In ionic liquids [Bmim][PF6] or [Bmim][BF4], a highly regioselective N-substitution of pyrrole with alkyl halides, sulfonyl chlorides, and benzoyl chloride gave substituted pyrroles in excellent yields. Michael addition of pyrrole with electrophilic olefins was completed in a highly regioselective manner to afford N-alkylpyrroles.
Z.-G. Lea, Z.-C. Chen, Y. Hu, Q.-G. Zheng Synthesis, 2004, 1951-1954.
Reaction of 4-bromo-NH-1,2,3-triazoles with alkyl halides in the presence of K2CO3 in DMF produced the corresponding 2-substituted 4-bromo-1,2,3-triazoles in a regioselective process. Subsequent Suzuki cross-coupling reaction provided an efficient synthesis of 2,4,5-trisubstituted triazoles, whereas hydrogenation furnished an efficient synthesis of 2,4-disubstituted triazoles.
X.-j. Wang, K. Sidhu, L. Zhang, S. Campbell, N. Haddad, D. C. Reeves, D. Krishnamurthy, C. H. Senanayake, Org. Lett., 2009, 11, 5460-5493.
A series of N,N′-asymmetrically substituted imidazolium iodides have been synthesized, starting from N-arylimidazoles and the less expensive, but less reactive, 1-chlorobutane or (3-chloropropyl)trimethoxysilane. The addition of potassium iodide and the use of 1,2-dimethoxyethane as a solvent allowed the synthesis of multigram quantities of these salts.
A. M. Oertel, V. Ritleng, M. J. Chetcuti, Synthesis, 2009, 1647-1650.
N-Methylimidazole is a promising catalyst for aza-Michael reactions. Various N-heterocycles were introduced to α,β-unsaturated carbonyl compounds employing N-methylimidazole in a highly efficient, rapid and high yielding synthesis of N-heterocyclic derivatives.
B. K. Liu, Q. Wu, X. Q. Qian, D. S. Lv, X. F. Lin, Synthesis, 2007, 2653-2659.
A convenient, efficient, and selective N-Alkylation of N-acidic heterocyclic compounds with alkyl halides is accomplished in ionic liquids in the presence of potassium hydroxide as a base. In this manner, phthalimide, indole, benzimidazole, and succinimide can be successfully alkylated.
Z.-G. Le, Z.-C. Chen, Y. Hu, Q.-G. Zheng, Synthesis, 2004, 208-212.
Due to the poor nucleophilicity of the nitrogen atom of indoles and the competing alkylation reaction at the C-3 position, the use of more sterically hindered ketones with a lower electrophilicity as N-alkylation reagents has been a great challenge. A dearomatization-rearomatization strategy enables a reductive cross-coupling of indoles with ketones in water in good yield.
Z. Wang, H. Zeng, C.-J. Li, Org. Lett., 2019, 21, 2302-2306.