Microwave-assisted Cyclizations Promoted by Polyphosphoric Acid Esters: A General Method for 1-Aryl-2-iminoazacycloalkanes

JIMENA E. DÍAZ; MARÍA CRUZ MOLLO; LILIANA R. ORELLI

BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY

BEILSTEIN-INSTITUT

Año: 2016 vol. 12 p. 2026 - 2031

1860-5397

The first general procedure for the synthesis of 5 to 7-membered 1-aryl-2-iminoazacycloalkanes is presented, by microwave-assisted ring closure of omega-arylaminonitriles promoted by polyphosphoric acid (PPA) esters. 1-Aryl-2-iminopyrrolidines were easily prepared from the acyclic precursors employing a chloroformic solution of ethyl polyphosphate (PPE). The use of trimethylsilyl polyphosphate (PPSE) in solvent-free conditions allowed for the synthesis of 1-aryl-2-iminopiperidines and hitherto unreported 1-aryl-2-iminoazepanes. The cyclization reaction involves good to high yields and short reaction times, and represents a novel application of PPA esters in heterocyclic synthesis.