122nd General Meeting of the KCS

Type Symposium
Area Current Trends in Organic Chemistry II: Synthetic Methology and Catalysis
Room No. Room 325A+B
Time FRI 09:00-:
Code ORGN2-1
Subject Ligand-enforced Carbopalladation and Kinetically Favored Hydropalladation Leading to Skipped- and Conjugated Enynes
Authors Jin Kyoon Park
Department of Chemistry, Pusan National University, Korea
Abstract

An examination of the previously reported palladium-catalyzed hydroalkynylation of allenes revealed that there exist a common trans geometry and conjugated branch selectivity (β-alkynylation) for neutral and electron-deficient allenes, presumably governed by the thermodynamic stability of the product. The β-alkynylation proceeds via the formation of π-allyl-Pd intermediate through carbopalladation pathway. Given this known propensity of allenes, the possibility of divergent β- and γ-alkynylation stood as a challenging and unprecedented task. In order to address this challenge, we attempted to take advantage of the potential chelating amide group of the substrate for control of the stereoselectivity and to screen sterically and electronically differentiated phosphine ligands for the desired regiocontrol. Herein, we present a complementary, highly regiodivergent, and stereospecific cross-coupling approach for the syntheses of conjugated and skipped ynenamides promoted by two different ligands, using a single metal catalyst (Figure). We also proposed reasonable mechanisms in which the hydro- and carbopalladation processes in the current divergent reaction operate separately by the formation of σ-vinyl-Pd intermediate, based upon experimental results.

E-mail pjkyoon@pusan.ac.kr