RESUMO
We report herein the facile and practical construction of α,ß-unsaturated ketones via rhodium-catalyzed direct acylation of vinylsilanes with readily available and abundant carboxylic acids. This protocol features access to a diverse array of synthetically useful functionalities with moderate to excellent yields. More importantly, the late-stage functionalization of pharmaceuticals was also realized with synthetically useful yield.
RESUMO
An efficient synthesis of (3-isoindazolyl)allenes from 2-alkynyl azobenzenes and terminal alkynes via cooperative Pd(PPh3)2Cl2/CuI-catalyzed cross-coupling has been developed. By making use of this approach, (3-isoindazolyl)allenes with various substituents can be synthesized in good to excellent yields. A rapid synthesis of biologically active indazolo[2,3-a]quinoline was also achieved using this method as the key step.
RESUMO
A practical and simple method for deaminoborylation of aryltriazene with bis(pinacolato)diboron has been developed that is mediated by BF(3)·OEt(2). Various arylboronic esters are prepared in moderate to good yields with this facile transition-metal-free procedure.
RESUMO
A simple method for the synthesis of amides has been developed by molybdenum-mediated carbamoylation of aryl halides. Whereas the conventional palladium-catalyzed three-component coupling reaction requires a large excess of gaseous carbon monoxide, the incorporation of carbon monoxide in this Mo-mediated carbamoylation reaction is so efficient that it requires only a slight excess amount of carbon monoxide in the form of its molybdenum complex, Mo(CO)(6). The reaction is applicable for the synthesis of a wide variety of not only secondary and tertiary amides but also primary amides by using aqueous ammonia.
RESUMO
When aryl halide is treated with molybdenum carbonyl amine complex in the presence of base, carbamoylation proceeds to give amide in good yield. The proposed mechanism involves oxidative addition of aryl halide to molybdenum(0) complex, migratory insertion to carbon monoxide giving acyl(amino)molybdenum(II) or aryl(carbamoyl)molybdenum(II) intermediate, and reductive elimination of the amide. This method is simple and provides an alternative method to the conventional palladium-catalyzed amide formation using gaseous carbon monoxide.
Assuntos
Amidas/síntese química , Halogênios/química , Molibdênio/química , Tungstênio/química , Aminas/química , Monóxido de Carbono/química , Catálise , Estrutura Molecular , OxirreduçãoRESUMO
In the presence of aminepentacarbonyltungsten, base, and a catalytic amount of palladium(0) complex, carbamoylation of aryl halide proceeds to afford amide. The reaction may involve transmetalation between palladium(II) intermediate and carbamoyltungstenate that is generated in situ. This catalytic cross-coupling reaction provides an alternative method to the conventional palladium-catalyzed amidation by using gaseous carbon monoxide.