Journal of Organic Chemistry p. 455 - 462 (1994)
Update date:2022-08-04
Topics:
Jefferson
Warkentin
Studies of the thermal rearrangements of five 3H-pyrazoles are described, in which the migrating groups were methoxymethyl, tert-butyl, 1-adamantyl, p- methoxybenzyl, and benzyl. On the basis of reaction products, rearrangement of the (methoxymethyl)pyrazole in benzene, dichloromethane, and methanol at room temperature occurs by a stepwise mechanism, involving discrete ion-pair intermediates. Observed first-order rate constants, for the rearrangement of four of the 3H-pyrazoles in benzene-d6 and acetone-d6 at higher temperatures, were determined. The tert-butyl compound also rearranges by a stepwise mechanism in benzene-d6, acetone-d6, and methanol-d4 based on the fact that isobutene and tert-butyl methyl ether (in methanol) are coproducts of rearrangement. The mechanism of rearrangement of the adamantyl and methoxybenzyl systems, in both benzene-d6 and acetone-d6 solvents, is ambiguous, the distinction between stepwise, with tight ion-pair intermediates, and concerted, with some charge separation, being unclear. However, both afforded a methyl ether in low yield during rearrangement in methanol solvent, which suggests a stepwise, ion-pair mechanism for rearrangement in that medium. No methanolysis product could be detected from the rearrangement of the benzyl compound in methanol, which suggests concerted rearrangement. Additional evidence that it rearranges by a concerted mechanism is the fact that it affords only one pyrazole product, whereas the others afford two or more.
View MoreNanjing Zelang Medical Technology Co. Ltd
Contact:86-25-83063290/13770714480
Address:Ganjiabian 108# 01 Unit,701-702 room,Yao Hua Street,Qixia District,Nanjing,Jiangsu,China
Ningbo Tide Imp. & Exp. Co., Ltd.
Contact:+86-571-8993 7933; +86-571-8993 6453
Address:7/F Anno Domini Building, Tower South, 8 Qiu Shi Road,Hangzhou,China.
LianYunGang Chiral Chemical(CHINA) CO.,LTD
Contact:+86-518-83616958 +86-519-82884848
Address:LianYunGang Chemical Industry Park (JiangSu)
Zhengzhou Yuanli Biological Technology Co., Ltd.
Contact:+86-371-67897870/67897895
Address:No. 38, Qingyang Street, Zhengzhou, Henan, China
lianyungang jinkang pharmaceutical technology co., ltd.
Contact:008651885445517
Address:Jinshan industrial park, Ganyu county, Lianyungang, Jiangsu Province, 222115, China
Doi:10.1002/hlca.19940770127
(1994)Doi:10.1016/0960-894X(96)00324-1
(1996)Doi:10.1002/zaac.200700462
(2008)Doi:10.1016/j.ejmech.2013.08.018
(2013)Doi:10.1080/00958972.2013.841902
(2013)Doi:10.1016/j.carres.2017.03.002
(2017)