{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/72291"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/72291","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Silicon-Directed Nazarov Cyclization: Stereochemical, Mechanistic, and Substituent-Compatibility Studies","abstract":"In the Silicon-Directed Nazarov Cyclization (SDNC) an organosilyl group, attached to a divinyl ketone at a position beta to the carbonyl, directs the location of the double bond in the cyclopentenone ring. Various studies are described that explore the stereochemistry, scope, and mechanism of the reaction. The cyclization proceeds with good to excellent stereoselectivity in cyclohexenyl systems bearing a variety of ring substituents. In all cases the trans family of isomers predominates; cis ring-fused products are formed almost exclusively. The stereoselectivity is high ($>$9:1) with bulky substituents. The potential for improving stereocontrol by increasing the bulk of silicon substituents was explored with 3-methyl-substituted cyclopentenyl-, cyclohexenyl-, and cycloheptenyl-vinyl ketones. Augmenting the bulk of the silyl group enhances the stereoselectivity with five- and six-membered rings. Selectivity is poor in cycloheptenyl systems with a methyl group on the stereogenic center, irrespective of the bulk of the silicon appendage. However, with cycloheptenyl- and cyclooctenyl-substrates bearing a 3-benzyloxymethyl group the products are principally ($>$92%) of the cis stereochemical family. Stereochemical results in the five- and six-ring systems are consistent with a steric approach control model, in which the vinylsilane prefers to attack the least-hindered face of the internal olefin.","abstract_html":"In the Silicon-Directed Nazarov Cyclization (SDNC) an organosilyl group, attached to a divinyl ketone at a position beta to the carbonyl, directs the location of the double bond in the cyclopentenone ring. Various studies are described that explore the stereochemistry, scope, and mechanism of the reaction. The cyclization proceeds with good to excellent stereoselectivity in cyclohexenyl systems bearing a variety of ring substituents. In all cases the trans family of isomers predominates; cis ring-fused products are formed almost exclusively. The stereoselectivity is high ($>$9:1) with bulky substituents. The potential for improving stereocontrol by increasing the bulk of silicon substituents was explored with 3-methyl-substituted cyclopentenyl-, cyclohexenyl-, and cycloheptenyl-vinyl ketones. Augmenting the bulk of the silyl group enhances the stereoselectivity with five- and six-membered rings. Selectivity is poor in cycloheptenyl systems with a methyl group on the stereogenic center, irrespective of the bulk of the silicon appendage. However, with cycloheptenyl- and cyclooctenyl-substrates bearing a 3-benzyloxymethyl group the products are principally ($>$92%) of the cis stereochemical family. Stereochemical results in the five- and six-ring systems are consistent with a steric approach control model, in which the vinylsilane prefers to attack the least-hindered face of the internal olefin.","abstract_has_math":true,"creators":["Habermas, Karl Louis"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Chemistry","degree_department":null,"school":null,"contributors":["Denmark, Scott E."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014-12-17T21:29:12Z","date_published":"2014-12-17T21:29:12Z","updated_at":"2026-07-22T22:26:06Z","subjects":["Chemistry, Organic"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(UMI)AAI9411642"],"render_values":[{"text":"(UMI)AAI9411642","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/72291","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Denmark, Scott E."]},{"key":"dc:creator","label":"Author","values":["Habermas, Karl Louis"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2014-12-17T21:29:12Z","10000-01-01","1993"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemistry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Chemistry, Organic"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/72291","(UMI)AAI9411642"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["In the Silicon-Directed Nazarov Cyclization (SDNC) an organosilyl group, attached to a divinyl ketone at a position beta to the carbonyl, directs the location of the double bond in the cyclopentenone ring. Various studies are described that explore the stereochemistry, scope, and mechanism of the reaction. The cyclization proceeds with good to excellent stereoselectivity in cyclohexenyl systems bearing a variety of ring substituents. In all cases the trans family of isomers predominates; cis ring-fused products are formed almost exclusively. The stereoselectivity is high ($>$9:1) with bulky substituents. The potential for improving stereocontrol by increasing the bulk of silicon substituents was explored with 3-methyl-substituted cyclopentenyl-, cyclohexenyl-, and cycloheptenyl-vinyl ketones. Augmenting the bulk of the silyl group enhances the stereoselectivity with five- and six-membered rings. Selectivity is poor in cycloheptenyl systems with a methyl group on the stereogenic center, irrespective of the bulk of the silicon appendage. However, with cycloheptenyl- and cyclooctenyl-substrates bearing a 3-benzyloxymethyl group the products are principally ($>$92%) of the cis stereochemical family. Stereochemical results in the five- and six-ring systems are consistent with a steric approach control model, in which the vinylsilane prefers to attack the least-hindered face of the internal olefin.","The ability to incorporate alkyl, alkenyl, aryl, and heteroatomic groups into substrates for the SDNC and their subsequent reactions is reported. The reaction is compatible with vinyl, allyl, or phenyl groups attached to the alpha position of the vinylsilane, and to most other positions of the substrate. Alkyl groups at the beta position of the internal or external olefin retard the reaction, while allyl or phenyl substituents on an alpha position dramatically accelerate cyclization. Oxygen- and nitrogen-containing functions are tolerated except when attached to the $\\alpha$-vinyl carbon atom of the divinyl ketone. The influence of various substituents on the rate of reaction is consistent with the rate-determining step of the SDNC being cyclization of the pentadienylic cation to the cyclopentenylic cation. A novel cationic cyclization that forms the bicyclo (3.3.1) nonane ring system is also described.","Made available in DSpace on 2014-12-17T21:29:12Z (GMT). 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Various studies are described that explore the stereochemistry, scope, and mechanism of the reaction. The cyclization proceeds with good to excellent stereoselectivity in cyclohexenyl systems bearing a variety of ring substituents. In all cases the trans family of isomers predominates; cis ring-fused products are formed almost exclusively. The stereoselectivity is high ($>$9:1) with bulky substituents. The potential for improving stereocontrol by increasing the bulk of silicon substituents was explored with 3-methyl-substituted cyclopentenyl-, cyclohexenyl-, and cycloheptenyl-vinyl ketones. Augmenting the bulk of the silyl group enhances the stereoselectivity with five- and six-membered rings. Selectivity is poor in cycloheptenyl systems with a methyl group on the stereogenic center, irrespective of the bulk of the silicon appendage. However, with cycloheptenyl- and cyclooctenyl-substrates bearing a 3-benzyloxymethyl group the products are principally ($>$92%) of the cis stereochemical family. Stereochemical results in the five- and six-ring systems are consistent with a steric approach control model, in which the vinylsilane prefers to attack the least-hindered face of the internal olefin.","The ability to incorporate alkyl, alkenyl, aryl, and heteroatomic groups into substrates for the SDNC and their subsequent reactions is reported. The reaction is compatible with vinyl, allyl, or phenyl groups attached to the alpha position of the vinylsilane, and to most other positions of the substrate. Alkyl groups at the beta position of the internal or external olefin retard the reaction, while allyl or phenyl substituents on an alpha position dramatically accelerate cyclization. Oxygen- and nitrogen-containing functions are tolerated except when attached to the $\\alpha$-vinyl carbon atom of the divinyl ketone. The influence of various substituents on the rate of reaction is consistent with the rate-determining step of the SDNC being cyclization of the pentadienylic cation to the cyclopentenylic cation. A novel cationic cyclization that forms the bicyclo (3.3.1) nonane ring system is also described.","Made available in DSpace on 2014-12-17T21:29:12Z (GMT). No. of bitstreams: 1 9411642.pdf: 6313099 bytes, checksum: 2dc12ae2f8f617adedc85d5ea670eeb7 (MD5) Previous issue date: 1993","Embargo set by: Seth Robbins for item 72459 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","188 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993."],"dc:identifier":["http://hdl.handle.net/2142/72291","(UMI)AAI9411642"],"dc:subject":["Chemistry, Organic"],"dc:title":["Silicon-Directed Nazarov Cyclization: Stereochemical, Mechanistic, and Substituent-Compatibility Studies"],"dc:type":["text"],"thesis:degree_discipline":["Chemistry"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:06Z"}