Search results for " Heterocycles"
showing 10 items of 70 documents
Preparation and Characterization of P2 BCh Ring Systems (Ch=S, Se) and Their Reactivity with N-Heterocyclic Carbenes
2018
Four-membered rings with a P2BCh core (Ch = S, Se) have been synthesized via reaction of phosphinidene chalcogenide (Ar*P=Ch) and phosphaborene (Mes*P=BNR2). The mechanistic pathways towards these rings are explained by detailed computational work that confirmed the preference for the formation of P–P, not P–B, bonded systems, which seems counterintuitive given that both phosphorus atoms contain bulky ligands. The reactivity of the newly synthesized heterocycles, as well as that of the known (RPCh)n rings (n = 2, 3), was probed by the addition of Nheterocyclic carbenes, which revealed that all investigated compounds can act as sources of low-coordinate phosphorus species. peerReviewed
Electrochemical Synthesis of Fluorinated Orthoesters from 1,3‐Benzodioxoles
2019
Abstract Invited for this month's cover picture is the group of Professor Siegfried Waldvogel. The cover picture displays the robustness achieved by the installation of fluorinated alcohols on 1,3‐benzodioxoles, protecting the obtained orthoesters against acids and bases, like the shield of a knight. The simple protocol allows access to interesting compounds, whose lipophilicity is tremendously increased by the incorporation of fluorinated groups. This makes it possible to adjust the physicochemical properties of the biologically active 1,3‐benzodioxole motif. The surprisingly high stability against acids and bases gives rise to subsequent functionalizations or direct application in medicin…
Synthesis of Fluorinated and Non-Fluorinated Bicyclic Amidines through Ring-Closing Metathesis
2011
[EN] An efficient method for the synthesis of fluorinated and non-fluorinated imidazoazepines by a ring-closing metathesis reaction as the key step is described. The influence of the fluorine atoms on the preparation of these bicyclic systems is also studied.
Biosynthesis of heterocycles: From isolation to gene cluster
2015
This book describes biosynthetic methods to synthesize heterocyclic compounds, offering a guide for the development of new drugs based on natural products. The authors explain the role of natural products in chemistry and their formation along with important analytical methods and techniques for working with heterocycles. Covers methods and techniques: isotopic labelling, enzymes and mutants, and pathway identification. Provides a thorough resource of information specifically on heterocyclic natural products and their practical biosynthetic relevance. Explains the role of natural products in chemistry and their formation. Discusses gene cluster identification and the use of biogenetic engin…
Experimental and DFT studies on competitive heterocyclic rearrangements. part 2: A one-atom side-chain versus the classic three-atom side-chain (Boul…
2007
The experimental investigation of the base-catalyzed rearrangements of 3-acylamino-1,2,4-oxadiazoles evidenced a new reaction pathway which competes with the well-known ring-degenerate Boulton- Katritzky rearrangement (BKR). The new reaction consists of a one-atom side-chain rearrangement that is base-activated, occurs at a higher temperature than the BKR, and irreversibly leads to the corresponding 2-acylamino-1,3,4-oxadiazoles. An extensive DFT study is reported to elucidate the proposed reaction mechanism and to compare the three possible inherent routes: (i) the reversible three-atom side-chain ring-degenerate BKR, (ii) the ring contraction-ring expansion route (RCRE), and (iii) the one…
New approach to condensed pyrid-2-ones
2002
We wish to report a simple procedure for the preparation of 5-substituted-thienopyridin-7-ones and 7-substituted-1,6-naphthyridin-5(6H)-ones, in good yields, from the dianions of 3-methylthiophene-2-carboxylic and 2-methylnicotinic acids on treatment with nitriles. Brun Sanchez, Eva Maria, Eva.M.Brun@uv.es ; Gil Grau, Salvador, Salvador.Gil@uv.es ; Parra Alvarez, Margarita, Margarita.Parra@uv.es
Eight-membered heterocycles with two heteroatoms in a 1,3-relationship of interest in medicinal chemistry
2022
This chapter deals with 1,3-diheterocines, eight-membered heterocyclic systems with two heteroatoms, N, O and S, in a 1,3 relationship, exhibiting biological properties and exhaustively covers the literature from 2007 to the end of November 2019. The biological results of 1,3-diazocines, 1,3-oxazocines, 1,3-dioxocins and 1,3-thiazocines, that are the largest class of 1,3-diheterocines, were collected together with the few results available for 1,3-oxathiocin and 1,3-dithiocin derivatives at that time.
Iodolactonization of 3-Alkynylthiophene-2-Carboxylic and 3-Alkynylpicolinic Acids for the Synthesis of Fused Heterocycles
2020
The iodolactonization of 3-alkynylthiophene-2-carboxylic acids and 3-alkynylpicolinic acids has been investigated. Using I2 as the iodine source and NaHCO3 as the base in MeCN, the process took place smoothly to afford thienopyranones and pyranopyridinones, respectively, from 6-endo-dig cyclization. The method also worked nicely for the transformation of 2-(phenylethynyl)thiophene-3-carboxylic acid and 3-(phenylethynyl) isonicotinic acid into 7-iodo-6-phenyl-4H-thieno[3,2-c]- pyran-4-one and 4-iodo-3-phenyl-1H-pyrano[4,3-c]pyridin-1- one, respectively. Although with some 3-alkynylpicolinic acids the process led to a mixture of the 6-endo-dig and 5-exo-dig products, it could be still made se…
1,2,3-Triazole in Heterocyclic Compounds, Endowed with Biological Activity, through 1,3-Dipolar Cycloadditions
2014
1,3-Dipolar cycloaddition reactions can be considered a powerful synthetic tool in the building of heterocyclic rings, with applications in different fields. In this review we focus on the synthesis of biologically active compounds possessing the 1,2,3-triazole core through 1,3-dipolar cycloaddition reactions. The 1,2,3-triazole skeleton can be present as a single disubstituted ring, as a linker between two molecules, or embedded in a polyheterocycle. The cycloaddition reactions are usually catalysed by copper or ruthenium. Domino reactions can be achieved through dipolarophile anion formation, generally followed by cyclisation. The variety of attainable heterocyclic structures gives an ill…
Dehydrogenative Anodic C−C Coupling of Phenols Bearing Electron‐Withdrawing Groups
2019
Abstract We herein present a metal‐free, electrosynthetic method that enables the direct dehydrogenative coupling reactions of phenols carrying electron‐withdrawing groups for the first time. The reactions are easy to conduct and scalable, as they are carried out in undivided cells and obviate the necessity for additional supporting electrolyte. As such, this conversion is efficient, practical, and thereby environmentally friendly, as production of waste is minimized. The method features a broad substrate scope, and a variety of functional groups are tolerated, providing easy access to precursors for novel polydentate ligands and even heterocycles such as dibenzofurans.