Synthesis of 2-arylpyrroles via catalytic dehydrogenation of 2-aryl-1-pyrrolines in the presence of palladium-supported on alumina

• Published in: Tetrahedron Vol. 71; no. 25; pp. 4362 - 4371
• Main Authors: Figueira, Cláudia A., Lopes, Patrícia S., Gomes, Pedro T.
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 24.06.2015; Elsevier
• Subjects: Chemistry; Chemistry, Organic; Dehydrogenation; Heterogeneous catalysis; Nitrogen heterocycles; Palladium; Physical Sciences; Science & Technology; OQCVANDBXOOKQN-UHFFFAOYSA-N; GYRVPSPSNHVDHL-KJEVSKRMSA-N; NDIVUQKOBWUIIV-UHFFFAOYSA-N; OHMHBPYFSSIRDK-UHFFFAOYSA-N; QKYQLGSVQLSHER-UHFFFAOYSA-N; MNMXTZNNWVVPLQ-UHFFFAOYSA-N; BVRMHGPJEAUGAX-UHFFFAOYSA-N; GNUCXNWRQGBDFG-UHFFFAOYSA-N; Palladium; KRHBKIZDQQIZJV-UHFFFAOYSA-N; ZNPLSOLZEBKMIK-UHFFFAOYSA-N; USYFMOFHEFGSJG-UHFFFAOYSA-N; Heterogeneous catalysis; IABRCJFSZGFYEY-UHFFFAOYSA-N; Nitrogen heterocycles; WXLKQTDSSMUYHH-UHFFFAOYSA-N; JRRUSEUPPPFQED-UHFFFAOYSA-N; Dehydrogenation; FUVYKLHZUMRUDB-UHFFFAOYSA-N; FEAMNHISNWMBOV-UHFFFAOYSA-N; PQZAWZGYOZRUFT-UHFFFAOYSA-N; BIS(IMINOPYRROLYL) COMPLEXES; DIRECT ARYLATION; SCHMIDT REACTION; IMINES; EFFICIENT SYNTHESIS; COBALT(II); GENERAL-METHOD; PYRROLIDINES; PYRROLE DERIVATIVES; CYCLIZATION
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2015.04.043

A convenient synthesis of 2-arylpyrroles from the catalytic dehydrogenation of 2-aryl-1-pyrrolines in the presence of commercial palladium-supported on alumina (Pd/Al2O3) is described. The reaction scope was tested for aryl substituents with different steric hindrances and electronic natures. The dehydrogenation reaction conditions such as temperature, reflux time and amount of catalyst, revealed to be highly dependent on the 2-aryl substituent group, moderate to high yields and selectivities being obtained in a reaction involving straightforward work-up and purification procedures. In addition, the synthesis of the corresponding 2-aryl-1-pyrroline starting materials, through the cyclisation reaction involving 4-chlorobutyronitrile and aryl Grignard reagents, is also reported. [Display omitted] Different 2-aryl-1-pyrrolines, obtained by cyclisation reaction of 4-chlorobutyronitrile with aryl Grignard reagents, were dehydrogenated in the presence of a commercial palladium-supported on alumina catalyst (Pd/Al2O3), giving rise to the corresponding 2-arylpyrroles in moderate to high yields and selectivities.