نتایج جستجو برای: disubstituted urea
تعداد نتایج: 40692 فیلتر نتایج به سال:
A novel and efficient method for the one-pot synthesis of 2,4-disubstituted thiazoles from carboxylic acids or anhydrides is presented. Based on this new method, the total synthesis of the bis-2,4-disubstituted bis(thiazoles) natural product cystothiazole C is also presented.
We report efficient Pd-catalyzed cyclizations of oxime esters with 1,1-disubstituted alkenes as the basis of a general entry to α,α-disubstituted pyrrolidine derivatives. We also demonstrate that catalytic asymmetric variants of this chemistry are feasible by employing a suitable chiral ligand.
Lipase B from Candida antarctica (CALB) has been selected as the most suitable enzyme to catalyze the regioselective monoacetylation of 1,5-diol isoprostane intermediate, using vinyl acetate as an acyl transfer reagent in THF. We next applied this reaction on linear 2-substituted, 2,2'-disubstituted-1,5-pentanediols, and cyclic 2,3-disubstituted-1,5-pentanediols. To rationalize the regioselecti...
An efficient method for the synthesis of 3,5-disubstituted pyrazoles is described. The reactions of 1,3-dialkynes with hydrazine proceeded smoothly in dimethyl sulfoxide under mild reaction conditions to produce 3,5-disubstituted pyrazoles in satisfactory to excellent yields. A one-pot procedure of the transformation has been developed.
The coupling of an acyl chloride with an isocyanide affords 2,5-disubstituted oxazoles under mild basic conditions instead of 4,5-disubstituted derivatives when using Schöllkopf conditions (butyllithium); this reaction constitutes a remarkable example of a base-induced chemoselective process in isocyanide chemistry.
The reaction of N,N’-persubstituted selenoacrylamides with alkyl bromoacetates gives rise to the formation of alkyl derivatives of N,N-disubstituted 2-aminoselenophene-5-carboxylates which can be transformed by saponification into corresponding 5-carboxylic acids. These compounds decompose by heating under formation of hitherto unknown N,N-disubstituted 2-amino-5H-selenophenes their spectral an...
Abstract Hydrofunctionalization, the direct addition of an X–H (e.g., X=O, N) bond across alkene, is a desirable strategy to make heterocycles that are important structural components naturally occurring molecules. Described here design and discovery “donor–acceptor”-type platinum catalysts highly effective in both hydroalkoxylation hydroamination unactivated alkenes over broad range substrates...
In this article, simple, convenient synthesis of 2-aryl-1- arylmethyl-1H-1,3-benzimidazole (1,2-disubstituted benzimidazoles) via condensation of 1,2-phenylenediamine and aromatic aldehydes using SBA-Pr-SO3H as a nanoporous solid acid catalyst in green protocol was reported.
the 2-mono and 2,6-disubstituted methyl-1,4-dihydropyridines were synthesized by reaction of morpholine, thiophenol, 8-hydroxyquinoline, 2-naphthol and 2-mercopto-1-methyl imidazole with the 2-mono bromo and 2,6-dibromo-1,4-dihidropyridines.
Nickel-catalyzed intermolecular benzylation and heterobenzylation of unactivated alkenes to provide functionalized allylbenzene derivatives are described. A wide range of both the benzyl chloride and alkene coupling partners are tolerated. In contrast to analogous palladium-catalyzed variants of this process, all reactions described herein employ electronically unbiased aliphatic olefins (inclu...
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