Intramolecular Cyclization Reaction (intramolecular + cyclization_reaction)

Distribution by Scientific Domains

Selected Abstracts

Intramolecular Cyclization Reactions of Unsaturated Amino Fischer Chromium Carbenes Forming Indoles and Quinolines.

CHEMINFORM, Issue 8 2004
Bjoern C. G. Soederberg
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Reductive-Cyclization-Mediated Synthesis of Fused Polycyclic Quinolines from Baylis,Hillman Adducts of Acrylonitrile: Scope and Limitations,,

Virender Singh
Abstract The synthesis of a variety of polycyclic quinolines is described. The target molecules were obtained in two steps by an initial reductive cyclization followed by another intramolecular cyclization in the allylamines afforded from either the acetates or allyl bromides of Baylis,Hillman adducts of 2-nitrobenzaldehydes and acrylonitrile. The two steps proceeded in one-pot for those substrates in which a formyl or hydroxy group reacted with the amino group of the 2-aminoquinoline in the second intramolecular cyclization. In contrast, a basic medium was necessary for the second intramolecular cyclization reaction in substrates in which an alkoxycarbonyl group and the amino group participated. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

On the mechanisms of oligopeptide reactions in solution and clay dispersion

Dr Juraj Bujdk
Abstract Mechanisms of the reactions of representative dipeptides (Gly2, Gly-Ala), oligopeptides (Gly3, Gly4) and the polypeptide (poly-Gly)n) in solution and clay suspensions at 85 C were investigated. The reaction products and their yields were analysed and determined by means of HPLC. Interestingly, hydrolysis, where water molecules act as the reactant, was not the main reaction, even for oligopeptides. Formation of cyclic dipeptides prevailed in the reactions of dimers as well as oligopeptides. The breakdown of oligopeptide molecules proceeded via an intramolecular cyclization reaction. For example, the reaction of Gly3 led to the formation of equal amounts of cyclic dipeptide, c(Gly)2 and Gly. The presence of clay (montmorillonite) significantly increased yields in the reactions of dipeptides but it did not have much effect on the reactions of oligopeptides. However, an opposite effect of clay, protection of poly(Gly)n against decomposition, was proven. Copyright 2004 European Peptide Society and John Wiley & Sons, Ltd. [source]

Synthesis of 2,4,6-trisubstituted naphthalenes via novel copper-promoted tandem coupling and intramolecular cyclization

Yuguang Wang
Abstract An unprecedented copper-promoted tandem coupling and intramolecular cyclization reaction is disclosed. This strategy offers a simple and promising method for accessing 2,4,6-trisubstituted naphthalenes. A reaction mechanism involving initial formation of diynes followed by a 6- exo -dig cyclization and subsequent rearrangement is proposed. Copyright 2009 John Wiley & Sons, Ltd. [source]

Bifunctional Heterogeneous Catalysis of Silica,Alumina-Supported Tertiary Amines with Controlled Acid,Base Interactions for Efficient 1,4-Addition Reactions

Ken Motokura Dr.
Abstract We report the first tunable bifunctional surface of silica,alumina-supported tertiary amines (SA,NEt2) active for catalytic 1,4-addition reactions of nitroalkanes and thiols to electron-deficient alkenes. The 1,4-addition reaction of nitroalkanes to electron-deficient alkenes is one of the most useful carbon,carbon bond-forming reactions and applicable toward a wide range of organic syntheses. The reaction between nitroethane and methyl vinyl ketone scarcely proceeded with either SA or homogeneous amines, and a mixture of SA and amines showed very low catalytic activity. In addition, undesirable side reactions occurred in the case of a strong base like sodium ethoxide employed as a catalytic reagent. Only the present SA-supported amine (SA,NEt2) catalyst enabled selective formation of a double-alkylated product without promotions of side reactions such as an intramolecular cyclization reaction. The heterogeneous SA,NEt2 catalyst was easily recovered from the reaction mixture by simple filtration and reusable with retention of its catalytic activity and selectivity. Furthermore, the SA,NEt2 catalyst system was applicable to the addition reaction of other nitroalkanes and thiols to various electron-deficient alkenes. The solid-state magic-angle spinning (MAS) NMR spectroscopic analyses, including variable-contact-time 13C cross-polarization (CP)/MAS NMR spectroscopy, revealed that acid,base interactions between surface acid sites and immobilized amines can be controlled by pretreatment of SA at different temperatures. The catalytic activities for these addition reactions were strongly affected by the surface acid,base interactions. [source]