2-Amidinylindole-3-carbaldehydes: Versatile Synthons for the Preparation of α-Carboline Derivatives

• Published in: Tetrahedron Vol. 56; no. 51; pp. 9991 - 9997
• Main Authors: Erba, Emanuela, Luisa Gelmi, M, Pocar, Donato
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 15.12.2000; Elsevier
• Subjects: 5-amino- v-triazolines; amidines; Chemistry; Chemistry, Organic; Physical Sciences; pyrido[2,3- b]indole; Science & Technology; α-carboline; α-carboline; amidines; pyrido[2,3- b]indole; 5-amino- v-triazolines; alpha-carboline; PYRIDO<2,3-B>INDOLES; pyrido[2,3-b]indole; 5-amino-nu-triazolines
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/S0040-4020(00)00950-9

The 2-amidinylindole-3-carbaldehydes 1 are the key starting materials for the preparation of three classes of carbolines 2, 6 and 7 in which the pyridine ring is characterised by a different substitution patterns. The carbolines 2 which are functionalized with an amino group in position 2, were obtained directly by heating 1 in presence of SiO 2. The condensation of amidines 1 with arylmethylketones afforded unsaturated ketones 5 which on heating were transformed into 2,9-dialkyl-3-aroyl-9 H-pyrido[2,3- b]indoles 7. Instead, prolonged reaction of amidines 1 with arylmethylketones in t-BuOH/ t-BuOK gave 2-aryl-9 H-pyrido[2,3- b]indoles 6.