A Three-Step Synthetic Approach to Asymmetrically Functionalized 4H-Cyclopenta[2,1-b:3,4-b′]dithiophenes

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• 作者：Sarah Van Mierloo ; Peter J. Adriaensens ; Wouter Maes ; Laurence Lutsen ; Thomas J. Cleij ; Edith Botek ; Benot Champagne ; Dirk J. Vanderzande
• 刊名：Journal of Organic Chemistry
• 出版年：2010
• 出版时间：November 5, 2010
• 年：2010
• 卷：75
• 期：21
• 页码：7202-7209
• 全文大小：887K
• 年卷期：v.75,no.21(November 5, 2010)
• ISSN：1520-6904

文摘

A convenient and efficient three-step route toward both symmetrically and asymmetrically functionalized 4H-cyclopenta[2,1-b:3,4-b′]dithiophenes has been developed. Using this method a broad collection of functionalized bridged bithiophenes can smoothly be accessed. Starting from 3-bromo-2,2′-bithiophene, prepared by Kumada coupling of 2-thienylmagnesium bromide with 2,3-dibromothiophene under Pd(dppf)Cl₂ catalysis, lithiation and subsequent reaction with dialkyl ketones afforded (a)symmetrically dialkylated tertiary alcohol derivatives. By means of final Friedel−Crafts dehydration cyclization in sulfuric acid medium, these derivatives were converted to 4,4-dialkyl-4H-cyclopenta[2,1-b:3,4-b′]dithiophenes. Upon replacement of the dialkyl ketone reagent by ethyl levulinate, an ester-functionalized 4H-cyclopenta[2,1-b:3,4-b′]dithiophene was prepared, representing an attractive precursor for variously functionalized cyclopentadithiophene compounds.