Ring Closure Reactions in Heterocyclic Systems with Implementation of Wittig and aza-Wittig Reactions

Transition Metal‐Catalyzed Synthesis of Fused Five‐Membered Aromatic Heterocycles

“…The authors demonstrated that electronic effects of substituents on the aromatic ring have very little influence on this arylation reaction, as complete conversion was observed for substrates possessing both electron-donating and electron-withdrawing groups. Wadsworth-Emmons process [144], namely, in this case, a modified Madelung-type indole synthesis, into a one-pot transformation. First, reaction between orthocarbonyl-functionalized aniline 240 and diazocompound 241 in the presence of the Rh(II)-catalyst generated the phosphonate 243, which, upon treatment with base, was transformed into multisubstituted indoles 242 in moderate to high yields (Scheme 9.86) [145].…”

A Triphenylphosphine‐Based Microporous Polymer for a Wittig Reaction Cycle in the Solid State

“…[1,2] Not only in research laboratories but also in industry the Wittig reaction is a well-established synthetic route to synthesise this motif. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] The relevance of this reaction becomes apparent by looking into synthetic routes for chemicals such as vitamin A or other carotenes, which are produced on an industrial scale. [18][19][20][21] The Wittig reaction itself was developed in 1953 by Georg Wittig [22,23] and various additional modifications, such as the Horner-Wadsworth-Emmons reaction [24][25][26] or the Schlosser modification, [27] were developed over time in order to target a specific product with Z-or E-selectivity.…”

“…Carbon‐carbon double bonds are a key motive in many organic compounds [1,2] . Not only in research laboratories but also in industry the Wittig reaction is a well‐established synthetic route to synthesise this motif [3–17] . The relevance of this reaction becomes apparent by looking into synthetic routes for chemicals such as vitamin A or other carotenes, which are produced on an industrial scale [18–21] .…”

Four-component Synthesis of 1,3,4-Oxadiazole Derivatives from (N-Isocyanimino)triphenylphosphorane, (E)-Cinnamic Acids, Acetaldehyde and Secondary Amines

“…The electron distribution around the P + -N − bond and its consequent chemical implications have been probed and assessed through theoretical, spectroscopic and crystallographic investigations [9]. The proton affinity of these iminophosphoranes can be 0932-0776 / 11 / 0200-0184 $ 06.00 c 2011 Verlag der Zeitschrift für Naturforschung, Tübingen · http://znaturforsch.com used as a molecular guide to assess their utility as synthetic reagents and their function as ligands in coordination and organometallic chemistry [9][10][11][12][13][14][15][16][17].…”

“…The nucleophilicity of the nitrogen atom is a factor of essential mechanistic importance in the use of these iminophosphoranes as aza-Wittig reagents. Iminophosphoranes are important reagents in synthetic organic chemistry, especially in the synthesis of naturally occurring products and of compounds with biological and pharmacological activity [9][10][11][12][13][14][15]. There are several reports for the use of (N-isocyanimino)triphenylphosphorane (4) in the preparation of metal complexes [16,17] (Scheme 1).…”