193893-34-4Relevant academic research and scientific papers
Efficient Syntheses of 2-Functionalized Thiophenes, Cyclopent[b]thiophenes, and Polysubstituted Benzo[b]thiophenes from 2-(Benzotriazol-1-ylmethyl)thiophenes
Katritzky, Alan R.,Serdyuk, Larisa,Xie, Linghong,Ghiviriga, Ion
, p. 6215 - 6221 (1997)
Diverse 2-(functionalized-alkyl)- and 2-alkenylthiophenes 2a,b, 4a,b, and 6a-d are prepared via the side chain elaboration of 2-(benzotriazol-1-ylmethyl)thiophenes 3a,b, themselves readily available from the condensation of 1-(hydroxymethyl)benzotriazole with thiophenes 1a,b. Treatment of 2-(benzotriazol-1-ylmethyl)thiophenes 3b and 5g,j with styrenes in the presence of zinc bromide results in formal [3 + 2] cycloaddition to give in good yields substituted cyclopent[b]thiophenes 16a/17a, 16b/17b, and 18. Lithiation and 1,4-addition to a variety of α,β-unsaturated ketones and aldehydes, and subsequent acid-catalyzed intramolecular cyclization followed by debenzotri-azolylation-dehydration converts 3 and 5 to a range of polysubstituted benzo[b]thiophenes 19a-d and 25a-e in moderate to excellent yields. NOE difference spectroscopy and NMR 1H-13C long-range correlation support structures of types 19 and 25 and exclude those of type 26, thus confirming the cyclization pathway.
