Efficient and general method for the synthesis of benzopyrans by ethylenediamine diacetate-catalyzed reactions of resorcinols with α,β-unsaturated aldehydes. One step synthesis of biologically active (±)-confluentin and (±)-daurichromenic acid

An Efficient and Rapid Synthetic Route to Biologically Interesting Pyranochalcone Natural Products

“…The benzopyran 15 was first prepared starting from 2,4-dihydroxyacetophenone (13) as shown in Scheme 4. A reaction of 13 with 3-methyl-2-butenal in the presence of 10 mol % of ethylenediamine diacetate in refluxing toluene for 12 h gave desmethyl isoencecalin (15) in 52% yield, which was isolated from Blepharispermum subseeile [16]. It has also shown to have strong antifungal, antibacterial, and anti-implantation activities [17].…”

“…Accordingly, there has been considerable research on improved synthetic approaches of pyranochalcone derivatives. Recently, we developed an efficient and simple methodology for preparing benzopyrans by ethylenediamine diacetate-catalyzed reactions of resorcinols to α,β-unsaturated aldehydes [15]. These reactions involve a formal [3+3]-cycloaddition via a 6π-electrocyclization (Scheme 2).…”

Ecocatalysis for 2H-chromenes synthesis: an integrated approach for phytomanagement of polluted ecosystems

“…The performances of our ecocatalysts are at least similar (entry 3) and even higher (entries 1, 5, 6, and 7) than previous methodologies, allowing the synthesis of 2H-chromenes (Adler and Baldwin 2009;Dintzner et al 2006;Lee et al 2005;Pettigrew et al 2005;Tiabi and Zamarlik 1991;Zeng et al 2011). Moreover, the catalysis by Eco-Zn avoids the use of harsh conditions and sensitive reagents previously reported (Sartori et al 1979).…”

“…2H-chromenes were isolated after washing with dichloromethane, and filtration, concentration under reduced pressure, and then chromatographic purification on silica gel were performed with a hexane/ethyl acetate mixture (9:1) as an eluent. They were identified by comparison with previously reported spectral data (Iyer and Trivedi 1990;Lee et al 2005;Lykakis et al 2011). -Procedure for low reactivity derivatives: phenol, naphthol, and 3-bromophenol In a sealed tube, 0.1 mmol of phenol, 0.8 mmol of 3-methyl-2-butenal, 150 mg of 4 Å activated molecular sieves, 101 mg of Eco-Zn (0.1 mmol in Zn), and 2 mL of anhydrous toluene were introduced.…”

Efficient synthesis of tetrahydroquinolinones by acetic acid-mediated formal [3+3] cycloaddition

“…For this reason, Brønsted acids were employed in our new methodology for the preparation of various benzopyrans [25][26][27][28][29][30][31][32][33][34]. As a part of our ongoing evaluation of the synthetic efficacy of Brønsted acids, we first investigated the reaction of b-enaminone 1a with 3-methyl-2-butenal using several Brønsted acids, but also Lewis acids and other reagents ( Table 1).…”