Shee, Sayan <br/><br/>
N-Heterocyclic carbene-catalyzed enantioselective synthesis of C-O axially chiral diaryl ethers, tricyclic lactones and lactams 

 - Bangalore :   Indian Institute of Science,  2024. 
 - v, 286 p. :   col. ill.   e-Thesis  17.00 Mb 
<br/><br/> Includes bibliographical references 
<br/><br/>PhD;2024;Organic Chemistry 
<br/><br/> N-heterocyclic carbene (NHC)-catalyzed transformations with distinctive activation modes allow the facile synthesis of atropoisomers. In this context, we have demonstrated the NHC-catalyzed synthesis of axially chiral diaryl ethers via atroposelective esterification of dialdehyde-containing diaryl ethers. Additionally, we have developed a dynamic kinetic resolution approach towards the NHC-catalyzed synthesis of C-O axially chiral benzonitrile derivatives. NHCs are also well-known to catalyze cascade process to synthesize various carbocycles and heterocycles. In this regard, we have disclosed the NHC-catalyzed desymmetrization of cyclic-1,3-diketones allowing the enantioselective construction of tricyclic β-lactones with five contiguous stereocenters, including two quaternary stereocenters. Furthermore, we have described an aza-Michael-Mannich-lactamization cascade for NHC-catalyzed synthesis of functionalized pyrazoloquinolin-3-ones. In addition to the non-umpolung (normal) reactivity, we have also explored umpolung reactivity of NHCs where NHC-homoenolate intermediate undergo an efficient Michael-isomerization-lactonization cascade sequence to produce the dihydrocoumarin scaffolds. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>N-Heterocyclic Carbene<br/>Organocatalysis<br/>Michael-Isomerization-Lactonization<br/>Atroposelective esterification<br/>Dihydrocoumarin scaffolds
<br/><br/><label>Dewey Class. No.: </label>547  / SHE