Mechanistic Variations of the Povarov Multicomponent Reaction and Related Processes

Aluminum triflate catalyzed Povarov reaction for the synthesis of pyranotetrahydroquinolines

“…This limitation led us to conduct re-optimization of the reaction in solvents which were previously reported to be suitable for the Povarov reaction. [19][20][21] The solvents screened include acetonitrile, methylene chloride, THF, and toluene. Reactions were carried out by treating a solution of aniline, benzaldehyde and DHP in either THF or toluene with 5-20 mol% Al(OTf) 3 but at room temperature or higher (60-80 °C) no formation of pyranotetrahydroquinolines 4a and 5a was observed.…”

“…[1][2][3][4][5] Owing to their importance, a number of synthetic strategies have been developed for their synthesis. 1,[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] The reaction of an aromatic imine (in a two component reaction) or aniline (in a three component reaction) with benzaldehyde and electron rich dihydropyran (DHP) in the presence of an acid catalyst/promotor, known as the Povarov reaction, 1,[19][20][21][22][23][24] has been the common and convenient synthetic protocol for the preparation of such important compounds. Several acid catalysts/promoters, which include the following, have been reported in the literature: InCl 3 , 9 Sc(OTf) 3 32 Tritylium Cation, 33 and phosphoric acid.…”

Efficient Synthesis of Tetrahydroquinolines from the Reaction of Aldehyde, Aniline, and Alkene under the In Situ Redox of SnCl2 and FeCl3

“…In our case, the results wherein using the benzaldehyde (Table , entries 4 and 5), occurring under our experimental conditions, first afforded N ‐benzylideneaniline led us to speculate that a stepwise mechanism could account for the formation of tetrahydroquinoline from aniline, aldehyde, and alkene mediated by in situ redox of SnCl 2 and FeCl 3 . Thus, the reaction would be viewed as a nucleophilic‐type attack of alkene to the N ‐arylimine with a concomitant cyclization with formation of zwitterionic intermediates .…”

Synergy Effects in the Chemical Synthesis and Extensions of Multicomponent Reactions (MCRs)—The Low Energy Way to Ultra-Short Syntheses of Tailor-Made Molecules

“…Main field of application remains the production of heterocyclic compounds and many natural products by means of MCR [38,[77][78][79][80][81][82][83][84][85][86][87][88][89], leading directly towards drug design and discovery [90][91][92][93][94]. Scheme 9 presents a current brief of well-known multicomponent reactions [35,40,9,[95][96][97][98][99][100][101][102][103][104][105][106][107][108][109][110]. …”