Amination of 3,6-dinitro-1,8-naphthyridines

Treatment of 2-amino-3,6-dinitro-1,8-naphthyridines with liquid ammonia/potassium permanganate gives 2,4-diamino-3,6-dinitro-1,8-naphthyridine. From 2-ethoxy-3,6-dinitro-1,8-naphthyridine a mixture of 4-amino-and 5-amino-3,6-dinitro-1,8-naphthyridine was obtained. 2-Chloro-3,6-dinitro-1,8-naphthyridine afforded a mixture of four compounds i. e. 2,4- and 2,5-diamino-3,6-dinitro-1,8-naphthyridine and 2-chloro-5-amino-3,6-dinitro-1,8-naphthyridine and 2-amino-3,6-dinitro-1,8-naphthyridine. A study on covalent amination has shown that 4-amino-2-ethoxy-3,6-dinitro-1,8-naphthyridine undergoes covalent amination at C-5, whereupon in this adduct amino-deethoxylation takes place. In a similar way, 2-chloro- and 2-ethoxy-5-amino-3,6-dinitro-1,8-naphthyridine give covalent amination at C-4.     

Synthesis and molecular structure of indium complexes based on 3,6-di-tert-butyl-o-benzoquinone. Looking for indium(I) o-semiquinolate

The interaction of 3,6-di-tert-butyl-o-benzoquinone (3,6-Q) with indium in toluene leads to the tris-o-semiquinolate derivative (3,6-SQ)(3)In (3,6-SQ - radical-anion of 3,6-Q). According to single-crystal X-ray diffraction analysis, this complex has a trigonal prismatic structure. Magnetic measurements revealed that the exchange interactions between odd electrons of the paramagnetic ligands in (3,6-SQ)(3)In are antiferromagnetic in character. The treatment of (3,6-SQ)(3)In with 2,2'-dipyridyl (Dipy) causes the displacement of one o-quinone ligand and the formation of the (3,6-SQ)In(Dipy)(3,6-Cat) (3,6-Cat - dianion of 3,6-Q) derivative containing mixed charged o-quinoid ligands. The reaction of InI with (3,6-SQ)K in THF solution is accompanied by a redox process and the potassium-indium(iii) catecholate derivative was obtained as a result. The oxidation of InI with 3,6-Q in THF produces the dimeric In(iii) iodo-catecholate complex [(3,6-Cat)(2)In·2THF]InI(2). The same derivative can be synthesized by the interaction of indium metal with a mixture of I(2) and 3,6-Q.     

3,6-diisopropyl-2-hydroxypyrazine and 3,6-diisopropyl-2-pyrazinethiol as carriers of some alkoxycarbonyl groups

Some derivatives of benzyloxycarbonylated 3,6-diisopropyl-2-hydroxypyrazine and 3,6-diisopropyl-2-pyrazinethiol were prepared and shown to be the versatile benzyloxycarbonylation reagents for amines and amino acids. It was also ascertained that 3,6-diisopropyl-2-hydroxypyrazine and 3,6-diisopropyl-2-pyrazine-thiol serve effectively as carriers of the β,β,β,-trichloroethoxycarbonyl group.     

Coordination complexes of molybdenum with 3,6-di-tert-butylcatechol. Addition products of DMSO, pyridine N-oxide, and triphenylarsine oxide to the putative [MoVIO(3,6-DBCat)2] monomer and self-assembly of the chiral [(MoVIO(3,6-DBCat)2)4] square

Molybdenum complexes of 3,6-di-tert-butylcatechol have been prepared from the reaction between [Mo(CO)(6)] and 3,6-di-tert-butyl-1,2-benzoquinone. A putative "[MoO(3,6-DBCat)(2)]" monomer is assumed to form initially by reaction with trace quantities of oxygen. Condensation of the reaction mixture leads to the formation of oligomeric products, including the [(MoO(3,6-DBCat)(2))(4)] chiral square isolated by chromatographic separation. Molybdenum centers at the corner of the square are bridged by oxo ligands centered along edges. Four-fold and inversion crystallographic symmetry gives tetramers as either LambdaLambdaLambdaLambda or DeltaDeltaDeltaDelta isomers, and the crystal structure consists of parallel columns of squares with the same chirality. Addition of O-Subst (O-Subst = dmso, pyridine N-oxide, triphenylarsine oxide) ligands to [MoO(3,6-DBCat)(2)] occurs selectively to give cis-[MoO(O-Subst)(3,6-DBCat)(2)] products. All three addition complexes are fluxional in solution. The temperature-dependent stereodymanic behavior of [MoO(dmso)(3,6-DBCat)(2)] has been shown to occur via a trigonal prismatic intermediate (Bailar twist) that conserves the cis disposition of oxo and dmso ligands. Electrochemical and chemical reduction reactions have been investigated for [MoO(dmso)(3,6-DBCat)(2)] with interest in displacement of SMe(2) with formation of cis-[MoO(2)(3,6-DBCat)(2)](2-). Cyclic voltammetry shows an irreversible two-electron reduction for the complex at -0.852 V (vs Fc/Fc(+)). Chemical reduction using CoCp(2) was observed to give a product with an electronic spectrum that is generally associated with cis-[MoO(2)(Cat)(2)](2-) complexes. Structural characterization revealed that the product was [CoCp(2)][MoO(3,6-DBCat)(2)], possibly formed as the product of dmso displacement upon one-electron reduction of [MoO(dmso)(3,6-DBCat)(2)].     

Determination of the configuration of substituted 1,4:3,6-dianhydrohexitols by 13C NMR spectroscopy

The configurations of 1,4:3,6-dianhydro-2,5-di-O-mesyl-D -mannitol, 1,4:3,6-dianhydro-2,5-di-O-mesyl-D -glucitol, 1,4:3,6-dianhydro-2,5-di-O-mesyl-L -iditol, 1,4:3:6-dianhtydro-2-deoxy-2-iodo-5-O-mesyl-D -mannitol, 1,4:3:6-dianhtydro-2-deoxy-2-iodo-5-O-mesyl-D -glucitol, 1,4:3,6-dianhydro-2-deoxy-2-iodo-5-O-mesyl-L -iditol, 1,4:3,6-dianhydro-2,5-dideoxy-2,5-diiodo-D -glucitol and 1,4:3,6-dianhydro-2,5-dideoxy-2,5-diiodo-L -iditol were determined by ¹³C NMR spectroscopy, by invoking the field-effect.     

Oxidative C -H alkynylation of 3,6-dihydro-2H-pyrans

Current synthesis of α-substituted 3,6-dihydro-2H-pyrans dominantly relies on functional group transformation. Herein, a direct and practical oxidative C-H alkynylation and alkenylation of 3,6-dihydro-2H-pyran skeletons with a range of potassium trifluoroborates is developed. The metal-free process is well tolerated with a wide variety of 3,6-dihydro-2H-pyrans, rapidly providing a library of 2,4-disubstituted 3,6-dihydro-2H-pyrans with diverse patterns of α-functionalities for further diversification and bioactive small molecule identification.     

Zinc and cadmium complexes based on 3,6-di-tert-butyl-o-benzoquinone

Zinc and cadmium bis-o-semuquinolate and catecholate complexes are synthesized by the reduction of 3,6-di-tert-butyl-o-benzoquinone (3,6-Q) with amalgamated metals in a medium of various solvents. The oxidation of the metal catecholate derivatives results in the corresponding mono-o-semiquinone complexes, which undergo symmetrization to form the metal bis-o-semiquinolates. The molecular structures of the complexes (3,6-SQ)₂Zn · Py, (3,6-SQ)₂Zn · H₂O, and (3,6-SQ)₂Cd · α,α′-Bipy (3,6-SQ is the radical anion of 3,6-Q) are studied by X-ray diffraction analysis. Magnetochemical studies are carried out for the zinc and cadmium bis-o-semiquinone complexes.     

Syntheses and redox properties of bis(hydroxoruthenium) complexes with quinone and bipyridine ligands. Water-oxidation catalysis

The novel bridging ligand 1,8-bis(2,2':6',2"-terpyridyl)anthracene (btpyan) is synthesized by three reactions from 1,8-diformylanthracene to connect two [Ru(L)(OH)]+ units (L = 3,6-di-tert-butyl-1,2-benzoquinone (3,6-tBu2qui) and 2,2'-bipyridine (bpy)). An addition of tBuOK (2.0 equiv) to a methanolic solution of [RuII2(OH)2(3,6-tBu2qui)2(btpyan)](SbF6)2 ([1](SbF6)2) results in the generation of [RuII2(O)2(3,6-tBu2sq)2(btpyan)]0 (3,6-tBu2sq = 3,6-di-tert-butyl-1,2-semiquinone) due to the reduction of quinone coupled with the dissociation of the hydroxo protons. The resultant complex [RuII2(O)2(3,6-tBu2sq)2(btpyan)]0 undergoes ligand-localized oxidation at E1/2 = +0.40 V (vs Ag/AgCl) to give [RuII2(O)2(3,6-tBu2qui)2(btpyan)]2+ in MeOH solution. Furthermore, metal-localized oxidation of [RuII2(O)2(3,6-tBu2qui)2(btpyan)]2+ at Ep = +1.2 V in CF3CH2OH/ether or water gives [RuIII2(O)2(3,6-tBu2qui)2(btpyan)]4+, which catalyzes water oxidation. Controlled-potential electrolysis of [1](SbF6)2 at +1.70 V in the presence of H2O in CF3CH2OH evolves dioxygen with a current efficiency of 91% (21 turnovers). The turnover number of O2 evolution increases to 33,500 when the electrolysis is conducted in water (pH 4.0) by using a [1](SbF6)2-modified ITO electrode. On the other hand, the analogous complex [RuII2(OH)2(bpy)2(btpyan)](SbF6)2 ([2](SbF6)2) shows neither dissociation of the hydroxo protons, even in the presence of a large excess of tBuOK, nor activity for the oxidation of H2O under similar conditions.     

Synthesis of 3,6-diazahomoadamantane

Condensation of 1-phenylsulfanylpropan-2-one with 1,3,6,8-tetraazatricyclo[4.4.1.1^3,8]dodecane gave 1-phenylsulfanyl-3,6-diazahomoadamantan-9-one which was reduced to 1-phenylsulfanyl-3,6-diazahomoadamantane, and the latter was subjected to desulfurization over Raney nickel to obtain previously unknown 3,6-diazahomoadamantane. Heating of 9-phenyl-3,6-diazahomoadamantan-9-ols with Raney nickel resulted in reduction of the hydroxy group with formation of 9-phenyl-3,6-diazahomoadamantanes.     

Ag/K2S2O8-Mediated Direct Thiolation and Selenylation of Carbazoles

The first direct and selective 3,6-di-thiolation and 3,6-di-selenylation of carbazoles using diaryl disulfides/diselenide as the sulfur/selenium source were demonstrated. This simple, general, and efficient method could deliver a wide range of 3,6-di-sulfenyl-carbazoles and 3,6-di-selenyl-carbazoles from readily available starting materials with high regioselectivity in an easily-operated one-step reaction via a Ag/K₂S₂O₈-mediated protocol.     

Diastereoselective synthesis of 3,6-disubstituted 3,6-dihydropyridin-2-ones

In a short sequence, 5-vinyloxazolidin-2-ones were converted into the 3,6-disubstituted 3,6-dihydropyridin-2-ones via Pd-catalysed carbonylation and enolate alkylation with high diastereoselectivity. Alkylation of 6-substituted N-methylpyridin-2-ones gives stereoselectively the 3,6-anti diastereoisomer with MeI, BuI and i-PrI. Alkylation of the corresponding N-BOC pyridinones gives the 3,6-syn diastereoisomer with high selectivity.     

Reactions of 1,2,4,5-Tetrafluoro-3,6-bis(vinylsulfonyl)benzene with Nucleophilic Reagents Containing a Mercapto Group

Addition of 2-aminoethanethiol and 2-mercaptoethanol at both vinylsulfonyl groups of 1,2,4,5-tetrafluoro-3,6-bis(vinylsulfonyl)benzene occurs through the thiol group of the reagent and yields the corresponding 3,6-bis[2-(2-aminoethylthio)ethylsulfonyl] and 3,6-bis[2-(2-hydroxyethylthio)ethylsulfonyl] derivatives. The reaction of the title compound with 1,2-ethanedithiol leads to formation of only polymeric addition products.     

Acidity of several chromotropic acid azo derivatives

Both potentiometric and spectrophotometric methods have been used for the determination of the stability constants of hydrogen complexes of 4,5-dihydroxynaphthalene-2,7-disulphonic acid (Chromotropic Acid, CA), 3,6-bis(phenylazo)-4,5-dihydroxynaphthalene-2, 7-disulphonic acid (Azo III, A III), 3,6-bis(2'-sulphophenylazo)-4, 5-dihydroxynaphthalene-2,7-disulphonic acid (Sulphonazo III, SA III), 3,6-bis(4'-methyl-2'-sulphophenylazo)-4,5-dihydroxynaphthalene 2,7-disulphonic acid (Dimethylsulphonazo III, DMSA III), 3-(4'-chloro - 2' - phosphonophenylazo) -4,5- dihydroxynaphthalene -2,7-disulphonic acid (Chlorophosphonazo I, CPA I), 3,6-bis(4'-chloro-2'-phosphonophenylazo)-4,5-dihydroxynaphthalene-2,7-disulphonic acid (Chlorophosphonazo III, CPA III), 3-(2'-arsonophenylazo)-4, 5-dihydroxynaphthalene-2,7-disulphonic acid (Arsenazo I, AA I) and 3,6-bis(2'-arsonophenylazo)-4,5-dihydroxynaphthalene-2,7-disulphonic acid (Arsenazo III, AA III).     

The reaction of β-lactam carbenes with 3,6-dipyridyltetrazines: switch of reaction pathways by 2-pyridyl and 4-pyridyl substituents of tetrazines

The reactions of β-lactam carbenes with both 3,6-di(2-pyridyl)tetrazine and 3,6-di(4-pyridyl)tetrazine were studied. It was found that β-lactam carbenes reacted with 3,6-di(2-pyridyl)tetrazine to produce 5-triazolo[1,5-a]pyridylpyrrol-2-ones in good yields, while with 3,6-di(4-pyridyl)tetrazine, they afforded pyrido[c]cyclopenta[b]pyrrol-2-ones in moderate yields. Both reactions were proposed to follow cascade mechanisms containing a 3,6a-dipyridylpyrrolo[3,2-c]pyrazol-5-one intermediate. The different pathways of the transformation of pyrrolo[3,2-c]pyrazol-5-ones were switched by the 2- and 4-pyridyl substituents. This work not only provided a simple and efficient strategy for the construction of novel triazolo[1,5-a]pyridine and pyrido[c]cyclopenta[b]pyrrole derivatives, respectively, but also revealed two different thermal transformation patterns of 3H-pyrazole compounds.     

Electronic structures of tris(dioxolene)chromium and tris(dithiolene)chromium complexes of the electron-transfer series [Cr(dioxolene)(3)](z) and [Cr(dithiolene)(3)](z) (z = 0, 1-, 2-, 3-). A combined experimental and density functional theoretical study

From the reaction mixture of 3,6-di-tert-butylcatechol, H2[3,6L(cat)], [CrCl3(thf)3], and NEt3 in CH3CN in the presence of air, the neutral complex [CrIII(3,6L*(sq))3] (S = 0) (1) was isolated. Reduction of 1 with [Co(Cp)2] in CH2Cl2 yielded microcrystals of [Co(Cp)2][CrIII(3,6L*(sq))2(3,6L(cat))] (S = 1/2) (2) where (3,6L*(sq)(1-) is the pi-radical monoanionic o-semiquinonate of the catecholate dianion (3,6Lcat)(2-). Electrochemistry demonstrated that both species are members of the electron-transfer series [Cr(3,6LO,O)]z (z = 0, 1-, 2-, 3-). The corresponding tris(benzo-1,2-dithiolato)chromium complex [N(n-Bu)4][CrIII(3,5L*S,S)2(3,5LS,S)] (S = 1/2) (3) has also been isolated; (3,5LS,S)(2-) represents the closed-shell dianion 3,5-di-tert-butylbenzene-1,2-dithiolate(2-), and (3,5L*S,S)(1-) is its monoanionic pi radical. Complex 3 is a member of the electron-transfer series [Cr(3,5L(S,S))3]z (z = 0, 1-, 2-, 3-). It is shown by Cr K-edge and S K-edge X-ray absorption, UV-vis, and EPR spectroscopies, as well as X-ray crystallography, of 1 and 3 that the oxidation state of the central Cr ion in each member of both electron-transfer series remains the same (+III) and that all redox processes are ligand-based. These experimental results have been corroborated by broken symmetry density functional theoretical calculations by using the B3LYP functional.     

Redox reactions involving the indium(III) catecholate complexes

Indium catecholate complexes 3,6-CatInR (3,6-Cat is the 3,6-di-tert-butyl-o-benzoquinone dianion (3,6-Q), R = Me (I) and Et (II)) are synthesized by the exchange reaction between RInI₂ and thallium catecholate 3,6-CatTl₂. Compounds I and II are trimeric in both the solution and crystalline state. The oxidation of compound I and earlier described complex [3,6-CatInI(THF)]₂ (THF is tetrahydrofuran) by various substrates (iodine, 3,6-Q, and tetramethylthiuram disulfide) is studied. Different indium(III) o-semiquinone complexes are the reaction products, depending on the reaction conditions.     

Stereodivergent synthesis of new amino sugars, furanodictines A and B, starting from d-glucuronolactone

An efficient and divergent strategy for the total synthesis of the first 3,6-dihydroaminosugars, furanodictines A (2-acetamido-3,6-anhydro-2-deoxy-5-O-isovaleryl-d-glucofuranose) and B (2-acetamido-3,6-anhydro-2-deoxy-5-O-isovaleryl-d-mannofuranose), has been developed. The synthetic process is featured by readily accessible and stereodefined manipulation of highly functionalized bicyclic tetrahydrofuran derivatives incorporating the glucuronolactone (common starting material)-derived skeleton.     

Total synthesis of cucurbitaxanthin A, cycloviolaxanthin and capsanthin 3,6-epoxide by applying a regioselective ring opening of tetrasubstituted epoxides

The synthesis of 3,6-epoxy carotenoids cucurbitaxanthin A 1, cycloviolaxanthin 2 and capsanthin 3,6-epoxide 3, was accomplished via the C(15)-3,6-epoxides 20e and 20f, prepared by the regioselective ring opening of the 3-hydroxy-5,6-epoxides 10e and 10f.     

3,6-二脱氧达格列净的合成及其降血糖活性研究

利用达格列净作为原料经过两条路线合成了3,6-二脱氧达格列净,其3,6-二脱氧的位置进一步经过了NOE技术确认,体外h SGLT2抑制试验和大鼠尿糖排泄试验表明,所合成的3,6-二脱氧达格列净几乎没有SGLT2抑制活性,说明SGLT2抑制剂结构中葡萄糖片段上3-OH和6-OH同时脱除会导致SGLT2抑制剂完全丧失活性。     

Synthesis of 1-benzyl-3,6-diazahomoadamantane

By condensation of 4-phenylbutan-2-one with tetramethylenediethylenetetramine 1-benzyl-3,6-diazahomoadamantan-9-one was synthesized. Further nitration of 1-benzyl-3,6-diazahomoadamantan-9-one yielded 1-(4-nitrobenzyl)-3,6-dia?ahomoadamantan-9-one. The modification of the nitro and carbonyl groups resulted in the formation of 1-benzyl-3,6-diazahomoadamantane and its derivatives with functional groups in the benzene ring and at the bridge carbon atom C⁹.