Homologues of N-heterocyclic carbenes: Detection and electronic structure of N-bridgehead pyrido[a]-anellated 1,3,2-diazagermol-2-ylidenes

Novel N-bridgehead pyrido[a]-anellated 1,3,2-diazagermol-2-ylidenes 1a,b were obtained from GeCl₂ · dioxane and dilithium reagents formed from N-tert-butyl pyridine-2-aldimines and excess lithium in THF whereas attempts to generate the analogous silylene by reduction of the dichloro-pyrido[a]-1,3,2-diazasilole 4a, synthesized from SiCl₄ and the new dilithium reagent, failed. Characteristic chemical shifts of the pyrido ¹H and ¹³C nuclei between those of pyridine compounds and the not fully cyclodelocalized electron-rich 4a with dihydropyridine substructure hint to a cyclodelocalized 10π electron system in 1a,b. Quantum chemical investigations of a series of pyrido[a]- and benzo-anellated imidazol-2-ylidenes and their silylene and germylene homologues show for all compounds cyclodelocalized 10π-systems but for pyrido[a]-anellation an increase of the energy of the π-MO’s relative to those of element(II) lone electron pairs which leads to destabilization compared to the benzo-anellated isomers.     

1-氮杂环-2-(6-甲氧基萘-2-基)丙-2-醇的合成、表征与生物活性

6-甲氧基-2-萘基乙酮经硫酸单酯三甲锍环氧化和氮杂环开环反应, 合成了4种新的唑类化合物. 目标物经核磁共振和MS测定其结构; 分析目标物中萘环质子偶合分裂情况, 并确定萘环上各质子的归属. 生物活性测试结果表明, 部分新化合物具有杀菌活性.     

Investigation of the regioselectivity of the Hurd-Mori reaction for the formation of bicyclic 1,2,3-thiadiazoles

A series of new pyrrolo[d][1,2,3]thiadiazole carboxylates and 5,6-dihydro-4H-cyclopenta[d][1,2,3]thiadiazoles has been synthesized via the Hurd-Mori reaction. The regioselectivity of the cyclization has been studied and trends were established to predict the cyclization direction to afford bicyclic 1,2,3-thiadiazoles. Effects promoting and disfavoring the reaction have also been investigated to guide the synthesis of scaffolds of this type.     

N-杂环油酰胺、亚油酰胺的合成及抑菌活性测定

采用具有天然活性的植物源成分油酸、亚油酸为先导化合物,经过酰氯化、酰胺化,引入高活性的含氮杂环,合成了7个新化合物,经核磁共振氢谱、红外光谱和元素分析测定,确认了新化合物的结构.初步进行了防治中草药半夏、太子参病害的抑菌活性测试.结果表明,部分化合物对半夏枯萎病、太子参轮纹病有一定的抑菌活性.     

几个新型含氟化合物的合成

以3-硝基-4-氯三氟甲苯(1)为起始原料, 合成了新型含氟杂环化合物8和3个含氟中间体4, 5, 6. 通过IR, NMR, MS和元素分析对它们的结构进行了表征. 探讨了反应条件对产物结构的影响, 提出了化合物4可能的形成机理.     

Synthesis of 2-methoxy-6-oxo-1, 4, 2-diazaphosphorinane-2-oxide, A New Potential Antitumor Phosphorus Heterocycle Compound

The discoveries that the bisdioxopiperazines ICal- 154', ICal-- 159(razoxane)' and MST16(sobuzoxan)' are inhibitors of mammalian DNA topoisomerase II'-', have led to arenewed interest in these compounds as antitumor agents'. Among the drugs, MST-16(sobuzoxan) was approved in Japan (in 1994) as a potent antit'Umor agent for treatmentof adult T-cell leukemia and malignant lymphoma'. However, the bisdioxopiperazinesexhibited extremely small water-solubility, which reduced its absorption in…     

Design and Synthesis of Novel 5-Sulfoxide-substituted Pyrazolo[5,1-d] [1,2,3,5]tetrazin-4（3H）ones

A series of novel 5-sulfoxide-substituted pyrazolo[5,1-d] [1,2,3,5]tetrazin-4（3H）ones 4a-j were designed and efficiently synthesized via a diazotization of 5-amine-3-methylsulfinyl- 1H-pyrazole, followed by cycloaddition with aryl isocyanate. A possible reaction mechanism is outlined and discussed. These new compounds exhibit some biological activity as preliminary bioassay indicated. Their structures were confirmed with ^1H NMR, IR and elemental analysis.     

[2+4] vs [4+2] Cycloaddition reactions of o-thioquinones with 1,3-dienes

Under kinetic control, the reaction of o-thioquinones with acyclic 1,3-dienes afforded, as main products, the spiro cycloadducts deriving from the participation of the thiones as dienophiles. Under thermodynamic control, or with cyclic dienes, the thioquinones behave as hetero dienes to give the benzoxathiin derivatives with complete regioselectivity.     

Cu-assisted C–N bond formations in six-membered N-heterocycle synthesis

Abstract

One of the highly emerging and important aspect of organic chemistry is the metal-catalyzed synthesis of the heterocycles. The methodologies used earlier for its synthesis were less approachable to the organic chemist because of their high cost, highly specified instrumentation and inconvenient methods. For both the stereoselective and regioselective synthesis of six-membered nitrogen-containing heterocycles, cyclic reactions that are Cu-catalyzed have known to be very efficient. The presented review covers the varied applications of Cu as a catalyst and its importance in the formation of six-membered nitrogen-containing heterocycles. The fascinating research that has been done in this area is also enclosed in this review.     

Stereochemistry of eight-membered heterocycles. 4. Dipole moments of cyclic acetals with two planar fragments

An additive system of polarities in 12H-dibenzo(dinaphtho)[d,g][1,3]dioxocins is proposed, and alkyl—oxygen and phenyl—oxygen group dipole moments in these compounds were determined. The stereospecific relation of the polarity of the C _sp 2-O bond to the mutual orientation of p orbitals of unshared electron pairs of oxygen atoms and orbitals of the aromatic ring is shown.A. N. Butlerov Scientific-Research Chemical Institute, V. I. Ul'yanov-Lenin Kazan State University, Kazan 420008. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 607–612, March, 1992.