title: Synthesis of regiospecifically fluorinated conjugated dienamides.
abstract: Modular synthesis of regiospecifically fluorinated 2,4-diene Weinreb amides, with defined stereochemistry at both double bonds, was achieved via two sequential Julia-Kocienski olefinations. In the first step, a Z-a-fluorovinyl Weinreb amide unit with a benzothiazolylsulfanyl substituent at the allylic position was assembled. This was achieved via condensation of two primary building blocks, namely 2-(benzo[d]thiazol-2-ylsulfonyl)-2-fluoro-N-methoxy-N-methylacetamide (a Julia-Kocienski olefination reagent) and 2-(benzo[d]thiazol-2-ylthio)acetaldehyde (a bifunctional building block). This condensation was highly Z-selective and proceeded in a good 76% yield. Oxidation of benzothiazolylsulfanyl moiety furnished a second-generation Julia-Kocienski olefination reagent, which was used for the introduction of the second olefinic linkage via DBU-mediated condensations with aldehydes, to give (2Z,4E/Z)-dienamides in 50%-74% yield. Although olefinations were 4Z-selective, (2Z,4E/Z)-2-fluoro-2,4-dienamides could be readily isomerized to the corresponding 5-substituted (2Z,4E)-2-fluoro-N-methoxy-N-methylpenta-2,4-dienamides in the presence of catalytic iodine.
authors.affiliation: Department of Chemistry, The City College and The City University of New York, 160 Convent Avenue, NY 10031, USA.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Chowdhury
authors.affiliation: Department of Chemistry, The City College and The City University of New York, 160 Convent Avenue, NY 10031, USA.
authors.forename: Samir K
authors.initials: SK
authors.lastname: Mandal
authors.affiliation: Department of Chemistry, The City College and The City University of New York, 160 Convent Avenue, NY 10031, USA.
authors.forename: Shaibal
authors.initials: S
authors.lastname: Banerjee
authors.affiliation: Department of Chemistry, The City College and The City University of New York, 160 Convent Avenue, NY 10031, USA. barbaraz@sci.ccny.cuny.edu.
authors.forename: Barbara
authors.initials: B
authors.lastname: Zajc
mesh_terms: D000475:Alkenes / Q000138:chemical synthesis*; D000577:Amides / Q000138:chemical synthesis*; D002384:Catalysis; D054879:Halogenation; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013237:Stereoisomerism
chemical_list: D000475:Alkenes; D000577:Amides
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