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Yan P, Stegbauer S, Wu Q, Kolodzeiski E, Stein CJ, Lu P, Bach T. Enantioselective Intramolecular ortho Photocycloaddition Reactions of 2-Acetonaphthones. Angew Chem Int Ed Engl 2024; 63:e202318126. [PMID: 38275271 DOI: 10.1002/anie.202318126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 01/22/2024] [Accepted: 01/23/2024] [Indexed: 01/27/2024]
Abstract
2-Acetonaphthones, which bear an alkenyl group tethered to its C1 carbon atom via an oxygen atom, were found to undergo an enantioselective intramolecular ortho photocycloaddition reaction. A chiral oxazaborolidine Lewis acid leads to a bathochromic absorption shift of the substrate and enables an efficient enantioface differentiation. Visible light irradiation (λ=450 nm) triggers the reaction which is tolerant of various groups at almost any position except carbon atom C8 (16 examples, 53-99 % yield, 80-97 % ee). Consecutive reactions were explored including a sensitized rearrangement to tetrahydrobiphenylenes, which occurred with full retention of configuration. Evidence was collected that the catalytic photocycloaddition occurs via triplet intermediates, and the binding mode of the acetonaphthone to the chiral Lewis acid was elucidated by DFT calculations.
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Affiliation(s)
- Peng Yan
- Research Center for Molecular Recognition and Synthesis, Department of Chemistry, Fudan University, 220 Handan Lu, Shanghai, 200433, China
| | - Simone Stegbauer
- Department Chemie and Catalysis Research Center (CRC) School of Natural Sciences, Technische Universität München, Lichtenbergstraße 4, D-85747, Garching, Germany
| | - Qinqin Wu
- Research Center for Molecular Recognition and Synthesis, Department of Chemistry, Fudan University, 220 Handan Lu, Shanghai, 200433, China
| | - Elena Kolodzeiski
- Department Chemie and Catalysis Research Center (CRC) School of Natural Sciences, Technische Universität München, Lichtenbergstraße 4, D-85747, Garching, Germany
| | - Christopher J Stein
- Department Chemie and Catalysis Research Center (CRC) School of Natural Sciences, Technische Universität München, Lichtenbergstraße 4, D-85747, Garching, Germany
| | - Ping Lu
- Research Center for Molecular Recognition and Synthesis, Department of Chemistry, Fudan University, 220 Handan Lu, Shanghai, 200433, China
| | - Thorsten Bach
- Department Chemie and Catalysis Research Center (CRC) School of Natural Sciences, Technische Universität München, Lichtenbergstraße 4, D-85747, Garching, Germany
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2
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Harvey FM, Heidecker AH, Merten C, Bach T. Diastereoselective, Lewis acid-mediated Diels-Alder reactions of allenoic acid derivatives and 1,3-cyclopentadienes. Org Biomol Chem 2023; 21:4422-4428. [PMID: 37184215 DOI: 10.1039/d3ob00598d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Allenes with different substituents at their terminal carbon atom display axial chirality and can be obtained in enantiopure form by a photochemical deracemization protocol. It has now been studied under which conditions allenoic acid derivatives undergo a Diels-Alder reaction with 1,3-cyclopentadienes and which products result. Cyclic derivatives (lactams, lactones) underwent an exo-selective reaction catalyzed by the Lewis acid Eu(fod)3, while acyclic derivatives yielded with high preference the endo-products (EtAlCl2 as the preferred Lewis acid). The exocyclic double bond forms with exquisite diastereoselectivity and the chirality transfer is close to perfect. The method was applied to the synthesis of the sesquiterpenes β-santalol (1) and 10(E)-β-santalic acid (13).
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Affiliation(s)
- Freya M Harvey
- Technische Universität München, School of Natural Sciences, Department of Chemistry and Catalysis Research Center, Lichtenbergstrasse 4, 85747 Garching, Germany.
| | - Alexandra H Heidecker
- Technische Universität München, School of Natural Sciences, Department of Chemistry and Catalysis Research Center, Lichtenbergstrasse 4, 85747 Garching, Germany.
| | - Christian Merten
- Organische Chemie II, Fakultät für Chemie und Biochemie, Ruhr-Universität Bochum, Universitätsstraße 150, 44801 Bochum, Germany
| | - Thorsten Bach
- Technische Universität München, School of Natural Sciences, Department of Chemistry and Catalysis Research Center, Lichtenbergstrasse 4, 85747 Garching, Germany.
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3
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Bakanas I, Tang JC, Sarpong R. Skeletal diversification by C-C cleavage to access bicyclic frameworks from a common tricyclooctane intermediate. Chem Commun (Camb) 2023; 59:3858-3861. [PMID: 36916206 PMCID: PMC10518267 DOI: 10.1039/d3cc00945a] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
Herein, the diversification of tricyclo[3.2.1.03,6]octane scaffolds to afford diverse bicyclic scaffolds is described. The strained tricyclooctanes are prepared in two steps featuring a blue light-mediated [2+2] cycloaddition. Strategies for the cleavage of this scaffold were then explored resulting in the selective syntheses of the bicyclo[3.1.1]heptane, bicyclo[3.2.1]octane, and bicyclo[3.2.0]heptane cores. These findings may guide future studies of C-C cleavage reactions in strained carbon frameworks and their application in complex molecule synthesis.
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Affiliation(s)
- Ian Bakanas
- Department of Chemistry, University of California-Berkeley, Berkeley, California, USA.
| | - Jess C Tang
- Department of Chemistry, University of California-Berkeley, Berkeley, California, USA.
| | - Richmond Sarpong
- Department of Chemistry, University of California-Berkeley, Berkeley, California, USA.
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Wu J, Li SJ, Jiang L, Ma XC, Lan Y, Shen L. UV light-driven late-stage skeletal reorganization to diverse limonoid frameworks: A proof of concept for photobiosynthesis. SCIENCE ADVANCES 2023; 9:eade2981. [PMID: 36706176 PMCID: PMC9882982 DOI: 10.1126/sciadv.ade2981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 12/29/2022] [Indexed: 06/18/2023]
Abstract
Late-stage skeletal reorganization (LSSR) is a type of fascinating organic transformation processes in natural product total synthesis. However, few facile and effective LSSR methodologies have hitherto been developed. Here, LSSR of limonoid natural products via photochemical cascades is first reported. Starting from xyloelves A and B, nine distinct limonoid products with five unprecedented scaffolds are generated. The photocascade pathways of these natural products and mechanistic rationale via intramolecular triplet energy transfer are revealed by quantum mechanical calculations. Most notably, ultraviolet light-driven transannular and stereoselective C → C 1,4-acyl migration is first found as a photochemical approach, particularly for LSSR of natural products. This approach holds promise for designing LSSR strategies to access bioactive cage-like molecules. Besides that, our findings provide a clear proof of concept for natural product photobiosynthesis. Xyloelf A, substantially ameliorating concanavalin A-induced liver injury in mice, could be used as a unique molecular template for hepatoprotective drug discovery.
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Affiliation(s)
- Jun Wu
- Guangdong Key Laboratory of Natural Medicine Research and Development, College of Pharmacy, The First Dongguan Affiliated Hospital, Guangdong Medical University, Dongguan 523808, China
| | - Shi-Jun Li
- College of Chemistry, Zhengzhou University, Zhengzhou 450001, China
| | - Long Jiang
- School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Xiao-Chi Ma
- Pharmaceutical Research Center, Second Affiliated Hospital, Dalian Medical University, Dalian 116044, China
| | - Yu Lan
- College of Chemistry, Zhengzhou University, Zhengzhou 450001, China
- School of Chemistry and Chemical Engineering, Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 400030, China
| | - Li Shen
- Guangdong Key Laboratory of Natural Medicine Research and Development, College of Pharmacy, The First Dongguan Affiliated Hospital, Guangdong Medical University, Dongguan 523808, China
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Proessdorf J, Jandl C, Pickl T, Bach T. Arene Activation through Iminium Ions: Product Diversity from Intramolecular Photocycloaddition Reactions. Angew Chem Int Ed Engl 2022; 61:e202208329. [PMID: 35920713 PMCID: PMC9826208 DOI: 10.1002/anie.202208329] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Indexed: 01/11/2023]
Abstract
While 2-alk-ω-enyloxy-sustituted benzaldehydes do not display any photochemical reactivity at the arene core, the respective iminium perchlorates were found to undergo efficient reactions either upon direct irradiation (λ=366 nm) or under sensitizing conditions (λ=420 nm, 2.5 mol% thioxanthen-9-one). Three pathways were found: (a) Most commonly, the reaction led to benzoxacyclic products in which the olefin in the tether underwent a formal, yet unprecedented carboformylation (13 examples, 44-99 % yield). The cascade process occurred with high diastereoselectivity and was found to be stereoconvergent. (b) If a substituent resides in the 3-position of the benzene ring, a meta photocycloaddition was observed which produced tetracyclic skeletons with five stereogenic centers in excellent regio- and diastereoselectivity (2 examples, 58-79 % yield). (c) If the tether was internally substituted at the alkene, an arene photocycloaddition was avoided and an azetidine was formed in an aza Paternò-Büchi reaction (2 examples, 95-98 % yield).
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Affiliation(s)
- Johanna Proessdorf
- Department Chemie and Catalysis Research Center (CRC)School of Natural SciencesTechnische Universität MünchenLichtenbergstraße 485747GarchingGermany
| | - Christian Jandl
- Department Chemie and Catalysis Research Center (CRC)School of Natural SciencesTechnische Universität MünchenLichtenbergstraße 485747GarchingGermany
| | - Thomas Pickl
- Department Chemie and Catalysis Research Center (CRC)School of Natural SciencesTechnische Universität MünchenLichtenbergstraße 485747GarchingGermany
| | - Thorsten Bach
- Department Chemie and Catalysis Research Center (CRC)School of Natural SciencesTechnische Universität MünchenLichtenbergstraße 485747GarchingGermany
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Bach T, Gilbert A. The Awakening of a Sleeping Beauty: The ortho Photocycloaddition in the Total Synthesis of Protoilludane- and Prezizaene-Type Sesquiterpenes. Synlett 2022. [DOI: 10.1055/s-0042-1751354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
AbstractPhotochemical cascade (domino) reactions provide a unique opportunity for the construction of complex molecular architectures. Specifically, an intramolecular ortho photocycloaddition of 7-(alkenyloxy)-indanones triggers a sequence of consecutive reactions that can lead in a single operation to the complete skeleton of two important classes of sesquiterpenes: protoilludanes and prezizaenes. In the former case, two transformations follow the initial photocycloaddition, while in the latter case, there are three consecutive transformations, two of which are initiated by a photon. Remarkably, the reaction cascades proceed with exquisite diastereoselectivity, generating three (protoilludane) or five (prezizaene) stereogenic centers with defined relative configurations.1 Introduction2 First Encounter and Initial Studies3 Protoilludane-Type Sesquiterpenes4 Prezizaene-Type Sesquiterpenes5 Enantioselectivity6 Perspective and Summary
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7
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Proessdorf J, Jandl C, Pickl T, Bach T. Arene Activation through Iminium Ions: Product Diversity from Intramolecular Photocycloaddition Reactions. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202208329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Johanna Proessdorf
- Technische Universität München: Technische Universitat Munchen Department Chemie GERMANY
| | - Christian Jandl
- Technische Universität München: Technische Universitat Munchen Department Chemie GERMANY
| | - Thomas Pickl
- Technische Universität München: Technische Universitat Munchen Department Chemie GERMANY
| | - Thorsten Bach
- Technische Universität München Lehrstuhl für Organische Chemie I Lichtenbergstr. 4 85747 Garching GERMANY
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Peraka S, Gorachand B, Hussain A, Sravanthi R, Ramachary DB. Organocatalytic One‐pot Synthesis of Pseudo‐Terpenoids. European J Org Chem 2022. [DOI: 10.1002/ejoc.202200674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Swamy Peraka
- University of Hyderabad School of Chemistry INDIA
| | | | | | | | - Dhevalapally B. Ramachary
- University of Hyderabad School of Chemistry Prof. C.R.Rao RoadCentral University PostGachi BowliHyderabad 500 046 Hyderabad INDIA
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Abstract
Terpenoids constitute a broad class of natural compounds with tremendous variability in structure and bioactivity, which resulted in a strong interest of the chemical community to this class of natural products over the last 150 years. The presence of strained small rings renders the terpenoid targets interesting for chemical synthesis, due to limited number of available methods and stability issues. In this feature article, a number of recent examples of total syntheses of terpenoids with complex carbon frameworks featuring small rings are discussed. Specific emphasis is given to the new developments in strategical and tactical approaches to construction of such systems.
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Affiliation(s)
- Gleb A Chesnokov
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
| | - Karl Gademann
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
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Gorobets E, Papatzimas JW, Dourado J, Yousefalizadeh G, Lee J, Brownsey DK, Stamplecoskie K, Davis R, Derksen DJ. A Vinylogous Norrish Reaction as a Strategy for Light-Mediated Ring Expansion. Chem Commun (Camb) 2022; 58:2910-2913. [DOI: 10.1039/d2cc00513a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reactions of bicyclic divinyl ketones display wavelength-dependent changes in product formation. UV irradiation results in the formation of competitive [6,3,5] and [7,3,5] tricyclic unsaturated ketones that subsequently undergo ring...
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