A concise synthesis of substituted stilbenes and styrenes from propargylic phosphonium salts by a cobalt-catalyzed Diels-Alder/Wittig olefination reaction sequence |
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Authors: | Hilt Gerhard Hengst Christoph |
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Institution: | Fachbereich Chemie, Philipps-Universit?t Marburg, Hans-Meerwein-Strasse, 35043 Marburg, Germany. hilt@chemie.uni-marburg.de |
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Abstract: | The cobalt(I)-catalyzed Diels-Alder reaction of propargylic phosphonium salts and longer chained alkyne-functionalized phosphonium salts with 1,3-dienes led to dihydroaromatic phosphonium salt intermediates which were directly used in a one-pot Wittig-type olefination reaction with aldehydes. Subsequent oxidation led to styrene- and stilbene-type products under formation of three new carbon-carbon bonds in a single synthetical step starting from three variable starting materials. The E/Z stereoselectivities of the products revealed that the dihydroaromatic phosphonium ylides behave as semistabilized ylides giving predominantly the E-configured products. The application of unsymmetrical 1,3-dienes as well as internal phosphonium functionalized alkynes is also described. |
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