{"id":{"repo_id":"aachen","oai_identifier":"oai:publications.rwth-aachen.de:51646"},"canonical_url":"https://search.dev.ndltd.org/etd/aachen/oai:publications.rwth-aachen.de:51646","repository":{"repo_id":"aachen","name":"RWTH Aachen University","base_url":"https://publications.rwth-aachen.de/oai2d"},"display":{"title":"Entwicklung von Carben-katalysierten asymmetrischen intermolekularen Stetter-Reaktionen und direkt gekreuzter intermolekularer Benzoin-Reaktionen","abstract":"A new chiral triazolium based carbene precatalyst was synthesized and successfully employed in the asymmetric intermolecular Stetter reaction. The resulting 1,4-diketones were obtained in moderate to excellent yields (49-98%) and good enantioselectivities (56-78% ee). For several Stetter products the enantiomeric excess could be enhanced by a single recrystallization up to 99% ee. Examination of the reaction course revealed that the corresponding 1,4-diketones are generated via two coupled catalytic cycles. A direct intermolecular cross-benzoin reaction catalyzed by an N-heterocyclic carbene has been developed. The cross-coupling of aromatic aldehydes and trifluoromethyl ketones results in alpha-hydroxy-alpha-trifluoromethyl ketones bearing a quaternary stereocenter with excellent chemoselectivity and good to excellent yields (64-99%). This method could be enhanced to a nucleophilic acylation of trifluoromethyl ketimines via the employment of various furan-2-carbaldehydes in the presence of a carbene precatalyst. The corresponding alpha-amino-alpha-trifluoromethyl ketones could be obtained in moderate to very good yields (32-87%) via this method. A novel chiral bifunctional N-heterocyclic carbene precatalyst could be generated in high yields starting from the commercially available and inexpensive chiral source L-pyroglutamic acid. This structure represents the first combination of a N-heterocyclic carbene precatalyst with a broensted acidic thioureafunction. The developed precatalyst was tested in the intermolecular benzoin condensation of benzaldehyde, showing promising initial results.","abstract_html":"A new chiral triazolium based carbene precatalyst was synthesized and successfully employed in the asymmetric intermolecular Stetter reaction. The resulting 1,4-diketones were obtained in moderate to excellent yields (49-98%) and good enantioselectivities (56-78% ee). For several Stetter products the enantiomeric excess could be enhanced by a single recrystallization up to 99% ee. Examination of the reaction course revealed that the corresponding 1,4-diketones are generated via two coupled catalytic cycles. A direct intermolecular cross-benzoin reaction catalyzed by an N-heterocyclic carbene has been developed. The cross-coupling of aromatic aldehydes and trifluoromethyl ketones results in alpha-hydroxy-alpha-trifluoromethyl ketones bearing a quaternary stereocenter with excellent chemoselectivity and good to excellent yields (64-99%). This method could be enhanced to a nucleophilic acylation of trifluoromethyl ketimines via the employment of various furan-2-carbaldehydes in the presence of a carbene precatalyst. The corresponding alpha-amino-alpha-trifluoromethyl ketones could be obtained in moderate to very good yields (32-87%) via this method. A novel chiral bifunctional N-heterocyclic carbene precatalyst could be generated in high yields starting from the commercially available and inexpensive chiral source L-pyroglutamic acid. This structure represents the first combination of a N-heterocyclic carbene precatalyst with a broensted acidic thioureafunction. The developed precatalyst was tested in the intermolecular benzoin condensation of benzaldehyde, showing promising initial results.","abstract_has_math":false,"creators":["Henseler, Alexander"],"institution":"Mainz","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Enders, Dieter"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2010,"date_issued":"2010","date_published":"2010","updated_at":"2026-07-30T19:40:42Z","subjects":["info:eu-repo/classification/ddc/540","Heterocyclische Carbene <-N>","Organokatalyse","Stetter-Reaktion","Benzoin-Kondensation","Asymmetrische Synthese","Chemie","N-heterocyclic carbenes","organocatalysis","Stetter reaction","benzoin reaction","asymmetric synthesis"],"languages":["ger"],"rights":["info:eu-repo/semantics/openAccess"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-113917%22"],"render_values":[{"text":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-113917%22","href":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-113917%22","code":true}]}]},"links":{"outbound_url":"https://publications.rwth-aachen.de/record/51646","outbound_label":"Repository record","outbound_source":"dc:identifier"},"source_record":{"url":"https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A51646","prefix":"oai_dc"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Enders, Dieter"]},{"key":"dc:creator","label":"Author","values":["Henseler, Alexander"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:coverage","label":"Dc Coverage","values":["DE"]},{"key":"dc:date","label":"Dc Date","values":["2010"]},{"key":"dc:publisher","label":"Institution","values":["Mainz"]},{"key":"dc:relation","label":"Dc Relation","values":["info:eu-repo/semantics/altIdentifier/isbn/3-86130-615-8","info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-31893"]},{"key":"dc:type","label":"Dc Type","values":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["info:eu-repo/classification/ddc/540","Heterocyclische Carbene <-N>","Organokatalyse","Stetter-Reaktion","Benzoin-Kondensation","Asymmetrische Synthese","Chemie","N-heterocyclic carbenes","organocatalysis","Stetter reaction","benzoin reaction","asymmetric synthesis"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["ger"]},{"key":"dc:rights","label":"Dc Rights","values":["info:eu-repo/semantics/openAccess"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/record/51646","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-113917%22"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["A new chiral triazolium based carbene precatalyst was synthesized and successfully employed in the asymmetric intermolecular Stetter reaction. The resulting 1,4-diketones were obtained in moderate to excellent yields (49-98%) and good enantioselectivities (56-78% ee). For several Stetter products the enantiomeric excess could be enhanced by a single recrystallization up to 99% ee. Examination of the reaction course revealed that the corresponding 1,4-diketones are generated via two coupled catalytic cycles. A direct intermolecular cross-benzoin reaction catalyzed by an N-heterocyclic carbene has been developed. The cross-coupling of aromatic aldehydes and trifluoromethyl ketones results in alpha-hydroxy-alpha-trifluoromethyl ketones bearing a quaternary stereocenter with excellent chemoselectivity and good to excellent yields (64-99%). This method could be enhanced to a nucleophilic acylation of trifluoromethyl ketimines via the employment of various furan-2-carbaldehydes in the presence of a carbene precatalyst. The corresponding alpha-amino-alpha-trifluoromethyl ketones could be obtained in moderate to very good yields (32-87%) via this method. A novel chiral bifunctional N-heterocyclic carbene precatalyst could be generated in high yields starting from the commercially available and inexpensive chiral source L-pyroglutamic acid. This structure represents the first combination of a N-heterocyclic carbene precatalyst with a broensted acidic thioureafunction. The developed precatalyst was tested in the intermolecular benzoin condensation of benzaldehyde, showing promising initial results."]},{"key":"dc:source","label":"Dc Source","values":["Aachen : Mainz, Aachener Beiträge zur Chemie 94, 177 S. (2010). = Zugl.: Aachen, Techn. Hochsch., Diss., 2010"]},{"key":"dc:title","label":"Title","values":["Entwicklung von Carben-katalysierten asymmetrischen intermolekularen Stetter-Reaktionen und direkt gekreuzter intermolekularer Benzoin-Reaktionen"]}]}],"canonical_facts":{"dc:contributor":["Enders, Dieter"],"dc:coverage":["DE"],"dc:creator":["Henseler, Alexander"],"dc:date":["2010"],"dc:description":["A new chiral triazolium based carbene precatalyst was synthesized and successfully employed in the asymmetric intermolecular Stetter reaction. The resulting 1,4-diketones were obtained in moderate to excellent yields (49-98%) and good enantioselectivities (56-78% ee). For several Stetter products the enantiomeric excess could be enhanced by a single recrystallization up to 99% ee. Examination of the reaction course revealed that the corresponding 1,4-diketones are generated via two coupled catalytic cycles. A direct intermolecular cross-benzoin reaction catalyzed by an N-heterocyclic carbene has been developed. The cross-coupling of aromatic aldehydes and trifluoromethyl ketones results in alpha-hydroxy-alpha-trifluoromethyl ketones bearing a quaternary stereocenter with excellent chemoselectivity and good to excellent yields (64-99%). This method could be enhanced to a nucleophilic acylation of trifluoromethyl ketimines via the employment of various furan-2-carbaldehydes in the presence of a carbene precatalyst. The corresponding alpha-amino-alpha-trifluoromethyl ketones could be obtained in moderate to very good yields (32-87%) via this method. A novel chiral bifunctional N-heterocyclic carbene precatalyst could be generated in high yields starting from the commercially available and inexpensive chiral source L-pyroglutamic acid. This structure represents the first combination of a N-heterocyclic carbene precatalyst with a broensted acidic thioureafunction. The developed precatalyst was tested in the intermolecular benzoin condensation of benzaldehyde, showing promising initial results."],"dc:identifier":["https://publications.rwth-aachen.de/record/51646","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-113917%22"],"dc:language":["ger"],"dc:publisher":["Mainz"],"dc:relation":["info:eu-repo/semantics/altIdentifier/isbn/3-86130-615-8","info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-31893"],"dc:rights":["info:eu-repo/semantics/openAccess"],"dc:source":["Aachen : Mainz, Aachener Beiträge zur Chemie 94, 177 S. (2010). = Zugl.: Aachen, Techn. 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