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Benzopyrans
About: Benzopyrans is a research topic. Over the lifetime, 694 publications have been published within this topic receiving 8830 citations.
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TL;DR: In this article, an asymmetric two-step approach to chiral bridged tricyclic benzopyrans, core structures featured in various natural products, is described, and an unprecedented enantioselective catalytic decarboxylative Diels-Alder reaction is developed using readily available coumarin-3-carboxylic acids and aldehydes as reactants under mild reaction conditions.
Abstract: An asymmetric two-step approach to chiral bridged tricyclic benzopyrans, core structures featured in various natural products, is described. In the synthesis, an unprecedented enantioselective catalytic decarboxylative Diels–Alder reaction is developed using readily available coumarin-3-carboxylic acids and aldehydes as reactants under mild reaction conditions. Notably, the decarboxylation-assisted release of the catalyst enables the process to proceed efficiently with high enantio- and diastereoselectivity. Furthermore, a one-pot procedure for either a LiAlH4- or NaBH4-mediated reduction with subsequent acid-catalyzed intramolecular cyclization of the Diels–Alder adducts was identified for the efficient formation of the chiral bridged tricyclic benzopyrans.
TL;DR: In this article, the DBU-catalyzed reactions of salicylic aldehydes with 3-methylpenta-3,4-dien-2-one, 3-benzylmethylbuta-2,3dienoate gave the corresponding functionalized 2H-1-chromenes in good to excellent yields and good diastereoselectivities in some cases in DMSO.
Abstract: DBU-catalyzed reactions of salicylic aldehydes with 3-methylpenta-3,4-dien-2-one, 3-benzylpenta-3,4-dien-2-one, or ethyl 2-methylbuta-2,3-dienoate gave the corresponding functionalized 2H-1-chromenes in good to excellent yields and good diastereoselectivities in some cases in DMSO, respectively.
TL;DR: In the presence of K2CO3, 2-hydroxyethyltripheny phosphonium bromide (1) reacts with substituted salicylaldehyde (2) and 2hydroxy-1 naphthaldehyde (4) at 110 °C in a sealed tube as mentioned in this paper.
Abstract: In the presence of K2CO3, 2-hydroxyethyltripheny phosphonium bromide (1) reacts with substituted salicylaldehyde (2) and 2-hydroxy-1 naphthaldehyde (4) at 110 °C in a sealed tube. The title compounds were prepared in medium yield. The ratio of bromide (1) to aldehyde derivatives was also discussed in this paper.
TL;DR: Salicylaldehydes react with 5-methyl-4-hexen-1-ol (4a) or 6methyl-5-hepten-2-ol(4b) in benzene in the presence of trimethyl orthoformate and a catalytic amount of p-toluenesulfonic acid at rt to give angularly-fused trans-5,5-dimethyl-3,4,4a,10b-tetrahydro-2H,5H-pyrano[3,2
Abstract: Salicylaldehydes reacted with 5-methyl-4-hexen-1-ol (4a) or 6-methyl-5-hepten-2-ol (4b) in benzene in the presence of trimethyl orthoformate and a catalytic amount of p-toluenesulfonic acid at rt to give angularly-fused trans-5,5-dimethyl-3,4,4a,10b-tetrahydro-2H,5H-pyrano[3,2-c][1]benzopyrans (6) in high yields with complete stereoselectivity.