{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/22403"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/22403","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Nitroalkene (4+2) cycloadditions of achiral and chiral vinyl ethers. The stereochemical consequence of the Lewis acid promoter and studies toward the total synthesis of (+)-pretazettine","abstract":"Chiral enol ether dienophiles derived from (1R,2S)-($-$)-2-phenylcyclohexanol and (R)-($-$)-2,2-diphenylcyclopentanol (($-$)-6 have been found to provide high levels of asymmetric induction in tandem inter (4+2) /intra (3+2) nitroalkene cycloadditions. Either enantiomeric series of tandem cycloaddition/hydrogenolysis product is available from the chiral auxiliary of a single absolute configuration by judicious selection of the Lewis acid promoter, Ti(Oi-Pr)$\\sb{2}$Cl$\\sb{2}$ (98% ee, ($-$)) or methylaluminum bis-(2,6-diphenylphenoxide) (MAPh) (93% ee, (+)). Propenyl ethers derived from ($-$)-6 undergo endo-selective (4+2) cycloadditions (2.3/1-8.2/1) in the presence Ti(Oi-Pr)$\\sb2$Cl$\\sb2$, however, exoselective (4+2) cycloadditions (10.2/l-54.8/l) are observed in the presence of MAPh.","abstract_html":"Chiral enol ether dienophiles derived from (1R,2S)-($-$)-2-phenylcyclohexanol and (R)-($-$)-2,2-diphenylcyclopentanol (($-$)-6 have been found to provide high levels of asymmetric induction in tandem inter (4+2) /intra (3+2) nitroalkene cycloadditions. Either enantiomeric series of tandem cycloaddition/hydrogenolysis product is available from the chiral auxiliary of a single absolute configuration by judicious selection of the Lewis acid promoter, Ti(Oi-Pr)$\\sb{2}$Cl$\\sb{2}$ (98% ee, ($-$)) or methylaluminum bis-(2,6-diphenylphenoxide) (MAPh) (93% ee, (+)). Propenyl ethers derived from ($-$)-6 undergo endo-selective (4+2) cycloadditions (2.3/1-8.2/1) in the presence Ti(Oi-Pr)$\\sb2$Cl$\\sb2$, however, exoselective (4+2) cycloadditions (10.2/l-54.8/l) are observed in the presence of MAPh.","abstract_has_math":true,"creators":["Schnute, Mark Edward"],"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":2011,"date_issued":"2011-05-07T13:38:43Z","date_published":"2011-05-07T13:38:43Z","updated_at":"2026-07-22T22:25:19Z","subjects":["Chemistry, Organic"],"languages":["eng"],"rights":["Copyright 1995 Schnute, Mark Edward"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9543716","(UMI)AAI9543716"],"render_values":[{"text":"AAI9543716","href":null,"code":true},{"text":"(UMI)AAI9543716","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/22403","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":["Schnute, Mark Edward"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T13:38:43Z","10000-01-01","1995"]},{"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":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1995 Schnute, Mark Edward"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9543716","(UMI)AAI9543716","http://hdl.handle.net/2142/22403"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Chiral enol ether dienophiles derived from (1R,2S)-($-$)-2-phenylcyclohexanol and (R)-($-$)-2,2-diphenylcyclopentanol (($-$)-6 have been found to provide high levels of asymmetric induction in tandem inter (4+2) /intra (3+2) nitroalkene cycloadditions. Either enantiomeric series of tandem cycloaddition/hydrogenolysis product is available from the chiral auxiliary of a single absolute configuration by judicious selection of the Lewis acid promoter, Ti(Oi-Pr)$\\sb{2}$Cl$\\sb{2}$ (98% ee, ($-$)) or methylaluminum bis-(2,6-diphenylphenoxide) (MAPh) (93% ee, (+)). Propenyl ethers derived from ($-$)-6 undergo endo-selective (4+2) cycloadditions (2.3/1-8.2/1) in the presence Ti(Oi-Pr)$\\sb2$Cl$\\sb2$, however, exoselective (4+2) cycloadditions (10.2/l-54.8/l) are observed in the presence of MAPh.","2-(Acyloxy)vinyl ethers undergo regioselective (4+2) cycloadditions with nitroalkenes (promoted by SnCl$\\sb4$) to afford substituted 5-acetoxy nitronates in good yields (68%-91%). The endo/exo selectivity in the cycloadditions has been found to be dependent on the nitroalkene substitution; 2-aryl-1-nitroalkenes provided exclusively exo cycloadducts while 2-cyclohexyl-1-nitroethene afforded predominately endo cycloadducts (12/1). The resulting nitronates can be elaborated to N-tosyl-4-substituted-3-hydroxypyrrolidines by hydrogenolysis (160 psi of H$\\sb2$/PtO$\\sb2$) or to bicyclic $\\alpha$-hydroxy lactams by (3+2) cycloaddition followed by hydrogenation (14.7 psi of H$\\sb2$/Raney nickel). A chiral 2-acetoxyvinyl ether derived from ($-$)-6 has been employed in the cycloaddition-hydrogenation sequence to prepare an optically active N-tosyl-3-hydroxypyrrolidine in high enantiomeric excess (96% ee). The strategy of nitroalkene (4+2) cycloadditions employing 2-acetoxyvinyl ethers as dienophiles has been explored toward the total synthesis of the Amaryllidaceae alkaloid (+)-pretazettine.","Made available in DSpace on 2011-05-07T13:38:43Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9543716.pdf: 17055410 bytes, checksum: bb07202659ccf6f30889b6e5747a3fd2 (MD5) Previous issue date: 1995","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:57:23Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:26:54-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"]},{"key":"dc:title","label":"Title","values":["Nitroalkene (4+2) cycloadditions of achiral and chiral vinyl ethers. The stereochemical consequence of the Lewis acid promoter and studies toward the total synthesis of (+)-pretazettine"]}]}],"canonical_facts":{"dc:contributor":["Denmark, Scott E."],"dc:creator":["Schnute, Mark Edward"],"dc:date":["2011-05-07T13:38:43Z","10000-01-01","1995"],"dc:description":["Chiral enol ether dienophiles derived from (1R,2S)-($-$)-2-phenylcyclohexanol and (R)-($-$)-2,2-diphenylcyclopentanol (($-$)-6 have been found to provide high levels of asymmetric induction in tandem inter (4+2) /intra (3+2) nitroalkene cycloadditions. Either enantiomeric series of tandem cycloaddition/hydrogenolysis product is available from the chiral auxiliary of a single absolute configuration by judicious selection of the Lewis acid promoter, Ti(Oi-Pr)$\\sb{2}$Cl$\\sb{2}$ (98% ee, ($-$)) or methylaluminum bis-(2,6-diphenylphenoxide) (MAPh) (93% ee, (+)). Propenyl ethers derived from ($-$)-6 undergo endo-selective (4+2) cycloadditions (2.3/1-8.2/1) in the presence Ti(Oi-Pr)$\\sb2$Cl$\\sb2$, however, exoselective (4+2) cycloadditions (10.2/l-54.8/l) are observed in the presence of MAPh.","2-(Acyloxy)vinyl ethers undergo regioselective (4+2) cycloadditions with nitroalkenes (promoted by SnCl$\\sb4$) to afford substituted 5-acetoxy nitronates in good yields (68%-91%). The endo/exo selectivity in the cycloadditions has been found to be dependent on the nitroalkene substitution; 2-aryl-1-nitroalkenes provided exclusively exo cycloadducts while 2-cyclohexyl-1-nitroethene afforded predominately endo cycloadducts (12/1). The resulting nitronates can be elaborated to N-tosyl-4-substituted-3-hydroxypyrrolidines by hydrogenolysis (160 psi of H$\\sb2$/PtO$\\sb2$) or to bicyclic $\\alpha$-hydroxy lactams by (3+2) cycloaddition followed by hydrogenation (14.7 psi of H$\\sb2$/Raney nickel). A chiral 2-acetoxyvinyl ether derived from ($-$)-6 has been employed in the cycloaddition-hydrogenation sequence to prepare an optically active N-tosyl-3-hydroxypyrrolidine in high enantiomeric excess (96% ee). The strategy of nitroalkene (4+2) cycloadditions employing 2-acetoxyvinyl ethers as dienophiles has been explored toward the total synthesis of the Amaryllidaceae alkaloid (+)-pretazettine.","Made available in DSpace on 2011-05-07T13:38:43Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9543716.pdf: 17055410 bytes, checksum: bb07202659ccf6f30889b6e5747a3fd2 (MD5) Previous issue date: 1995","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:57:23Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:26:54-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"],"dc:identifier":["AAI9543716","(UMI)AAI9543716","http://hdl.handle.net/2142/22403"],"dc:language":["eng"],"dc:rights":["Copyright 1995 Schnute, Mark Edward"],"dc:subject":["Chemistry, Organic"],"dc:title":["Nitroalkene (4+2) cycloadditions of achiral and chiral vinyl ethers. The stereochemical consequence of the Lewis acid promoter and studies toward the total synthesis of (+)-pretazettine"],"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":"2026-07-22T22:25:19Z"}