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The biomimetic synthesis of substituted tetrahydro coumestan (3–8) derivatives is accomplished from 4-hydroxycoumarins (1a–f) and cyclohexanone derivatives (2a–n) using a 20 mol% FeCl3·6H2O catalyst in DMSO solvent upon heating at 110 °C. The significant features of the present strategy are mild reaction conditions, easy handling, readily available starting materials, no need for dry solvents, additives, and inert atmospheric reaction conditions, broad substrate scope, good to excellent yields, and high atom economy. In addition, coumestan derivatives (9) were obtained from the corresponding tetrahydro coumestan derivatives by dehydrogenation with DDQ. Moreover, synthesizing naturally occurring coumestan, coumestrol dimethyl ether, and 4-O-methyl coumestrol validated the two-step synthetic route. [ABSTRACT FROM AUTHOR]

[17] Our research group recently reported [17] the synthesis of 2,3-diarylquinolines using 10 mol% Cu(OTf) SB 2 sb in DMSO from arylamines, styrene oxide, and benzaldehyde. Arylamines, styrene oxides, aromatic aldehydes, 2,3-diaryl quinolines, environmentally benign synthesis, p -TSA-H 2 O, atomic economy, three-component reaction Keywords: arylamines; styrene oxides; aromatic aldehydes; 2,3-diaryl quinolines; environmentally benign synthesis; p -TSA-H 2 O; atomic economy; three-component reaction EN arylamines styrene oxides aromatic aldehydes 2,3-diaryl quinolines environmentally benign synthesis p -TSA-H 2 O atomic economy three-component reaction 3195 3203 9 09/11/23 20231004 NES 231004 Graph In recent times, multicomponent reactions approach has emerged as an important synthetic tool in modern organic chemistry for the total synthesis of natural products and synthetic building blocks. To further check the practicability of this protocol, the reaction was carried out at a 10 mmol scale with 3,4-dimethoxy aniline ( B 1a b ), benzaldehyde ( B 2a b ), and styrene oxide ( B 3a b ), under identical reaction conditions. [Extracted from the article]

The hitherto unreported synthesis of 2-aryl-2 H ,5 H -thiopyrano[2,3- b ]thiochromen-5-one derivatives was achieved from 4-hydroxydithiocoumarin and cinnamaldehyde using 20 mol% L-proline, an environmentally benign organocatalyst in methanol under reflux conditions. The current approach involves imine formation, followed by a Mannich reaction, instead of a 1,4-addition or thia-Michael reaction, and finally, cyclization. The salient features of this method are mild reaction conditions, broad substrate scope, good yield, atom economy, and shorter reaction time.

The regioselective ring-opening of aryl oxiranes was investigated with various 4-hydroxycoumarins in dimethyl sulfoxide in the presence of 20 mol% FeCl 3 as a catalyst at 110 °C. This approach provided a short and concise synthetic route for the regioselective synthesis of 2-aryl-4 H -furo[3,2- c ] coumarin derivatives. Product formation occurred through regioselective ring-opening of the aryl oxirane at a less hindered site, followed by dehydration and concomitant cyclization. The salient features of our protocol were: cost-effectiveness; short reaction time; step- and atom economy; easy handling; broad scope of substrates; regioselectivity; good-to-excellent yields; non-requirement of dry solvents, co-catalysts, ligands, or any other additives; inert atmospheric conditions.

An environmentally benign and metal-free synthesis of 4-aryl quinolines is reported by employing readily available arylamine, arylacetylene, and DMSO in the presence of 20 mol% p -TSA·H 2 O. In the present protocol, the solvent DMSO serves as a reactant cum solvent for providing the C2 carbon atom of the quinoline skeleton. Notably, the reaction proceeds effectively and efficiently without the involvement of any metal catalyst, ligand, and co-catalyst as additives and inert atmospheric reaction conditions. This method provides high atom economy and good yields, and two C - C and one C - N bonds are formed in a single step through a three-component reaction.