Advances in chromone-based reactants in the ring opening and skeletal reconstruction reaction: access to skeletally diverse salicyloylbenzene/heterocycle derivatives

Abstract

Salicyloylbenzene/heterocycles are privileged scaffolds found in many natural products and bioactive molecules. Numerous useful approaches for the preparation of these privileged scaffolds have been developed in recent years. Among these...

Recent advances in organocatalytic cascade reactions for enantioselective synthesis of chiral spirolactone skeletons

“…The three-dimensional complexity and diversity of the privileged natural product frameworks could be easily improved by the introduction of contiguous stereocenters [45,46] . In 2020, the synthesis of complicated spiro [benzolactone-hexahydroxanthone] framework 14 was reported.…”

Visible-light-enabled cascade cross-dehydrogenative-coupling/cyclization to construct α-chromone substituted α-amino acid derivatives

“…2 Moreover, 3-substituted chromones have been employed as useful building blocks in many research areas such as organic synthesis, biochemistry, and medicinal chemistry. 3 Consequently, tremendous efforts have been devoted to constructing various C3-functionalized chromones. 4 Conventional methods for 3-substituted chromones are mainly focused on the transition-metal-catalyzed cross-coupling reactions of halochromones as well as direct C–H functionalization of chromones.…”

Access to Chromenopyrrolidines Enabled by Organophotocatalyzed [2 + 2 + 1] Annulation of Chromones with N-Arylglycines

“…The existing approaches toward chromenopyrrolidines routinely rely on the [3 + 2] cycloaddition of chromones or their derivatives with in situ -generated azomethine ylides (Scheme b) via heating, acid, transition-metal, or Lewis base catalysis in which highly active carbonyl compounds, such as formaldehyde or α-activated ketones, were required. On the other hand, even though chromones were extensively utilized as reactants in many cases of photocatalysis, they were merely used as Giese-type addition acceptors to deliver 2-functionalized chroman-4-ones as the final products, while photocatalyzed annulation of chromones was rarely disclosed . To the best of our knowledge, some elegant photocatalyzed reports have been disclosed with regard to the annulation of two folds of N -arylglycines with CN or NN bonds to construct distinct imidazolidine derivatives and 1,2,4-triazolidines, respectively, but there has been no example of photochemical assembly of the pyrrolidine ring with N -arylglycines (Scheme c). − ,,− Inspired by the pioneering works on N -arylglycines in photocatalysis , and our continued interest in photocatalyzed cascade reactions, herein, we describe an aerobic decarboxylative [2 + 2 + 1] annulation reaction of chromones (offering CC) with N -arylglycines (offering C–N∼C) to give chromenopyrrolidines under mild conditions (Scheme d).…”