An investigation of oxidative animation of 2-methyl-1,4-benzoquinone with pyrrolidine

Oxidative amination of 2-methyl-1,4-benzoquinone with pyrrolidine yielded 2-methyl-6-pyrrolidino-1,4-benzoquinone as the major product along with 2-methyl-5-pyrrolidino-1,4-benzoquinone formed as the minor product. No detectable amount of 2-methyl-3,6-bis-(pyrrolidino)-1,4-benzoquinone was observed.     

The 1,4-cyclohexanedione-bromate-acid oscillatory system I. Its organic chemistry

The organic chemistry of the 1,4-cyclohexanedione (CHD)-bromate-sulfuric acid oscillatory system has been revealed by following the reaction of 1,4-CHD with bromate using a GC/MS technique. We could identify 1,4-dihydroxybenzene as an intermediate, 1,4-benzoquinone as the main oxidation, and mono- and dibromocyclohexanedione as the main bromination products. Acid bromate does not cleave the alicyclic ring.     

Coordination chemistry of 1,4-bis-carboxymethylcyclam, H(2)(1,4-bcc)

Zinc metal reduction of the cobalt(III) complex [Co(1,4-bcc)](+) (1,4-bcc = 1,4-bis-carboxymethylcyclam) produces the corresponding cobalt(II) complex which crystallises as the coordination polymer {[Co(1,4-bcc)]ZnCl(2)}(n). A method has been developed for removal of the cobalt(III) ion from [Co(1,4-bcc)](+) and isolation of the free ligand as its hydrochloride salt, H(2)(1,4-bcc).4HCl. This has been used for the preparation of new metal complexes, and the syntheses and characterisation of the copper(ii), nickel(ii), zinc(ii) and chromium(iii) complexes containing the 1,4-bcc ligand are described. X-Ray crystal structures of {[Co(1,4-bcc)]ZnCl(2)}(n).2.5H(2)O, {[Cu(1,4-bcc)]CuCl(2)}(n).0.25MeOH.H(2)O and [Cu(1,4-bcc)H]ClO(4) show the complexes to have the trans(O) geometry of the 1,4-bcc ligand, while the structure of [Cr(1,4-bcc)H(0.5)](ClO(4))(1.5).EtOH exhibits the cis(O) configuration.     

Etude structurale du polypentadiene-1,3 par spectrometrie de RMN du 13C

The structure of stereoregular polymers of 1,3-pentadiene was determined by ¹³C-NMR spectroscopy at 22.6 MHz. Not only was it possible to distinguish between cis-1,4 and trans-1,4 but also between isotactic and syndiotactic cis-1,4 structures. Triad effects were detected in the trans-1,2 syndiotactic polypentadiene; 1,4–1,2 as well as 1,4–4,1 linkages were observed.     

Stereochemistry of cyclobutanone resulted from cycloadditions of t-butylcyanoketene to bicyclo[2.2.1]heptene derivatives, as evidence for a π2s+π2a reaction mode

The stereochemistry of the cyclobutanones 1-7, resulted from the reaction of t-butylcyanoketene with bicyclo[2.2.1]heptene, bicyclo[2.2.1]heptadiene, 1,4 - dihydro - 1,4 - methanonaphthalene, 1,4 - dihydro - 9 - (1 - methylethylidene) - 1,4 - methanonaphthalene, 1,4 - dihydro - 1,4 - epoxynaphthalene, l,4,4a,8b - tetrahydro - 1,4 - methanobiphenylene (l,4,4a,8b) and 1,4,4a,8b - tetrahydro - 1,4 - methanobiphenylene(1,4,4aβ,8bβ) was established as having the cyclobutanone ring exo and the t-Bu group in the configuration. These findings represent a stereochemical argument in favour of a _π2_s + _π2_a reaction mode of t-butylcyanoketene to the above mentioned bicyclo[2.2.1]heptene derivatives. Observations regarding preservation of the original configurations of alkenes as well as the geometrical distorsion of the cyclobutanones are shortly discussed.     

Thermotropic copolyesters. II. Synthesis and characterization of copolyesters containing the bicyclo[2.2.2]oct-2-ene mesogenic unit

Random copolyesters based on 1,4-benzenedimethanol, trans-1,4-cyclohexanedimethanol, and 1,4-bicyclo[2.2.2]octanedimethanol as spacers in ratios of 2 : 3 of the mesogenic group, bicyclo[2.2.2]oct-2-ene-1,4-diol were prepared and characterized. The copolyesters containing the 1,4-benzenedimethanol moiety formed a more brightly colored birefringent fluid in the melt.     

一种简便合成2-丁炔-1,4-二醇衍生物的新方法

由2-丁炔-1,4-二醇可以很方便地得到2-丁炔-1,4-二氯,这一试剂在有机合成中有着广泛的应用。而在其它条件相同的情况下,制备2-丁炔-1,4-二溴并未得到相应较好的结果。我们用无水苯为反应溶剂,以温和的 (PPh3)PBr2作为卤代试剂(冰浴下液溴逐滴滴入PPh3苯溶剂中当场生成)卤化2-丁炔-1,4-二醇,选择性合成得到2-丁炔-1,4-二溴衍生物。同时也实现了2-丁炔-1,4-二醋酸酯的合成。     

Oxidation of 2-Chloro-1-phenylethane-1,1-dithiol

Oxidation of 2-chloro-1-phenylethane-1,1-dithiol with bromine, iodine, and elemental sulfur, as well as under UV irradiation, leads to formation of 1,4-bis(chloromethyl)-1,4-diphenyl-2,3,5,6-tetrathiane in 50–95% yield. Oxidation of the same substrate with selenium dioxide gives 1,5-bis(chloromethyl)-1,5-diphenyl-2,4-dithia-3-selenapentane-1,5-dithiol. On heating to 60°C, the latter loses selenium to afford 1,4-bis-(chloromethyl)-1,4-diphenyl-2,3-dithiabutane-1,4-dithiol.     

The Versatile Chemistry of 1,4-Diazines: Organic,Inorganic and Biochemical Aspects

In chemical research attention is increasingly being focussed on composite “complex” systems with special properties and functions. As components of such systems 1,4-diazines are steadily gaining in popularity. Here, 1,4-diazines means pyrazine and its derivatives as well as compounds with partial pyrazine structure; examples are quinoxaline, phenazine, pteridine, flavin and their derivatives. All these compounds are characterized by a low lying unoccupied π-molecular orbital and by the ability to act as bridging ligand. Due to these two properties 1,4-diazines, and especially their parent compound pyrazine, possess a characteristic reactivity. 1,4-Diazines may be employed to study inter- and intramolecular electron transfer in organic, inorganic and biochemical reactions. In the redox system of 1,4-diazines the paramagnetic 7π-electron intermediate exhibits exceptional stability, whereas the 1,4-dihydro-1,4-diazines with 8π-electrons in a six-membered ring are not generally accessible due to their potential antiaromaticity and their large excess of π electrons. Its inherent bifunctionality and the low lying unoccupied molecular orbital permit pyrazine to form coordination polymers having unusual electrical and magnetic properties. Finally, the phenomena observed for pyrazines may be used in the interpretation of the reactivity of naturally occurring 1,4-diazines, such as flavins and bioluminescent natural products.     

Hydride abstraction in positive-ion electrospray interface: oxidation of 1,4-dihydropyridines in electrospray ionization mass spectrometry

During the positive-ion mode electrospray ionization mass spectrometry analysis of 1,4-diphenyl-3-benzoyl-1,4-dihydropyridines with methanol as the solvent, the major ion generated is one mass unit lower than the analyte, which can be rationalized as the oxidative aromatization of 1,4-dihydropyridines to pyridine cations.     

A New Route for the Synthesis of 1,4-Dicarbonyl Compounds: Synthesis of Jasmone,Dlhydrojasmone and a Prostaglandin Intermediate

1,4-Dicarbonyl compounds are versatile intermediates for the synthesis of a variety of natural products such as jasmonoids, prostanoids, steroids and terpenoids having a cyclopentenone or furan ring system. Although many synthetic routes for the preparation of these compounds are known and continue to appear¹, most of the existing methods involve lengthy procedures and are limited to the synthesis of 1,4-diketones. Herein, we report a convenient three step approach for the synthesis of 1,4-dicarbonyl compounds starting from tosyl methyl isocyanide² (TosMIC). This method is general for the preparation of 1,4-ketoaldehydes as well as 1,4-diketones.     

Potent competitive inhibition of α-galactosidase and α-glucosidase activity by 1,4-dideoxy-1,4-iminopentitols: syntheses of 1,4-dideoxy-1,4-imino-d-lyxitol and of both enantiomers of 1,4-dideoxy-1,4-iminoarabinitol

The syntheses of 1,4-dideoxy-1,4-imino-D-lyxitol (3), 1,4-dideoxy-1,4-imino-d-arabinitol (4) and 1,4-dideoxy-1,4-imino-l-arabinitol (5) are reported; (3) is a potent competitive inhibitor of α-galactosidase (green coffee beans) and (4) a competitive inhibitor of α-glucosidase (Brewer's yeast) suggesting that iminopentitols have considerable potential as glycosidase inhibitors. (4) was found to be identical to an alkaloid recently isolated from $\text{Angylocalyx boutiqueanus}$.     

Molecular level model for the agonist/antagonist selectivity of the 1,4-dihydropyridine calcium channel receptor

Summary Crystal structures of the 1,4-dihydropyridine (1,4-DHP) calcium channel activators Bay K 8643 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(3-nitrophenyl)-pyridine-5-carboxylate], Bay O 8495 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(3-trifluoromethylphenyl)-pyridine-5-carboxylate], and Bay O 9507 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(4-nitrophenyl)-pyridine-5-carboxylate] were determined. The conformations of the 1,4-DHP rings of these activator analogues of Bay K 8644 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-pyridine-5- carboxylate] do not suggest that their activator properties are as strongly correlated with the degree of 1,4-DHP ring flattening as was indicated for members of the corresponding antagonist series. The solid state hydrogen bonding of the N(1)-H groups of the activators is not, unlike that of their antagonist counterparts, to acceptors that are directly in line with the donor. Rather, acceptor groups are positioned within ± 60 degrees of the N(1)-H bond in the vertical plane of the 1,4-DHP ring. Previously determined structure-activity relationships have indicated the importance of this N(1)-H group to the activity of the 1,4-DHP antagonists. Based on these observations, a model is advanced to describe the 1,4-DHP binding site of the voltage-gated Ca²⁺ channel and its ability to accommodate both antagonist and activator ligands.     

The acid catalysed reaction of 1,4-diketones with hydrogen sulphide : A convenient route to substituted thiophens

Various 1,4-diketones and 2-ethoxycarbonyl-1,4-diketones have been reacted with H₂S in acidic ethanol to give 2,5- or higher substituted thiophens as resulting from a spontaneous ring-closure reaction of initially formed sulphur analogues of the starting diketones. In some the corresponding 2-mercapto-2,3-dihydrothiophens and/or 2,5-dimercaptotetrahydrothiophens were formed as by-products. 1,4-Diphenyl-1,4-diketones behaved exceptionally under similar reaction conditions yielding preferentially 2,5-diphenylfurans.     

Lamellar and three-dimensional hybrid compounds formed by cyclohexene- and cyclohexanedicarboxylates of Pb, La, and Cd

To establish factors that determine the formation of three-dimensional hybrid structures of metal dicarboxylates involving metal-oxygen-metal linkages, we have investigated metal dicarboxylates derived from 1,2-cyclohexene as well as 1,2-, 1,3-, and 1,4-cyclohexane dicarboxylic acids. Thus, we have synthesized a 1,2-cyclohexenedicarboxylate of Cd, [Cd(1,2-CHeDC)(H2O)] (I), a 1,2-cyclohexanedicarboxylate of Pb, [Pb(1,2-CHDC)] (II), and three 1,4-cyclohexanedicarboxylates of La [La2(1,4-CHDC)3(H2O)4] (III), [La3(1,4-HCHDC)2(1,4-CHDC)5(H2O)2].H2O (IV) and [La2(1,4-CHDC)3(H2O)].2.5 H2O (V) under hydrothermal conditions and determined their structures. A mixed dicarboxylate involving both 1,3- and 1,4-cyclohexenedicarboxylates of Pb, [Pb3O(1,3-CHDC)(1,4-CHDC)].0.5 H2O (VI) and a 1,4-cyclohexanedicarboxylate of Pb, [Pb(6)O(2)(1,4-CHDC)3(1,4-HCHDC)2], have also been synthesized and characterized. While the 1,2-dicarboxylates have layered structures, the 1,4-dicarboxylates and the mixed dicarboxylates possess three-dimensional structures. Interestingly, both the 1,2 and 1,4-dicarboxylates are true hybrid compounds composed of infinite M-O-M linkages. The equatorial-equatorial (e,e) conformation is adopted commonly in all these compounds, although less stable conformations are encountered occasionally. The formation of the layered and the three-dimensional structures can be understood based on the relative disposition of the two carboxylic groups, the 1,4-isomer favoring the three-dimensional structure. Based on the results of the present study along with the available literature, we conclude that in order to obtain three-dimensional hybrid structures with metal-oxygen-metal networks, it appears necessary to make use of the 1,4-cyclohexanedicarboxylic acid.     

A versatile approach to N-alkylated 1,4-dideoxy-1,4-imino-D-arabinitols and 1,4-dideoxy-1,4-imino-L-xylitols

A versatile and concise synthesis of N-alkylated 1,4-dideoxy-1,4-imino-D-arabinitol and 1,4-dideoxy-1,4-imino-L-xylitol derivatives is described. These were prepared using pseudohemiketal lactams as key intermediates, which in turn were obtained from sucrose. The key intermediates were prepared by a diastereospecific tandem reaction which facilitated the introduction of various substituents on the nitrogen atom of the iminosugars.     

Simons electrochemical fluorination of substituted homopiperazines(hexahydro-1,4-diazepines) and piperazines

Simons electrochemical fluorination (ECF) of 1,4-dimethyl-1,4-homopiperazine, methyl 4-ethylhomopiperazin-1-ylacetate and 1,4-bis(methoxycarbonylmethyl)-1,4-homopiperazine was studied. For comparison, ECF of three piperazines with a N-(methoxycarbonylmethyl) group(s) was also studied. ECF of 1,4-dimethyl-1,4-homopiperazine gave a low yield of corresponding perfluoro(1,4-dimethyl-1,4-homopiperazine) together with perfluoro(2,6-diaza-2,6-dimethylheptane) as the major product. Corresponding perfluoro(homopiperazines) with mono- and/or di-(fluorocarbonyldifluoromethyl) groups [CF₂C(O)F] at the 1- and/or 4-position were formed in low yields from methyl 4-ethylhomopiperazin-1-ylacetate and 1,4-bis(methoxycarbonylmethyl)-1,4-homopiperazine, respectively. These new seven-membered perfluoro(1,4-dialkyl-1,4-homopiperazines) were accompanied by the formation of mono- and/or di-basic linear perfluoroacid fluorides resulting from the CC bond scission at the 2- and 3-positions of the ring. From mono- and/or di-N-(methoxycarbonylmethyl)-substituted piperazines, corresponding perfluoropeperazines having the acid fluoride group(s) were formed in low yields.     

1,4-disubstituted pyridazino[4,5-d] pyridazines

1,4-Bis(methyIthio)pyridazino[4,5-d]pyridazine (IV) was synthesized from 4,5-pyridazinedi-carboxylic acid in three steps. By employing IV as an intermediate, various 1,4-disubstituted pyridazino[4,5-d]pyridazine derivatives of classes 1,4-N,S; 1,4-N,O; 1,4-O,S; and 1,4-O,O were prepared by one-step or two-step nucleophilic substitution reactions. Steric, polar and resonance effects were observed in some of these reactions and are discussed.     

A divergent approach for the synthesis of some polyhydroxy pyrrolidines and piperidines from ribosylamine

A simple and efficient synthesis of 1,4-dideoxy-1,4-imino-d-ribitol, 1,4-dideoxy-1,4-imino-l-lyxitol, N-benzyl derivative of d-ribitol, 3,4,5-trihydroxy-piperidine, l-4-epi-isofagomine and d-3-epi-isofagomine, which are glycosidase inhibitors has been described from the commercially available d-ribose as a starting material.     

A New Protocol to Generate Catalytically Active Species of Group 4–6 Metals by Organosilicon-Based Salt-Free Reductants

Herein, we provide a new protocol to reduce various transition-metal complexes by using organosilicon compounds in a salt-free fashion with the great advantage of generating pure low-valent metal species and metallic(0) nanoparticles, in sharp contrast to reductant-derived salt contaminants obtained by reduction with metal reductants. The organosilicon derivatives 1,4-bis(trimethylsilyl)-2,5-cyclohexadiene ( 1 a ), 1-methyl-3,6-bis(trimethylsilyl)-1,4-cyclohexadiene ( 1 b ), 1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene ( 2 a ), 2,5-dimethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene ( 2 b ), 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene ( 2 c ), and 1,1′-bis(trimethylsilyl)-1H,1′H-4,4′-bipyridinylidene ( 3 ) all served as versatile reductants for early transition-metal complexes and produced only easy-to-remove organic compounds, such as trimethylsilylated compounds and the corresponding aromatics, for example, benzene, toluene, pyrazine, and 4,4′-bipyridyl, as the byproducts. The high solubility of the reductants in organic solvents enabled us to monitor the catalytic reactions directly and to detect any catalytically active species so that we could elucidate the reaction mechanism.