Zn(OTf)2-Promoted Chemoselective Esterification of Hydroxyl Group Bearing Carboxylic Acids
摘要:
Selective esterification of aliphatic and aromatic carboxylic acids with various alcohols is studied using triphenylphosphine, I-2, and a catalytic amount of Zn(OTf)(2). Use of this catalyst allows the formation of esters at a faster rate with good to excellent yield by activating the in situ generated acyloxyphosphonium ion intermediate. During the esterification process, both their aromatic and aliphatic hydroxyl groups are fully preserved from trans-esterification. The results show that the bulkiness and the reactivity of this doubly activated intermediate III control the selectivity and the rate of the reaction, respectively. The method is also useful for direct amidation reactions.
Multifunctional transformation of amide C–N bond cleavage is reported. The protocol applies to benzamide, thioamide, alcohols, and mercaptan under similar reaction conditions catalyzed by NaOTs. It is noteworthy that NaOTs can not only be recycled and reused for up to three cycles without significant loss in catalytic activity, but also catalyze gram-grade reactions. This study provides a novel solution
Niobium Pentachloride Promoted Conversion of Carboxylic Acids to Carboxamides: Synthesis of the 4-Aryl-1,2,3,4-tetrahydroisoquinoline Alkaloid Structures
作者:Claudio C. Lopes、Rosangela S. Lopes、Marcelo S. Nery、Renata P. Ribeiro
DOI:10.1055/s-2003-36823
日期:——
A practical method for the conversion of carboxylic acids to the corresponding carboxamides mediated by niobium pentachloride under mild conditions is described. The synthesis of the 4-aryl-1,2,3,4-tetrahydroisoquinoline alkaloid structures was accomplished via benzylic lithiation of N-methyl-3,4-dimethoxy-2-(4'-methoxybenzyl)benzamide.
The first zinc-catalyzed oxidativeamidation of benzylalcohols has been developed. Both aliphatic and aromatic amines can be tolerated and applied in this reaction. Various amides were prepared in good yields undersolvent-free and mild conditions.
Compounds of formula I
in free or salt or solvate form, where R
1
, R
2
and R
5
have the meanings as indicated in the specification, are useful for treating diseases mediated by the ALK-
5
and/or ALK-
4
receptor. Pharmaceutical compositions that contain the compounds and processes for preparing the compounds are also described.
Cp*Co<sup>III</sup>-catalyzed formal [4+2] cycloaddition of benzamides to afford quinazolinone derivatives
作者:Jingshu Yang、Xiao Hu、Zijie Liu、Xueyuan Li、Yi Dong、Gang Liu
DOI:10.1039/c9cc07173c
日期:——
A Cp*CoIII-catalyzed arene C–H bond amidation/annulation of benzamides was developed to afford quinazolinone derivatives in one-pot with high yields and broad substrate scope. This method could be applied to the synthesis of quinazolinone drugs and late-stage modification of natural products.
开发了一种由Cp * Co III催化的苯甲酰胺C / H键酰胺化/环化反应,可一锅制得喹唑啉酮衍生物,并具有高收率和广泛的底物范围。该方法可用于喹唑啉酮类药物的合成和天然产物的后期修饰。