Directed Lithiation of N-Benzenesulfonyl-3-bromopyrrole. Electrophile-Controlled Regioselective Functionalization via Dynamic Equilibrium between C-2 and C-5 Lithio Species

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• 作者：Tsutomu Fukuda ; Takeshi Ohta ; Ei-ichi Sudo ; Masatomo Iwao
• 刊名：Organic Letters
• 出版年：2010
• 出版时间：June 18, 2010
• 年：2010
• 卷：12
• 期：12
• 页码：2734-2737
• 全文大小：141K
• 年卷期：v.12,no.12(June 18, 2010)
• ISSN：1523-7052

文摘

Directed lithiation of N-benzenesulfonyl-3-bromopyrrole (1) with LDA in THF at −78 °C generated C-2 lithio species 3 selectively. Reactions of 3 with reactive electrophiles produced the corresponding 2-functionalized pyrroles 4. On the other hand, quenching with less reactive electrophiles generated the corresponding 5-substituted pyrroles 5. The latter unusual functionalization at C-5 could be rationalized by dynamic equilibrium between C-2 and C-5 lithio species.