The demethylation chemistry of 3-substituted 2-methoxypyridines

Upon acylation of 3-amino-2-methoxypyridines, two side products were discovered, a pyridone, 5,6 , and 8 , and a pyridyloxazine, 4 and 9. The ratios of these products can be affected by changes in the reaction parameters. When oxalyl chloride was the acylating agent a pyridone 13 was isolated.     

Zinc Hydrogen Ortho Arsenate Trihydrate,ZnHAsO4 · 3 H2O

Zinc hydrogen ortho arsenate trihydrate, ZnHAsO₄ · 3 H₂O has been studied by static isothermal dehydration, X-ray powder diffraction, and infra-red absorption spectral techniques. The results of these studies clearly indicate that the compound is to be formulated as zinc hydroxide dihydrogen ortho arsenate dihydrate, Zn(OH)(H₂ASO₄) · 2 H₂O.     

Platinum(II) complexes of 2-, 3-, and 4-formyl-pyridine thiosemicarbazone and 2-, 3- and 4-acetyl-pyridine thiosemicarbazone

Seven platinum(II) complexes isolated from thiosemicarbazones derived from 2-, 3- and 4-formylpyridine and 2-, 3-, and 4-acetylpyridine have been characterised by microanalyses, molar conductivities and by their i.r. and ¹H-n.m.r. spectra.     

Syntheses of 1-, 2-, 3- and 4-acridinecarbaldehydes

The four acridinecarbaldehydes, namely, acridine-1-carbaldehyde, acridine-2-carbaldehyde, acridine-3-carbaldehyde, and acridine-4-carbaldehyde have been synthesized for the first time.     

A proton NMR analysis of the OCH3 group conformation in 2-methoxypyridines

The absence of H? H couplings between the methoxy group and the ring protons observed in 2-methoxy-, 2,6-dimethoxy- and 2-methoxy-6-chloropyridines is interpreted in terms of a cis conformation between the methyl fragment and the nitrogen ring atom. Other data, taken from the current literature, support this conclusion.     

Pyridine-substituted hydroxythiophenes. IV. Preparation of 3- and 4-(2-, 3- and 4-pyridyl)-2-hydroxythiophenes

3-(2-, 3- and 4-Pyridyl)-2-methoxythiophenes have been prepared in good yields through the Pd(0)-cat-alyzed coupling of the three isomeric bromopyridines with 3-trimethylstannyl-2-methoxythiophene. This compound was prepared through halogen-metal exchange of 3-bromo-2-methoxythiophene followed by stannylation. 3-Bromo-2-methoxythiophene was prepared by dibromination and α-debromination of 2-methoxythiophen. Most attempts to demethylate 2-methoxy-3-pyridylthiophenes using a large variety of reagents failed, probably due to the instability and high reactivity of the desired 3-pyridyl-2-hydroxythiophene systems. Only 2-methoxy-3-(3-pyridyl)thiophene reacted with boron tribromide to give 3-(3-pyridyl)-3-thiolene-2-one, which only was stable in ether solution at ?20°. The attempted demethylation of 2-methoxy-3-(2-pyridyl)thiophene with trimethylsilane chloride/sodium iodide in refluxing acetonitrile led to a dimer. Demethylation of the 2-methoxy-3-pyridylthiophenes with dibenzyl diselenide and sodium borohydride gave 3-pyridylthiophan-2-ones. A number of other routes to prepare 3-pyridyl-2-hydroxythiophenes were also explored, but none of them gave the desired compounds. On the other hand, the 4-(2-, 3-, and 4-pyridyl)-2-hydroxythiophene systems could easily be prepared by hydrogen peroxide oxidation of the corresponding 4-pyridyl-2-thiopheneboronic esters, which were obtained from 2-bromo-4-pyridylthiophenes by halogen-metal exchange followed by reaction with ethyl borate. The 2-bromo-4-pyridylthiophenes were prepared by dibromination of the known 3-pyridylthiophenes to the 2,5-dibromo derivatives, and removal of the 2-bromine by halogen-metal exchange at ?100°, followed by hydrolysis. The ¹H nmr and ir spectroscopic investigations show that these quite stable 2-hydroxythiophene systems exist exclusively in the 4-pyridyl-3-thiolen-2-one forms.     

Ortho effects in 3-methyl-5-(o-r-styryl)-4-aminoisoxazoles on electron impact. III

Electron impact mass spectra of eight of the title compounds are discussed. Based on our data a mechanism for the formation of the m/e 91 ion is proposed. Fragmentation pathways have been confirmed by measurement of the metastable peaks.     

The preparation of synthetically useful carbonyl-protected δ- and -lithio ketones via reductive lithiation

The aromatic radical-anion induced reductive lithiation of the acetals or thioacetals of δ- and -(phenylthio)ketones provides δ- and -lithioketone equivalents. Primary and tertiary organolithiums have been generated and the ketone function may be part of a ring. The major synthetic use demonstrated in this report is the conversion to mixed heterocuprates which react with acyl chlorides to yield mono-protected 1,6- or 1,7-diketones. The cuprates also undergo conjugate addition to enones.     

Trimethylstannyllithium mediated synthesis of 2-, 3- and 4-trimethylstannylcyclohexanols

The use of trimethylstannyllithium for the preparation of 2-, 3- and 4- trimethylstannylcyclohexanols is described. The stereochemistries of these products are discussed on the basis of the ¹H, ¹³C, and ¹¹⁹Sn NMR data.     

Studies on the preparation of 3,4-disubstituted 2-methoxypyridines

The synthesis of 2-methoxy-4-methylpyridine-3-carbonitrile (3) and its conversion, by way of alkylation of the C(4) methyl group, into the pyrodyl acetic acid ester 6 is described.     

3-(2'-苯基-1', 2', 3'-连三唑-4'-基)-6-烷基/芳基-均三唑并[3, 4-b]-1, 3, 4-噻二唑的合成

研究了3-(2'-苯基-1', 2', 3'-连三唑-4'-基)-4-氨基-5-巯基-1, 2, 4-三唑(1)与取代苯甲酸和脂肪酸(2a-r)在POCl3催化下的反应, 共合成得到18个新的3-(2'-苯基-1', 2', 3'-连三唑-4'-基)-6-烷基/芳基-均三唑并[3, 4-b]-1, 3, 4-噻二唑(3a-r), 经元素分析,IR, 1H NMR和MS进行了结构确证。     

Synthesis and Phosphorylation of 2-, 3-, and 4-Halomethyl-5-tert-butylfurans

Synthetic methods for preparing of 2-, 3-, 4-halomethyl-5-tert-butylfurans are developed. Itwas established that the bromination of 3- and 4-methyl-2-tert-butylfurans with N-bromosuccinimide proceedsmainly at the free -position of the furan ring, and not at the methyl group. Therefore, the target halomethyl- furans were prepared through the corresponding 3- and 4-methoxymethyl derivatives. The obtained five products were phosphorylated with sodium diethyl phosphite under the conditions of the Michaelis-Becker reaction to give the corresponding phosphonates.     

Synthesis, Structure and Photoluminescence of(CH3-4, 4'-H2bipy)-(HgCl4)with CH3-4, 4'-H2bipy Generated in Situ

A novel viologen(4,4'bipyridinium)-based complex(CH3-4,4'-H2bipy)(HgCl4)(1),in which the CH3-4,4'-H2bipy(MQ2+)was generated in situ,has been synthesized via hydrothermal reaction and structurally characterized.Complex 1 crystallizes in the space group P21/c of monoclinic system with four formula units in a cell:a = 8.1848(6),b = 21.809(2),c = 9.0285(6)(A),β =.107.377(1)°,V= 1538.0(2)(A)3,C11H11Cl4HgN2,Mr = 513.61,Dc = 2.218 g/cm3,S = 1.009,μ(MoKα)= 10.685 mm-1,F(000)= 956,R = 0.0360 and wR = 0.0812.The crystal structure analysis reveals that the title complex features an isolated structure based on a CH3-4,4'-H2bipy moiety and a mercury atom terminally bound by four chlorine atoms.Photoluminescence investigation reveals a strong emission in blue region,which may originate from π→π* charge-transfer interaction of the CH3-4,4'-H2bipy moiety.     

3-烷基/芳基-6-(2', 4'-二氯苯基)-7H-1, 2, 4-三唑[3, 4-b]- 1, 3, 4-噻二 嗪的合成及波谱性质

以间二氯苯与氯乙酰氯反应,生成ω-氯代-2,4-二氯苯乙酮(1),再使之分别与3-烷基/芳基-4-氨基-5-巯基-1,2,4-三唑(2a～2l)反应,合成了12种新的3-烷基/芳基-6-(2',4'-二氯苯基)-7H-1,2,4-三唑并[3,4-b]1,3,4-噻二嗪(4a～4l)。利用EA,IR,^1HNMR确定了其结构,并提出该反应的可能机制。     

3-[(5-取代硫基)-4H-1,2,4-三唑-3-基]苯并吡喃-2-酮的合成与抑菌活性

为寻找具有杀菌活性的三唑类先导化合物,采用活性亚结构拼接方法,将香豆素环和硫醚结构单元引入到三唑类化合物分子中,合成一系列未见文献报道的新型含香豆素环和硫醚结构的三唑类衍生物。经~1H NMR、~(13)C NMR、IR、MS和元素分析对所合成化合物的结构进行了表征。初步生物活性测试表明,部分目标化合物在试验浓度下具有一定的抑菌活性。     

Oxidation and nitrosation of 4-(3-alkylureido)-2, 2, 6, 6-tetramethylpiperidine-1-oxyls to 4-(3-alkyl-3-nitrosoureido)-2, 2, 6, 6-tetramethyl-1-oxopiperidinium salts

4-(3-Alkylureido)-2, 2, 6, 6-tetramethylpiperidine-1-oxyls are rapidly oxidized by N₂O₄ or NOCl to 4-(3-alkylureido)-2, 2, 6, 6-tetramethyl-1-oxopiperidinium nitrates and chlorides, which are then nitrosated to 4-(3-alkyl-3-nitrosoureido)-2, 2, 6, 6-tetramethyl-1-oxopiperidinium salts. The perchlorates of the latter were prepared by an exchange reaction with HClO₄. The nitrosation of alkylureidooxoammonium salts is the first example of chemical modification of oxoammonium derivatives in which the highly reactive >N⁺=O group is inert toward the reagent.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 542–547, March, 1993.