Different modes of acid-catalyzed cyclization of 4-(γ-oxoalkyl)semicarbazide hydrazones: 7-membered versus 14-membered cyclic semicarbazones formation
摘要:
Acid-catalyzed cyclization of 4-(gamma-oxoalkyl)semicarbazide hydrazones has been studied. 7-Membered cyclic semicarbazones, 2,4,5,6-tetrahydro-3H-1,2,4-triazepin-3-ones, were obtained from the gamma-phenyl-substituted semicarbazides, while the cyclization of the gamma-methyl-substituted semicarbazides involved two molecules of the starting material to result in 14-membered cyclic bis-semicarbazones, 1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-diones. The 4-(gamma-oxoalkyl)semicarbazide hydrazones were prepared according to a four-step synthesis based on amidoallcylation of the sodium enolates of 1,3-diketones with ethyl N-(1-tosylallc-1-yl)carbamates followed by base-promoted retro-Claisen reaction and treatment of the obtained ethyl N-(gamma-oxoalkyl)carbamates with hydrazine. (C) 2015 Elsevier Ltd. All rights reserved.
first catalytic addition reactions of sulfonylimidates have been accomplished. In the presence of a catalytic amount of DBU (normally 5−10 mol %), sulfonylimidates reacted with several N-protected imines, methyl acrylate, and azodicarboxylate to afford the corresponding addition adducts, sulfonylimidates, in excellent yields. In the addition reactions to imines, high anti-selectivity was observed. A
磺酰亚胺酯的第一次催化加成反应已经完成。在催化量的 DBU(通常为 5-10 mol%)存在下,磺酰亚胺酯与几种 N 保护的亚胺、丙烯酸甲酯和偶氮二羧酸酯反应,以极好的收率提供相应的加合物磺酰亚胺酯。在与亚胺的加成反应中,观察到高抗选择性。还描述了从醛和磺酰亚胺酸酯直接形成 β-氨基酸衍生物的新方法。
Highly Efficient Aza-Michael Reactions of Enones with Carbamates Using a Combination of Quaternary Ammonium Salts and BF<sub>3</sub>·OEt<sub>2</sub>as a Catalyst
作者:Chun-Gu Xia、Li-Wen Xu、Lyi Li、Shao-Lin Zhou、Jing-Wei Li、Xiao-Xue Hu
DOI:10.1055/s-2003-43333
日期:——
Aza-Michael reactions of enones with carbamates took efficiently in the presence of a catalytic amount of quaternary ammonium salts and BF 3 .OEt 2 to afford the total products in high yields. The new catalytic system was also efficient in the aza-Michael reaction of chalcone, which was difficult to react with carbamates by transition metal salts catalysts.
An efficient and inexpensive catalyst system for the aza-Michael reactions of enones with carbamatesElectronic supplementary information (ESI) available: experimental. See http://www.rsc.org/suppdata/cc/b3/b307733k/
作者:Li-Wen Xu、Chun-Gu Xia、Xiao-Xue Hu
DOI:10.1039/b307733k
日期:——
A new strategy which uses very cheap FeCl3 as an effective catalyst in the presence of Me3SiCl has been developed for the conjugate addition of enones and chalcone with unactivated weakly nucleophilic carbamates.
Catalytic Mannich-Type Reactions of Sulfonylimidates
作者:Ryosuke Matsubara、Florian Berthiol、Huy V. Nguyen、Shu Kobayashi
DOI:10.1246/bcsj.82.1083
日期:2009.9.15
case of Ts-imidate. Alkali earth metal alkoxide and its HMDS salt also catalyze Mannich-type reactions of sulfonylimidates. The reactionscatalyzed by Mg(O t Bu) 2 in DMF provided the adducts with high anti selectivity, while those catalyzed by [Sr(HMDS) 2 ] 2 gave syn selectivity. The asymmetric variant of Mannich-type reaction of sulfonylimidate was also achieved. Several transformations of sulfonylimidates
Bismuth triflate was found to be an efficient catalyst in the Mannich-typereaction of silylenolates with N-alkoxycarbonylamino sulfones. The reaction proceeded smoothly with a low catalyst loading of bismuth triflate (0.5–1.0 mol %) to afford the corresponding protected β-aminocarbonyl compound in very good yields (up to 96 %).