Sulfur–DMSO promoted oxidative coupling of active methylhetarenes with amines: access to amides

Abstract

Elemental sulfur-DMSO couple was found to efficiently promote oxidative coupling of active methylhetarenes with amines to yield amides under simple heating conditions. When 2-methylquinoline was used as methylhetarene component, the...

Sulfur-Mediated Decarboxylative Amidation of Cinnamic Acids via C═C Bond Cleavage

“…Therefore, the reaction conditions were slightly reoptimized with reference to the use of anilines and benzylamines to enhance the product yield, which disclosed a 1:1.5 molar ratio of 1 and 2 for 24 h as being ideal for the formation of the desired products 3p – 3z in good yields. However, the reaction of cinnamic acid with benzylamine invariably offered the anticipated product 3 along with the benzylamine homocoupled product amide/thioamide . The reaction of cinnamic acid with cyclohexylamine also afforded product 3z in 62% yield under the established conditions.…”

“…However, the use of external H 2 O (1–3 equiv) in DMSO reduced the yield of the desired product considerably (Scheme , eq d). On the basis of these two control experiments, we concluded that the H 2 O as such has no positive role in the reaction and, instead, DMSO plays the key role as an oxidant for the conversion of thioamide to amide …”

Electrochemical synthesis of pyridine carboxamides from pyridine carbohydrazides and amines in an aqueous medium

“…1 Consequently, the synthesis of pyridine carboxamides has always been the focus of organic chemists. 2–6 Traditionally, pyridine carboxamides were synthesized from pyridine carboxylic acids and their activated derivatives using amines with a high step economy. 2 However, excess amounts of expensive dehydrating or unstable preactivation agents were required, resulting in tedious synthetic operation, low yields and so on.…”

“…Later, several improved protocols were developed via oxidative amidation of aldehydes 3 or methylarenes. 4 To some extent, high temperature and chemical oxidants restricted these methods. Very recently, Laha reported the synthesis of pyridine carboxamides via a TBHP-mediated denitrogenative strategy (Scheme 1a).…”

One-Pot Tandem Nickel-Catalyzed α-Vinyl Aldol Reaction and Cycloaddition Approach to [1,2,3]Triazolo[1,5-a]quinolines

“…The optimal Ni(OAc) 2 ·4H 2 O catalyst loading turned out to be 15 mol % (entries 13–16), where the formation of product 4a peaked at 92% yield (entry 14). The control experiments also confirmed the possible use of another nickel catalyst NiCl 2 ·6H 2 O (entry 18), the importance of NEt 3 (entry 19), and the defined catalyst role of nickel in the [3 + 2] cycloaddition reaction (entry 20).…”