Hydrogen-bond-assisted transition-metal-free catalytic transformation of amides to esters

The amide C-N cleavage has drawn a broad interest in synthetic chemistry,biological process and pharmaceutical industry.Transition-metal,luxury ligand or excess base were always vital to the transformation.Here,we developed a transition-metalfree hydrogen-bond-assisted esterification of amides with only catalytic amount of base.The proposed crucial role of hydrogen bonding for assisting esterification was control experiments,density functional theory(DFT)calculations and kinetic studies.Besides broad substrate scopes and excellent functional groups tolerance,this base-catalyzed protocol complements the conventional transition-metal-catalyzed esterification of amides and provides a new pathway to catalytic cleavage of amide C–N bonds for organic synthesis and pharmaceutical industry.     

Aminolysis of allyl esters with bislithium aryl amides

The aminolysis of allyl esters with bislithium amides is reported. Tertiary aryl amides were synthesized in a one-pot reaction with bislithium amides and a suitable electrophile in good yields. The scope of this reaction was demonstrated with a variety of anilines and aminopyridines and applied to the synthesis of triphenylmethylacetamides.     

Reactivity of phosphonium diylids with esters and amides

The phosphonium diylid (C₆H₅)₂P(CH₂)(CH₂Li) reacts readily with various esters and amides to give acylated phosphonium salts and Wittig products. In the case of N,N-dimethylbenzamide the reaction can be directed mainly to the Wittig products by protonation. Depending on the nature of the carbonyl group, unexpected reactions, such as conjugate additions to α,β-unsaturated compounds or enolization of α-hydrogenated amides, can also take place.     

Synthesis of new esters and amides of cephalosporin G

Synthetic methods for cephalosporin G derivatized at the carboxyl were developed. Dinitroglycerine, acetoxymethyl, and choline esters of cephalosporin G and its amide in addition to amides of cephalosporin G with glutamic acid and arginine were synthesized. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 85–88, January–February, 2007.     

脱氢丙氨酸酯、酰胺的合成方法研究

本文从Boc保护的丝氨酸出发，经两种途径合成了脱氢丙氨酸酯及其酰胺衍生物，两种合成方法操作简便、产率高、反应条件温和。     

A facile direct conversion of aldehydes to esters and amides using acetone cyanohydrin

Aromatic aldehydes with electron-withdrawing groups undergo rapid reactions with a variety of alcohols and secondary amines to afford the corresponding esters and amides, respectively, in high yields, when treated with NaCN or acetone cyanohydrin and base under ambient reaction conditions. In case of α,β-unsaturated aldehydes, simultaneous reduction of the CC bond along with esterification occurred to produce the saturated esters in high yields.     

A convenient scalable one-pot conversion of esters and Weinreb amides to terminal alkynes

Esters and amides undergo reduction to the corresponding aldehydes using DIBAL-H followed by same pot conversion to terminal alkynes utilizing the Bestmann-Ohira reagent in good to excellent yields. Additionally chiral nonracemic substrates undergo this transformation with complete preservation of stereochemical integrity.     

Zinc‐catalyzed transformation of diarylphosphoryl azides to diarylphosphate esters and amides

We have developed a facile and efficient procedure for the synthesis of diarylphosphate esters and amides. Using Zn(acac)₂ as the catalyst, the reaction of diarylphosphoryl azides with aliphatic alcohols and phenols through an unusual P?N bond cleavage provided a number of diarylphosphate esters in good yields (22 examples, up to 94%). Additionally, various diarylphosphate amides were obtained from the corresponding amines in excellent yields as well (8 examples, up to 96%).     

Atomic and bond properties in functionalized esters and amides

The properties of various atomic groups of molecules containing a carbonyl unit (XCOY) consisting of an ester (Y=OR) or amide function (Y=NHR) in different molecular environments (X=H, Me, Et, OH, OMe, NH₂, NHMe, F, Cl), as well as their influence on the properties of the alkyl chain (R=C₈H₁₇) in the molecule, were analyzed by use of the theory of atoms in molecules (AIM). To this end, the main atomic and bond properties for each atom in 18 carbonyl compounds of the aforementioned types were determined on the basis of 6-31++G**//6-31G* wave functions. The properties of the C and O atoms in the carbonyl group, and those of their bonds, are directly related to the nature and electronegativity of the X substituent and to the character of the Y group. The nature of the C Y bond and the properties of the Y group are also dependent on the proximity of the X group. Based on the precision with which integrated properties were determined, assessed by L(Ω), the properties of the methylene groups of the R chain located in α and β with respect to Y are essentially dependent on the nature of Y and, to a lesser extent, on that of X. The methylene group in γ with respect to Y exhibits a dependence on the nature of the latter that vanishes in more distinct groups; therefore, the methylene in ε can be assimilated to one in an alkane. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 1444–1454, 1999     

Palladium-catalysed α-arylation of esters and amides under microwave conditions

A rapid and convenient approach for the α-arylation of esters and amides using Reformatsky reagents under a microwave accelerated reaction protocol has been established.     

Lanthanide triflate-promoted palladium-catalyzed cyclization of alkenyl beta-keto esters and amides

[reaction: see text] Lanthanide triflates were found to promote the palladium-catalyzed cyclization of alkenyl beta-keto esters and amides. In the presence of catalytic amounts of PdCl(2)(MeCN)(2) and Ln(OTf)(3), various alkenyl beta-keto esters and amides underwent regioselective cyclization reactions to give six-, seven-, or eight-membered-ring carbocycles in moderate to excellent yields.     

Palladium-catalyzed alpha-arylation of esters and amides under more neutral conditions

Two procedures for the alpha-arylation of carbonyl compounds under conditions that are more neutral than those of reactions of aryl halides with alkali metal enolates are reported. The first procedure rests upon the development of catalysts bearing the hindered pentaphenylferrocenyl di-tert-butylphosphine (Q-phos) and the highly reactive dimeric Pd(I) complex {P(t-Bu)3]PdBr}2. By this procedure, zinc enolates prepared from alpha-bromo esters and amides react with aryl halides to form alpha-aryl esters and amides in high yields under mild conditions with 1-2 mol % catalyst and with remarkable functional group tolerance. By the second procedure, silyl ketene and silyl ketimine acetals react with aryl bromides in the presence of substoichiometric zinc fluoride, 1 mol % Pd(dba)2, and 2 mol % P(t-Bu)3 in DMF solvent at 80 degrees C. Reactions of zinc tert-butyl acetate and propionate enolates and trimethylsilyl ketene acetals of tert-butyl propionate and methyl isobutyrate with aryl bromides bearing electron-donating and potentially reactive, base-sensitive electron-withdrawing groups and with pyridyl bromides are reported. In addition, the diastereoselective coupling of phenyl bromide with an imide enolate bearing the Evans auxiliary is reported, and this study shows that racemization of base-sensitive stereocenters does not occur during the coupling process under these more neutral conditions.     

Facile N-derivatization of alpha-amino esters and amides via benzotriazolylmethyl derivatives

Alpha-(N-substituted amino)esters were prepared in a two-step procedure from available unsubstituted alpha-amino esters. alpha-Amino esters are first converted into the corresponding N-benzotriazolylmethyl derivatives; in the second step, the benzotriazole group is substituted by various nucleophiles with or without the presence of a Lewis acid to give substituted alpha-amino esters in high overall yield under mild conditions with no signs of racemization. Boc-protected amino acids were converted into alpha-amino amides; subsequent deprotection allowed the conversion into N-substituted derivatives analogously to the alpha-amino esters, without racemization in high yields under mild conditions.     

Ru-catalyzed oxidation of substituted acetylenes to α-keto esters and α-keto amides with iodosylbenzene

Oxidation of alkynyl ethers and -amines with iodosylbenzene in presence of Ru-catalysts affords α-keto esters and α-keto amides in 44–85% yield. These conversions can also be effected with RuO₄.