pH‐Transformed ZnO‐NPs /NaPTS: The First Room‐Temperature Brisk Synthesis of Flavanones in Aqueous Medium

Abstract

We investigated pH transformed ZnO NPs viz ZnO nanobullets and ZnO nanograins at pH 11 and 12 respectively, synthesized by co‐precipitation method. The structural, morphological, chemical, compositional and optical properties of synthesized ZnO NPs were analysed by using X‐ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X‐ray Spectroscopy (EDAX) and Ultra‐Violate Visible spectroscopy (UV‐Vis). The Noteworthy feature of ZnO NPs in presence of NaPTS leads a speedy formation of flavanones from the reaction of an aldehyde and o‐hydroxy acetophenone. Thus, it imparted the first room‐temperature brisk synthesis of flavanones in an aqueous medium.

Crossing borders: On‐Water Synthesis of Flavanones

“…According to the literature, there are five methodologies for the on‐water synthesis of flavanones (Scheme 2). Three of them ( a , b , c ) study the cyclization of chalcones, [47,66,67] the two remaining ( d , e ) are one‐pot methodologies [51,57] . Normally, the cyclization of chalcones (methodologies a and b ) uses a mixture of catalyst – additive (KOH plus an organic secondary base) and short reaction times are necessary to obtain the flavanone.…”

“…[27][28][29][30][31] Flavanone structure is an important framework for the development of lead compounds with important biological activities, [32,33] whereby it has been intensively used for research and development during the last three decades, by synthetic and medicinal chemists. [34][35][36][37] Thus, a large number of methodologies considering the starting material for their obtention have been reported and they can be classified into four categories as follows (Scheme 1): 1) two steps Claisencyclization, [27,28,[38][39][40][41][42][43] 2) cyclization from chalcones, [3,4,[44][45][46][47][48] 3) one pot procedures starting from substituted benzaldehydes and 2hydroxyacetophenones [8,[49][50][51][52][53][54][55][56][57] and 4) Miscellaneous (a-d). [58][59][60] Among them, cyclization from chalcone (category 2) is the most used methodology.…”

Recent advances in nanoparticles towards sustainability and their application in organic transformations in aqueous media

“…Shinde et al studied the effect of change in pH on ZnO NPs and used them as a catalyst for the synthesis of flavanone in aqueous hydrotropic media at room temperature. 41 The authors observed that ZnO NPs at pH = 12 show enhanced catalytic activity compared to ZnO NPs prepared at pH = 11 due to the decrease in particle size [ Scheme 13]. After the completion of the reaction, the ZnO NPs were separated from the reaction mixture via simple centrifugation.…”

A decennary update on applications of metal nanoparticles (MNPs) in the synthesis of nitrogen- and oxygen-containing heterocyclic scaffolds

“…363 The rst aldol condensation at rt between o-hydroxy acetophenone (111e) and benzaldehydes (21a) driven under aqueous hydrotropic and basic medium formed by ZnO nanobullets or nanograins and sodium p-toluenesulfonate (NaPTS) was designed for the brisk synthesis of avanones (314, Scheme 202). 364 The ZnO NPs were obtained from zinc chloride and NaOH via co-precipitation and 90-96% yield of avanones was obtained during the ve times recycling of the ZnO NPs at pH 12. ZnO nanograins with a ner particle size of 90 nm were found to give higher yields of avanones in a shorter time than ZnO nanobullets (particle size of 600 nm  110 nm).…”