isocyanates via base-induced β-elimination of haloform N-monosubstituted trihaloacetamides is described. The rate of reaction exhibits a strong dependence on the nature of the trihalomethyl group. Thus, while the reaction of tribromoacetamides proceeds at room temperature and the reaction of trichloroacetamides requires heating in polar solvents, no reaction could be observed for any of the corresponding
Metal-Free Synthesis of Unsymmetrical Ureas and Carbamates from CO<sub>2</sub> and Amines via Isocyanate Intermediates
作者:Yiming Ren、Sophie A. L. Rousseaux
DOI:10.1021/acs.joc.7b02905
日期:2018.1.19
A mild and metal-free synthesis of aryl isocyanates from arylamines under an atmosphere of CO2 was developed. The carbamic acid intermediate, derived from the arylamine starting material and CO2 in the presence of DBU, is dehydrated by activated sulfonium reagents to generate the corresponding isocyanate. The latter can be detected by in situ IR and trapped by various amines and alcohols to make unsymmetrical
Chemoselective isocyanide insertion into the N–H bond using iodine–DMSO: metal-free access to substituted ureas
作者:Porag Bora、Ghanashyam Bez
DOI:10.1039/c8cc05019h
日期:——
Insertion of isocyanides into the N–H bond gives access to many medicinally important and structurally diverse complex nitrogen-containing heterocycles. Although the transition metal catalyzed isocyanideinsertion into the N–H bond is very common, polymerization of isocyanides in the presence of a transition metal and their strong coordination with metals are the common drawbacks. On the other hand
Synthesis of N,N′-disubstituted ureas from carbamates
作者:Anwer Basha
DOI:10.1016/s0040-4039(00)86102-x
日期:1988.1
A simple synthesis of N,N′-disubstituted ureasfromcarbamates is described involving displacement of an alkoxy group by the magnesium salt of an amine generated in situ by treatment with ethylmagnesium bromide.
Facile one-pot synthesis of unsymmetrical ureas, carbamates, and thiocarbamates from Cbz-protected amines
作者:Hee-Kwon Kim、Anna Lee
DOI:10.1039/c6ob01290f
日期:——
A novel one-potsynthesis of unsymmetricalureas, carbamates and thiocarbamates from Cbz-protected amines has been developed. In the presence of 2-chloropyridine and trifluoromethanesulfonyl anhydride, isocyanates are generated in situ, which facilitate rapid reaction with amines, alcohols, and thiols to afford the corresponding ureas, carbamates and thiocarbamates in high yields.