Synthesis and characterization of substituted (benzo[b]thiophen-2-yl)-4-methyl-4,5-dihydro-1H-imidazol-5-ones

✍ Scribed by Miloš Sedlák; Pavel Drabina; Václav Lánský; Jiří Svoboda

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2008
• Tongue: English
• Weight: 303 KB
• Volume: 45
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570450334

✦ Synopsis

Abstract

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Reactions of 3‐chlorobenzo[b]thiophene‐2‐carbonyl chloride with 2‐alkyl‐2‐aminopropanamides have been used to prepare a series of carboxamides 1a‐d (yields 61‐85%). The products were submitted to base‐catalysed ring closure reactions to give the corresponding 4,5‐dihydro‐1__H__‐imidazol‐5‐ones 2a‐d (yields 69‐97%). By N‐methylation and N‐benzylation were prepared the corresponding 1‐alkyl derivatives 3a(91%) and 3b (85%). These two alkyl derivatives were studied from the standpoint of potential replacement of 3‐chlorine substituent by piperidine via the Buchwald‐Hartwig reaction. It was found that the reaction gives besides except required products of C‐N coupling 5a (14%) and 5b (12%) also products of reductive dechlorination 4a (max. 57%) and 4b (max. 56%). The reductive dechlorination product 4a is formed exclusively (42%) if butyl‐di‐(1‐adamantyl)phosphine (BDAP) is used.