Reactions of N-Aminopyrazoles with Halogenating Reagents and Synthesis of 1, 2, 3-Triazines

• Published in: Chemical & pharmaceutical bulletin Vol. 36; no. 10; pp. 3838 - 3848
• Main Authors: OHSAWA, AKIO, KAIHOH, TERUMITSU, ITOH, TAKASHI, OKADA, MAMIKO, KAWABATA, CHIKAKO, YAMAGUCHI, KENTARO, IGETA, HIROSHI
• Format: Journal Article
• Language: English
• Published: TOKYO The Pharmaceutical Society of Japan 1988; Pharmaceutical Soc Japan; Maruzen; Japan Science and Technology Agency
• Subjects: 1, 2, 3-triazine; 1-aminohalopyrazole; 1-aminopyrazole; Chemistry; Chemistry, Medicinal; Chemistry, Multidisciplinary; Exact sciences and technology; halo-1, 2, 3-triazine; halogenation; Heterocyclic compounds; Heterocyclic compounds with several n hetero atoms in the same ring, in separated rings or in fused rings; Life Sciences & Biomedicine; Organic chemistry; oxidation; Pharmacology & Pharmacy; Physical Sciences; Preparations and properties; pyrazole; ring expansion; Science & Technology; synthesis; Bromine; Five membered ring; Chlorine; Nitrogen heterocycle; Competitive reaction; Iodine Chlorides; Ring expansion; Bromine Chlorides; Six membered ring; Halogenation; Iodine Bromides; Reaction mechanism; Oxidation; Iodine
• ISSN: 0009-2363; 1347-5223
• DOI: 10.1248/cpb.36.3838

Reactions of N-aminopyrazoles with halogenating reagents (Cl2, Br2, I2, BrCl, ICl, IBr, N-chlorosuccinimide, and N-bromosuccinimide) were examined. Some of these reagents preferentially lead to oxidation of the amino group to give the corresponding 1, 2, 3-triazines as major products, while others mainly gave either or both of 1-amino-4-halopyrazoles and 5-halo-1, 2, 3-triazines as the result of halogenation of the 4-position of the pyrazole ring prior to the oxidation of the amino group. In some cases, the oxidation of the amino group and the halogenation of the pyrazole ring proceeded concurrently to form not only the unhalogenated triazines but also the l -amino-4-halopyrazoles and the 5-halotriazines. Various reagents and reaction conditions were explored to utilize the reaction for the synthesis of halogenated and unhalogenated 1, 2, 3-triazines.