Palladium(II)-Catalyzed Asymmetric Synthesis of (Z)-α-Alkylidene-γ-butyrolactams from (Z)-N-Allylic 2-Alkynamides.  Total Synthesis of (−)-Isocynometrine

Abstract

Pd(OAc)2 combined with nitrogen-containing ligands catalyzed the cyclization of (Z)-N-allylic 2-alkynamides in acetic acid to afford the alpha-(Z)-acetoxyalkylidene-gamma-butyrolactams in high yield and high stereoselectivity. When chiral nitrogen-containing ligands were used, the catalytic asymmetric protocol was achieved with moderate enantioselectivity (up to 80 degrees C). The utility of this new methodology was exemplified by the total synthesis of (-)-isocynometrine.

Intermolecular Asymmetric Carboesterification of Alkenes by Using Chiral Amine Auxiliaries under O2: Synthesis of Enantioenriched α‐Methylene‐γ‐Lactones through Chloropalladation of Alkynes

“…However, compared with the impressive development of oxypalladation‐initiated asymmetric cyclization reactions,9 halopalladation‐initiated enantioselective transformations through chiral ligands and palladium complexes still remain a challenge, as the halide ions act as both a nucleophile and a ligand, which inhibits the coordination of the palladium species with other chiral ligands 2d. 9e…”

Gold catalysis in total synthesis—an update

“…From this intermediate, a reported four-step sequence leads to the final target. 44 2.17 Diyne tandem reaction Diynes 57 and 58 were used as key intermediates for the syntheses of various Drimane type sesquiterpenes, a group of natural products possessing a variety of interesting biological activities (Scheme 29). 45 The gold-catalysed key step creates a remarkable increase of molecular complexity.…”

Intramolecular cyclization of N-allyl propiolamides: a facile synthetic route to highly substituted γ-lactams (a review)

“…The author found that when the reaction was carried out in the presence of chiral nitrogen-containing ligands, an asymmetric version of this protocol with moderate enantioselectivity was established. 28 In 2010, the same group reported an elegant approach for the synthesis of a-alkylidene-b-hydroxy-g-lactams 18 via Pd(II)catalyzed cascade reaction of propiolamides 16 and arylboronic acids 17. The optimum conditions for this reaction utilize Pd(OAc) 2 as the catalyst, bpy as ligand and DCE/H 2 O (20 : 1) as solvent.…”