Journal of the Chemical Society. Perkin transactions II p. 1589 - 1592 (1986)
Update date:2022-08-10
Topics:
Al-Awadi, Nouria
Taylor, Roger
We have measured the rates of thermal elimination of ethylene from the title compounds between 587.3 and 722.9 K.The reactivities relative to 2-ethoxypyridine at 650 K are: 3-ethoxyisoquinoline (0.21), 2-ethoxyquinoline (3.13), 1-ethoxyisoquinoline (6.47), 2-ethoxythiazole (63.1).These reactivities parallel the ?-bond order of the C=N bond, though the exceptional reactivity of 2-ethoxythiazole is attributed to additional acceleration through +M electron release from sulphur to nitrogen.This emphasizes the greater relative importance of nucleophilic attack by the nitrogen upon the β-hydrogen atom as compared with the analogous mechanism for pyrolysis of esters.Because of semi-concentrated nature of the reaction, interruption of aromaticity is much less significant than in, for example, electrophilic aromatic substitution.Thus retention of the benzenoid character of the ring not involved in the elimination is not an important rate-determining feature, as shown by the lower reactivity of 3-ethoxyisoquinoline relative to 2- ethoxypyridine.The unimportance of the interruption of aromaticity of the benzenoid ring means that conjugative effects are better relayed to nitrogen in the β-naphthalene-like position (isoquinoline) than in the α-naphthalene-like position (quinoline).This is the reverse of the familiar pattern for reactions of naphthalene-like systems where full charges are involved, and may be an additional factor contributing to the higher reactivity of 1-ethoxyisoquinoline than of 2-ethoxyquinoline, as may also be the -I effect of the benzo substiutent.The conclusions are used to predict elimination rates for alkoxyheterocycles not yet studied.
View MoreSanming Coffer Fine Chemical Industrial Co., Ltd
website:http://www.cofferxm.com/
Contact:+86-598-5853979
Address:Jin-sha Yuan Chuang-ye Park,Hi-Tech Development Zone,Sanming City P.R.China
Zhengzhou Minzhong Pharmaceutical Co.,ltd
Contact:0086-371-65797115
Address:15/F,Jiangshan Bldg, NO.126 Huanghe Road,Zhengzhou, China
Contact:86-931-8272767
Address:Room 602, No.461, Nanchang Road, Chengguan District, Lanzhou City, China PRC
Contact:852-29282288
Address:HONGKONG
Suzhou Sinosun Imp.&Exp. Corporation
website:http://www.szsinosun.com
Contact:+86-512-63488895,63488616
Address:No.758 East Jiangling Road Wujiang Economic & Technological Developmenty Zone Jiangsu China
Doi:10.1039/c6cc02932a
(2016)Doi:10.1002/chir.23085
(2019)Doi:10.1021/acs.orglett.7b02959
(2017)Doi:10.1016/j.tet.2009.09.101
(2009)Doi:10.1007/s10600-008-9051-x
(2008)Doi:10.1021/jo01271a086
(1968)
