5-endo-dig Cyclization of O-Propargyl Mandelic Acid Amides towards 2,5-Dihydrofurans
5-endo-dig cyclization of O-propargyloxyamides, obtained through a Passerini reaction mediated by boric acid and subsequent propargylation, affords 2,5-dihydrofurans in the presence of tert-butylate. The mechanism of the reaction was studied by using DFT calculations and the results were compared with the behavior of analogous N-propargylamide derivatives.
Gaied, Lilia Ben,Fincias, Nicolas,Garrec, Julian,Ka?m, Laurent El
Direct synthesis of esters and amides from unprotected hydroxyaromatic and -aliphatic carboxylic acids
A facile method for the activation of hydroxy-substituted carboxylic acids using benzotriazole chemistry without prior protection of the hydroxy substituents is presented. The N-acylbenzotriazole intermediates 2a-g, 6a-d, and 9a-c have been used for high-yielding synthesis of both aliphatic (3a-1) and aromatic (7a-h, 10a-f) hydroxy carboxamides. High yields of aromatic hydroxy esters 12a-h and 13a-i were obtained using either neat alcohols in neutral microwave conditions or nucleophilic alkoxides and the intermediate N-(arylacyl)benzotriazoles. Moderate yields were obtained in the case of aliphatic hydroxy esters 11a,b and thiolesters 11e-g from the intermediates 2a-c.
Katritzky, Alan R.,Singh, Sanjay K.,Cai, Chunming,Bobrov, Sergey
p. 3364 - 3374
(2007/10/03)
Synthesis of carboxamides by LDA-catalyzed Haller-Bauer and Cannizzaro reactions
Equation presented. The first direct synthesis of N-alkylcarboxamides and N,N-dialkylcarboxamides by Haller-Bauer (HB) and Cannizzaro-type reactions has been realized. Lithium N,N-diisopropylamide (LDA) catalyst was successfully used in not only the HB reaction of benzylic ketones with lithium N-alkylamides to give the corresponding carboxamides and hydrocarbons but also in the Cannizzaro-type reaction of aldehydes with lithium N-alkylamides or lithium N,N-dialkylamides to give the corresponding carboxamides and alcohols.
Ishihara, Kazuaki,Yano, Takayuki
p. 1983 - 1986
(2007/10/03)
Direct Aminolysis of Nonactivated and Thermally Unstable Esters at High Pressure
The preparation of the amides 3 from a wide variety of nonactivated esters 1 and secondary amines 2 has been achieved at 8 kbar and around 45 deg C; scope and limitations are discussed.The method was also successfully applied for the aminolysis of alkyl 2-arylsulfinylacetates 7 that are relatively sensitive to heat. - Key Words: Aminolysis/ High-pressure synthesis