Catalytic Asymmetric Aza-Diels–Alder Reactions: The Povarov Cycloaddition Reaction

Abstract

The Povarov reaction provides a straightforward and modular entry to 1,2,3,4-tetrahydroquinolines (THQs). Despite its importance, it was only very recently that several highly efficient catalytic asymmetric protocols for this reaction have been developed, as summarized in this review which falls on the 50 th anniversary of Povarov's pioneering disclosure. Furthermore, this review collects and critically discusses the interrupted versions of the reaction, often featuring intriguing and still unclear mechanicistic pathways.

The Future of Catalysis by Chiral Lewis Acids

“…Chiral Lewis acids find the greatest number of their applications in hetero-DielsAlder (HDA) reactions [33,[46][47][48][49]. These transformations generate heterocyclic compounds by incorporating the heteroatom through either the dienophile (normal HDA) or through the "diene" (inverse-electron-demand HDA), and their scope is broad.…”

Organocatalytic alkylation of carbohydrate‐containing aldehydes with dihydroquinoline N,O‐acetals: Absolute configuration of 1,2‐dihydroquinolines

“…The stereoselective direct functionalization of nitrogen heterocycles, such as partially hydrogenated quinolines, is of special importance in synthetic organic chemistry as these nuclei are an integral part of many medicinally relevant compounds. [1][2][3] The most striking example is Nethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), a powerful irreversible dopamine-receptor antagonist. 4,5 Most approaches for the preparation of chiral 2substituted dihydroquinolines in nonracemic form are able to introduce only rather simple organic frameworks making use of sophisticated metal catalysts in strictly anhydrous and/or oxygen-free reaction conditions.…”

Aluminum triflate catalyzed Povarov reaction for the synthesis of pyranotetrahydroquinolines

“…[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.…”