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Jankovic CL, McIntosh KC, Lofstrand VA, West FG. Stereoselective Intramolecular [2+2] Trapping of 1,2-Cyclohexadienes: a Route to Rigid, Angularly Fused Tricyclic Scaffolds. Chemistry 2023; 29:e202301668. [PMID: 37352092 DOI: 10.1002/chem.202301668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 06/22/2023] [Accepted: 06/23/2023] [Indexed: 06/25/2023]
Abstract
1,2-Cyclohexadienes generated under mild fluoride-mediated desilylative conditions undergo efficient intramolecular [2+2] trapping, providing tricyclic alkylidene cyclobutanes with complete diastereoselectivity for the cis-fused products. Pendent styrenes or electron-deficient olefins can trap simple 1,2-cyclohexadienes or their oxygenated counterparts, with 14 substrates being disclosed. Reactions proceed at ambient temperature using just cesium fluoride in up to 91 % yield, and the necessary precursors are easily accessed from substituted 2-bromocyclohexenones. Multiple synthetic routes have been developed to install the appropriate functional groups required for [2+2] trapping.
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Affiliation(s)
| | - Kyle C McIntosh
- Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada
| | - Verner A Lofstrand
- Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada
| | - F G West
- Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada
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Lofstrand VA, McIntosh KC, Almehmadi YA, West FG. Strain-Activated Diels-Alder Trapping of 1,2-Cyclohexadienes: Intramolecular Capture by Pendent Furans. Org Lett 2019; 21:6231-6234. [PMID: 31343882 DOI: 10.1021/acs.orglett.9b02085] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Intramolecular [4 + 2] cycloaddition reactions of substituted 1,2-cyclohexadienes with pendent furans enables the synthesis of complex tetracyclic scaffolds in a single step under mild conditions. All Diels-Alder cycloadducts were obtained as single diastereomers, assigned as the endo isomer. Substrates were easily assembled via Stork-Danheiser alkylation of 3-ethoxy-2-bromocyclohex-2-enone to accommodate a range of tethers and furan traps. Cleavage of enol acetate moieties resulted in room-temperature Diels-Alder cycloreversion to tethered furyl cyclohexenones.
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Affiliation(s)
- Verner A Lofstrand
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta T6G 2G2 , Canada
| | - Kyle C McIntosh
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta T6G 2G2 , Canada
| | - Yaseen A Almehmadi
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta T6G 2G2 , Canada
| | - F G West
- Department of Chemistry , University of Alberta , 11227 Saskatchewan Drive , Edmonton , Alberta T6G 2G2 , Canada
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Abstract
1,2-Cyclohexadienes are transient intermediates that undergo rapid dimerization and intermolecular trapping with activated olefins and heteroatomic nucleophiles. Fluoride-mediated desilylative elimination of readily accessible 6-silylcyclohexene-1-triflates allows the mild, chemoselective, and functional-group tolerant generation of cyclic allene intermediates, which undergo efficient trapping reactions with stable 1,3-dipoles. The reactions proceed with high levels of both regio- and diastereoselectivity. The reaction of cyclic allenes with azides is accompanied by the facile loss of dinitrogen, resulting in the formation of tetrahydroindoles or polycylic aziridines depending on the azide employed.
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Affiliation(s)
- Verner A Lofstrand
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, AB., T6G 2G2, Canada), Fax
| | - Frederick G West
- Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, AB., T6G 2G2, Canada), Fax.
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Lofstrand VA, Matsuura BS, Furst L, Narayanam JMR, Stephenson CRJ. Formation and Trapping of Azafulvene Intermediates Derived from Manganese-Mediated Oxidative Malonate Coupling. Tetrahedron 2016; 72:3775-3780. [PMID: 27551160 DOI: 10.1016/j.tet.2016.03.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The one-pot, three-component, coupling reaction of indoles/pyrroles, dimethyl malonate, and acetic acid was performed using Mn(III) acetate as an oxidant. In the presence of Mn(OAc)3, indole-2, and indole-3-carbonyl compounds were alkylated at the 3- and 2- positions, respectively, with subsequent oxidation and nucleophilic capture occurring at the newly formed benzylic carbon. In contrast, oxidation of 2- and 3-indole carboxylic acids afforded the corresponding 2-oxindol-3-ylidenes and 3-oxindol-2-ylidenes. The reaction conditions, scope, and mechanism are discussed herein.
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Affiliation(s)
- Verner A Lofstrand
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, MI 48109, USA
| | - Bryan S Matsuura
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, MI 48109, USA
| | - Laura Furst
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, MI 48109, USA
| | - Jagan M R Narayanam
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, MI 48109, USA
| | - Corey R J Stephenson
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, MI 48109, USA
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Ylijoki KEO, Witherell RD, Kirk AD, Böcklein S, Lofstrand VA, McDonald R, Ferguson MJ, Stryker JM. Synthesis, Structure, and Reactivity of Alkyl-Substituted Half-Sandwich η5-Pentadienyl Complexes of Cobalt. Organometallics 2009. [DOI: 10.1021/om900754h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kai E. O. Ylijoki
- Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 Canada
| | - Ross D. Witherell
- Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 Canada
| | - Andrew D. Kirk
- Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 Canada
| | - Sebastian Böcklein
- Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 Canada
| | - Verner A. Lofstrand
- Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 Canada
| | - Robert McDonald
- Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 Canada
| | - Michael J. Ferguson
- Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 Canada
| | - Jeffrey M. Stryker
- Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 Canada
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