Synlett 2020; 31(04): 359-362
DOI: 10.1055/s-0037-1610743
letter
© Georg Thieme Verlag Stuttgart · New York

Copper-Catalyzed Synthesis of Alkyl-Substituted Pyrrolo[1,2-a]quinoxalines from 2-(1H-Pyrrol-1-yl)anilines and Alkylboronic Acids

,
Rulong Yan
State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, Department of Chemistry, Lanzhou University, Lanzhou, 730000, Gansu, P. R. of China   Email: yanrl@lzu.edu.cn
› Author Affiliations
This work was supported by the National Natural Science Foundation of China (21672086) and by the Fundamental Research Funds for the Central Universities (lzujbky-2018-81).
Further Information

Publication History

Received: 03 December 2019

Accepted after revision: 02 January 2020

Publication Date:
17 January 2020 (online)


Abstract

A radical pathway for the construction of pyrrolo[1,2-a]quinoxalines by using 2-(1H-pyrrol-1-yl)anilines and alkylboronic acids has been developed. Features of this process include Cu catalysis, readily accessible starting materials, and simple operations. Alkylboronic acids are used for the construction of pyrrolo[1,2-a]quinoxaline derivatives, and the desired products are obtained in moderate yields.

Supporting Information

 
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  • 16 4-Propylpyrrolo[1,2-a]quinoxaline (3aa):2 Typical Procedure A mixture of 2-(1H-pyrrol-1-yl)aniline (1a; 1 equiv, 0.3 mmol), BuB(OH)2 (2a; 3 equiv, 0.9 mmol), PivOH (1 equiv, 0.3 mmol), Cu(OPiv)2 (10 mol%, 0.03 mmol), and DCM (1 mL) was stirred at 80 °C under O2 (balloon) for 8 h. Upon completion of the reaction (TLC), the mixture was concentrated in vacuo, and the crude product was purified by column chromatography [silica, gel, PE–EtOAc (10:1)] to give a light-yellow solid; yield: (40.3 mg, 73%); mp 45–46 °C. 1H NMR (400 MHz, CDCl3): δ = 7.94–7.90 (m, 1 H), 7.90–7.89 (m, 1 H), 7.84–7.80 (m, 1 H), 7.49–7.44 (m, 1 H), 7.44–7.39 (m, 1 H), 6.92–6.89 (m, 1 H), 6.85–6.83 (m, 1 H), 3.02–2.97 (m, 2 H), 1.99–1.89 (m, 2 H), 1.10–1.05 (m, 3 H). 13C NMR (100 MHz, CDCl3): δ = 157.4, 136.0, 129.4, 127.3, 126.8, 126.1, 125.0, 114.1, 113.6, 113.4, 106.3, 37.8, 22.0, 14.3. HRMS (ESI): m/z [M + H]+ calcd for C14H15N2: 211.1230; found: 211.1227.