Diversification of ortho-fused cycloocta-2,5-dien-1-one cores and 8 to 6-Ring conversion by sigma bond C-C cleavage
Sequential treatment of 2-C6H4Br(CHO) with LiC≡CR1 (R1 = SiMe3, tBu), nBuLi, CuBr∙SMe2 and HC≡CCHClR2 [R2 = Ph, 4-CF3Ph, 3-CNPh, 4-(MeO2C)Ph] at -50 oC leads to formation of an intermediate carbanion (Z)-1,2-C6H4{CA(=O)C≡CBR1}{CH=CH(CH–)R2} (4). Low temperatures (-50 oC) favour attack at CB leading...
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Wiley-VCH Verlag
2016
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| Online Access: | https://eprints.nottingham.ac.uk/34641/ |
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| author | Eccleshare, Lee Lozada-Rodriguez, Leticia Cooper, Phillippa Burroughs, Laurence Ritchie, John Lewis, William Woodward, Simon |
| author_facet | Eccleshare, Lee Lozada-Rodriguez, Leticia Cooper, Phillippa Burroughs, Laurence Ritchie, John Lewis, William Woodward, Simon |
| author_sort | Eccleshare, Lee |
| building | Nottingham Research Data Repository |
| collection | Online Access |
| description | Sequential treatment of 2-C6H4Br(CHO) with LiC≡CR1 (R1 = SiMe3, tBu), nBuLi, CuBr∙SMe2 and HC≡CCHClR2 [R2 = Ph, 4-CF3Ph, 3-CNPh, 4-(MeO2C)Ph] at -50 oC leads to formation of an intermediate carbanion (Z)-1,2-C6H4{CA(=O)C≡CBR1}{CH=CH(CH–)R2} (4). Low temperatures (-50 oC) favour attack at CB leading to kinetic formation of 6,8-bicycles containing non-classical C-carbanion enolates (5). Higher temperatures ( 10 oC to ambient) and electron deficient R2 favour retro σ-bond C-C cleavage regenerating 4 which subsequently closes on CA providing 6,6-bicyclic alkoxides (6). Computational modelling (CBS-QB3) indicates both pathways are viable and of similar energies. Reaction of 6 with H+ affords 1,2-dihydronaphthalen-1-ols, or under dehydrating conditions, 2-aryl-1-alkynylnaphthlenes. Enolates 5 react in situ with: H2O, D2O, I2, allylbromide, S2Me2, CO2 and lead to the expected C-E derivatives (E = H, D, I, allyl, SMe, CO2H) in 49-64% yield directly from intermediate 5. The parents (E = H; R1 = SiMe3, tBu; R2 = Ph) are versatile starting materials for NaBH4 and Grignard C=O additions, desilylation (when R1 = SiMe) and oxime formation. The latter allows formation of 6,9-bicyclics via Beckmann rearrangement. The 6,8-ring iodides are suitable Suzuki precursors for Pd-catalysed C-C coupling (81-87%); while the carboxylic acids readily form amides under T3P® conditions (71-95%). |
| first_indexed | 2025-11-14T19:23:33Z |
| format | Article |
| id | nottingham-34641 |
| institution | University of Nottingham Malaysia Campus |
| institution_category | Local University |
| last_indexed | 2025-11-14T19:23:33Z |
| publishDate | 2016 |
| publisher | Wiley-VCH Verlag |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | nottingham-346412020-05-04T17:59:48Z https://eprints.nottingham.ac.uk/34641/ Diversification of ortho-fused cycloocta-2,5-dien-1-one cores and 8 to 6-Ring conversion by sigma bond C-C cleavage Eccleshare, Lee Lozada-Rodriguez, Leticia Cooper, Phillippa Burroughs, Laurence Ritchie, John Lewis, William Woodward, Simon Sequential treatment of 2-C6H4Br(CHO) with LiC≡CR1 (R1 = SiMe3, tBu), nBuLi, CuBr∙SMe2 and HC≡CCHClR2 [R2 = Ph, 4-CF3Ph, 3-CNPh, 4-(MeO2C)Ph] at -50 oC leads to formation of an intermediate carbanion (Z)-1,2-C6H4{CA(=O)C≡CBR1}{CH=CH(CH–)R2} (4). Low temperatures (-50 oC) favour attack at CB leading to kinetic formation of 6,8-bicycles containing non-classical C-carbanion enolates (5). Higher temperatures ( 10 oC to ambient) and electron deficient R2 favour retro σ-bond C-C cleavage regenerating 4 which subsequently closes on CA providing 6,6-bicyclic alkoxides (6). Computational modelling (CBS-QB3) indicates both pathways are viable and of similar energies. Reaction of 6 with H+ affords 1,2-dihydronaphthalen-1-ols, or under dehydrating conditions, 2-aryl-1-alkynylnaphthlenes. Enolates 5 react in situ with: H2O, D2O, I2, allylbromide, S2Me2, CO2 and lead to the expected C-E derivatives (E = H, D, I, allyl, SMe, CO2H) in 49-64% yield directly from intermediate 5. The parents (E = H; R1 = SiMe3, tBu; R2 = Ph) are versatile starting materials for NaBH4 and Grignard C=O additions, desilylation (when R1 = SiMe) and oxime formation. The latter allows formation of 6,9-bicyclics via Beckmann rearrangement. The 6,8-ring iodides are suitable Suzuki precursors for Pd-catalysed C-C coupling (81-87%); while the carboxylic acids readily form amides under T3P® conditions (71-95%). Wiley-VCH Verlag 2016-07-25 Article PeerReviewed Eccleshare, Lee, Lozada-Rodriguez, Leticia, Cooper, Phillippa, Burroughs, Laurence, Ritchie, John, Lewis, William and Woodward, Simon (2016) Diversification of ortho-fused cycloocta-2,5-dien-1-one cores and 8 to 6-Ring conversion by sigma bond C-C cleavage. Chemistry - a European Journal, 22 (35). pp. 12542-12547. ISSN 1521-3765 Annulation Medium-ring compounds Synthetic methods Ring expansion C-C activation http://onlinelibrary.wiley.com/doi/10.1002/chem.201601970/abstract doi:10.1002/chem.201601970 doi:10.1002/chem.201601970 |
| spellingShingle | Annulation Medium-ring compounds Synthetic methods Ring expansion C-C activation Eccleshare, Lee Lozada-Rodriguez, Leticia Cooper, Phillippa Burroughs, Laurence Ritchie, John Lewis, William Woodward, Simon Diversification of ortho-fused cycloocta-2,5-dien-1-one cores and 8 to 6-Ring conversion by sigma bond C-C cleavage |
| title | Diversification of ortho-fused cycloocta-2,5-dien-1-one cores and 8 to 6-Ring conversion by sigma bond C-C cleavage |
| title_full | Diversification of ortho-fused cycloocta-2,5-dien-1-one cores and 8 to 6-Ring conversion by sigma bond C-C cleavage |
| title_fullStr | Diversification of ortho-fused cycloocta-2,5-dien-1-one cores and 8 to 6-Ring conversion by sigma bond C-C cleavage |
| title_full_unstemmed | Diversification of ortho-fused cycloocta-2,5-dien-1-one cores and 8 to 6-Ring conversion by sigma bond C-C cleavage |
| title_short | Diversification of ortho-fused cycloocta-2,5-dien-1-one cores and 8 to 6-Ring conversion by sigma bond C-C cleavage |
| title_sort | diversification of ortho-fused cycloocta-2,5-dien-1-one cores and 8 to 6-ring conversion by sigma bond c-c cleavage |
| topic | Annulation Medium-ring compounds Synthetic methods Ring expansion C-C activation |
| url | https://eprints.nottingham.ac.uk/34641/ https://eprints.nottingham.ac.uk/34641/ https://eprints.nottingham.ac.uk/34641/ |