排序方式: 共有2条查询结果,搜索用时 0 毫秒
1
1.
The synthesis of hydantoins and dihydrouracils from ureidoacetamides has been carried out at high temperature in glycol solvents. A series of substrates were prepared and examined to determine the effect of substrate structure, N-acyl substitution (X), and solvent on the course of the reaction. A dramatic effect was observed when using ureidoacetamides (e.g., X=N-methyl-N-phenyl), which led to higher yields, faster reaction times, and lower racemization of chiral substrates. The rate of racemization of a chiral hydantoin in the presence of dibenzylamine and N-methyl aniline has also been determined. The thermal cyclization methodology has been applied to the preparation of a complex hydantoin. 相似文献
2.
Jianhui Liu Yawen Dong Guanglan Li Xiangting Min Mustafa Hussain 《Tetrahedron letters》2019,60(26):1691-1695
A variety of N, 2-diaryl-2-ureidoacetamide prepared from the condensation of N-aryl-α-aminoamide with potassium cyanate (KOCN) undergo efficient Hendrickson’s reagent-mediated nucleophilic cyclization to afford 2,5-diamine-4-aryloxazoles. The two-step synthesis provides seven target products in yields of 61–78% under mild conditions. This reaction involves an unusual pathway in which the electrophilic amide carbonyl carbon is activated by Hendrickson’s reagent and attacked by a nucleophilic ureido oxygen in a 5-exo-trig O-cycloisomerization. 相似文献
1