesis of Derivatives of 1, 2, 6-Trisubstttuted-4-Piperidones

Robinson-Schöpf cyclisation was used to prepare several 1, 2, 6-trisubstituted-4-piperidones: 1, 2, 6-trimethyl-4-piperidone, tricyclic ketones 2 and 3 derivatives of coccinelline. In the case of 1, 2, 6-trimethyl-4-piperidone, a mixture of the trans and cis compounds 4 and 1 was obtained. The pure cis compound was prepared by another route.     

Synthesis of Purine Antiviral Agents,Hypoxanthine and 6-Mercaptopurine

Some potentially biologically active 6-substituted purine derivatives have been synthesized from simple organic reagents. The reaction of urea with ethyl cyanoacetate gave 6-aminopyrimidine-2,4-dione which was converted in two steps into purine derivative, xanthine. The latter was treated with formamide at 200°C to obtain hypoxanthine. The chlorination of hypoxanthine with POCl₃ gave 6-chloropurine which was converted into 6-mercaptopurine via reaction with thiourea in acetonitrile, followed by treatment with boiling ethanol. ethanol.     

6-三氟甲基苯并噻吩衍生物的合成

本文研究了苯环上含强吸电子基的2,6-二硝基-4-三氟甲基苯腈等在Na~2S-DMF-H~2O体系下与一些卤代化合物作用, 经桥接, 关环, 合成了一些2位取代的3-胺基-6-三氟甲基苯并噻吩及未环化的硫醚异构体, 并对其生成机理和^1H NMR进行了探讨.     

Synthesis,Structure, and Properties of LiNb6Cl15

Black single crystals of LiNb₆Cl₁₅ were obtained from reactions of Nb powder, NbCl₅ and LiCl in sealed niobium tubes at 850°C. The heavy atom structure of LiNb₆Cl₁₅ (Ia3 d (no. 230), Z = 16, a = 2055.5(2) pm at 100 K, R(F) = 0.028, R(F²) = 0.053) is isotypic with the structure of Ta₆Cl₁₅. The [Nb₆Cl₁₂]²⁺ clusters in the structure are three-dimensionally interconnected via three additional Cl^a?a. These bridge all vertices of niobium clusters, consistent with [Nb₆Cl₁₂ⁱCl]^? (the Nb? Cl^a–a? Nb angles are 140°). At low temperatures the lithium ions are disordered over one-third of sites (48 f), occupying cavities inside of two distorted corner-sharing tetrahedra of chloride. These positions for lithium represent the narrowest sections of infinite channels in the structure built up by chloride. An increased lithium ion mobility is obtained above 170 K by ⁷Li-NMR measurements.     

Synthesis of 2, 6-dicyclohexyl-substituted pyrylium salts

2, 6-Dicyclohexyl-substituted pyrylium salts are synthesized by condensing hexahydrobenzoyl chloride with isobutene, isomeric pentenes, diisobutene, and -methylstyrene. Treatment of the resultant pyrylium salts with ammonia converts them into the corresponding pyridine salts.     

A Synthesis of 2, 2-Ethylenedioxy-6-ketones

A facile two-step synthesis of the monoprotected diketones, 2, 2-ethylenedioxy-6-ketones from esters is reported.     

A Short,Efficient Synthesis of 6-Cyano-1-tetralones

A new, short and high-yield synthesis of 6-cyano-1-tetralones is described. Triflate intermediates 8 and 9 are versatile intermediates for the synthesis of other 6-substituted tetralones.     

Synthesis of 2, 6-derivatives of 1, 4-dioxane

Stereoisomers of 6-halomethyl-2-hydroxymethyl-1, 4-dioxanes have been obtained via the cyclization of the monoallyl ether of glycerol. The stereoisomeric bromides differ considerably in their physical properties. The bromine atoms of the stereoisomers differ in their reactivity towards thiourea.