The seven-membered ring is a common motif in various bioactive natural products. Many examples of natural product cores possessing fused-ring systems are also prevalent. Therefore, it is useful to provide methods that allow access to these cores rapidly and efficiently. We have previously reported the successful construction of fused-ring skeletons containing seven-membered rings via Rh-catalyzed carbocyclization and cycloaddition reactions. As our continuing study on higher order metal-catalyzed reactions, novel enediynes have been subjected to the Rh-catalyzed [2+2+2+1] cycloaddition reaction.            In the presence of a Rh catalyst under CO, cycloheptene-diynes were converted to the corresponding 5-7-7-5 tetracyclic products. Under similar conditions, linear enediyne-amides wre transformed to the corresponding 5-7-5 tricyclic g-lactams. For both cycloheptene-diyne and enediyne-amide substrates, variable amounts of [2+2+2] byproducts were also observed. The scope and the mechanisms of these novel processes will be discussed.

Formation of 5-7-7-5 tetracycles and 5-7-5 tricyclic gama-lactams via Rh-catalyzed [2+2+2+1] cycloaddition of enediynes

244th National Meeting (2012)

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