Alkyne Aminopalladation/Heck and Suzuki Cascades: An Approach to Tetrasubstituted Enamines

Abstract

Alkyne aminopalladation reactions starting from tosylamides are reported. The emerging vinylic Pd species are converted either in an intramolecular Heck reaction with olefinic units or in an intermolecular Suzuki reaction by using boronic acids exhibiting broad functional group tolerance. Tetra(hetero)substituted tosylated enamines are obtained in a simple one-pot process.

A solvent controlled regioselective synthesis of 2- and 4-substituted α-carbolines under palladium catalysis

“…In path b, an amino palladated species 15 A' might be formed selectively 16 in NMA from 2-aminotosyl indole ( 6' ). Next, insertion 12 of complex A' onto the activated alkene 7 could form species B' , present in equilibrium with Pd( ii ) enolate B 1 ' .…”

Access to isoindole-derived BODIPYs by an aminopalladation cascade

“…48,49 Our group employed N-(pentafluorobenzoyloxy)amides to extend this concept to an aza-Heck reaction with internal alkynes, thereby obtaining tetrasubstituted enamines. 50 Inspired by the scope of this alkyne aminopalladation/Heck cascade, we envisioned a synthesis of dipyrromethenes 2, key intermediates in every BODIPY synthesis, via an aminopalladation cascade. Treating precursor 1 with Pd 0 should result in an oxidative addition of Pd into the N-O bond of the oxime ester, followed by an intramolecular aza-Heck reaction leading to the formation of an isoindole moiety.…”

“…48,49 Our group employed N -(pentafluorobenzoyloxy)-amides to extend this concept to an aza-Heck reaction with internal alkynes, thereby obtaining tetrasubstituted enamines. 50…”