Diammonium Hydrogen Phosphate: An Efficient and Versatile Catalyst for the One‐Pot Synthesis of Tetrahydrobenzo[b]pyran Derivatives in Aqueous Media.

Abstract

NH4)2HPO4 is a mild, efficient, neutral and cheap catalyst for the synthesis of the title pyran derivatives, e.g. (IV). -(BALALAIE*, S.; BARARJANIAN, M.; SHEIKH-AHMADI, M.; HEKMAT, S.; SALEHI, P.; Synth.

Green Synthetic Approaches for Biologically Relevant 2-amino-4H-pyrans and 2-amino-4H-pyran-Annulated Heterocycles in Aqueous Media∗

“…In the same year, one more report on the catalyst-free synthesis in refluxing water for the synthesis of such scaffolds was given by Shaabani and his group [86] (Scheme 4). Balalaie and coworkers [87] synthesized a huge number of 4H-benzo [b]pyran derivatives using diammonium hydrogen phosphate (DAHP) as a mild, efficient, cheap, and nontoxic catalyst via a one-pot, three-component condensation of aromatic aldehydes, active methylene compounds (malononitrile, methyl 2-cyanoacetate, ethyl 2-cyanoacetate), and dimedone in aqueous media. In case of simple malononitrile, the reaction took place at room temperature while use of ethanol-water (1:1) solvent at reflux temperature of 50 °C was required when the malononitrile was replaced with ethyl/methyl 2-cyanoacetate.…”

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

“…Therefore, numbers of good methods were reported, amongst them, the more interesting and impressive involves the synthesis of 2-amino-3-cyano-4H-pyran [14][15][16][17] and spirooxindoles [18]. Owing to their medicinal utility, some reports on the multicomponent entries to 2-amino-3-cyano-4H-pyran and spirooxindoles appeared employing various catalysts [19][20][21][22][23][24][25][26][27][28][29]. Although these reported protocols find certain merits of their own, they still suffered from a number of disadvantages, such as longer reaction time, harsh reaction condition, heating, and tedious work-up procedures.…”

An Environmentally Benign Protocol for Aqueous Synthesis of Tetrahydrobenzo[b]Pyrans Catalyzed by Cost-Effective Ionic Liquid

“…Hence, considering the fascinating advantages of MCRs, some methodologies for the synthesis of tetrahedrondydro[ b ]pyrans via three components one-pot reactions catalyzed by 1,4-diazabicyclo[2.2.2]octane [14], N -methylimidazole [15], tetra-methyl ammonium hydroxide [16], (NH 4 ) 2 HPO 4 [17] K 3 PO 4 [18], ZnO-beta zeolite [19], nanosized Ce 1 MgXZr 1− x O 2 [20], Ru(II) complex [21], Na 2 SeO 4 [22], S -proline [23], l -proline [24], 1,8-diazabicyclo[5.4.0]undec-7-ene [25], sulfonic acid functionalized silica [26], phenylboronic acid [27], caro’s acid-silica gel [28], and cerium(III) chloride [29] have been reported. In addition, procedures of catalyst-free and 2,2,2-trifluoroethanol as reaction medium [30], microwave and ultrasonic irradiation [9,31,32] could also give satisfactory yields of pyrans.…”