AI Article Synopsis
- * A bifunctional hydrogen-bonding thiourea catalyst was used to achieve excellent selectivity, with a final product ratio exceeding 20:1 and high enantiomeric excess (up to 99%).
- * The enantioselectivity could be reversed using a different bifunctional catalyst, and density functional theory (DFT) calculations were employed to explain the observed stereochemistry and the switch in selectivity.
Article Abstract
An enantioselective dearomative 1,3-dipolar cycloaddition of 2-nitrobenzothiophenes and isatin-derived azomethine ylides with a bifunctional hydrogen-bonding thiourea catalyst was established, giving polyheterocyclic compounds in excellent results (up to 99% yield, >20:1 dr for all cases and up to 99% ee). The enantioselectivity could be reversed by the bifunctional hydrogen-bonding squaramide catalyst containing the same chiral source as in the thiourea catalyst. DFT calculations revealed the origin of the observed stereochemistry and the reversal of enantioselectivity.
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| http://dx.doi.org/10.1021/acs.orglett.1c03318 | DOI Listing |
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