Phenylcarbamoylation of N-Acetyl-1,2,4-triazolium-4-aminides Revisited
摘要:
The reaction of N-acetyl-1,2,4-triazolium-4-aminides (I, i.e. 1Aa-d) with phenyl isocyanate affords ring functionalized products (4a-d) rather than linear adducts (II). Analogous compounds are obtained from the triazolium-1-aminide (1Ae) and the imidazolium congener (W). Twofold carbamoylation to give products of type (8) occurs on reaction of aminotriazolium salts (7A) in the presence of base. Azoliums having methyl at C(5)/(2) are inert throughout (B series).
Iridium-Catalyzed Direct Amidation of Imidazoles at the C-2 Position with Isocyanates in the Presence of Hydrosilanes Leading to Imidazole-2-Carboxamides
Regioselective coupling reaction of N-substituted imidazoles with isocyanates in the presence of a stoichiometric amount of hydrosilanes catalyzed by Ir4(CO)12 to give imidazole-2-carboxamides is reported. Imidazoles bearing an (O-silyl)carboximidate group at the 2-position appear to be initially formed in the reaction; these are then hydrolyzed to the final products in situ. The addition of the hydrosilane
Di-<i>tert</i>-butyl Dicarbonate and 4-(Dimethylamino)pyridine Revisited. Their Reactions with Amines and Alcohols<sup>1</sup>
作者:Yochai Basel、Alfred Hassner
DOI:10.1021/jo000257f
日期:2000.10.1
The reaction of BOC2O in the presence and absence of DMAP was examined with some amines, alcohols, diols, amino alcohols, and aminothiols. Often, unusual products were observed depending on the ratio of reagents, reaction time, polarity of solvent, pK(a) of alcohols, or type of amine (primary or secondary). In reactions of aliphatic alcohols with BOC2O/DMAP, we isolated for the first time carbonic-carbonic anhydride intermediates; this helps explain the formation of symmetrical carbonates in addition to the O-BOC products. In the case of secondary amines, we succeeded to isolate unstable carbamic-carbonic anhydride intermediates that in the presence of DMAP led to the final N-BOC product. The effect of N-methylimidazole in place of DMAP was also examined.
α-Nitrogen activating effect in the room temperature copper-promoted N-arylation of heteroarylcarboxamides with phenyl siloxane or p-toluylboronic acid
作者:Patrick Y.S Lam、Sophie Deudon、Elisabeth Hauptman、Charles G Clark
DOI:10.1016/s0040-4039(01)00203-9
日期:2001.3
Heteroarylcarboxamides containing a-nitrogens undergo copper-promoted N-phenylation with hypervalent phenyl trimethylsiloxane at room temperature, in the absence of base and in air. Arylboronic acid can substitute for phenyl trimethylsiloxane as the organometalloid. The ol-heteroatom chelating effect is in the decreasing order of N>O, S. This discovery opens up the possibility of using other alpha -nitrogen functional groups to direct the N-arylation of peptides and simple amides under conditions as mild as that of amide bond formation. (C) 2001 Dupont Pharmaceutical Company. Published by Elsevier Science Ltd. All rights reserved.
Phenylcarbamoylation of N-Acetyl-1,2,4-triazolium-4-aminides Revisited
作者:Dietrich Moderhack、Matthias Noreiks
DOI:10.3987/com-06-10836
日期:——
The reaction of N-acetyl-1,2,4-triazolium-4-aminides (I, i.e. 1Aa-d) with phenyl isocyanate affords ring functionalized products (4a-d) rather than linear adducts (II). Analogous compounds are obtained from the triazolium-1-aminide (1Ae) and the imidazolium congener (W). Twofold carbamoylation to give products of type (8) occurs on reaction of aminotriazolium salts (7A) in the presence of base. Azoliums having methyl at C(5)/(2) are inert throughout (B series).
Conformational Properties of Aromatic Amides Bearing Imidazole Ring and Acid-Induced <i>Trans</i>–<i>Cis</i> Amide Switching
bearing secondary amide bond exist in trans conformation both in the crystal and in solution, whereas the conformation of the N-methylated derivatives is cis in the crystal and predominantly cis in various solvents. The cis conformational preference of N-alkylated benzanilide provides access to aromatic foldamers such as oligo(N-alkyl-p-benzamide)s, which adopt dynamic helical structures. Here, the conformational