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Solntsev KM, Bartolo EA, Pan G, Muller G, Bommireddy S, Huppert D, Tolbert LM. Excited-State Proton Transfer in Chiral Environments: Photoracemization of BINOLs. Isr J Chem 2009; 49:227-233. [PMID: 20046928 DOI: 10.1560/ijc.49.2.227] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We have studied excited-state proton transfer (ESPT) from chiral proton donors to chiral and achiral acceptors. The key role of the exergonicity of the reaction and the transition-state position along the reaction coordinate for the existence of an enantiomeric effect was established. This effect was observed for "super" photoacids (ΔG ≪ 0) and vanished for endergonic reactions (ΔG > 0) where a "late" transition state similar to planar achiral binaphtholate anion occurs. As a result, photoracemization was observed, as confirmed by circular dichroism spectroscopy. The photoracemization effects were studied for several chiral photoacids (BINOLs and their ethers) and proton acceptors (amines, aminoalcohols, and water) using UV-vis, steady-state fluorescence, and time-resolved fluorescence spectroscopies. The nature of the solvent and the proton acceptor, as well as the chemical structure of the BINOL, played a pivotal role in the photochemical reactivity of the system. Two proposed pathways competed for photoracemization: excited-state inter- and intra-molecular proton transfer, the former being more effective. Irradiation of the dimethoxy BINOL derivative, which lacks an acidic proton and cannot undergo ESPT, produced no appreciable reaction or racemization.
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Affiliation(s)
- Kyril M Solntsev
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, Georgia 30332-0400, USA
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Bao J, Wulff WD, Dominy JB, Fumo MJ, Grant EB, Rob AC, Whitcomb MC, Yeung SM, Ostrander RL, Rheingold AL. Synthesis, Resolution, and Determination of Absolute Configuration of a Vaulted 2,2‘-Binaphthol and a Vaulted 3,3‘-Biphenanthrol (VAPOL). J Am Chem Soc 1996. [DOI: 10.1021/ja952018t] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Jianming Bao
- Contribution from the Searle Chemistry Laboratory, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, and Department of Chemistry, The University of Delaware, Newark, Delaware 19716
| | - William D. Wulff
- Contribution from the Searle Chemistry Laboratory, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, and Department of Chemistry, The University of Delaware, Newark, Delaware 19716
| | - James B. Dominy
- Contribution from the Searle Chemistry Laboratory, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, and Department of Chemistry, The University of Delaware, Newark, Delaware 19716
| | - Michael J. Fumo
- Contribution from the Searle Chemistry Laboratory, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, and Department of Chemistry, The University of Delaware, Newark, Delaware 19716
| | - Eugene B. Grant
- Contribution from the Searle Chemistry Laboratory, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, and Department of Chemistry, The University of Delaware, Newark, Delaware 19716
| | - Alexander C. Rob
- Contribution from the Searle Chemistry Laboratory, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, and Department of Chemistry, The University of Delaware, Newark, Delaware 19716
| | - Mark C. Whitcomb
- Contribution from the Searle Chemistry Laboratory, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, and Department of Chemistry, The University of Delaware, Newark, Delaware 19716
| | - Siu-Man Yeung
- Contribution from the Searle Chemistry Laboratory, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, and Department of Chemistry, The University of Delaware, Newark, Delaware 19716
| | - Robert L. Ostrander
- Contribution from the Searle Chemistry Laboratory, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, and Department of Chemistry, The University of Delaware, Newark, Delaware 19716
| | - Arnold L. Rheingold
- Contribution from the Searle Chemistry Laboratory, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, and Department of Chemistry, The University of Delaware, Newark, Delaware 19716
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Tanaka K, Shogase Y, Osuga H, Suzuki H, Nakanishi W, Nakamura K, Kawai Y. Complexation with helical molecules: helical crystal structure of bis(hydroxymethyl)[7]thiaheterohelicene·ethanol clathrate. ACTA ACUST UNITED AC 1995. [DOI: 10.1039/c39950001873] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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