posted on 2020-11-17, 13:05authored byChristian H. Schiwek, Christian Jandl, Thorsten Bach
The benzene ring of indolin-2-ones (2-oxindoles) and 3,4-dihydroquinol-2-ones
was converted to a saturated cyclohexane ring by hydrogenation in
the presence of the rhodium complex Cy(CAAC)Rh(cod)Cl.
The stereoselectivity of the process was found to be high with respect
to both external substituent R1 within the saturated part
of the heterocyclic ring and substituent X on the benzene ring. Twenty-one
hexahydroindolin-2(3H)-ones (70–99% yield,
dr = 83/17 to >99/1) and twelve octahydro-2(1H)-quinolinones (87–96% yield, dr = 64/36 to >99/1) were
obtained with the major diastereoisomer exhibiting the hydrogen atoms
in an all-cis arrangement. The high tolerance toward
functional groups and the compatibility with existing stereogenic
centers are key features of the hydrogenation protocol presented here.