Iodoarene-catalyzed cyclizations of <i>N</i>-propargylamides and β-amidoketones: synthesis of 2-oxazolines
作者:Somaia Kamouka、Wesley J Moran
DOI:10.3762/bjoc.13.177
日期:——
Two complementary iodoarene-catalyzed methods for the preparation of 2-oxazolines are presented. The first involves the cyclization of N-propargylamides and the second involves the cyclization of β-amidoketones. These are proposed to proceed through different mechanisms and have different substrate scopes.
Gold-Catalyzed Radical-Involved Intramolecular Cyclization of Internal <i>N</i>-Propargylamides for the Construction of 5-Oxazole Ketones
作者:Hejun An、Shaoyu Mai、Qingqing Xuan、Yao Zhou、Qiuling Song
DOI:10.1021/acs.joc.8b02334
日期:2019.1.4
An expedient strategy for the synthesis of 5-oxazole ketones was developed via homogeneous gold catalysis with 4-MeO-TEMPO as an oxidant. The desired 5-oxazole ketones were achieved in decent yields with an excellent functional group compatibility under mild conditions. The current protocol also represents the first example for merging a gold catalyst and radical chemistry in one-pot synthesis with
6-endo-dig cyclization of propargylic amides, using N-bromosuccinimide (NBS) as an electrophilic source. The metal-free reaction can be conducted under mild conditions with good functional group compatibility, delivering excellent yields of the desired products. Mechanistic studies suggest that the reaction proceeds via a double electrophilic attack by NBS on the propargylic amide substrate.
Synthesis of oxazoles through Pd-catalyzed cycloisomerization–allylation of N-propargylamides with allyl carbonates
作者:Akio Saito、Koichi Iimura、Yuji Hanzawa
DOI:10.1016/j.tetlet.2010.01.018
日期:2010.3
In the presence of Pd-2(dba)(3)-Cy3P catalyst, IPr center dot HCl salt [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene], and Cs2CO3, N-propargylarnicles react with allyl carbonates to give 2,5-disubstituted oxazoles having homoallyl groups through the tandem cycloisomerization-allylation. (C) 2010 Elsevier Ltd. All rights reserved.