Preparation of 1,7- and 3,9-Dideazapurines from 2-Amino-3-iodo- and 3-Amino-4-iodopyridines and Activated Acetylenes by Conjugate Addition and Copper-Catalyzed Intramolecular Arylation

Recent developments in the synthesis of azaindoles from pyridine and pyrrole building blocks

The azaindole framework is ubiquitous in bioactive natural products and pharmaceuticals. This review highlights the synthetic approaches to azaindoles with advantages and limitations, mechanistic pathways and biological importance.

Synthesis of 2-Aminopyridines via a Base-Promoted Cascade Reaction of N-Propargylic β-Enaminones with Formamides

N-Substituted formamides as nucleophiles react with in situ-generated 1,4-oxazepines from N-propargylic β-enaminones followed by spontaneous N-deformylation to deliver densely substituted 2-aminopyridines in good yields (31-88%). The formyl group is found to be a superior traceless activating group of free amines and would ultimately be removed in situ. This reaction proceeds smoothly at room temperature, in the presence of NaOH as sole additive, without protection from the atmosphere and generates H₂O and sodium formate as byproducts.

Rh(iii)-catalyzed 7-azaindole synthesis via C–H activation/annulative coupling of aminopyridines with alkynes

An efficient Rh(iii)-catalyzed 7-azaindole synthesis was developed via C–H activation/annulative coupling of aminopyridines with alkynes.