Enantioselective semireduction of allenes

A RhII-Catalyzed [4 + 3]-Cycloaddition via the Stereoselective Cyclopropanation of Vinyl Allenes En Route to Oxepino[b]indoles and Subsequent Elaboration to Spirooxindole Frameworks

Oxepino[b]indoles were obtained in good to excellent yields employing a [4 + 3]-cycloaddition initiated by a stereo- and regioselective, RhII-catalyzed cyclopropanation between a vinyl allene and diazooxindole to afford an intermediate cyclopropyl allene that engaged the oxindole carbonyl in a spontaneous hetero-[3,3]-rearrangement. A survey of functional group tolerance revealed a diverse array of substrates amenable to oxepino[b]indole formation. In addition to the intriguing architecture of the cycloadducts, exposure to either Brønsted acid or base enables the assembly of functionalized spirroxindoles via the unusual conversion of a 5-7 fused ring system to a 5-5 spirocycle.

Challenging Task of Ni-Catalyzed Highly Regio-/Enantioselective Semihydrogenation of Racemic Tetrasubstituted Allenes via a Kinetic Resolution Process

The first earth-abundant transition metal Ni-catalyzed highly regio- and enantioselective semihydrogenation of racemic tetrasubstituted allenes via a kinetic resolution process as a challenging task was well established. This protocol furnishes expedient access to a diversity of structurally important enantioenriched tetrasubstituted allenes and chiral allylic molecules with high regio-, enantio-, and Z/E-selectivity. Remarkably, this semihydrogenation proceeded with one carbon-carbon double bond of allenes, which was regioselective complementary to the Rh-catalyzed asymmetric version. Deuterium labeling experiments and density functional theory (DFT) calculations were carried out to reveal the reasonable reaction mechanism and explain the regio-/stereoselectivity.

[Exploring non-hormonal therapies and drug repositioning for endometriosis: insights from mouse model studies]

The mainstay of treatment for endometriosis is hormonal therapy, which suppresses ovulation; therefore, patients cannot conceive during treatment. There is a dilemma with ovarian-sparing surgery, known as laparoscopic cystectomy, as it can potentially damage the ovaries. Therefore, there is a need for non-hormonal drug therapies. We addressed these challenges in endometriosis treatment, aiming to maintain ovarian function while achieving effective treatment through basic research. Herein, we present two studies using different mouse models of endometriosis. The first study investigates the effects of a nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain-containing (NLRP) 3 inhibitor in a mouse model of ovarian endometriotic cysts. We confirmed the increased expression of NLRP in ovarian endometriotic cysts compared with that in the uterine endometrium in both patient-derived samples and mouse model lesions. Administering an NLRP3 inhibitor to model mice resulted in lesion reduction. The second study used a peritoneal lesion mouse model to examine bacterial infection in the endometrium and its association with endometriosis development. Using existing databases and patient-derived samples, we identified that Fusobacterium was involved in the development of endometriosis and lesion enlargement when infecting the endometrium in the model. Furthermore, antibiotic treatment led to a reduction in the lesions. These studies highlight the potential of repositioning existing drugs with NLRP3 inhibitory effects or antibiotics as new non-hormonal treatments for endometriosis.

Bisphospholane Josiphos-type Ligands in Rhodium Asymmetric Catalysis

Asymmetric catalysis has become a universal and powerful method for constructing chiral compounds. In rhodium asymmetric catalysis, bisphospholane Josiphos-type ligands and their rhodium complexes are receiving increasing attention. This review provides comprehensive information on the bisphospholane Josiphos-type ligands in rhodium asymmetric catalysis. The scope of the literature covers from 2013 to now. The application of bisphospholane Josiphos-type ligands in rhodium asymmetric catalysis is summarized as follows: (i) asymmetric addition to C(sp2 )-C(sp2 ) bonds, (ii) asymmetric addition to C(sp2 )-C(sp) bonds of allenes, (iii) asymmetric hydrogenation of C(sp2 )-N bonds, C(sp2 )-O bonds and pyridinium salts, and (iv) asymmetric silanization of C-H and O-H bonds.

Ligand-Controlled Regiodivergence for Catalytic Stereoselective Semireduction of Allenamides

Ligand-controlled regiodivergence has been developed for catalytic semireduction of allenamides with excellent chemo- and stereocontrol. This system also provides an example of catalytic regiodivergent semireduction of allenes for the first time. The divergence of the semireduction is enabled by ligand switch with the same palladium pre-catalyst under operationally simple and mild conditions. Monodentate ligand XPhos exclusively promotes selective 1,2-semireduction to afford allylic amides, while bidentate ligand BINAP completely switched the regioselectivity to 2,3-semireduction, producing (E)-enamide derivatives.

Reducing Challenges in Organic Synthesis with Stereoselective Hydrogenation and Tandem Catalysis

Tandem catalysis enables the rapid construction of complex architectures from simple building blocks. This Perspective shares our interest in combining stereoselective hydrogenation with transformations such as isomerization, oxidation, and epimerization to solve diverse challenges. We highlight the use of tandem hydrogenation for preparing complex natural products from simple prochiral building blocks and present tandem catalysis involving transfer hydrogenation and dynamic kinetic resolution. Finally, we underline recent breakthroughs and opportunities for asymmetric hydrogenation.

Synthesis of C5-Allylindoles through an Iridium-Catalyzed Asymmetric Allylic Substitution/Oxidation Reaction Sequence of N-Alkyl Indolines

Iridium/Brønsted acid cooperative catalyzed asymmetric allylic substitution reactions at the C5 position of indolines have been reported for the first time. The highly efficient protocol allows rapid access to various C5-allylated products in good to high yields (48-97%) and enantioselectivities (82% to >99% ee) with wide functional group tolerance. The transformations allow not only the formation of C5-allylindoline derivatives but also the synthesis of C5-allylindole analogues in good yields and excellent stereoselectivities via an allylation/oxidation reaction sequence.

Rhodium-Catalyzed Highly Regio- and Enantioselective Hydrogenation of Tetrasubstituted Allenyl Sulfones: An Efficient Access to Chiral Allylic Sulfones

A highly regio- and enantioselective hydrogenation of challenging tetrasubstituted allenyl sulfones has been developed, affording chiral allylic sulfones in good yields with excellent regio- and enantioselectivities (up to 99 % yield and 99 % ee). This method provides an efficient and concise route to chiral allylic sulfones, thus offering an atom-economic process with a wide range of potential applications in organic synthesis and medicinal chemistry.

Alkanethiolate-Capped Palladium Nanoparticles for Regio- and Stereoselective Hydrogenation of Allenes

Colloidal Pd nanoparticles capped with octanethiolate ligands have previously shown an excellent selectivity toward the mono-hydrogenation of both isolated and conjugated dienes to internal alkenes. This paper reports an efficient stereoselective mono-hydrogenation of cumulated dienes (allenes) to either Z or E olefinic isomers, depending on the substitution pattern around C=C bonds. Kinetic studies indicate that the reaction progresses through the hydrogenation of less hindered C=C bonds to produce internal Z olefinic isomers. In the cases of di-substitued olefinic products, this initial hydrogenation step is followed by the subsequent isomerization of Z to E isomers. In contrast, the slow isomerization of Z to E isomers for tri-substituted olefinic products results in the preservation of Z stereochemistry. The high selectivity of Pd nanoparticles averting an additional hydrogenation is steered from the controlled electronic and geometric properties of the Pd surface, which are the result of thiolate-induced partial poisoning and surface crowding, respectively. The high activity of colloidal Pd nanoparticle catalysts allows the reactions to be completed at room temperature and atmospheric pressure.

Regio- and Enantioselective Rhodium-Catalyzed Allylic Alkylation of Racemic Allylic Alcohols with 1,3-Diketones

Highly regio- and enantioselective rhodium-catalyzed allylic alkylation of 1,3-diketones with racemic secondary allylic alcohols is reported. In the presence of a Rh-catalyst derived from the Carreira (P, olefin)-ligand and TFA as an additive, chiral branched α-allylated 1,3-diketones could be obtained in good to excellent yields, with excellent regio- and enantioselectivity ( b/ l > 19/1, 86-98% ee). The direct utilization of allyl alcohols as electrophiles represents an improvement from the viewpoint of an atom economy. Both aryl- and aliphatic-substituted allyl alcohols are suitable substrates with excellent reaction outcomes. This reaction features mild conditions, broad substrate scope, and readily available substrates.