A convenient and straightforward approach for the construction of indole alkaloid scaffolds from indole-containing alkene-tethered aryl halides and alkynes through a sequential C−H activation, five-membered palladacycle formation, and alkyne insertion process has been described. The approach provides a series of indole alkaloid compounds in moderate to excellent yields with good functional tolerance.
A facile Pd-catalyzed cascade of intramolecular Heck cyclization/alkylpalladium activated dearomatization of aryl alkynetethered indole is described. In this single step two nonadjacent allcarbon quaternary centers, two nitrogen-containing heterocycles, and three C(sp 2 )−C(sp 3 ) bonds are efficiently furnished. These products could also undergo 5-to-6 ring migration-expansion reaction under Brønsted-acid conditions to transform into the benzo[c]carbazole skeletons. Scheme 1. Strategies for the Formation of All-Carbon Quaternary Centers Letter pubs.acs.org/OrgLett
An efficient Pd-catalyzed cascade alkynylation of aryl
phenol-tethered
alkynes with alkynyl bromides is described. This protocol could provide
various conjugated 1,3-enynes possessing a polysubstituted spirocyclohexadienone,
as well as an all-carbon tetrasubstituted alkene moiety. The products
could also undergo ring-expansion and cyclization transformations
under different conditions to convert to diverse fused cyclic scaffolds.
A palladium-catalyzed cascade allylative
dicarbofunctionalization
of aryl phenol-tethered alkynes with allyl iodides is described. A
series of polysubstituted spirocyclo-containing skipped dienes with
an all-carbon tetrasubstituted alkene unit are synthesized through
this convenient process. The cascade reaction proceeds selectively
through dearomative C-allylation instead of O-allylation of aryl phenols.
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