Silver(I)-Catalyzed Tandem Reaction of Enynones and 4-Alkenyl Isoxazoles: Synthesis of 2-(Furan-2-yl)-1,2-dihydropyridines

One-pot reaction of 3-vinylchromones, aromatic aldehydes, and ammonium acetate: an efficient approach to highly functionalized 1,6-dihydropyridine derivatives

In this work, we present an efficient strategy for the straightforward synthesis of functionalized 1,6-dihydropyridine derivatives via a three-component reaction of 3-vinylchromones, aromatic aldehydes, and ammonium acetate. A tandem procedure including in situ NH aldimine formation/Michael-type addition/opening of the pyrone ring/isomerization/6π-electrocyclization/[1,5]-H shift allows rapid access to a series of dihydropyridines bearing an ortho-hydroxybenzoyl and a benzoyl scaffold in good yields. Readily available precursors, simple heating conditions, and operational simplicity are some highlighted advantages of this transformation.

General access to furan-substituted gem-difluoroalkenes enabled by PFTB-promoted cross-coupling of ene-yne-ketones and difluorocarbene

Replacement of a carbonyl group with fluorinated bioisostere (e.g., CF2[double bond, length as m-dash]C) has been adopted as a key tactical strategy in drug design and development, which typically improves potency and modulates lipophilicity while maintaining biological activity. Consequently, new gem-difluoroalkenation reactions have undoubtedly accelerated this shift, and conceptually innovative practices would be of great benefit to medicinal chemists. Here we describe an expeditous protocol for the direct assembly of furan-substituted gem-difluoroalkenes via PFTB-promoted cross-coupling of ene-yne-ketones and difluorocarbene. In this multi-step tandem reaction process, the furan ring and the gem-difluorovinyl group are constructed simultaneously in an efficient manner. These products can serve as bioisosteres of the α-carbonyl furan core, which is an important scaffold present in natural products and drug candidates. The broad generality and practicality of this method for late-stage modification of bioactive molecules, gram-scale synthesis and versatile derivatisation of products has been described. Biological activity evaluation showed that the gem-difluoroalkene skeleton exhibited dramatic antitumor activity.

Manganese-Promoted Cyclization Reaction of Enynones with Tetrasulfides: Synthesis of Multisubstituted Furanmethyl Disulfides

A tandem cyclization reaction of enynones with tetrasulfides has been developed under manganese-promoted conditions, leading to the high-yield formation of various furanmethyl disulfides. This reaction is characterized by readily available starting materials, mild reaction conditions, and a broad substrate scope, making it attractive and practical. It provides a new strategy for the synthesis of disulfide-containing functionalized furans.

Controllable Access to Diazo-functionalized 2-Methylene-2,3-dihydrofurans and Diazo-functionalized Furans from Enynones and Diazo Carbonyl Compounds

Using enynones and diazo carbonyl compounds as identical starting materials, methods for chemoselective and regioselective constructs of diazo-functionalized 2-methylene-2,3-dihydrofurans and diazo-functionalized trisubstituted furans have been established in a AgSbF6/DBU/DCE/0 °C system and a AgSbF6/DBU/Et2O·BF3/DCE/0 °C system, respectively. A Lewis acid and organic base cocontrolled reaction for the synthesis of diazo-functionalized trisubstituted furans is infrequent. For diazo-functionalized 2-methylene-2,3-dihydrofuran synthesis, the reaction possesses excellent diastereoselectivity and Z-selectivity. On the basis of Rh2(OAc)4-mediated unique decomposition of diazo-functionalized 2-methylene-2,3-dihydrofurans, an application to diastereoselective construction of a 5-methylene-4,7-dihydro-5H-furo[2,3-c]pyran frame has been achieved for the first time.