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Roth A, Ramgren DR, Wen Y, Michie MS, Thamattoor DM. Photochemical Generation of Allenylidenes from Cyclopropanated Phenanthrenes: An Experimental and Computational Study. J Org Chem 2024; 89:7503-7512. [PMID: 38808505 PMCID: PMC11165590 DOI: 10.1021/acs.joc.4c00147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 05/11/2024] [Accepted: 05/17/2024] [Indexed: 05/30/2024]
Abstract
To address the scarcity of generally applicable photochemical routes to allenylidenes in solution, phenanthrene-based sources have been investigated. Specifically, the syntheses of 1-vinylidene-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene, 1-(2-phenylvinylidene)-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene, and 1-(2-methylvinylidene)-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene, photochemical precursors to propadienylidene, 3-phenylpropadienylidene, and 3-methylpropadienylidene have been carried out. Photolysis of these new precursors in olefin traps and benzene afforded the expected cyclopropane adducts of the corresponding allenylidenes. Quantum chemical calculations show that the ground state of all three carbenes is a singlet with a singlet-triplet gap of ∼29, 30, and 33 kcal/mol for propadienylidene, 3-phenylpropadienylidene, and 3-methylpropadienylidene, respectively.
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Affiliation(s)
- Alexander
D. Roth
- Department of Chemistry, Colby
College, Waterville, Maine 04901, United States
| | - David R. Ramgren
- Department of Chemistry, Colby
College, Waterville, Maine 04901, United States
| | - Yuewei Wen
- Department of Chemistry, Colby
College, Waterville, Maine 04901, United States
| | - Megan S. Michie
- Department of Chemistry, Colby
College, Waterville, Maine 04901, United States
| | - Dasan M. Thamattoor
- Department of Chemistry, Colby
College, Waterville, Maine 04901, United States
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Roth AD, Thamattoor DM. Carbenes from cyclopropanated aromatics. Org Biomol Chem 2023. [PMID: 37994575 DOI: 10.1039/d3ob01525d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2023]
Abstract
Although a ripe old discipline by now, carbene chemistry continues to flourish as both theorists and experimentalists have shown sustained interest in this area of research. While there are numerous ways of generating carbenes, the thermal and/or photochemical decomposition of diazo compounds and diazirines remains, by far, the most commonly used method of producing these intermediates. There is no disputing the fact that these nitrogenous precursors have served carbene researchers well, but their use is not without problems. They are often sensitive and hazardous to handle and, sometimes, the desired nitrogenous precursor simply may not be available, e.g., for synthetic reasons, to study the particular carbene of interest. Furthermore, there is a legitimate concern that the photochemical generation of carbenes in solution from diazo compounds and diazirines may be contaminated by reactions in the excited states (RIES) of the precursors themselves. As an alternative, several laboratories, including ours, have used cyclopropanated aromatic systems to generate a wide range of carbenes. In each case, the cheleotropic extrusion of carbenes is accompanied by the formation of stable aromatic by-products such as phenanthrene, indane, naphthalene, and 1,4-dihydronaphthalene. The emergence of these "non-traditional" carbene sources, their versatility, and promise are reviewed in this work.
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Affiliation(s)
- Alexander D Roth
- Department of Chemistry, Colby College, Waterville, ME 04901, USA.
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Roth A, Wamsley CE, Haynes SM, Thamattoor DM. Adamantylidenecarbene: Photochemical Generation, Trapping, and Theoretical Studies. J Org Chem 2023; 88:14413-14422. [PMID: 37768172 PMCID: PMC10594661 DOI: 10.1021/acs.joc.3c01399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Indexed: 09/29/2023]
Abstract
Photolysis of 1-(2-adamantylidene)-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene in benzene (or benzene-d6) at ambient temperature produces adamantylidenecarbene. The carbene undergoes dimerization to a cumulene and may also be trapped in a stereospecific fashion by cis- and trans-4-methyl-2-pentene. No products attributable to 4-homoadamantyne, resulting from ring expansion of the carbene, could be detected. Coupled cluster/density functional theory calculations place the singlet carbene ∼49 kcal/mol below the triplet and show that the former must overcome a barrier of ∼13.5 kcal/mol to rearrange into 4-homoadamantyne.
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Affiliation(s)
- Alexander
D. Roth
- Department of Chemistry, Colby College, Waterville, Maine 04901, United States
| | | | - Sarah M. Haynes
- Department of Chemistry, Colby College, Waterville, Maine 04901, United States
| | - Dasan M. Thamattoor
- Department of Chemistry, Colby College, Waterville, Maine 04901, United States
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Sarkar SK, Ko M, Bai X, Du L, Thamattoor DM, Phillips DL. Detection of Ylide Formation between an Alkylidenecarbene and Acetonitrile by Femtosecond Transient Absorption Spectroscopy. J Am Chem Soc 2021; 143:17090-17096. [PMID: 34618473 DOI: 10.1021/jacs.1c07074] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Femtosecond laser flash photolysis of 3-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-ylidene)tetrahydrofuran produces singlet 3-oxacyclopentylidenecarbene which reacts with acetonitrile solvent to form an ylide. This is the first direct detection of ylide formation by an alkylidenecarbene. This new type of ylide was observed to have a broad absorption band in the visible region with λmax ∼450 nm and a lifetime of ∼13.5 ps. As with other "conventional" carbenes (the divalent carbon atom is separately bound to two substituents), this ylide formation method could be also useful for detecting alkylidenecarbenes, especially those that do not absorb at wavelengths suitable for direct observation. Furthermore, the mechanisms by which 3-oxacyclopentylidenecarbene forms the ylide and the overall favorability of ylide formation, vis-à-vis ring expansion of the carbene to strained 3-oxacyclohexyne, were supported by results from density functional theory calculations.
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Affiliation(s)
- Sujan K Sarkar
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong S.A.R
| | - Minji Ko
- Department of Chemistry, Colby College, Waterville, Maine 04901, United States
| | - Xueqin Bai
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong S.A.R
| | - Lili Du
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong S.A.R.,School of Life Science, Jiangsu University, Zhenjiang 212013, PR China
| | - Dasan M Thamattoor
- Department of Chemistry, Colby College, Waterville, Maine 04901, United States
| | - David Lee Phillips
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong S.A.R
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Ring Expansion of Alkylidenecarbenes Derived from Lactams, Lactones, and Thiolactones into Strained Heterocyclic Alkynes: A Theoretical Study. Molecules 2019; 24:molecules24030593. [PMID: 30736417 PMCID: PMC6384652 DOI: 10.3390/molecules24030593] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2018] [Revised: 02/06/2019] [Accepted: 02/06/2019] [Indexed: 12/20/2022] Open
Abstract
Strained cycloalkynes are of considerable interest to theoreticians and experimentalists, and possess much synthetic value as well. Herein, a series of cyclic alkylidenecarbenes—formally obtained by replacing the carbonyl oxygen of four-, five-, and six-membered lactams, lactones, and thiolactones with a divalent carbon—were modeled at the CCSD(T)/cc-pVTZ//B3LYP/6-311+G** and CCSD(T)/cc-pVTZ//CCSD/6-311+G** levels of theory. The singlet carbenes were found to be more stable than the triplets. The strained heterocyclic alkynes formed by ring expansion of these singlet carbenes were also modeled. Interestingly, the C≡C bonds in the five-membered heterocycles, obtained from the rearrangement of β-lactam- and β-lactone-derived alkylidenecarbenes, displayed lengths intermediate between formal double and triple bonds. Furthermore, 2-(1-azacyclobutylidene)carbene was found to be nearly isoenergetic with its ring-expanded isomer, and 1-oxacyclopent-2-yne was notably higher in energy than its precursor carbene. In all other cases, the cycloalkynes were lower in energy than the corresponding carbenes. The transition states for ring-expansion were always lower for the 1,2-carbon shifts than for 1,2-nitrogen or oxygen shifts, but higher than for the 1,2-sulfur shifts. These predictions should be verifiable using carbenes bearing appropriate isotopic labels. Computed vibrational spectra for the carbenes, and their ring-expanded isomers, are presented and could be of value to matrix isolation experiments.
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Esquivel-Amores E, Rogers K, Thamattoor LR, Thamattoor DM. Double trap: A single product from the THF-initiated interception of a cyclopropylidene(oid) and its rearranged strained cyclic allene. J Mol Struct 2018. [DOI: 10.1016/j.molstruc.2018.01.061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Maurer DP, Fan R, Thamattoor DM. Photochemical Generation of Strained Cycloalkynes from Methylenecyclopropanes. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201701275] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Daniel P. Maurer
- Department of Chemistry Colby College 5765 Mayflower Hill Waterville ME 04901 USA
| | - Rui Fan
- Department of Chemistry Colby College 5765 Mayflower Hill Waterville ME 04901 USA
| | - Dasan M. Thamattoor
- Department of Chemistry Colby College 5765 Mayflower Hill Waterville ME 04901 USA
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Maurer DP, Fan R, Thamattoor DM. Photochemical Generation of Strained Cycloalkynes from Methylenecyclopropanes. Angew Chem Int Ed Engl 2017; 56:4499-4501. [DOI: 10.1002/anie.201701275] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Indexed: 11/09/2022]
Affiliation(s)
- Daniel P. Maurer
- Department of Chemistry Colby College 5765 Mayflower Hill Waterville ME 04901 USA
| | - Rui Fan
- Department of Chemistry Colby College 5765 Mayflower Hill Waterville ME 04901 USA
| | - Dasan M. Thamattoor
- Department of Chemistry Colby College 5765 Mayflower Hill Waterville ME 04901 USA
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Yang X, Languet K, Thamattoor DM. An Experimental and Computational Investigation of (α-Methylbenzylidene)carbene. J Org Chem 2016; 81:8194-8. [DOI: 10.1021/acs.joc.6b01143] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xi Yang
- Department of Chemistry, Colby College, Waterville, Maine 04901, United States
| | - Keith Languet
- Department of Chemistry, Colby College, Waterville, Maine 04901, United States
| | - Dasan M. Thamattoor
- Department of Chemistry, Colby College, Waterville, Maine 04901, United States
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