Development of an Allenyne-Alkyne [4+2] Cycloaddition and its Application to Total Synthesis of Selaginpulvilin A |
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Authors: | Anh Le Saswata Gupta Man Xu Prof. Yuanzhi Xia Prof. Daesung Lee |
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Affiliation: | 1. Department of Chemistry, University of Illinois Chicago, 845 West Taylor Street, 60607 Chicago, Illinois, USA;2. College of Chemistry and Materials Engineering, Wenzhou University, 325035 Wenzhou, Zhejiang Province, P. R. China |
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Abstract: | A new [4+2] cycloaddition of allenyne-alkyne is developed. The reaction is believed to proceed with forming an α,3-dehydrotoluene intermediate. This species behaves as a σπ-diradical to react with a hydrogen atom donor, whereas it displays a zwitterionic reactivity toward weak nucleophiles. The efficiency of trapping α,3-dehydrotoluene depends not only on its substituents but also the trapping agents. Notable features of the reaction are the activating role of the extra alkyne of the 1,3-diyne that reacts with the allenyne moiety and the opposite mode of trapping with oxygen and nitrogen nucleophiles. Oxygen nucleophiles result in the oxygen-end incorporation at the benzylic position of the α,3-dehydrotoluene, whereas with amine nucleophiles the nitrogen-end is incorporated into the aromatic core. Relying on the allenyne-alkyne cycloaddition as an enabling strategy, a concise total synthesis of phosphodiesterase-4 inhibitory selaginpulvilin A is realized. |
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Keywords: | allenyne α,3-dehydrotoluene cycloaddition cycloaromatization selaginpuvilin A |
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