Barium Dichloride as a Powerful and Inexpensive Catalyst for the Pechmann Condensation without Using Solvent

Abstract

Various coumarin derivatives have been efficiently synthesized via barium dichloride-catalyzed Pechmann condensation reaction of various phenols and β-keto esters under solvent-free conditions. This novel and inexpensive method has advantages such as short reaction times, excellent product yields, and avoidance of organic solvents in agreement with green chemistry principles.

Rapid one-pot iterative diselenide–selenoester ligation using a novel coumarin-based photolabile protecting group

“…Several coumarin groups exist for the protection of carboxylic acids, amines, alcohols, diols, and thiols. [36][37][38] However, in the case of alcohols and thiols, irradiation leads to irreversible photoisomerisation of the heteroatom onto the 3-position of the coumarin. 39 The installation of a 3-methyl group was therefore deemed necessary to prevent formation of this by-product (i.e.…”

Recent Advances in Synthesis of 4-Arylcoumarins

“…Selectfluor TM , a well-known fluorinating agent, is reported to be an efficient catalyst for the synthesis of 4-arylcoumarins as it is acidic (Entry 8) [ 19 ]. Metal halides such as ZrCl 4 [ 20 ], VCl 3 [ 21 ], SnCl 4 [ 22 ], CuCl 2 , CuBr 2 [ 23 ], BaCl 2 [ 24 ], and LiBr [ 25 ] were investigated for use in a mild and solvent-free Pechmann condensation to provide 4-arylcoumarins (Entries 9–14). Ultrasound was found to synergistically accelerate the condensation in the presence of BiCl 3 [ 26 ] (Entry 15).…”