| Autor: |
Kuan KY; Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842, United States., Singleton DA; Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842, United States. |
| Jazyk: |
angličtina |
| Zdroj: |
The Journal of organic chemistry [J Org Chem] 2021 May 07; Vol. 86 (9), pp. 6305-6313. Date of Electronic Publication: 2021 Apr 23. |
| DOI: |
10.1021/acs.joc.1c00099 |
| Abstrakt: |
13 C kinetic isotope effects (KIEs) for the photoredox-promoted [2 + 2] cycloaddition of enones were determined in homocoupling and heterocoupling examples. The only significant KIEs were observed at the β carbon, indicating that C β -C β bond formation is irreversible. However, these KIEs were much lower than computational predictions, suggesting that product selectivity is determined in part by a step prior to C β -C β bond formation. The results are explained as arising from a competition between C-C bond formation and electron exchange between substrate alkenes. This idea is supported by a relatively small substituent effect on substrate selectivity. The possible rates for electron transfer and bond-forming steps are analyzed, and the competition appears plausible, particularly if the mechanism involves a complex between reduced and neutral enone molecules. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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