American Chemical Society
ol9b02498_si_001.pdf (3.59 MB)

Calcium-Catalyzed Formal [5 + 2] Cycloadditions of Alkylidene β‑Ketoesters with Olefins: Chemodivergent Synthesis of Highly Functionalized Cyclohepta[b]indole Derivatives

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journal contribution
posted on 2019-09-12, 13:33 authored by Ariel N. Parker, M. Cynthia Martin, Raynold Shenje, Stefan France
The calcium-catalyzed, formal [5 + 2] cycloaddition of indolyl alkylidene β-ketoesters with mono- and disubstituted aryl olefins to form cyclohepta­[b]­indole derivatives has been established. Unanticipated chemodivergence with phenyl vinyl sulfide/ether revealed a double [5 + 2] cycloaddition cascade providing ethano-bridged cyclohepta­[b]­indoles. Overall, the method’s highlights include: (1) use of a green, calcium-based catalyst (2.5 mol % loading); (2) reaction times under 1 h; (3) mild reaction conditions; (4) substrate-derived chemodivergence; (5) functional group tolerance; and (6) examples of derivatization.