A diastereoselective synthesis of tetrahydro- and dihydro-pyrido[2,3- c ]coumarin derivatives via a one-pot three-component Povarov reaction catalyzed by bismuth(III) chloride

Asymmetric syntheses of four stereoisomers of 13‐hydroxy‐14‐methylhexadecanoic acid as potential antibacterial agents

“…The data that support the findings of this study are openly available in figshare at http://doi.org/10.1002/chir.23352, reference number [1–43].…”

“…The unsaturated C‐C bonds were hydrogenated completely with PtO 2 , 29 and the following hydrolysis with KOH and acid‐catalyzed lactonization afforded the mixtures of chiral lactones 4a and 4b (dr 1:1.27, determined by 1 H NMR) 30 . The two chiral lactones were isolated by preparative thin layer chromatography, and the absolute configuration of the newly formed chiral center of 4a was confirmed as ( S ) due to the NOE effects observed between the hydrogens of methyl at C‐3 and H‐4 31,32 . Therefore, the stereochemistry of 4a was (3 S , 4 R ), and that of its diastereomer 4b was (3 R , 4 R ), which was consistent with the analysis of vibrational circular dichroism (VCD) 33 …”

First Examples of Povarov Reaction of Cyclopentadienones

“…Inspired by the theoretical studies of the Povarov 's reaction mechanism, these reactions may proceed via a stepwise ion pair mechanism ] where the first step is the electrophilic interaction of the substituted cyclopentadienone with the in situ formed iminium G probably activated by protonation with TFA, which would then undergo ring closure via intramolecular electrophilic attack on the phenyl ring ( Friedel–Crafts ) via a reactive intermediate H, furnishing the desired products 1a , 1b and 2a , 2b ( Scheme ). This hypothesis is supported by Mellor , which has showed that with o ‐phenylenediamine and cyclopentadiene, in similar conditions, a tricyclic amine with a 7‐ring skeleton was formed as by‐product, which proves that mechanism is not concerted …”

“…The Povarov and related aza‐ Diels–Alder reactions have been developed as the most powerful synthetic route for building nitrogen‐containing six‐membered heterocycles . The Povarov reaction can be considered as a formal [4 + 2] cycloaddition of N ‐arylimines, derived from anilines and aromatic aldehydes, with electron‐rich alkenes catalyzed by either protic, lanthanide, or Lewis acids .…”

A Concise Review on Pyridocoumarin/Azacoumarin Derivatives: Synthesis and Biological Activity

“…Diastereoselective tetrahydropyrido[2,3‐ c ]coumarin derivatives 26 synthesised by Ch Gurumurthy et al . via a one‐pot three‐component aza‐Diels‐Alder reaction using aromatic aldehydes 9 , 3‐amino coumarin 1 and 3, 4‐dihydro‐2 H‐ pyran 24 in the presence of 5 mol% BiCl 3 as a catalyst in acetonitrile solvent at room temperature (Scheme ).…”