- Dehydrative Nazarov-type electrocyclizations of alkenyl (hetero)aryl carbinols via calcium catalysis: Access to cyclopenta[b]thiophenes and indene derivatives
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A general approach to the understudied cyclopenta[b]thiophenes is reported. The products were directly generated from calcium-catalyzed, dehydrative, Nazarov-type electrocyclizations of alkenyl thienyl carbinols in up to 82% yield. The thienyl carbinols demonstrated good tolerance for aryl and heteroaryl substituents on the alkene. Aryl carbinols were also amenable to the calcium-catalyzed conditions and afforded indene derivatives in good yields. In most cases, the reaction was selective for the thermodynamic alkene isomer; however, substituent effects played a role in determining product outcomes. Mechanistically, the calcium catalyst initiated formation of alkenyl (hetero)aryl carbinyl cations which subsequently underwent a 4π electrocyclization and elimination that is reminiscent of the Nazarov reaction. This transformation is significant for two main reasons: 1) it represents one of the only examples of catalysis for dehydrative, Nazarov-type electrocyclizations in which thiophene was compatible; 2) it allowed for the direct formation of cyclopenta[b]thiophenes while circumventing the need for cyclopenta[b]thiophenones as precursors.
- Martin, M. Cynthia,Sandridge, Matthew J.,Williams, Corey W.,Francis, Zola A.,France, Stefan
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p. 4093 - 4108
(2017/06/29)
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- Protocol for the synthesis of heteroaromatic ring-Fused cyclohexanones
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A general protocol for the catalytic homo-Nazarov cyclization of cyclopropyl heteroaryl ketones has been developed,which employs indiumtriflate as the promoter. A range of heteroaromatic ring-fused cyclohexanones was synthesized in 56-91% yield using this
- Phun, Lien H.,Patil, Dadasaheb V.,Cavitt, Marchello A.,France, Stefan
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supporting information; scheme or table
p. 1952 - 1955
(2011/06/25)
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- Controlled synthesis of functionalized mixed thiophene/furan oligomers
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A novel and simple synthetic route for the preparation of a series of functionalized mixed thiophene/furan oligomers is described. This method, involving a Mn(OAc)3-mediated oxidative addition βthienyl-β-keto esters (=βoxothiophenepropanoates) to methyl 3-thienylprop-2-enoates, allows the construction of highly functionalized heteropolyaromatic oligomers possessing various chain lengths (Schemes 2, 4, and 5). Moreover, the straightforward transformation of the carbonyl functions appended to the furan rings leads to polycarboxylic acid precursors of H2O-soluble conducting polymers (Scheme 6).
- Garzino, Frederic,Meou, Alain,Brun, Pierre
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p. 1989 - 1998
(2007/10/03)
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- PIPERAZINE, PIPERIDINE AND 1,2,5,6- TETRAHYDROPYRIDINE
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A compound selected from those of formula: STR1 wherein: A-B, n, D and E are as defined in the specification,their racemic mixtures, and their optical isomers,and also the physiologically tolerable salts thereof with appropriate acids. The products of the invention may be used therapeutically.
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