Synlett

A novel palladium-catalyzed stereoselective remote ­hydroamination reaction is disclosed. A series of azoles and skipped dienes undergo the migratory allylic C–H amination in good yields and selectivities. A desymmetric migratory azolation process is also developed to highlight the reliability of the transformation. Preliminary mechanistic experiments corroborate the designed metal walking and allylic substitution cascade strategy via Pd–H catalysis, different from prior ligand-to-ligand hydrogen transfer pathway for conjugated dienes.

A dearomative [3+2]-cycloaddition reaction of oxindole-embedded azaoxyallyl cations with indoles at the C3 position has been developed. The use of this new class of azaoxyallyl cation species in the reaction permits access to more-elaborate hexahydropyrrolo[2,3-b]indole moieties that contain a spiro-oxindole ring. The transformation displays a broad substrate scope and good regio- and stereoselectivity for the cycloaddition step. Several observations suggested that this class of azaoxyallyl cations can display a different reactivity pattern from those of commonly employed azaoxyallyl cation systems.

A bimetallic Pd/Cu catalyst supported on a metal-organic-framework-derived cobalt oxide was prepared and characterized by SEM, EDS, XRD, XPS, and ICP-OES analyses. The catalyst promoted the Sonogashira reaction of aryl iodides with terminal alkynes at a low loading of the palladium (0.032 mol%) and copper species (0.012 mol%) to give the corresponding disubstituted alkynes in moderate to good yields. When the catalyst was recovered by using an external magnetic field, its catalytic activity decreased slightly in a second cycle.

First time, Pd-Rice Husk Ash (Pd/RHA) and Pd-Banana Peel Ash (Pd-BPA) were used as eco-friendly catalysts in the C–S cross-coupling reaction of 5-bromo-2,1,3-benzothiadiazole with various benzene thiols in DMF under microwave irradiation at 75 °C, 200 W (100 psi) for 15–25 min. These catalysts were produced from agro-industrial wastes, such as rice husk ash and banana peel ash. These can be recycled and reused up to five catalytic cycles without loss of catalytic efficiency.

We report the enantioselective synthesis of azaborole helicenes from enantioenriched axially chiral precursors. The borylation/metal-exchange reaction sequence affords the target compounds with full transfer of chirality from the corresponding biaryls. Experimental studies provided insights into the configurational stability of the heterobiaryls and their (chir)optical properties. The structure of the ­phenyl-substituted helicene was unambiguously confirmed by single-crystal X-ray analysis.

Synlett 2022; 33: V-DOI: 10.1055/s-0041-1738691Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

Spirocyclic diindenothiophenes were prepared by cyclization of tosylhydrazones, readily available from ketones, with 3,4-dibromo-2,5-bis(2-bromphenyl)thiophene. For bicyclic ketones, the bis-spirocycles were formed with very good diastereoselectivity.

Photoinduced tandem cyclization of alkynes with phenylsulfinic acids has been accomplished, which gives a mild strategy for the preparation of sulfone-substituted seven-membered N-heterocycles. A variety of scaled-up experiments, further transformations, and mechanistic studies were also operated in the follow-up work.

Hybrid water electrolysis has been explored for the electrochemical oxidation of biomass, glucose, alcohols, amines, urea, etc. to produce value-added products. The integration of cathodic hydrogen evolution reaction (HER) with anodic organic reaction (AOR) improves the energy efficiency of the electrolyzer by reducing the cell voltage of the overall process. Tremendous progress has been achieved in AOR by using transition-metal-based catalysts. These transition-metal-based catalysts undergo anodic activation in the alkali medium to form metal (oxy)hydroxide [M(O)x(OH)y] as the active catalyst. The atomic and electronic structure of M(O)x(OH)y essentially controls the conversion efficiency and product selectivity for AOR. In this Account, we have described the design of the AOR precatalyst, its anodic activation, and the basic principles of the integration of cathodic HER with AOR. The structural features of the precatalyst and the active catalyst have been described with representative examples. The recent progress and advancement in this field have been explained, and the future scope and challenges associated with AOR have been addressed.1 Introduction2 Anodic Organic Oxidation Reactions3 Activity and Selectivity of Anodic Organic Reaction4 Anodic Activation of Transition-Metal-Based Catalysts5 Mechanism of Anodic Organic Oxidation6 Perspective and Outlook

The difference of reaction design principles between traditional, small-molecule synthetic chemistry and biomolecular chemical reactions prevented the simple translation of small-molecule chemistry into biomolecular reactions. One of the key challenges of bioconjugation, or reactions on biomolecules, are the necessity of aqueous solutions as the solvent. In this Synpacts article, we describe our pursuit of using an ionic liquid as a nonaqueous reaction medium to conduct phosphine- and azide-based bioconjugation reactions.