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Abstract
Cyclopropenium ions are the smallest class of aromatic compounds, satisfying Hückel's rules of aromaticity with two π electrons within a three-membered ring. First prepared by Breslow in 1957, cyclopropenium ions have been found to possess extraordinary stability despite being both cationic and highly strained. In the 65 years since their first preparation, cyclopropenium ions have been the subject of innumerable studies concerning their synthesis, physical properties, and reactivity. However, prior to our work, the reactivity of these unique carbocations had not been exploited for reaction promotion or catalysis.Over the past 13 years, we have been exploring aromatic ions as unique and versatile building blocks for the development of catalysts for organic chemistry. A major portion of this work has been focused on leveraging the remarkable properties of the smallest of the aromatic ions─cyclopropeniums─as a design element in the invention of highly reactive catalysts. Indeed, because of its unique profile of hydrolytic stability, compact geometry, and relatively easy oxidizability, the cyclopropenium ring has proven to be a highly advantageous construction module for catalyst invention.In this Account, we describe some of our work using cyclopropenium ions as a key element in the design of novel catalysts. First, we discuss our early work aimed at promoting dehydrative reactions, starting with Appel-type chlorodehydrations of alcohols and carboxylic acids, cyclic ether formations, and Beckmann rearrangements and culminating in the realization of catalytic chlorodehydrations of alcohols and a catalytic Mitsunobu-type reaction. Next, we describe the development of cyclopropenimines as strong, neutral organic Brønsted bases and, in particular, the use of chiral cyclopropenimines for enantioselective Brønsted catalysis. We also describe the development of higher-order cyclopropenimine superbases. The use of tris(amino)cyclopropenium (TAC) ions as a novel class of phase-transfer catalysts is discussed for the reaction of epoxides with carbon dioxide. Next, we describe the formation of a cyclopropenone radical cation that has a portion of its spin density on the oxygen atom, leading to some peculiar metal ligand behavior. Finally, we discuss recent work that employs TAC electrophotocatalysts for oxidation reactions. The key intermediate for this chemistry is a TAC radical dication, which as an open-shell photocatalyst has remarkably strong excited-state oxidizing power. We describe the application of this strategy to transformations ranging from the oxidative functionalization of unactivated arenes to the regioselective derivatization of ethers, C-H aminations, vicinal C-H diaminations, and finally aryl olefin dioxygenations. Collectively, these catalytic platforms demonstrate the utility of charged aromatic rings, and cyclopropenium ions in particular, to enable unique advances in catalysis.
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Affiliation(s)
- Rebecca M Wilson
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Tristan H Lambert
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
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Xiao W, Wu J. Recent advance in carbocation-catalyzed reactions. CHINESE CHEM LETT 2022. [DOI: 10.1016/j.cclet.2022.06.060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Ranga PK, Ahmad F, Singh G, Tyagi A, Vijaya Anand R. Recent advances in the organocatalytic applications of cyclopropene- and cyclopropenium-based small molecules. Org Biomol Chem 2021; 19:9541-9564. [PMID: 34704583 DOI: 10.1039/d1ob01549d] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The development of novel small molecule-based catalysts for organic transformations has increased noticeably in the last two decades. A very recent addition to this particular research area is cyclopropene- and cyclopropenium-based catalysts. At one point in time, particularly in the mid-20th century, much attention was focused on the structural aspects and physical properties of cyclopropene-based compounds. However, a paradigm shift was observed in the late 20th century, and the focus shifted to the synthetic utility of these compounds. In fact, a wide range of cyclopropene derivatives have been found serving as valuable synthons for the construction of carbocycles, heterocycles and other useful organic compounds. In the last few years, the catalytic applications of cyclopropene/cyclopropenium-based compounds have been uncovered and many synthetic protocols have been developed using cyclopropene-based compounds as organocatalysts. Therefore, the main objective of this review is to highlight recent developments in the catalytic applications of cyclopropene-based small molecules in different areas of organocatalysis such as phase-transfer catalysis (PTC), Brønsted base catalysis, hydrogen-bond donor catalysis, nucleophilic carbene catalysis, and electrophotocatalysis developed within the past two decades.
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Affiliation(s)
- Pavit K Ranga
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, S.A.S Nagar, Manauli (PO), Punjab - 140306, India.
| | - Feroz Ahmad
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, S.A.S Nagar, Manauli (PO), Punjab - 140306, India.
| | - Gurdeep Singh
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, S.A.S Nagar, Manauli (PO), Punjab - 140306, India.
| | - Akshi Tyagi
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, S.A.S Nagar, Manauli (PO), Punjab - 140306, India.
| | - Ramasamy Vijaya Anand
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, S.A.S Nagar, Manauli (PO), Punjab - 140306, India.
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Ranga PK, Ahmad F, Nager P, Rana PS, Vijaya Anand R. Bis(amino)cyclopropenium Ion as a Hydrogen-Bond Donor Catalyst for 1,6-Conjugate Addition Reactions. J Org Chem 2021; 86:4994-5010. [PMID: 33721500 DOI: 10.1021/acs.joc.0c02940] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The catalytic application of the bis(amino)cyclopropenium ion has been investigated in conjugate addition reactions. The hydrogen atom, which is attached to the cyclopropene ring of bis(amino)cyclopropenium salts, is moderately acidic and can potentially serve as a hydrogen-bond donor catalyst in some organic transformations. This hypothesis has been successfully realized in the 1,6-conjugate addition reactions of p-quinone methides with various nucleophiles such as indole, 2-naphthol, thiols, phenols, and so forth. The spectroscopic studies (NMR and UV-vis) as well as the deuterium isotope labeling studies clearly revealed that the hydrogen atom (C-H) that is present in the cyclopropene ring of the catalyst is indeed solely responsible for catalyzing these transformations. In addition, these studies also strongly indicate that the C-H hydrogen of the cyclopropene ring activates the carbonyl group of the p-quinone methide through hydrogen bonding.
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Affiliation(s)
- Pavit Kumar Ranga
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, Manauli (P.O.), S. A. S. Nagar, Punjab 140306, India
| | - Feroz Ahmad
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, Manauli (P.O.), S. A. S. Nagar, Punjab 140306, India
| | - Prashant Nager
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, Manauli (P.O.), S. A. S. Nagar, Punjab 140306, India
| | - Prabhat Singh Rana
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, Manauli (P.O.), S. A. S. Nagar, Punjab 140306, India
| | - Ramasamy Vijaya Anand
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, Manauli (P.O.), S. A. S. Nagar, Punjab 140306, India
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Litterscheidt J, Bandar JS, Ebert M, Forschner R, Bader K, Lambert TH, Frey W, Bühlmeyer A, Brändle M, Schulz F, Laschat S. Self-Assembly of Aminocyclopropenium Salts: En Route to Deltic Ionic Liquid Crystals. Angew Chem Int Ed Engl 2020; 59:10557-10565. [PMID: 32119178 PMCID: PMC7317216 DOI: 10.1002/anie.202000824] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 02/25/2020] [Indexed: 01/27/2023]
Abstract
Aminocyclopropenium ions have raised much attention as organocatalysts and redox active polymers. However, the self-assembly of amphiphilic aminocyclopropenium ions remains challenging. The first deltic ionic liquid crystals based on aminocyclopropenium ions have been developed. Differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction provided insight into the unique self-assembly and nanosegregation of these liquid crystals. While the combination of small headgroups with linear p-alkoxyphenyl units led to bilayer-type smectic mesophases, wedge-shaped units resulted in columnar mesophases. Upon increasing the size and polyphilicity of the aminocyclopropenium headgroup, a lamellar phase was formed.
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Affiliation(s)
- Juri Litterscheidt
- Institute of Organic ChemistryUniversity of StuttgartPfaffenwaldring 5570569StuttgartGermany
| | - Jeffrey S. Bandar
- Department of ChemistryColorado State UniversityFort CollinsCO80523USA
| | - Max Ebert
- Institute of Organic ChemistryUniversity of StuttgartPfaffenwaldring 5570569StuttgartGermany
| | - Robert Forschner
- Institute of Organic ChemistryUniversity of StuttgartPfaffenwaldring 5570569StuttgartGermany
| | - Korinna Bader
- Institute of Organic ChemistryUniversity of StuttgartPfaffenwaldring 5570569StuttgartGermany
| | - Tristan H. Lambert
- Department of Chemistry & Chemical BiologyCornell University122 Baker LaboratoryIttacaNY14853USA
- Department of ChemistryColumbia UniversityNew YorkNY10027USA
| | - Wolfgang Frey
- Institute of Organic ChemistryUniversity of StuttgartPfaffenwaldring 5570569StuttgartGermany
| | - Andrea Bühlmeyer
- Institute of Organic ChemistryUniversity of StuttgartPfaffenwaldring 5570569StuttgartGermany
| | - Marcus Brändle
- Institute of Organic ChemistryUniversity of StuttgartPfaffenwaldring 5570569StuttgartGermany
| | - Finn Schulz
- Institute of Organic ChemistryUniversity of StuttgartPfaffenwaldring 5570569StuttgartGermany
| | - Sabine Laschat
- Institute of Organic ChemistryUniversity of StuttgartPfaffenwaldring 5570569StuttgartGermany
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Litterscheidt J, Bandar JS, Ebert M, Forschner R, Bader K, Lambert TH, Frey W, Bühlmeyer A, Brändle M, Schulz F, Laschat S. Self‐Assembly of Aminocyclopropenium Salts: En Route to Deltic Ionic Liquid Crystals. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202000824] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Juri Litterscheidt
- Institute of Organic Chemistry University of Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Jeffrey S. Bandar
- Department of Chemistry Colorado State University Fort Collins CO 80523 USA
| | - Max Ebert
- Institute of Organic Chemistry University of Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Robert Forschner
- Institute of Organic Chemistry University of Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Korinna Bader
- Institute of Organic Chemistry University of Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Tristan H. Lambert
- Department of Chemistry & Chemical Biology Cornell University 122 Baker Laboratory Ittaca NY 14853 USA
- Department of Chemistry Columbia University New York NY 10027 USA
| | - Wolfgang Frey
- Institute of Organic Chemistry University of Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Andrea Bühlmeyer
- Institute of Organic Chemistry University of Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Marcus Brändle
- Institute of Organic Chemistry University of Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Finn Schulz
- Institute of Organic Chemistry University of Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Sabine Laschat
- Institute of Organic Chemistry University of Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany
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Smajlagic I, Guest M, Durán R, Herrera B, Dudding T. Mechanistic Insight toward Understanding the Role of Charge in Thiourea Organocatalysis. J Org Chem 2020; 85:585-593. [PMID: 31790584 DOI: 10.1021/acs.joc.9b02682] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pyranylation and glycosylation are pivotal for accessing a myriad of natural products, pharmaceuticals, and drug candidates. Catalytic approaches for enabling these transformations are of utmost importance and integral to advancing this area of synthesis. In exploring this chemical space, a combined experimental and computational mechanistic study of pyranylation and 2-deoxygalactosylation catalyzed by a cationic thiourea organocatalyst is reported. To this end, a thiourea-cyclopropenium organocatalyst was employed as a model system in combination with an arsenal of mechanistic techniques, including 13C kinetic isotope effect experiments, deuterated labeling studies, variable-temperature 1H NMR spectroscopy, and density functional theory calculations. From these studies, two distinct reaction pathways were identified for this transformation corresponding to either dual hydrogen bond (H-bond) activation or Brønsted acid catalysis. The former involving thiourea orchestrated bifurcated hydrogen bonding proceeded in an asynchronous concerted fashion. In contrast, the latter stepwise mechanism involving Brønsted acid catalysis hinged upon the formation of an oxocarbenium intermediate accompanied by subsequent alcohol addition.
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Affiliation(s)
- Ivor Smajlagic
- Brock University , 1812 Sir Isaac Brock Way , St. Catharines , ON L2S 3A1 , Canada
| | - Matt Guest
- Brock University , 1812 Sir Isaac Brock Way , St. Catharines , ON L2S 3A1 , Canada
| | - Rocío Durán
- Laboratorio de Química Teórica Computacional (QTC), Departamento de Química-Física, Facultad de Química y de Farmacia , Pontificia Universidad Católica de Chile , Av. Vicuña Mackenna 4860 , Macul, Santiago , Chile
| | - Barbara Herrera
- Laboratorio de Química Teórica Computacional (QTC), Departamento de Química-Física, Facultad de Química y de Farmacia , Pontificia Universidad Católica de Chile , Av. Vicuña Mackenna 4860 , Macul, Santiago , Chile
| | - Travis Dudding
- Brock University , 1812 Sir Isaac Brock Way , St. Catharines , ON L2S 3A1 , Canada
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Mir R, Rowshanpour R, Dempsey K, Pilkington M, Dudding T. Selective Aerobic Oxidation of Benzylic Alcohols Catalyzed by a Dicyclopropenylidene-Ag(I) Complex. J Org Chem 2019; 84:5726-5731. [PMID: 30896944 DOI: 10.1021/acs.joc.9b00624] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The unprecedented synthesis, single-crystal X-ray structure, and first catalytic application of a dicarbene-Ag(I) complex [Ag(BAC)2][CO2CF3] (BAC = bis(diisopropyl)aminocyclopropenylidene) is reported. This novel complex provides a versatile catalytic platform for selective aerobic oxidation of benzylic alcohols to aldehyde or ketone products in high yields. Ease of experimental execution coupled with the use of abundant atmospheric molecular oxygen as an oxidant and low catalyst loading are inherit strengths of these oxidations.
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Affiliation(s)
- Roya Mir
- Department of Chemistry , Brock University , 1812 Sir Isaac Brock Way , St. Catharines , Ontario , Canada L2S 3A1
| | - Rozhin Rowshanpour
- Department of Chemistry , Brock University , 1812 Sir Isaac Brock Way , St. Catharines , Ontario , Canada L2S 3A1
| | - Katie Dempsey
- Department of Chemistry , Brock University , 1812 Sir Isaac Brock Way , St. Catharines , Ontario , Canada L2S 3A1
| | - Melanie Pilkington
- Department of Chemistry , Brock University , 1812 Sir Isaac Brock Way , St. Catharines , Ontario , Canada L2S 3A1
| | - Travis Dudding
- Department of Chemistry , Brock University , 1812 Sir Isaac Brock Way , St. Catharines , Ontario , Canada L2S 3A1
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Yin H, Sheng J, Zhang KF, Zhang ZQ, Bian KJ, Wang XS. Nickel-catalyzed monofluoromethylation of (hetero)aryl bromides via reductive cross-coupling. Chem Commun (Camb) 2019; 55:7635-7638. [DOI: 10.1039/c9cc03737c] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Nickel-catalyzed direct monofluoromethylation of (hetero)aryl bromides with industrial raw material BrCH2F by reductive cross-coupling has been developed.
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Affiliation(s)
- Han Yin
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemistry
- University of Science and Technology of China
- Hefei
- P. R. China
| | - Jie Sheng
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemistry
- University of Science and Technology of China
- Hefei
- P. R. China
- School of Environment and Civil Engineering
| | - Kai-Fan Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemistry
- University of Science and Technology of China
- Hefei
- P. R. China
| | - Zi-Qi Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemistry
- University of Science and Technology of China
- Hefei
- P. R. China
| | - Kang-Jie Bian
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemistry
- University of Science and Technology of China
- Hefei
- P. R. China
| | - Xi-Sheng Wang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemistry
- University of Science and Technology of China
- Hefei
- P. R. China
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Zhang Y, Xiong W, Cen J, Yan W, Wu Y, Qi C, Wu W, Jiang H. Direct bromocarboxylation of arynes using allyl bromides and carbon dioxide. Chem Commun (Camb) 2019; 55:12304-12307. [DOI: 10.1039/c9cc05495b] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
An unprecedented multicomponent reaction involving arynes, allyl bromides, and CO2 has been developed to construct various allyl o-bromobenzoate scaffolds.
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Affiliation(s)
- Yu Zhang
- Key Lab of Functional Molecular Engineering of Guangdong Province
- School of Chemistry and Chemical Engineering
- South China University of Technology
- Guangzhou 510640
- P. R. China
| | - Wenfang Xiong
- Key Lab of Functional Molecular Engineering of Guangdong Province
- School of Chemistry and Chemical Engineering
- South China University of Technology
- Guangzhou 510640
- P. R. China
| | - Jinghe Cen
- Key Lab of Functional Molecular Engineering of Guangdong Province
- School of Chemistry and Chemical Engineering
- South China University of Technology
- Guangzhou 510640
- P. R. China
| | - Wuxin Yan
- Key Lab of Functional Molecular Engineering of Guangdong Province
- School of Chemistry and Chemical Engineering
- South China University of Technology
- Guangzhou 510640
- P. R. China
| | - Yaodan Wu
- Key Lab of Functional Molecular Engineering of Guangdong Province
- School of Chemistry and Chemical Engineering
- South China University of Technology
- Guangzhou 510640
- P. R. China
| | - Chaorong Qi
- Key Lab of Functional Molecular Engineering of Guangdong Province
- School of Chemistry and Chemical Engineering
- South China University of Technology
- Guangzhou 510640
- P. R. China
| | - Wanqing Wu
- Key Lab of Functional Molecular Engineering of Guangdong Province
- School of Chemistry and Chemical Engineering
- South China University of Technology
- Guangzhou 510640
- P. R. China
| | - Huanfeng Jiang
- Key Lab of Functional Molecular Engineering of Guangdong Province
- School of Chemistry and Chemical Engineering
- South China University of Technology
- Guangzhou 510640
- P. R. China
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