Group-assisted purification (GAP) chemistry for dihydrofurans: water as a medium for catalyst free synthesis in a one pot four component reaction

Abstract

A simple, catalyst free, water mediated, one pot four component, green protocol was developed for title compounds 7 starting from aromatic aldehydes (1), malononitrile (2), 1,3-diones (3) and N-chlorosuccinimide (NCS) in a sequential addition reaction at ambient temperature. The approach presented herein, for the first time, is through an unusual rearrangement where NCS was reacted with 2-amino-7,7-dimethyl-5-oxo-4-aryl-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (4), which was formed by the Knoevenagel condensation of aldehyde and malononitrile followed by the Michael addition of 3. In addition, this novel protocol is compatible with various aldehydes and active C-H functional derivatives, accomplishes high yields and follows the GAP chemistry principle. Interestingly, compound 4 when reacted with NCS in alcohol medium gave 2-cyano-6,6-dimethyl-4-oxo-3-aryl-2,3,4,5,6,7-hexahydrobenzofuran-2-carboxylate (5).

PEG-assisted two-component approach for the facile synthesis of 5-aryl-1,2,4-triazolidine-3-thiones under catalyst-free conditions

“…2 In addition, a catalyst-free synthetic attitude is one of the remarkable tool in scientific society because they are associated with minimization of pollution, cost and purity orientated troubles. 3 Utility of polyethylene glycol (PEG) as a greener alternative in organic synthesis have become more precious over toxic organic solvents due to its non-toxicity, bio-compatibility, bio-degradability and miscibility with both aqueous and several non-aqueous solvents. 4 PEG mediated numerous organic transformations have been reported frequently including the reactions, such as, oxidation and reduction reactions, 5 Heck reaction, 6 substitution reactions, 7 Suzuki cross-coupling reaction, 8 partial reductions of alkynes, 9 asymmetric dihydroxylation 10 and Wacker reaction.…”

A cesium fluoride promoted efficient and rapid multicomponent synthesis of functionalized 2-amino-3-cyano-4H-pyran and spirooxindole derivatives

“…1). The 4H-pyran derivatives are also used as photoactive materials [12] and as synthetic intermediates for dihydrofurans [13].…”

Hypervalent Iodine (III) Catalyzed Regio- and Diastereoselective Aminochlorination of Tailored Electron Deficient Olefins via GAP Chemistry

“…Recently, our group has established a concept called GAP chemistry for greener synthesis where functionalities of special interest are incorporated into the substrates to facilitate the purification of crude products based on solubility without column chromatography or recrystallization. The pure products can be readily obtained simply by washing the crude mixture with common solvents or cosolvents (Wang et al, 2013 ; Chennapuram et al, 2014 ; Dommaraju and Prajapati, 2015 ; Seifert et al, 2016 ; Patel et al, 2019 ). Indeed, GAP chemistry would be the first concept consisting of both chemical aspects (reagent and reaction) and physical aspects (separation and purification).…”