jo501293m_si_001.pdf (6.87 MB)
Download fileOrganocatalytic Chemo‑, (E/Z)- and Enantioselective Formal Alkenylation of Indole-Derived Hydroxylactams Using o‑Hydroxystyrenes as a Source of Alkenyl Group
journal contribution
posted on 2014-08-01, 00:00 authored by Hong-Hao Zhang, Yue-Ming Wang, Yuan-Wei Xie, Zi-Qi Zhu, Feng Shi, Shu-Jiang TuThe
first organocatalytic asymmetric formal alkenylation of multicyclic
alcohols using non-metal-based alkenes instead of alkenyl metals as
a source of an alkenyl group has been established via chiral phosphoric
acid catalyzed tandem reactions. This transformation directly assembles
isoindolo-β-carboline-derived hydroxylactams with o-hydroxystyrenes via an asymmetric cascade vinylogous addition/hydrogen
elimination reaction sequence, offering an easy access to functionalized
chiral isoindolo-β-carbolines with one quaternary stereogenic
center in high chemo-, (E/Z)-, and enantioselectivities
(up to >95:5 cr, >95:5 E/Z, 97:3
er). This approach also represents the first catalytic asymmetric
formal alkenylation of isoindolo-β-carboline-derived hydroxylactams,
which provides a useful strategy for functionalization of isoindolo-β-carbolines
and synthesis of chiral isoindolo-β-carboline derivatives. In
addition, the investigation on the activating mode revealed that the
hydroxyl group in o-hydroxystyrene was essentially
important for generating a hydrogen-bond interaction with the catalyst.
The dual activation mode of hydrogen bond and ion pair between the
catalyst and the substrates cooperatively facilitated the desired
formal alkenylation reaction in a chemo- and stereoselective way.