1
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Uhlenbruck BJH, Josephitis CM, de Lescure L, Paton RS, McNally A. A deconstruction-reconstruction strategy for pyrimidine diversification. Nature 2024; 631:87-93. [PMID: 38697196 DOI: 10.1038/s41586-024-07474-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Accepted: 04/26/2024] [Indexed: 05/04/2024]
Abstract
Structure-activity relationship (SAR) studies are fundamental to drug and agrochemical development, yet only a few synthetic strategies apply to the nitrogen heteroaromatics frequently encountered in small molecule candidates1-3. Here we present an alternative approach in which we convert pyrimidine-containing compounds into various other nitrogen heteroaromatics. Transforming pyrimidines into their corresponding N-arylpyrimidinium salts enables cleavage into a three-carbon iminoenamine building block, used for various heterocycle-forming reactions. This deconstruction-reconstruction sequence diversifies the initial pyrimidine core and enables access to various heterocycles, such as azoles4. In effect, this approach allows heterocycle formation on complex molecules, resulting in analogues that would be challenging to obtain by other methods. We anticipate that this deconstruction-reconstruction strategy will extend to other heterocycle classes.
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Affiliation(s)
| | | | - Louis de Lescure
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | - Robert S Paton
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA.
| | - Andrew McNally
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA.
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2
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Lyu H, Tugwell TH, Chen Z, Kukier GA, Turlik A, Wu Y, Houk KN, Liu P, Dong G. Modular synthesis of 1,2-azaborines via ring-opening BN-isostere benzannulation. Nat Chem 2024; 16:269-276. [PMID: 37783725 DOI: 10.1038/s41557-023-01343-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 09/08/2023] [Indexed: 10/04/2023]
Abstract
1,2-Azaborines represent a unique class of benzene isosteres that have attracted interest for developing pharmaceuticals with better potency and bioavailability. However, it remains a long-standing challenge to prepare monocyclic 1,2-azaborines, particularly multi-substituted ones, in an efficient and modular manner. Here we report a straightforward method to directly access diverse multi-substituted 1,2-azaborines from readily available cyclopropyl imines/ketones and dibromoboranes under relatively mild conditions. The reaction is scalable, shows a broad substrate scope, and tolerates a range of functional groups. The utility of this method is demonstrated in the concise syntheses of BN isosteres of a PD-1/PD-L1 inhibitor and pyrethroid insecticide, bifenthrin. Combined experimental and computational mechanistic studies suggest that the reaction pathway involves boron-mediated cyclopropane ring-opening and base-mediated elimination, followed by an unusual low-barrier 6π-electrocyclization accelerated by the BN/CC isomerism. This method is anticipated to find applications for the synthesis of BN-isostere analogues in medicinal chemistry, and the mechanistic insights gained here may guide developing other boron-mediated electrocyclizations.
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Affiliation(s)
- Hairong Lyu
- Department of Chemistry, University of Chicago, Chicago, IL, USA
| | - Thomas H Tugwell
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA
| | - Zhijie Chen
- Department of Chemistry, University of Chicago, Chicago, IL, USA
| | - Garrett A Kukier
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, USA
| | - Aneta Turlik
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, USA
| | - Yifei Wu
- Department of Chemistry, University of Chicago, Chicago, IL, USA
| | - K N Houk
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, USA.
| | - Peng Liu
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA.
| | - Guangbin Dong
- Department of Chemistry, University of Chicago, Chicago, IL, USA.
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3
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Zhou Q, Kukier G, Gordiy I, Hoffmann R, Seeman JI, Houk KN. A 21st Century View of Allowed and Forbidden Electrocyclic Reactions. J Org Chem 2024; 89:1018-1034. [PMID: 38153322 PMCID: PMC10804416 DOI: 10.1021/acs.joc.3c02103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 11/09/2023] [Accepted: 11/15/2023] [Indexed: 12/29/2023]
Abstract
In 1965, Woodward and Hoffmann proposed a theory to predict the stereochemistry of electrocyclic reactions, which, after expansion and generalization, became known as the Woodward-Hoffmann Rules. Subsequently, Longuet-Higgins and Abrahamson used correlation diagrams to propose that the stereoselectivity of electrocyclizations could be explained by the correlation of reactant and product orbitals with the same symmetry. Immediately thereafter, Hoffmann and Woodward applied correlation diagrams to explain the mechanism of cycloadditions. We describe these discoveries and their evolution. We now report an investigation of various electrocyclic reactions using DFT and CASSCF. We track the frontier molecular orbitals along the intrinsic reaction coordinate and modeled trajectories and examine the correlation between HOMO and LUMO for thermally forbidden systems. We also investigate the electrocyclizations of several highly polarized systems for which the Houk group had predicted that donor-acceptor substitution can induce zwitterionic character, thereby providing low-energy pathways for formally forbidden reactions. We conclude with perspectives on the field of pericyclic reactions, including a refinement as the meaning of Woodward and Hoffmann's "Violations. There are none!" Lastly, we comment on the burgeoning influence of computations on all fields of chemistry.
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Affiliation(s)
- Qingyang Zhou
- Department
of Chemistry and Biochemistry, University
of California, Los Angeles, California90095, United States
| | - Garrett Kukier
- Department
of Chemistry and Biochemistry, University
of California, Los Angeles, California90095, United States
| | - Igor Gordiy
- Department
of Chemistry and Biochemistry, University
of California, Los Angeles, California90095, United States
| | - Roald Hoffmann
- Department
of Chemistry and Chemical Biology, Cornell
University, Ithaca, New York14850, United States
| | - Jeffrey I. Seeman
- Department
of Chemistry, University of Richmond, Richmond, Virginia 23173United States
| | - K. N. Houk
- Department
of Chemistry and Biochemistry, University
of California, Los Angeles, California90095-1569. United States
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4
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Hulley EB, Clennan EL. Dihydrophenanthrene Open-Shell Singlet Diradicals and Their Roles in the Mallory Photocyclization Reaction. J Am Chem Soc 2024; 146:1122-1131. [PMID: 38163932 DOI: 10.1021/jacs.3c12400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
A computational study (ωB97X-D/6-31G(d)) of the Mallory photocyclization reaction has revealed that the well-established dihydrophenanthrene (DHP) intermediates can adopt either closed-shell (CS) or open-shell-diradical (OS) singlet ground states. A detailed study of the properties of DHPs allowed their classifications as OS, borderline-OS, borderline-CS, or CS intermediates. The triplet electronic state and higher energy CS* isomer of all the OS singlet diradicals were computationally located, and the expected relationship between the diradical index, yo, and the triplet energy and the OS-CS* energy gaps was established. The importance of aromaticity in stabilizing the OS singlet diradicals was confirmed by using the Harmonic Oscillator Model of Aromaticity (HOMA). The thermal decompositions of DHPs by cycloreversions to regenerate the Mallory starting materials were also studied. The cycloreversion mechanism was described as a homolytic cleavage characterized by an anchimeric assistance continuum promoted by bis-β-homolytic cleavage.
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Affiliation(s)
- Elliott B Hulley
- Department of Chemistry, University of Wyoming, Laramie, Wyoming 82071, United States
| | - Edward L Clennan
- Department of Chemistry, University of Wyoming, Laramie, Wyoming 82071, United States
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5
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de Cózar A, Arrieta A, Arrastia I, Cossío FP. Higher-Order Electrocyclizations in Biological and Synthetic Processes. Chempluschem 2023; 88:e202300482. [PMID: 37753849 DOI: 10.1002/cplu.202300482] [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: 08/29/2023] [Revised: 09/26/2023] [Accepted: 09/27/2023] [Indexed: 09/28/2023]
Abstract
In general, electrocyclizations follow the Woodward-Hoffmann's rules of conservation of orbital symmetry. These rules have been extensively verified in low-order processes, both in thermal and photochemical reactions, up to eight π-electrons. However, when the number of π-electrons in the system increases, some deviations of that general rules can be found. This focused review highlights the main features of reported higher-order electrocyclizations involving 10, 12, 14, 16 and 18 π-electrons. Some of these examples constitute useful intermediates in the synthesis of biologically active compounds. When computational studies were not included in the reported examples, DFT calculations have been performed to be included in this review. Analysis of the respective pericyclic topologies shows the importance of computational tools for understanding the selectivity observed experimentally.
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Affiliation(s)
- Abel de Cózar
- Departamento de Química Orgánica I, Facultad de Química, Universidad del País Vasco and Donostia International Physics Center (DIPC), P. K. 1072, 20018, San Sebastián-Donostia, Spain
- Ikerbasque, Basque Foundation for Science, 48009, Bilbao, Spain
| | - Ana Arrieta
- Departamento de Química Orgánica I, Facultad de Química, Universidad del País Vasco and Donostia International Physics Center (DIPC), P. K. 1072, 20018, San Sebastián-Donostia, Spain
| | - Iosune Arrastia
- Departamento de Química Orgánica I, Facultad de Química, Universidad del País Vasco and Donostia International Physics Center (DIPC), P. K. 1072, 20018, San Sebastián-Donostia, Spain
| | - Fernando P Cossío
- Departamento de Química Orgánica I, Facultad de Química, Universidad del País Vasco and Donostia International Physics Center (DIPC), P. K. 1072, 20018, San Sebastián-Donostia, Spain
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6
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Lamhauge JN, McLeod DA, Barløse CL, Oliver GA, Viborg L, Warburg T, Anker Jørgensen K. Enantioselective Synthesis of Tropane Scaffolds by an Organocatalyzed 1,3-Dipolar Cycloaddition of 3-Oxidopyridinium Betaines and Dienamines. Chemistry 2023; 29:e202301830. [PMID: 37318111 DOI: 10.1002/chem.202301830] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 06/15/2023] [Accepted: 06/15/2023] [Indexed: 06/16/2023]
Abstract
Tropane alkaloids constitute a compound-class which is structurally defined by a central 8-azabicyclo[3.2.1]octane core. A diverse bioactivity profile combined with an unusual aza-bridged bicyclic framework has made tropanes molecules-of-interest within organic chemistry. Enantioselective examples of (5+2) cycloadditions between 3-oxidopyridinium betaines and olefins remain unexplored, despite 3-oxidopyridinium betaines being useful reagents in organic synthesis. The first asymmetric (5+2) cycloaddition of 3-oxidopyridinium betaines is reported, affording tropane derivatives in up to quantitative yield and with excellent control of peri-, regio-, diastereo-, and enantioselectivity. The reactivity is enabled by dienamine-activation of α,β-unsaturated aldehydes combined with in situ formation of the pyridinium reaction-partner. A simple N-deprotection protocol allows for liberation of the tropane alkaloid motif, and synthetic elaborations of the cycloadducts demonstrate their synthetic utility to achieve highly diastereoselective modification around the bicyclic framework. DFT computations suggest a stepwise mechanism where regio- and stereoselectivity are defined during the first bond-forming step in which the pyridinium dipole exerts critical conformational control over its dienamine partner. In the second bond-forming step, a kinetic preference toward an initial (5+4) cycloadduct was identified; however, a lack of catalyst turn-over, reversibility, and thermodynamic bias favoring a (5+2) cycloadduct rendered the reaction fully periselective.
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Affiliation(s)
- Johannes N Lamhauge
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
| | - David A McLeod
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
| | - Casper L Barløse
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
| | - Gwyndaf A Oliver
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
| | - Laura Viborg
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
| | - Tobias Warburg
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
| | - Karl Anker Jørgensen
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark
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7
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Corti V, Barløse CL, Østergaard NL, Kristensen A, Jessen NI, Jørgensen KA. Organocatalytic Enantioselective Thermal [4 + 4] Cycloadditions. J Am Chem Soc 2023; 145:1448-1459. [PMID: 36603159 DOI: 10.1021/jacs.2c12750] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Chiral eight-membered carbocycles are important motifs in organic chemistry, natural product chemistry, chemical biology, and medicinal chemistry. The lack of synthetic methods toward their construction is a challenge preventing their rational design and stereoselective synthesis. The catalytic enantioselective [4 + 4] cycloaddition is one of the most straightforward and atom-economical methods to obtain chiral cyclooctadiene derivatives. We report the first organocatalytic asymmetric [4 + 4] cycloaddition of 9H-fluorene-1-carbaldehydes with electron-deficient dienes affording cyclooctadiene derivatives in good yields and with excellent control of peri-, diastereo-, and enantioselectivities. The reaction concept is based on the aminocatalytic formation of a polarized butadiene component incorporated into a cyclic extended π-system, with restricted conformational freedom, allowing for a stereocontrolled [4 + 4] cycloaddition. FMO analysis unveiled that the HOMO and LUMO of the two reacting partners resemble those of butadiene. The methodology allows for the construction of cyclooctadiene derivatives decorated with various functionalities. The cyclooctadienes were synthetically elaborated, allowing for structural diversity demonstrating their synthetic utility for the formation of, for example, chiral cyclobutene- or cyclooctane scaffolds. DFT computational studies shed light on the reaction mechanism identifying the preference for an initial but reversible [4 + 2] cycloaddition delivering an off-cycle catalyst resting state, from which catalyst elimination is not possible. The off-cycle catalyst-bound intermediate undergoes a retro-[4 + 2] cycloaddition, followed by a [4 + 4] cycloaddition generating a cycloadduct from which catalyst elimination is possible. The reaction pathway accounts for the observed peri-, diastereo-, and enantioselectivity of the organocatalytic [4 + 4] cycloaddition.
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Affiliation(s)
- Vasco Corti
- Department of Chemistry, Aarhus University, Aarhus C DK-8000, Denmark
| | | | | | - Anne Kristensen
- Department of Chemistry, Aarhus University, Aarhus C DK-8000, Denmark
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8
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Mita T, Takano H, Hayashi H, Kanna W, Harabuchi Y, Houk KN, Maeda S. Prediction of High-Yielding Single-Step or Cascade Pericyclic Reactions for the Synthesis of Complex Synthetic Targets. J Am Chem Soc 2022; 144:22985-23000. [PMID: 36451276 DOI: 10.1021/jacs.2c09830] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Pericyclic reactions, which involve cyclic concerted transition states without ionic or radical intermediates, have been extensively studied since their definition in the 1960s, and the famous Woodward-Hoffmann rules predict their stereoselectivity and chemoselectivity. Here, we describe the application of a fully automated reaction-path search method, that is, the artificial force induced reaction (AFIR), to trace an input compound back to reasonable starting materials through thermally allowed pericyclic reactions via product-based quantum-chemistry-aided retrosynthetic analysis (QCaRA) without using any a priori experimental knowledge. All categories of pericyclic reactions, including cycloadditions, ene reactions, group-transfer, cheletropic, electrocyclic, and sigmatropic reactions, were successfully traced back via concerted reaction pathways, and starting materials were computationally obtained with the correct stereochemistry. Furthermore, AFIR was used to predict whether the identified reaction pathway can be expected to occur in good yield relative to other possible reactions of the identified starting material. In order to showcase its practical utility, this state-of-the-art technology was also applied to the retrosynthetic analysis of a natural product with a relatively high number of atoms (52 atoms: endiandric acid C methyl ester), which was first synthesized by Nicolaou in 1982 and provided the corresponding starting polyenes with the correct stereospecificity via three pericyclic reaction cascades (one Diels-Alder reaction as well as 6π and 8π electrocyclic reactions). Moreover, not only systems that obey the Woodward-Hoffmann rules but also systems that violate these rules, such as those recently calculated by Houk, can be retrosynthesized accurately.
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Affiliation(s)
- Tsuyoshi Mita
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan.,JST, ERATO Maeda Artificial Intelligence in Chemical Reaction Design and Discovery Project, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
| | - Hideaki Takano
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan.,JST, ERATO Maeda Artificial Intelligence in Chemical Reaction Design and Discovery Project, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
| | - Hiroki Hayashi
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan.,JST, ERATO Maeda Artificial Intelligence in Chemical Reaction Design and Discovery Project, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
| | - Wataru Kanna
- Department of Chemistry, Faculty of Science, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
| | - Yu Harabuchi
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan.,JST, ERATO Maeda Artificial Intelligence in Chemical Reaction Design and Discovery Project, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan.,Department of Chemistry, Faculty of Science, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
| | - K N Houk
- Department of Chemical and Biomolecular Engineering and Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095, United States
| | - Satoshi Maeda
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan.,JST, ERATO Maeda Artificial Intelligence in Chemical Reaction Design and Discovery Project, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan.,Department of Chemistry, Faculty of Science, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan.,Research and Services Division of Materials Data and Integrated System (MaDIS), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044, Japan
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9
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Abstract
Herein, we report the enantioselective total synthesis of dysiherbols A, C, and D, a unique group of 6/6/5/6/6 pentacyclic quinone/hydroquinone sesquiterpenes, featuring a photo-induced quinone-alkene [2 + 2] cycloaddition and a tandem [1,2]-anionic rearrangement/cyclopropane fragmentation as key elements. Based on our total synthesis, the originally proposed structures of dysiherbols C and D have been revised. Detailed computational studies were carried out to gain deep insight into the unprecedented [1,2]-anionic rearrangement, which revealed that the transformation, albeit a symmetry-forbidden process, proceeded through a concerted manner owing to the release of high ring-strain energy and the evolution of local aromaticity in the transition state. Taking all, the present work offers a mechanistically interesting and synthetically useful approach to accessing dysiherbols and related congeners.
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Affiliation(s)
- Shengkun Hu
- Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Yefeng Tang
- School of Pharmaceutical Sciences, MOE Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology, Tsinghua University, Beijing 100084, China
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10
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Seeman JI, Tantillo DJ. Understanding chemistry: from "heuristic (soft) explanations and reasoning by analogy" to "quantum chemistry". Chem Sci 2022; 13:11461-11486. [PMID: 36320403 PMCID: PMC9575397 DOI: 10.1039/d2sc02535c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 09/06/2022] [Indexed: 12/02/2022] Open
Abstract
"Soft theories," i.e., "heuristic models based on reasoning by analogy" largely drove chemistry understanding for 150 years or more. But soft theories have their limitations and with the expansion of chemistry in the mid-20th century, more and more inexplicable (by soft theory) experimental results were being obtained. In the past 50 years, quantum chemistry, most often in the guise of applied theoretical chemistry including computational chemistry, has provided (a) the underlying "hard evidence" for many soft theories and (b) the explanations for chemical phenomena that were unavailable by soft theories. In this publication, we define "hard theories" as "theories derived from quantum chemistry." Both soft and hard theories can be qualitative and quantitative, and the "Houk quadrant" is proposed as a helpful categorization tool. Furthermore, the language of soft theories is often used appropriately to describe quantum chemical results. A valid and useful way of doing science is the appropriate use and application of both soft and hard theories along with the best nomenclature available for successful communication of results and ideas.
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Affiliation(s)
- Jeffrey I Seeman
- Department of Chemistry, University of Richmond Richmond VA 23173 USA
| | - Dean J Tantillo
- Department of Chemistry, University of California - Davis Davis CA 95616 USA
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