The generation of quaternary and tertiary stereocentres at C‐10 of the pyrroloisoquinoline skeleton through intramolecular Mizoroki–Heck reactions of 2‐alkenyl‐substituted pyrroles and pyrrolidines has been studied. The cyclizations proceeded in moderate to good yields (up to 81 %), but with low enantioselectivity when chiral phosphanes such as (R)‐BINAP were used as ligands. However, enantiomerically pure 10‐substituted pyrrolo[1,2‐b]isoquinolines were efficiently obtained by a diastereoselective approach using chiral nonracemic pyrrolidines as substrates, generating a tertiary stereocentre.
A convergent route to pyrrolo [1,2-b]isoquinolines with a quaternary center at C-10 has been developed, which implies a sequential Pd(0)-catalyzed carbopalladation followed by cross-coupling reaction with boronic acids. The adequate catalytic system and experimental conditions, with and without the use of phosphane ligands, have been selected to control the chemoselectivity of the process, allowing a 6-exo-carbopalladation to generate a quaternary center and avoiding a direct Suzuki coupling. A variety of electron-rich and electron-deficient arylboronic acids can be used providing an efficient route to substituted pyrrolo [1,2-b]isoquinolines in moderate to good yields (up to 94%, 22 examples).
Highly substituted
coumarins, privileged and versatile scaffolds
for bioactive natural products and fluorescence imaging, are obtained
via a Pd(II)-catalyzed direct C–H alkenylation reaction (Fujiwara–Moritani
reaction), which has emerged as a powerful tool for the construction
and functionalization of heterocyclic compounds because of its chemical
versatility and its environmental advantages. Thus, a selective 6-endo cyclization led to 4-substituted coumarins in moderate
yields. Selected examples have been further functionalized in C3 through
a second intermolecular C–H alkenylation reaction to give coumarin-acrylate
hybrids, whose fluorescence spectra have been measured.
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