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Ahuja S, Raghunathan R, Kumarasamy E, Jockusch S, Sivaguru J. Realizing the Photoene Reaction with Alkenes under Visible Light Irradiation and Bypassing the Favored [2 + 2]-Photocycloaddition. J Am Chem Soc 2018; 140:13185-13189. [PMID: 30256105 DOI: 10.1021/jacs.8b08100] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The textbook photoreaction between two alkenes is the [2 + 2]-photocycloaddition resulting in functionalized cyclobutanes. Herein, we disclose an unusual reactivity of alkenes that favor photoene reaction over the [2 + 2]-photocycloaddition.
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Iyer A, Ahuja S, Jockusch S, Ugrinov A, Sivaguru J. Conjugate addition from the excited state. Chem Commun (Camb) 2018; 54:11021-11024. [PMID: 30215437 DOI: 10.1039/c8cc05924a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Conjugate addition occurs efficiently from excited hydrazide based acrylanilides under both UV and metal free visible light irradiations. The reaction proceeds via an excited state encounter complex that bifurcates either via an electron or energy transfer pathway. The generality of excited state conjugate addition is demonstrated using chloromethylation and by thiol addition.
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Hong S, Ratpukdi T, Sivaguru J, Khan E. Photolysis of glutaraldehyde in brine: A showcase study for removal of a common biocide in oil and gas produced water. JOURNAL OF HAZARDOUS MATERIALS 2018; 353:254-260. [PMID: 29677527 DOI: 10.1016/j.jhazmat.2018.03.056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 03/26/2018] [Accepted: 03/27/2018] [Indexed: 06/08/2023]
Abstract
Glutaraldehyde (GA) has been used extensively as a biocide in hydraulic fracturing fluid leading to its presence in oil and gas produced water. In this study, photolysis was used to degrade GA from brine solutions simulating produced water. Photolysis of GA was performed under ultraviolet (UV) irradiation. GA can be photolyzed by UV at all studied conditions with the efficiency ranging from 52 to 85% within one hour irradiation. Photolysis of GA followed pseudo-first order kinetics. A photolysis rate constant of GA at 0.1 mM in 200 g/L of salt at pH 7 was 0.0269 min-1 with a quantum yield of 0.0549 under 224 W illumination. The degradation rate of GA increased with increasing incident light intensity and decreasing pH. Increasing initial GA concentration resulted in decreasing degradation rate of GA. The degradation of GA was affected by salt concentration. At lower salt concentrations, notable retardation of GA photodegradation rate was observed while at higher salt concentrations GA photodegradation was improved compared to those without salt. OH was more dominant in sample without salt than sample with salt suggesting different photolytic mechanisms, indirect and direct photolysis, respectively. Oligomers were identified as the main photoproducts of GA photolysis.
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Clay A, Krishnan R, Sibi M, Webster D, Jockusch S, Sivaguru J. Photoacidity of vanillin derivatives. J Photochem Photobiol A Chem 2018. [DOI: 10.1016/j.jphotochem.2017.11.039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Pattabiraman M, Sivaguru J, Ramamurthy V. Cucurbiturils as Reaction Containers for Photocycloaddition of Olefins. Isr J Chem 2017. [DOI: 10.1002/ijch.201700100] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Wang W, Clay A, Krishnan R, Lajkiewicz NJ, Brown LE, Sivaguru J, Porco JA. Total Syntheses of the Isomeric Aglain Natural Products Foveoglin A and Perviridisin B: Selective Excited-State Intramolecular Proton-Transfer Photocycloaddition. Angew Chem Int Ed Engl 2017; 56:14479-14482. [PMID: 28950418 PMCID: PMC5876029 DOI: 10.1002/anie.201707539] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Indexed: 11/10/2022]
Abstract
Selective excited-state intramolecular proton-transfer (ESIPT) photocycloaddition of 3-hydroxyflavones with trans, trans-1,4-diphenyl-1,3-butadiene is described. Using this methodology, total syntheses of the natural products (±)-foveoglin A and (±)-perviridisin B were accomplished. Enantioselective ESIPT photocycloaddition using TADDOLs as chiral hydrogen-bonding additives provided access to (+)-foveoglin A. Mechanistic studies have revealed the possibility for a photoinduced electron-transfer (PET) pathway.
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Wang W, Clay A, Krishnan R, Lajkiewicz NJ, Brown LE, Sivaguru J, Porco JA. Total Syntheses of the Isomeric Aglain Natural Products Foveoglin A and Perviridisin B: Selective Excited‐State Intramolecular Proton‐Transfer Photocycloaddition. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201707539] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Iyer A, Clay A, Jockusch S, Sivaguru J. Evaluating brominated thioxanthones as organo-photocatalysts. J PHYS ORG CHEM 2017. [DOI: 10.1002/poc.3738] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Kumarasamy E, Kandappa SK, Raghunathan R, Jockusch S, Sivaguru J. Frontispiz: Realizing an Aza Paternò-Büchi Reaction. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201782561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Kumarasamy E, Kandappa SK, Raghunathan R, Jockusch S, Sivaguru J. Frontispiece: Realizing an Aza Paternò-Büchi Reaction. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/anie.201782561] [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]
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Kumarasamy E, Kandappa SK, Raghunathan R, Jockusch S, Sivaguru J. Realizing an Aza Paternò–Büchi Reaction. Angew Chem Int Ed Engl 2017; 56:7056-7061. [DOI: 10.1002/anie.201702273] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Indexed: 11/05/2022]
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Kumarasamy E, Kandappa SK, Raghunathan R, Jockusch S, Sivaguru J. Realizing an Aza Paternò–Büchi Reaction. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201702273] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Iyer A, Jockusch S, Sivaguru J. A photo-auxiliary approach - enabling excited state classical phototransformations with metal free visible light irradiation. Chem Commun (Camb) 2017; 53:1692-1695. [PMID: 28101552 DOI: 10.1039/c6cc09261f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Most traditional photoreactions require UV light to yield the desired product. To address this issue, photoreaction of hydrazide based chromophores was evaluated with visible light using a metal free photocatalyst to afford photoproducts in high yields. This hydrazide functionality itself may be removed/modified after the photoreaction, highlighting its role as a "photo-auxiliary". A preliminary mechanistic model based on photophysical experiments is provided to highlight the generality of the strategy.
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Kumarasamy E, Raghunathan R, Kandappa SK, Sreenithya A, Jockusch S, Sunoj RB, Sivaguru J. Transposed Paternò–Büchi Reaction. J Am Chem Soc 2016; 139:655-662. [DOI: 10.1021/jacs.6b05936] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Kumarasamy E, Ayitou AJL, Vallavoju N, Raghunathan R, Iyer A, Clay A, Kandappa SK, Sivaguru J. Tale of Twisted Molecules. Atropselective Photoreactions: Taming Light Induced Asymmetric Transformations through Non-biaryl Atropisomers. Acc Chem Res 2016; 49:2713-2724. [PMID: 27993011 DOI: 10.1021/acs.accounts.6b00357] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Photochemical transformations are a powerful tool in organic synthesis to access structurally complex and diverse synthetic building blocks. However, this great potential remains untapped in the mainstream synthetic community due to the challenges associated with stereocontrol originating from excited state(s). The finite lifetime of an excited state and nearly barrierless subsequent processes present significant challenges in manipulating the stereochemical outcome of a photochemical reaction. Several methodologies were developed to address this bottleneck including photoreactions in confined media and preorganization through noncovalent interactions resulting in stereoenhancement. Yet, stereocontrol in photochemical reactions that happen in solution in the absence of organized assemblies remained largely unaddressed. In an effort to develop a general and reliable methodology, our lab has been exploring non-biaryl atropisomers as an avenue to perform asymmetric phototransformations. Atropisomers are chiral molecules that arise due to the restricted rotation around a single bond (chiral axis) whose energy barrier to rotation is determined by nonbonding interactions (most often by steric hindrance) with appropriate substituents. Thus, atropisomeric substrates are chirally preorganized during the photochemical transformation and translate their chiral information to the expected photoproducts. This strategy, where "axial to point chirality transfer" occurs during the photochemical reaction, is a hybrid of the successful Curran's prochiral auxiliary approach involving atropisomers in thermal reactions and the Havinga's NEER principle (nonequilibrating excited-state rotamers) for photochemical transformations. We have investigated this strategy in order to probe various aspects such as regio-, enantio-, diastereo-, and chemoselectivity in several synthetically useful phototransformations including 6π-photocyclization, 4π-ring closure, Norrish-Yang photoreactions, Paternò-Büchi reaction, and [2 + 2]- and [5 + 2]-photocycloaddition. The investigations detailed in this Account clearly signify the scope of our strategy in accessing chirally enriched products during phototransformations. Simple design modifications such as tailoring the steric handle in atropisomers to hold reactive units resulted in permanently locked/traceless axial chirality in addition to incorporating multiple stereocenters in already complex scaffolds obtained from phototransformation. Further improvements allowed us to employ low energy visible light rather than high energy UV light without compromising the stereoenrichment in the photoproducts. Continued investigations on atropisomeric scaffolds have unraveled new design features, with outcomes that are unique and unprecedented for excited state reactivity. For example, we have established that reactive spin states (singlet or triplet excited state) profoundly influence the stereochemical outcome of an atropselective phototransformation. In general, the photochemistry and photophysics of atropisomeric substrates differ significantly from their achiral counterparts irrespective of having the same chromophore initiating the excited state reactivity. The ability of axially chiral chromophores to impart stereoenrichment in the intramolecular photoreactions appears to be promising. A challenging endeavor for the "axial to point chirality transfer" strategy is to enhance stereoenrichment or alter chemical reactivity in intermolecular photoreactions. Insights gained from our investigations will serve as a platform to venture into more complicated yet fruitful research in terms of broad synthetic utility.
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Raghunathan R, Jockusch S, Sibi MP, Sivaguru J. Evaluating thiourea/urea catalyst for enantioselective 6π-photocyclization of acrylanilides. J Photochem Photobiol A Chem 2016. [DOI: 10.1016/j.jphotochem.2015.12.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Shailaja J, Sivaguru J, Ramamurthy V. Zeolite matrix assisted decomposition of singlet oxygen sensitizers during photooxidation. J Photochem Photobiol A Chem 2016. [DOI: 10.1016/j.jphotochem.2016.02.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Vallavoju N, Sreenithya A, Ayitou AJ, Jockusch S, Sunoj RB, Sivaguru J. Photoreactions with a Twist: Atropisomerism‐Driven Divergent Reactivity of Enones with UV and Visible Light. Chemistry 2016; 22:11339-48. [DOI: 10.1002/chem.201601509] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Indexed: 11/06/2022]
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Clay A, Vallavoju N, Krishnan R, Ugrinov A, Sivaguru J. Metal-Free Visible Light-Mediated Photocatalysis: Controlling Intramolecular [2 + 2] Photocycloaddition of Enones through Axial Chirality. J Org Chem 2016; 81:7191-200. [DOI: 10.1021/acs.joc.6b01066] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Raghunathan R, Kumarasamy E, Jockusch S, Ugrinov A, Sivaguru J. Engaging electronic effects for atropselective [5+2]-photocycloaddition of maleimides. Chem Commun (Camb) 2016; 52:8305-8. [PMID: 27296234 DOI: 10.1039/c6cc02962k] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Atropisomeric maleimides were synthesized and subjected to atropselective [5+2]-photocycloaddition under direct irradiation to yield azepinone products with high enantio- (ee >98%) and diastereoselectivity (dr >98%). While the ee was dictated by the axial chirality, the dr was influenced by the substituent on the maleimide ring. Interestingly, by tuning the electronics of the substituent, the dr of the product can be reversed.
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Ramamurthy V, Sivaguru J. Supramolecular Photochemistry as a Potential Synthetic Tool: Photocycloaddition. Chem Rev 2016; 116:9914-93. [DOI: 10.1021/acs.chemrev.6b00040] [Citation(s) in RCA: 296] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Vallavoju N, Selvakumar S, Pemberton BC, Jockusch S, Sibi MP, Sivaguru J. Frontispiece: Organophotocatalysis: Insights into the Mechanistic Aspects of Thiourea‐Mediated Intermolecular [2+2] Photocycloadditions. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/anie.201681861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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48
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Vallavoju N, Selvakumar S, Pemberton BC, Jockusch S, Sibi MP, Sivaguru J. Organophotocatalysis: Insights into the Mechanistic Aspects of Thiourea‐Mediated Intermolecular [2+2] Photocycloadditions. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201600596] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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49
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Vallavoju N, Selvakumar S, Pemberton BC, Jockusch S, Sibi MP, Sivaguru J. Organophotocatalysis: Insights into the Mechanistic Aspects of Thiourea-Mediated Intermolecular [2+2] Photocycloadditions. Angew Chem Int Ed Engl 2016; 55:5446-51. [PMID: 27005562 DOI: 10.1002/anie.201600596] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Indexed: 11/08/2022]
Abstract
Mechanistic investigations of the intermolecular [2+2] photocycloaddition of coumarin with tetramethylethylene mediated by thiourea catalysts reveal that the reaction is enabled by a combination of minimized aggregation, enhanced intersystem crossing, and altered excited-state lifetime(s). These results clarify how the excited-state reactivity can be manipulated through catalyst-substrate interactions and reveal a third mechanistic pathway for thiourea-mediated organo-photocatalysis.
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Kumarasamy E, Raghunathan R, Sibi MP, Sivaguru J. Nonbiaryl and Heterobiaryl Atropisomers: Molecular Templates with Promise for Atropselective Chemical Transformations. Chem Rev 2015; 115:11239-300. [DOI: 10.1021/acs.chemrev.5b00136] [Citation(s) in RCA: 399] [Impact Index Per Article: 44.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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