β-Cyclodextrin in water: highly facile biomimetic one pot deprotection of phenolic THP/MOM/Ac/Ts ethers and concomitant regioselective cyclization of chalcone epoxides and 2′-aminochalcones

Abstract

A mild and efficient one-pot deprotection of THP/MOM/Ac/Ts ethers and concomitant cyclization of chalcone epoxides to 2-hydroxyindanones and 2'-aminochalcones to aza-flavanones using β-Cyclodextrin in water has been developed. β-CD was found to be highly effective in carrying out deprotection and sequel transformations under eco-friendly environment affording moderate to excellent yields (59-99%) at 60 o C in 8-22 min. Water, an eco-friendly reaction medium, has been utilized for the first time in this reaction. The merits of the presented protocol include high yields, catalyst reusability and preclude use of metals and organic solvents. The present method is very much milder but more advanced than those reported earlier.

Supramolecular Organocatalysis in Water Mediated by Macrocyclic Compounds

“…In the reaction mechanism proposed by the authors, the CD played a dual role: (a) activation of the THP ether and epoxide by H-bond interactions and, at the same time (b) formation of inclusion complex controlled the regioselective ring opening of epoxide at β-carbon. (Kumar et al, 2015 ). Later, the authors extended this procedure (Kumar and Ahmed, 2016 ).…”

Chalcone: A Valuable Scaffold Upgrading by Green Methods

“…84−86 The use of water, the ideal solvent, is usually associated with the use of microwave irradiation. 87,88 The work of Moemeni et al, 89 where ethanol is used as green solvent, can be emphasized due to the one-pot procedure described that allowed the synthesis of heterocyclic spiroindenoquinoxalineindolizidine ring systems from the 1,3-dipolar cycloaddition of substituted chalcones with pipecolinic acid, phenylenediamines and ninhydrin (Scheme 12). The reaction proved to be highly regio-and diastereoselective with yields ranging between 67 and 82%; however, it is a slow transformation (reaction time of 20 h).…”

“…This can be overcome using cyclodextrins, 91 for instance β-cyclodextrin; however, these procedures are more efficient if the heating is carried out by microwave irradiation. 87,88 The use of green solvents allows the transformation of chalcones affording high yields and is highly chemoselective, but it is slow when compared with approaches using conventional heating. To maximize the "green" effect of using these solvents, microwave and/or ultrasound irradiation must be used instead of conventional heating.…”

γ-Cyclodextrin as a Catalyst for the Synthesis of 2-Methyl-3,5-diarylisoxazolidines in Water

“…There are several examples in organic chemistry of reactions catalyzed by cyclodextrins. They have been used to catalyze oxidations, 29 reductions, 30,31 ring openings, 32 protections, 33 deprotections, 34,35 and even cycloadditions. 36,37 In all of these examples, the cyclodextrins have always been used in a catalytic amount and always recovered and reused.…”

“…There are several examples in organic chemistry of reactions catalyzed by cyclodextrins. They have been used to catalyze oxidations, reductions, , ring openings, protections, deprotections, , and even cycloadditions. , In all of these examples, the cyclodextrins have always been used in a catalytic amount and always recovered and reused. To the best of our knowledge, the use of cyclodextrins in a 1,3-dipolar cycloaddition between a nitrone as a dipole, and different styrenes or cinnamates as a dipolarophile to give isoxazolidines in the aqueous medium is not yet reported.…”