Diversity-oriented Synthesis of [2.2]Paracyclophane-derived Fused Imidazo[1,2-a]heterocycles by Groebke-Blackburn-Bienaymé Reaction: Accessing Cyclophanyl Imidazole Ligands Library.

This report describes the synthesis of a [2.2]paracyclophane-derived annulated 3-amino-imidazole ligand library via a Groebke-Blackburn-Bienayme three-component reaction (GBB-3CR) employing formyl-cyclophanes in combination with diverse aliphatic and aromatic isocyanides and heteroaromatic amidines. The GBB-3CR gives access to differently functionalized skeletally-diverse cyclophanyl imidazole ligands, namely 3-amino-imidazo[1,2- a ]pyridines and imidazo[1,2- a ]pyrazines. Additionally, a one-pot protocol for the GBB-3CR by an in-situ generation of cyclophanyl isocyanide is demonstrated. The product formation was analyzed by detailed spectroscopic techniques, and a cyclophanyl imidazo[1,2- a ]pyridine was confirmed unambiguously by single-crystal X-Ray crystallography. The cyclophanyl imidazole ligands can be readily transformed to showcase their useful utility in preparing N , C -palladacycles via regioselective ortho -palladation.