Synthesis of several types of 2,8-dioxabicyclo[3.3.1]nonanes using amberlyst-15 as an efficient recyclable heterogeneous catalyst

Abstract

Contents:1. General experimental procedure for synthesis of compounds 2-6 and S2their characterization data 2. Copies of 1 H NMR and 13 C NMR spectra S9-S24 3. References S25 S2 2. General Experimental Procedure for Synthesis of Compounds 2-6 and Their Characterization Data General Information Melting points were recorded on a Köfler block. IR spectra were recorded on a Perkin Elmer FT-IR spectrophotometer (Spectrum BX II) in KBr pellets. 1 H and 13 C NMR spectra were recorded in CDCl 3 on a Bruker AV-300 (300 MHz) or a Bruker AVANCE III HD (400 MHz) spectrometer. HRMS data were recorded with a Waters Xevo G2QTof HRMS spectrometer. Analytical samples were routinely dried in vacuo at room temperature. Microanalytical data were recorded on two Perkin-Elmer 2400 Series II C, H, N analyzers. TLC was performed with silica gel G made of SRL Pvt. Ltd. Petroleum ether had the boiling range 60-80 °C. General procedure for preparation of 2-hydroxychalcones (1)The 2-hydroxychalcones used as starting materials in the present work were synthesized by alkali-catalyzed condensation of 2-hydroxybenzaldehydes with acetophenones. Thus, a mixture of 2-hydroxybenzaldehyde (10 mmol) and an acetophenone (10 mmol) was taken in a 50 ml solution of 10% KOH in aqueous ethanol (3:2) and stirred overnight. The resulting mixture was acidified with 3 (N) HCl. The solid thus separated was filtered under suction. It was then collected and crystallized from ethanol. Chromatographic purification was also done in some cases according to requirement.

Facile Synthesis of a New Class of Pyrazolone Attached Chromene Derivatives Showing Good Binding with β‐Lactoglobulin

“…Our recent studies on amberlyst‐15 catalysed condensation of 2‐hydroxychalcones with a number of carbon nucleophiles under aerial condition showed that in cases of use of some carbon nucleophiles ( viz ., dimedone, 4‐hydroxycoumarin, 2‐hydroxy‐1,4‐napthoquinone, 1‐naphthol, 2‐naphthol and 4‐hydroxy‐6‐methyl‐2 H ‐pyran‐2‐one) 2,8‐dioxabicyclo‐[3.3.1]nonanes were formed,, while use of others ( viz ., indan‐1,3‐dione, cyclopentan‐1,3‐dione and 1,3‐dimethylbarbituric acid) gave 4 or its analogues through a different path with the occurrence of an aerial oxidation in the last step . A careful examination of the proposed mechanisms ( Scheme ),, suggests that the possible reason for this difference may be the different enolization ability of the attached moiety in the intermediates coming from the nucleophile.…”

Synthesis of A-Type Proanthocyanidins and Their Analogues: A Comprehensive Review

“…More recently, a large number of synthetic procedures have been reported in a brief period of time (2013–2019) to achieve the synthesis of A-type PAC analogues through chalcones. − In all of these studies, the optimization of the experimental conditions for the coupling reaction between a given chalcone and the π-nucleophile has carefully been performed, selecting the proper set of catalyst, solvent, and temperature for each individual reaction (Table ).…”

“…The main differences between all of these procedures lie in the electrophilic activation of α,β-unsaturated ketone and the reaction solvent used. In this sense, the activation has been performed by Lewis acid, ,,− Brønsted acid, ,,,, organobases, and also without any catalyst. , It seemed that the reaction started with a 1,4-conjugate addition between 2-hydroxychalcone ( 31 ) and the corresponding π nucleophile ( 35 ), affording the key intermediate (±)- 36 , which quickly evolved to the target bicyclic compound (±)- 38 through a double intramolecular cyclization (Scheme ). ,, …”