Photochemical transformations. 35. Stereochemistry of electron transfer from photoexcited aromatic rings to carbon-chlorine bonds. Syn stereochemistry of migration in photo-Wagner-Meerwein rearrangements
| Autor: | Ellen O. Aeling, Stanley J. Cristol, Dave G. Seapy |
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| Rok vydání: | 1983 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 105:7337-7345 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | Studies have been conducted on the ground-state and excited-state solvolyses of the isomeric 7,8-dichloro derivatives of benzonaphthobicyclo(2.2.2)octadiene and benzoveratrobicyclo(2.2.2)octadiene. The silver ion assisted ground-state reactions proceed, as anticipated, with clean anti-stereochemistry (inversion at the migration terminus) reflected in the Wagner-Meerwein rearranged solvolysis products. Unlike the previously reported observations that excitation transfer from a photoexcited benzene ring to a ..beta..-carbon-chlorine bond requires anti-stereochemistry, electron transfer from excited naphthalene or veratrole rings occurs to both syn and anti carbon-chlorine bonds, although that to the latter is preferred. The results are consistent with an electron-transfer process to give a zwitterionic biradical and are rationalized by the Weller equation. Separation of chloride ion from the presumed zwitterionic biradical is accompanied by ''Wagner-Meerwein'' rearrangement but is predominately syn, rather than anti as in the ground state. The rearrangement stereochemistry is consistent with the idea that, in the principal photochemical process, migration with retention of configuration is concerted with the loss of chloride ion. 3 tables. |
| Databáze: | OpenAIRE |
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