Stereoselective radical cyclizations of N-(2-halobenzoyl)-cyclic ketene-N,X(X=O, S)-acetals |
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Authors: | Aihua Zhou |
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Institution: | Department of Chemistry, Mississippi State University, Mississippi State, MS 39762, USA |
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Abstract: | 2-Alkyloxazolines and 2-alkylthiazolines react with 2-halobenzoyl chlorides to form N-(2-halobenzoyl)-cyclic ketene-N,O-acetals and N-(2-halobenzoyl)-cyclic ketene-N,S-acetals in excellent yields, respectively. These ketene acetals readily undergo stereocontrolled aryl radical cyclizations to afford the central six-membered rings of substituted-2,3,10,10α-tetrahydrooxazolo3,2-b]isoquinolin-5-ones and their 2,3,10,10α-tetrahydrothiazolo3,2-b]isoquinolin-5-one analogs. The tertiary N,O- and N,S-radicals formed upon aryl radical reaction at the ketene-N,X(X=O, S)-acetal double bond appear to have reasonable stability. The stereoselectivity in hydrogen abstractions by these intermediate radicals from both Bu3SnH and (Me3Si)3SiH was investigated. The N,S-heterocyclic fused ring products may have potential medical value. |
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Keywords: | Cyclizations Acetals Diastereomer Ketene acetals Ketene-N O-acetals Ketene-N S-acetals |
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