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Grob-Type Fragmentation Releases Paracyclophane Ring Strain in a Late-Stage Precursor of Haouamine A
Liming Cao1, Chenbo Wang1, Peter Wipf1
1Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States.
Abstract:
A ketene [2 + 2]-addition, an intramolecular aldol reaction, a Suzuki-Miyaura coupling, and a chemoselective lactam reduction were used to prepare a late-stage precursor of haouamine A. Exposure to acid led to a Grob-type fragmentation of the strained 3-aza[7]paracyclophane ring, followed by a tandem Pictet-Spengler reaction of the intermediate iminium ion and conversion to a novel 1,4a-propanocyclopenta[ b]pyridine. This cascade reaction might also be relevant for the mechanism of action of the natural product.
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