TheSemmler-Wolff aromatization andSchmidt reaction applied to some pyrido[2′,3′:3,4]pyrazolo[5,1-c][1,2,4]benzotriazines

Pyrido[2,3:3,4]pyrazolo[5,1-c][1,2,4]benzotriazin-4(1H)ones were transformed via their oximes in aSemmler-Wolff aromatization process in the tetracyclic heteroaromatic amines4 or bySchmidt reaction into a mixture of the same amine4 and a ring enlarged lactam3. Syntheses of some halo pyrazolo[3,4-b]pyridines and a photochemical transformation of 3-azidopyrazolo[3,4-b]pyridine are also described.

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Über dieSemmler-Wolff- undSchmidt-Reaktion einiger Pyrido[2,3:3,4]pyrazolo[5,1-c][1,2,4]benzotriazine

Zusammenfassung Pyrido[23:3,4]pyrazolo[5,1-c][1,2,4]benzotriazin-4(1H)one werden über Oxime in einerSemmler-Wolff-Reaktion in die tetracyklischen aromatischen Amine4 umgewandelt. In einerSchmidt-Reaktion wurden dieselben Ketone in ein Gemisch aus Amin4 und Lactam3 übergeführt. Synthesen von halogensubstituierten Pyrazolo[3,4-b]pyridinen und photochemische Umwandlung von 3-Azidopyrazolo[3,4-b]pyridin werden beschrieben.

     

内分子DIELS-ALDER反应合成DRIMANE类倍半萜化合物DRIMENIN, POLYGODIAL及CINNAMOLIDE的全合成

近年来有不少报道从事于生理活性Drimane类倍半萜的合成,较多采用了分子间Diels-Alder反应来建立Drimane的骨架。本文首次采用内分子Diels-Alder反应作为关键反应合成了Drimane类化合物。同时还在引入了手性诱导基团后,首次完成了从无手性的原料化合物β-紫罗兰酮至光学活性(-)-drimenin1的不对称合成。     

Analysis of phosphorus herbicides by ion-pairing reversed-phase liquid chromatography coupled to inductively coupled plasma mass spectrometry with octapole reaction cell

A reversed phase ion-pairing high performance liquid chromatographic (RPIP-HPLC) method is developed for the separation of two phosphorus herbicides, Glufosinate and Glyphosate as well as Aminomethylphosphonic acid (AMPA), the major metabolite of Glyphosate. Tetrabutylammonium hydroxide is used as the ion-pairing reagent in conjunction with an ammonium acetate/acetic acid buffering system at pH 4.7. An inductively coupled plasma mass spectrometer (ICP-MS) is coupled to the chromatographic system to detect the herbicides at m/z = 31P. Historically, phosphorus has been recognized as one of the elements difficult to analyze in argon plasma. This is due to its relatively high ionization potential (10.5 eV) as well as the inherent presence of the polyatomic interferences 14N16O1H+ and 15N16O+ overlapping its only isotope at m/z = 31. An octapole reaction cell is utilized to minimize the isobaric polyatomic interferences and to obtain the highest signal-to-background ratio. Detection limits were found to be in the low ppt range (25-32 ng/l). The developed method is successfully applied to the analysis of water samples collected from the Ohio River and spiked with a standard compounds at a level of 20 microg/l.     

Copper-catalyzed dimerization of chromium Fischer carbene complexes: synthesis of dialkoxytrienes and their Nazarov-type cyclization to 2-alkoxy-2-cyclopentenones

Fischer carbene complexes 1 underwent a clean ligand dimerization reaction yielding functionalized olefins and trienes 4 in the presence of copper (I) catalysts. If treated with trifluoroacetic acid (TFA), trienes 4c, d, f undergo a cyclization process (Nazarov reaction) which furnishes cyclopentenone derivatives 6c, d, 7c, d and 8 in good yields. Finally, the Fischer aminocarbene 9 efficiently cyclodimerizes to the substituted arene 10 in the presence of CuBr.     

Solvent-free reactions of fullerenes and N-alkylglycines with and without aldehydes under high-speed vibration milling

The solvent-free reactions of fullerenes and N-alkylglycines with and without aldehydes (RCHO) 2a-e under high-speed vibration milling (HSVM) conditions have been investigated. Fulleropyrrolidines 4a-e (C₆₀(CH₂N(CH₃)CHR), R=H (4a), C₆H₅ (4b), p-NO₂-C₆H₄ (4c), p-CH₃O-C₆H₄ (4d), p-(CH₃)₂N-C₆H₄ (4e)) were obtained in moderate yields from reactions of C₆₀ with aldehydes 2a-e and N-methylglycine (Prato reaction). In all these solvent-free reactions, 4a was found to be formed besides 4b-e, indicating that fullerenes can react with N-substituted glycines in the absence of aldehyde to give fulleropyrrolidines. For this novel reaction, a possible reaction mechanism involving an electron transfer process has been proposed. Intrigued by this observation, the dependence of the yield on the reagent ratio for the reaction of C₆₀ with paraformaldehyde and/or N-methylglycine was examined to search the optimal conditions. The reaction of C₇₀ with paraformaldehyde and/or N-methylglycine under HSVM conditions was also studied and was found to give the positional isomers of [70]fulleropyrrolidines.     

CoCl_2·6H_2O or LaCl_3·7H_2O Catalyzed Biginelli Reaction. One-Pot Synthesis of 3,4-Dihydropyrimidin-2(1 H)-ones

Ｉｎｔｒｏｄｕｃｔｉｏｎ1,4 Ｄｉｈｙｄｒｏｐｙｒｉｄｉｎｅｓｏｆｔｈｅｎｉｆｅｄｉｐｉｎｅｔｙｐｅ (ｅ .ｇ .Ｉ—ＩＩＩ)ａｒｅｔｈｅｍｏｓｔｓｔｕｄｉｅｄｃｌａｓｓｏｆｏｒｇａｎｉｃｃａｌｃｉｕｍｃｈａｎｎｅｌｍｅｄｉｃｉｎｅ ,ｗｈｉｃｈｈａｖｅｂｅｃｏｍｅａｌｍｏｓｔｉｎｄｉｓｐｅｎｓ ａｂｌｅｆｏｒｔｈｅｔｒｅａｔｍｅｎｔｏｆｃａｒｄｉｏｖａｓｃｕｌａｒｄｉｓｅａｓｅｓｓｕｃｈａｓｈｙｐｅｒｔｅｎｓｉｏｎ ,ｃａｒｄｉａｃａｒｒｈｙｔｈｍｉａｓ ,ｏｒａｎｇｉｎａ .1Ｉｎｔｈｅｐａｓｔｄｅｃａｄｅ…     

α-Oxolactam enamines as new synthons in the Nenitzescu reaction

-Oxolactam enamines, namely, 3-piperidino-5,6-dihydropyridin-2(1H)-one (1a) and 3-piperidino-1,5,6,7-tetrahydroazepin-2-one (1b), were introduced for the first time into the Nenitzescu reaction. The processes yield cyclic adducts 3a—e, 6. On heating in acetic acid, they are transformed into benzofuropyridone 7 and benzofuroazepinones 10a,d, and 12 and, unexpectedly, into chromenopyrrole 8 and chromenopyridines 9a—d and 11.     

Iron(III) chloride catalysed three-component Grieco condensation: Synthesis of tetrahydropyrido[2′,3′:3,4]pyrazolo[1,5-a]pyrimidines/quinazolines

Three-component Grieco condensation reaction of 3-aminopyrazolo[3,4-b]pyridine, formaldehyde/benzaldehyde and electron rich alkenes in presence of iron(III) chloride gave tetrahydropyrido[2′,3′:3,4]pyrazolo[1,5-a]pyrimidines/quinazolines in single pot. The sequence of reactions is formation of di-azadiene in situ and the subsequent regioselective addition of alkenes in aza-Diels Alder type reaction. The structure and stereochemistry of the products were confirmed by spectral data and single crystal X-ray crystallography.     

Synthesis and structural revision of naturally occurring ayapin derivatives

The synthesis of three highly oxygenated naturally occurring coumarins, 8-methoxy-6,7-methylenedioxycoumarin, 5-methoxy-6,7-methylenedioxycoumarin and 5,8-dimethoxy-6,7-methylenedioxycoumarin is described for the first time, together with a new method for the preparation of ayapin (6,7-methylenedioxycoumarin). Comparison of the spectroscopic data of the synthetic tetraoxygenated coumarin 5,8-dimethoxy-6,7-methylenedioxycoumarin with literature reports resulted in the structural revision of several natural coumarins. Two coumarins, both identified as 5,8-dimethoxy-6,7-methylenedioxycoumarin must have other structures, while the structure of another coumarin, described as the isomeric 7,8-dimethoxy-5,6-methylenedioxycoumarin has to be revised to 5,8-dimethoxy-6,7-methylenedioxycoumarin.     

Tuning the reactivity and chemoselectivity of electron-poor pyrroles as dienophiles in cycloadditions with electron-rich dienes

Activation by Lewis acid catalysis and high pressure allows pyrrole derivatives to react with electron-rich dienes in normal electron demand [4+2] cycloadditions, provided that the aromatic ring is substituted by at least two electron-withdrawing groups. The dienophilic behavior of the heterocycle is expressed through the involvement of either the aromatic carbon-carbon double bond in an all-carbon process or the carbonyl moiety of the substituent in a heterocycloaddition reaction. In this regard, the nature of the heterocyclic substituents is shown to have a dramatic influence and to direct both the reactivity and the chemoselectivity of the cycloaddition.