{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/70313"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/70313","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Compounds of Pentacoordinate (10-Boron-5) and Hexacoordinate (12-Boron-6) Hypervalent Boron","abstract":"Efficient synthetic routes to 2-substituted pyridines and 2,6-disubstituted pyridine 1-oxides are described, involving direct ortho lithiation with the sterically hindered base, lithium 2,2,6,6-tetramethylpiperidide, in the presence of electrophiles that are compatible with the base, e.g., trimethylsilyl chloride and hexafluoroacetone.","abstract_html":"Efficient synthetic routes to 2-substituted pyridines and 2,6-disubstituted pyridine 1-oxides are described, involving direct ortho lithiation with the sterically hindered base, lithium 2,2,6,6-tetramethylpiperidide, in the presence of electrophiles that are compatible with the base, e.g., trimethylsilyl chloride and hexafluoroacetone.","abstract_has_math":false,"creators":["Lee, David Yen"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Chemistry","degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014-12-15T23:18:34Z","date_published":"2014-12-15T23:18:34Z","updated_at":"2026-07-22T22:26:02Z","subjects":["Chemistry, Organic"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(UMI)AAI8600249"],"render_values":[{"text":"(UMI)AAI8600249","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/70313","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Lee, David Yen"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2014-12-15T23:18:34Z","10000-01-01","1985"]},{"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/2142/70313","(UMI)AAI8600249"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Efficient synthetic routes to 2-substituted pyridines and 2,6-disubstituted pyridine 1-oxides are described, involving direct ortho lithiation with the sterically hindered base, lithium 2,2,6,6-tetramethylpiperidide, in the presence of electrophiles that are compatible with the base, e.g., trimethylsilyl chloride and hexafluoroacetone.","Syntheses of the first isolable hypervalent 10-B-5 species 17, 25, and 28, and 12-B-6 species 30 and 35 are described. The ('1)H, ('13)C, and ('19)F NMR spectra support the assigned hypervalent structures. The ('11)B NMR downfield chemical shifts resulting from protonation of the 10-B-5 species 17 (-20.1 ppm) + H('+) (--->) 18 (-0.1 ppm, 25 (-41.0 ppm) + H('+) (--->) 26 (+5.7 ppm), and 28 (-35.7 ppm) + H('+) (--->) 29 (+12.0 ppm) fall in the range associated with 8-B-4 species with only first-row elements bonded to boron (-17.5 to +50 ppm). The ('11)B NMR chemical shifts resulting from monoprotonation of the 12-B-6 species 30 (-123.0 ppm) + H('+) (--->) 31 (-70.4 ppm) and 35 (-233.2 ppm) + H('+) (--->) 36 (-61.0 ppm) fall in the range near those of the other 10-B-5 species 17, 25, and 29. The ('11)B NMR chemical shifts of the doubly protonated species 32 + H('+) (--->) 33 (+4.7 ppm) and 36 + H('+) (--->) 37 (+11.5 ppm) fall in the range of ordinary borates. Hypervalent 10-B-5 species 36 is deprotonated by using 2,2,6,6-tetramethylpiperidine to recover 12-B-6 species 35. The spin-lattice (T(,1)) relaxation results indicate that the geometries of the hypervalent 10-B-5 and 12-B-6 species are more symmetrical than that of tetracoordinate borates. The values of T(,1) fall, with some exceptions, in the order 12-B-6 > 10-B-5 > 8-B-4.","Two electrons of the three-center four-electron 0-B-0 bond are delocalized into the diequatorial five- or six-membered ring of hypervalent 10-B-5 species 6 and 11, making them 6-(pi) Huckel aromatic systems that we call bis ipso aromatic. The proposed bis ipso aromaticity is evidenced by the great similarity of the electronic spectra of the hypervalent 10-B-5 species (6 and 11) to their carbon analogues (9-phenyl fluorenyl anion and anthracene). The hypervalent boron atom appears to have electronic properties almost identical to those of a carbon atom in the analogous (pi)-system with near identity of electronic spectra.","Made available in DSpace on 2014-12-15T23:18:34Z (GMT). No. of bitstreams: 1 8600249.pdf: 3117872 bytes, checksum: b79864629c1c62a0e01a6eabdba3e470 (MD5) Previous issue date: 1985","Embargo set by: Seth Robbins for item 70479 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","112 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985."]},{"key":"dc:title","label":"Title","values":["Compounds of Pentacoordinate (10-Boron-5) and Hexacoordinate (12-Boron-6) Hypervalent Boron"]}]}],"canonical_facts":{"dc:creator":["Lee, David Yen"],"dc:date":["2014-12-15T23:18:34Z","10000-01-01","1985"],"dc:description":["Efficient synthetic routes to 2-substituted pyridines and 2,6-disubstituted pyridine 1-oxides are described, involving direct ortho lithiation with the sterically hindered base, lithium 2,2,6,6-tetramethylpiperidide, in the presence of electrophiles that are compatible with the base, e.g., trimethylsilyl chloride and hexafluoroacetone.","Syntheses of the first isolable hypervalent 10-B-5 species 17, 25, and 28, and 12-B-6 species 30 and 35 are described. The ('1)H, ('13)C, and ('19)F NMR spectra support the assigned hypervalent structures. The ('11)B NMR downfield chemical shifts resulting from protonation of the 10-B-5 species 17 (-20.1 ppm) + H('+) (--->) 18 (-0.1 ppm, 25 (-41.0 ppm) + H('+) (--->) 26 (+5.7 ppm), and 28 (-35.7 ppm) + H('+) (--->) 29 (+12.0 ppm) fall in the range associated with 8-B-4 species with only first-row elements bonded to boron (-17.5 to +50 ppm). The ('11)B NMR chemical shifts resulting from monoprotonation of the 12-B-6 species 30 (-123.0 ppm) + H('+) (--->) 31 (-70.4 ppm) and 35 (-233.2 ppm) + H('+) (--->) 36 (-61.0 ppm) fall in the range near those of the other 10-B-5 species 17, 25, and 29. The ('11)B NMR chemical shifts of the doubly protonated species 32 + H('+) (--->) 33 (+4.7 ppm) and 36 + H('+) (--->) 37 (+11.5 ppm) fall in the range of ordinary borates. Hypervalent 10-B-5 species 36 is deprotonated by using 2,2,6,6-tetramethylpiperidine to recover 12-B-6 species 35. The spin-lattice (T(,1)) relaxation results indicate that the geometries of the hypervalent 10-B-5 and 12-B-6 species are more symmetrical than that of tetracoordinate borates. The values of T(,1) fall, with some exceptions, in the order 12-B-6 > 10-B-5 > 8-B-4.","Two electrons of the three-center four-electron 0-B-0 bond are delocalized into the diequatorial five- or six-membered ring of hypervalent 10-B-5 species 6 and 11, making them 6-(pi) Huckel aromatic systems that we call bis ipso aromatic. The proposed bis ipso aromaticity is evidenced by the great similarity of the electronic spectra of the hypervalent 10-B-5 species (6 and 11) to their carbon analogues (9-phenyl fluorenyl anion and anthracene). The hypervalent boron atom appears to have electronic properties almost identical to those of a carbon atom in the analogous (pi)-system with near identity of electronic spectra.","Made available in DSpace on 2014-12-15T23:18:34Z (GMT). No. of bitstreams: 1 8600249.pdf: 3117872 bytes, checksum: b79864629c1c62a0e01a6eabdba3e470 (MD5) Previous issue date: 1985","Embargo set by: Seth Robbins for item 70479 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","112 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985."],"dc:identifier":["http://hdl.handle.net/2142/70313","(UMI)AAI8600249"],"dc:subject":["Chemistry, Organic"],"dc:title":["Compounds of Pentacoordinate (10-Boron-5) and Hexacoordinate (12-Boron-6) Hypervalent Boron"],"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":"2026-07-22T22:26:02Z"}