Interesting reactivity of diketones with pyrrole under acidic condition

Self-Assembly of 4,4'-Linked Dipyrromethanes from Unconventional Reactants─Propargylamines, 2-(Vinyloxy)ethyl Isothiocyanate, and Alkylating Agents under Basic Conditions

Self-assembly of 4,4'-linked dipyrromethanes from 2-(vinyloxy)ethyl isothiocyanate, tertiary propargylamines, and alkylating agents has been discovered. The plausible reaction mechanism, the major stages of which have been confirmed experimentally, includes (1) the lithiation of propargylamine (with n-BuLi); (2) the formation of lithium N-[2-(vinyloxy)ethyl]but-2-ynimidothioate (product of the addition of monolithiated propargylamine to isothiocyanate); (3) isomerization of the latter in the corresponding allenylimidothioate (under the action of the t-BuOK/t-BuOH system); (4) low-temperature (<15 °C) intramolecular cyclization of the latter into potassium N-(5-amino-2-thienyl)-N-[2-(vinyloxy)ethyl]amide; (5) the base-induced cleavage of the C-O bond of the N-[2-(vinyloxy)ethyl] group and removal of vinyloxide-anion leading to acetaldehyde; (6) interaction of acetaldehyde with two molecules of N-(5-amino-2-thienyl)-N-[2-(vinyloxy)ethyl]amide-anion resulting in dithienomethane N-anionic intermediate; (7) recyclization of the latter into dipyrromethane S-anionic intermediate. Final S-alkylation affords synthetically challenging 4,4'-dipyrromethanes in a yield of 22-51%. The whole process is carried out in a single synthetic operation in a very short time (∼10-15 min, excluding alkylation time).

Magnetic solid sulfonic acid-enabled direct catalytic production of biomass-derived N-substituted pyrroles

Five-membered nitrogen heterocyclic pyrroles have extremely high physiological activity and are widely used in medicine, agriculture, material chemistry, industry, and supramolecular chemistry. Developing a mild and eco-friendly way to synthesize...