The effects of substituents and solvent polarity oh photochemical [1,3] sigmatropic shifts. Experimental evidence in favour of the occurrence of sudden |
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| Institution: | 1. Department of Natural Products Chemistry, School of Pharmacy, Fudan University, Shanghai 201203, PR China;2. State Key Laboratory of New Drug and Pharmaceutical Process, Center for Pharmacology, Shanghai Institute of Pharmaceutical Industry, Shanghai 201203, PR China;3. Department of Chemistry, University of Pennsylvania, 231 South 34 Street, Philadelphia, PA 19104-6323, USA;1. Photosensitive Materials Research Center, Toyo Gosei Co., Ltd, 4-2-1 Wakahagi, Inzai-shi, Chiba 270-160, Japan;2. Department of Health and Nutritional Sciences, Shokei Gakuin University, 4-10-1 Yurigaoka, Natori-shi, Miyagi 981-1295, Japan;1. Department of Chemistry, Krishnath College, Berhampore, Murshidabad 742101, India;2. Department of Chemistry, Jadavpur University, Kolkata 700032, India;3. Department of Chemistry, Dr. A. P. J. Abdul Kalam Govt. College, New Town, Kolkata 700156, India |
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| Abstract: | Further experimental evidence regarding the occurrence of sudden polarization in acyclic alkenes is presented. It is shown that the yield of formation of the product derived from an intramolecular photochemical 1,3]-OH shift in 1 is dependent only on the polarity of the solvent employed. This result could be well explained in terms of a stabilization of the zwitterionic intermediate formed upon irradiation of 1 by reorientation polarization of the dipole solvent molecules. Besides this, it was found that replacement of the alkyl group at the terminal carbon atom of the C3–C9 exocyclic double bond in 1 by a phenyl substituent led to the occurrence of a photochemical 1,3]-H shift. This directive effect of the substituents at the exocyclic double bond could be well explained on the basis of the sudden polarization model. |
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