Brønsted Acid‐Mediated Annulation of α‐Oxo Ketene Dithioacetals with Pyrroles: Efficient Synthesis of Structurally Diverse Cyclopenta[b]pyrroles |
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| Authors: | Xiaoge Yang Kaikai Wu Ping Wu Prof Dr Jiping Chen Prof Chenglin Sun Prof Dr Zhengkun Yu |
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| Institution: | 1. Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023 (China), Fax: (+86)?411‐8437‐9227;2. State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032 (China) |
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| Abstract: | Brønsted acid‐mediated annulation of internal olefins α‐oxo ketene dithioacetals to pyrroles was efficiently achieved to afford cyclopentab]pyrroles. A pair of Brønsted acids with acid strengths, that is, trifluoroacetic acid, and para‐toluenesulfonic acid hydrate, were applied to promote the annulation reactions. The resultant products were readily oxidized to sulfones by meta‐chloroperoxybenzoic acid. Subsequent treatment with 1,8‐diazabicyclo5.4.0]undec‐7‐ene gave desulfurized terminal olefins or 2+2] cycloaddition products from the desulfurized olefin intermediates. The present protocol provides facile access to structurally diverse cyclopentab]pyrrole derivatives under mild conditions. |
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| Keywords: | annulation Brø nsted acids pyrroles synthetic methods thioacetals |
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