Search results for "Role"
showing 10 items of 1994 documents
A versatile synthesis of 4,5-dihydropyrrolo[1,2-a]quinoxalines
2001
The reaction of 1-(2-aminophenyl)pyrrole with aromatic or heteroaromatic aldehydes in ethanol and catalytic amounts of acetic acid leads to 4,5-dihydropyrrolo[1,2-a]quinoxalines in high yields. When aliphatic aldehydes were used under the same conditions, a slow oxidation to the corresponding pyrrolo[1,2-a]quinoxalines can occur; the oxidation can be avoided by preparing in situ the 5-acetyl derivatives of the 4,5-dihydropyrrolo[1,2-a]quinoxalines.
ChemInform Abstract: A Versatile Synthesis of 4,5-Dihydropyrrolo[1,2-a]quinoxalines.
2010
The reaction of 1-(2-aminophenyl)pyrrole with aromatic or heteroaromatic aldehydes in ethanol and catalytic amounts of acetic acid leads to 4,5-dihydropyrrolo[1,2-a]quinoxalines in high yields. When aliphatic aldehydes were used under the same conditions, a slow oxidation to the corresponding pyrrolo[1,2-a]quinoxalines can occur; the oxidation can be avoided by preparing in situ the 5-acetyl derivatives of the 4,5-dihydropyrrolo[1,2-a]quinoxalines.
New synthesis of condensed heterocycles from isoxazole derivatives VI. 2,5-Dimethyl-3-aeetyl-7-amino-1H-pyrrolo[3,2-b] pyridine
1978
A new synthesis of pyrrolo[3,2-b] pyridine starting with pyrrole ring is described. The procedure allows the synthesis of 4-azaindoles bearing a sensitive group at C-7. The nitration of 4b with nitric acid and acetic anhydride at −15° gave 5. The hydrogenation of 5 led to simultaneous reduction of N-hydroxy and nitro groups and to hydrogenolysis of the isoxazole nucleus, affording an appropriate chain of atoms to building up the pyrrolo[3,2-b] pyridine ring.
Addition reactions of heterocycles. VI. Reactions of 1,2-dimethylpyrrole and 1-methyl-2-carbomethoxypyrrole with nitrilimines
1978
Addition reactions of 1,2-dimethylpyrrole and 1-methyl-2-carbomethoxypyrrole with C-acetyl-N-phenylnitrilimine, have been investigated. 1,2-Dimethylpyrrole gives three different types of adducts: i.e. bis-cycloadducts (Vc) and (VIc), spirocycloadduct (IX), and non cyclic bis-adduct (XII). On the other hand, 1-methyl-2-carbomethoxypyrrole gives the bis-cycloadduct (VIb) only. Compound XII arises probably through a double 1,3-addition reaction, whereas the formation of cycloadducts Vc, VIc, and IX depends on the substituents present at C2 of the pyrrole ring and consequentially on the intermediary occurence of mono-cycloadduct (IIIc), its methylenic tautomer VII, VIc, and XL The behaviour of …
Addition reactions of heterocycles. VII. Pyrrole andC-Acetyl-N-phenylnitrilimine
1978
The addition reaction of C-acetyl-N-phenylnitrilimine to pyrrole has been investigated. The products obtained show that the reaction proceeds via two distinct pathways. The 1,3-addition reaction leads to the non-cyclic-adduct III, whereas the 1,3-cycloaddition reaction gives a mixture of regioisomeric Δ2-pyrroline IV and V, and Δ1 -pyrroline VI and VII mono-cycloadducts. These latter compounds cannot be isolated because they undergo a further 1,3-cycloaddition reaction leading to the N-substituted bis-adducts X and XI, and to the bis-adduets XII and XIII. The stereochemical assignment for X, XI, XII and XIII is provided by nmr data which suggest also that in X and XI the rotation around the…
Significance of Induction Phenomena
1978
A number of foreign compounds induce the proliferation of the hepatic smooth endoplasmatic reticulum and thereby increase the activity of monooxygenases that metabolize drugs and other foreign compound. With reference to the safety of food additives some antioxidants have been examined by various authors for their inducing capacity, in doses well above those ingested with treated food and above the stipulated accepted daily intake (ADI). Thus feeding of rats with the very high dose of 500 mg/kg body weight of butylated hydroxtoluene (BHT) resulted in an increase in its own oxidative metabolism. Also in monkeys BHT produces an inductive increase of microsomal enzyme activity, cytochrome P 45…
Die copolymerisation des acroleins mit einigen vinylmonomeren. Polymere acroleine. 9. Mitt.
1958
Die Copolymerisation des Acroleins in wasrigem Medium wird untersucht und die copolymerisationsparameter folgender Systeme bestimmt: Acrolein/Aacrylnitril (r1 = 1,09; r2 = 0,77); Acrolein/Acrylamid (r1 = 2,0; r2 = 0,76); Acrolein/Acrylsauremethylester (r1 = 0,2; r2 = 10,0) und Acrolein/Vinylacetat (r1 = 3,3; r2 = 0,1). Ferner werden die Qund e-Werte fur Acrolein berechet und sein Verhalten bei der Copolymerisation diskutiert. The copolymerisation of acrolein in aqueous medium has been investigated and the reactivity ratios of the following systems were determined: acrolein/acrylonitrile (r1 = 1.09; r2 = 0.77 ); acrolein/acrylamide (r1 = 2.0; r2 = 0.76); acrolein/methacrylate (r1 = 0.2; r2 =…
ChemInform Abstract: One-Pot Synthesis of Pyrrole-2-carboxylates and -carboxamides via an Electrocyclization/Oxidation Sequence.
2015
An electrocyclic ring closure is the key step of an efficient one-pot method for the synthesis of pyrrole-2-carboxylates and -carboxamides from chalcones and glycine esters or amides. The 3,4-dihydro-2H-pyrrole intermediates generated in situ are oxidized to the corresponding pyrroles by stoichiometric oxidants or by catalytic copper(II) and air in moderate to high yields. A wide range of functional groups are tolerated, and further combination with an in situ bromination gives access to polyfunctional pyrrole scaffolds.
Improved routes for the synthesis of face-to-face bismacrocycles in porphyrin and corrole series
2005
Face-to-face bismacrocycles involving porphyrinoid species are still of great interest owing to their versatile properties. Despite the fact that their syntheses generally involve several steps, numerous modifications have been made in their synthetic pathways thus allowing their preparation in gram quantities. Here we report on recent improvements we could propose especially for the synthesis of bisporphyrin, biscorrole and porphyrin-corrole derivatives.