The rapid preparation of 2-aminosulfonamide-1,3,4-oxadiazoles using polymer-supported reagents and microwave heating
摘要:
Herein, we report on the preparation of a library of 5-substituted-2-amino-1,3,4-oxadiazoles and the corresponding thiadiazole analogues. Presented is a one-pot preparation of the 2-ammosulfonylated analogues through a three component coupling of an acylhydrazine, an isocyanate and sulfonyl chloride promoted by a polymer-supported phosphazine base under microwave dielectric heating. Also described is the optimization process and details pertaining to the elucidation of the reaction products. (c) 2005 Elsevier Ltd. All rights reserved.
of a proline derivative 6 bearing a chiral center in the N-amido moiety provide direct evidence for this conformation change upon its binding with anions in MeCN. The amplified effect of substituent X at the N′-phenyl ring of 5 on the anion binding constant supports the conclusion of anion-binding switched charge transfer in the anion binding complex. 1H NMR and absorption titrations for 5 indicated
N-(乙酰氨基)-N'-苯硫脲(4–6)被发现是有效的阴离子受体,其阴离子亲和力比它们的阴离子亲和力高N-苯甲酰胺基-N'-苯硫脲对应对象(1和2)。这N'-苯硫脲在4–6中的部分被证明是发色团,其最大吸收在。270纳米 已经发现,在阴离子的存在下,在约1μm的吸收。270 nm的4–6(5f除外)in乙腈(MeCN)呈蓝色偏移并增强,而大约在2020年出现红移的肩膀。295 nm,以及大约等渗点。240纳米 1:1的阴离子结合的常数4-6在10,例如6 -10 7中号-1数量级为ACO -在MeCN,被认为是比那些更高1和2,虽然硫脲基的酸度4–6中的-NH质子低于1和2中的-NH质子。1 H NMR数据表明4–6中的N–N单键是扭曲的,但小于1中的N–N单键。和2。建议在阴离子结合后在4–6的N–N单键处发生构象变化,这导致阴离子结合复合物中的平面氢键网络发生电荷转移,其中N-酰基部分