Recyclable heterogeneous metal foil-catalyzed cyclopropenation of alkynes and diazoacetates under solvent-free mechanochemical reaction conditions

Abstract

Silver and copper foil were found to be effective, versatile and selective heterogeneous catalysts for the cyclopropenation of terminal and internal alkynes under mechanochemical reaction conditions.

Direct Mechanocatalysis: Using Milling Balls as Catalysts

“…This combination lead to a degradation of the foil, which was unusable after the reaction . Switching to nickel pellets leads to more impacts, but subsequently leads to microscopic particles, which are abraded during the reaction and need to be removed afterwards . A commonly used compromise between possible number of impacts, abrasion resistance, availability and uncomplicated recovery is the use of 10 mm balls out of the desired material.…”

Terminal and Internal Alkyne Complexes and Azide-Alkyne Cycloaddition Chemistry of Copper(I) Supported by a Fluorinated Bis(pyrazolyl)borate

“…The π-backbonding contribution in EtC≡CEt and PhC≡CH counterparts is similar to that of 4 (Figure 4). For the dinuclear species, Cu 2 (µ-[3,5-(CF 3 ) 2 Pz]) 2 (HC≡CH) 2 (10), Cu 2 (µ-[3,5-(CF 3 ) 2 Pz]) 2 (EtC≡CEt) 2 (7), and Cu 2 (µ-[3,5-(CF 3 ) 2 Pz]) 2 (HC≡CPh) 2 ( 9), the Cu-alkyne interaction energy (∆E int ) amounts to −43.8, −49.4 and −47.8 kcal•mol −1 , respectively. These values are slightly lower than the somewhat related mononuclear, bis(pyrazolyl)borate species.…”

Recent Advances in Mechanochemical Organic Synthesis

“…Silver foil was found to be a recyclable metal catalyst which does not loose activity and diastereoselectivity after several reaction cycles [29]. The optimal results of [2+1] cycloadditions for internal alkynes were achieved with stainless steel vials and balls, with the addition of silver foil (Figure 3), whereas copper foil showed much better performance in cyclopropanations of terminal alkynes [30]. Silver foil in conjunction with PdCl 2 (PPh 3 ) 2 catalyst was also employed as the effective co-catalyst for mechanochemical Sonogashira coupling of aliphatic alkynes with aryl iodides.…”