Synthesis of α‐Carbolines Using Palladium‐Catalyzed Intramolecular Amination of 3‐(2‐Chlorophenyl)‐2‐Aminopyridines

Abstract

Synthesis of α‐carbolines is developed using palladium‐catalyzed intramolecular amination of 3‐(2‐chlorophenyl)‐2‐aminopyridines prepared by deprotection of 2‐iminopyridines synthesized using the conjugate addition reaction of ethyl 2‐(2‐chlorophenyl)‐2‐cyanoacetate to alkynyl imines. The palladium‐catalyzed intramolecular amination of the synthesized 2‐aminopyridines proceeded smoothly under microwave irradiation conditions to give the desired α‐carbolines in moderate to good yields.

The Construction of Nitrogen‐Containing Heterocycles from Alkynyl Imines

“…Additionally, β ‐carbolin‐1‐ones could be afforded smoothly via Pd(II)‐catalyzed intramolecular amination under the conditions reported by Buchwald. Similarly, Shimizu's group also developed the synthetic methods for α ‐carbolines using the Pd(II)‐catalyzed intramolecular amination of 3‐(2‐chlorophenyl)‐2‐aminopyridines, which was prepared by the conjugated addition of ethyl 2‐(2‐chlorophenyl)‐2‐cyanoacetate to ( Z )‐alkynyl imines (Scheme 15b) [27] …”

Domino 1,4- and 1,6-Addition Reactions of Ketene Silyl Acetals to Dialkynyl Imines Promoted by Aluminum Chloride: Synthesis of Multifunctionalized β-Lactams

“…Among various imines, there are α,β-unsaturated alkynyl imines having a triple bond. We have developed new efficient synthetic methods for various nitrogen-containing heterocycles using 1,4-additions of several carbon nucleophiles such as malonic esters, β-keto esters, and ethyl cyanoacetates to α,β-alkynyl imines. , In 2009, we developed the chemoselective reductions of iminocyclobutenones, which were synthesized using aluminum chloride-promoted 1,4-additions of ketene silyl acetals to α,β-alkynyl imines, to proceed using sodium cyanoborohydride under the influence of an acid to give the racemic aminocyclobutenones in high yields, and the subsequent thermal rearrangement of aminocyclobutenones in the presence of an appropriate amine afforded either racemic cis- or trans -β-lactams in good yields with high diastereoselectivities . In 2014, we also reported chiral either cis- or trans -β-lactam synthesis through the enantioselective reduction of iminocyclobutenones catalyzed by a chiral phosphoric acid and the subsequent thermal rearrangement of chiral aminocyclobutenones in the presence of appropriate amines (Scheme ).…”