Use of organocatalysts in stereoselective organic synthesis
type: CreativeWork
description: The main topic of thesis is the use of organocatalysis to synthesize cyclobutanones derivatives. Cyclobutanone derivatives are useful molecular building blocks for the construction of complex molecular structures. Surprisingly, however, the use of organocatalysts to functionalize cyclobutanones is rare, especially when the substrate bears substituents. In this thesis, we present four enantioselective transformations of substituted cyclobutanones which employ readily-available amino acids (or derivatives) and thiourea derivatives as organocatalysts. - The first transformation involves enantioselective aldol reaction between 2-hydroxy-cyclobutanone with a selection of aromatic aldehyde. The results show that the 2-hydroxycyclobutanone is particularly amenable to solvent-free L-threonine-catalyzed direct aldol reactions with reasonable stereocontrol. - After, we synthesized 2,3-disubstituted cyclobutanones through direct aldol reactions involving 3-substituted cyclobutanones and aryl aldehydes catalyzed by N-phenylsulfonyl (S)-proline and via asymmetric nitro-Michael reaction of 3-substituted cyclobutanones and several nitrostyrenes catalyzed by thiourea derivatives. In the first case the relative aldol products were obtained with an unprecedented control of all three contiguous stereocenters in the latter the relatives γ-nitro cyclobutanones were obtained in good yield but in modest enantioselectivity. - The last case concerns the conversion of 3-substituted cyclobutanones into 4-substituted-5-hydroxy-γ-lactam using L-proline-based catalysts. This reaction involves a ring-expanding O-nitroso-aldol–cyclization domino sequence. The synthetic protocol provides access to the five-membered ring system in good yield, and the formation of two new stereogenic centers is achieved with complete stereochemical control.
abstract: The main topic of thesis is the use of organocatalysis to synthesize cyclobutanones derivatives. Cyclobutanone derivatives are useful molecular building blocks for the construction of complex molecular structures. Surprisingly, however, the use of organocatalysts to functionalize cyclobutanones is rare, especially when the substrate bears substituents. In this thesis, we present four enantioselective transformations of substituted cyclobutanones which employ readily-available amino acids (or derivatives) and thiourea derivatives as organocatalysts. - The first transformation involves enantioselective aldol reaction between 2-hydroxy-cyclobutanone with a selection of aromatic aldehyde. The results show that the 2-hydroxycyclobutanone is particularly amenable to solvent-free L-threonine-catalyzed direct aldol reactions with reasonable stereocontrol. - After, we synthesized 2,3-disubstituted cyclobutanones through direct aldol reactions involving 3-substituted cyclobutanones and aryl aldehydes catalyzed by N-phenylsulfonyl (S)-proline and via asymmetric nitro-Michael reaction of 3-substituted cyclobutanones and several nitrostyrenes catalyzed by thiourea derivatives. In the first case the relative aldol products were obtained with an unprecedented control of all three contiguous stereocenters in the latter the relatives γ-nitro cyclobutanones were obtained in good yield but in modest enantioselectivity. - The last case concerns the conversion of 3-substituted cyclobutanones into 4-substituted-5-hydroxy-γ-lactam using L-proline-based catalysts. This reaction involves a ring-expanding O-nitroso-aldol–cyclization domino sequence. The synthetic protocol provides access to the five-membered ring system in good yield, and the formation of two new stereogenic centers is achieved with complete stereochemical control.
author: CAPITTA, FRANCESCA
language: eng
keywords: Organocatalisi, ciclobutanoni, cyclobutanones, desimmetrizzazione, enantioselective desymmetrization, enantioselettiva, organocatalysis, Settore CHIM/06 - Chimica Organica
date published: 2012-04-01
date modified: 2026-07-24T01:29:59Z
provider: Università di Cagliari
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Università degli Studi di Cagliari

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11584/266189