Transition metal-catalysed cross-coupling reactions, particularly those mediated by palladium, are some of the most broadly used chemical transformations. The fundamental reaction steps of such crosscouplings typically include oxidative addition, transmetalation, carbopalladation of a -bond, and/or reductive elimination. Herein, we describe an unprecedented fundamental reaction step: a C−C σ-bond carbopalladation. Specifically, an aryl palladium(II) complex interacts with a −bond of a strained bicyclo[1.1.0]butyl boronate complex to enable addition of the aryl palladium(II) species and an organoboronic ester substituent across a C−C -bond. The overall process couples readily available aryl triflates and organoboronic esters across a cyclobutane unit with total diastereocontrol. The pharmaceutically-relevant 1,1,3-trisubstituted cyclobutane products are decorated with an array of modular building blocks, including a boronic ester which can be readily derivatized.

Among all metathesis reactions known to date in organic chemistry, the metathesis of multiple bonds such as alkenes and alkynes has evolved into one of the most powerful methods to construct molecular complexity. In contrast, metathesis reactions involving single bonds are scarce and far less developed, particularly in the context of synthetically valuable ring-closing reactions. Herein, we report an iron-catalyzed ring-closing metathesis of aliphatic ethers for the synthesis of substituted tetrahydropyrans and tetrahydrofurans, as well as morpholines and polycyclic ethers. This transformation is enabled by a simple iron catalyst and likely proceeds via cyclic oxonium intermediates.

Parahydrogen (p‐H2) induced polarization (PHIP) NMR spectroscopy showed that [CpXRu] complexes with greatly different electronic properties invariably engage propargyl alcohol derivatives into gem‐hydrogenation with formation of pianostool ruthenium carbenes; in so doing, less electron rich CpX rings lower the barriers, stabilize the resulting complexes and hence provide opportunities for harnessing genuine carbene reactivity. The chemical character of the resulting ruthenium complexes was studied by DFT‐assisted analysis of the chemical shift tensors determined by solid‐state 13C NMR spectroscopy. The combined experimental and computational data draw the portrait of a family of ruthenium carbenes that amalgamate purely electrophilic behavior with characteristics more befitting metathesis‐active Grubbs‐type catalysts.

The unusual geminal hydrogenation of ap ropargyl alcohol derivative with [Cp X RuCl] as the catalyst entails formation of pianostool ruthenium carbenes in the first place; these reactive intermediates can be intercepted with tethered alkenes to give either cyclopropanes or cyclic olefins as the result of aformal metathesis event. The course of the reaction is critically dependent on the substitution pattern of the alkene trap.Recent investigations into the trans-hydrogenation of internal alkynes with the aid of [Cp*Ru]-based catalysts (Cp* = pentamethylcyclopentadienyl) showed that the perplexing stereochemical outcome of this reaction can be reached along two competing pathways (Scheme 1). [1][2][3][4] Theroutes bifurcate

An ew base metal catalyzed sustainable multicomponent synthesis of pyrroles from readily available substrates is reported. The developed protocolu tilizes an air-and moisture-stable catalyst system and enablest he replacement of themutagenic ahaloketones with readily abundant 1,2-diols. Moreover,the presented method is catalytic in base and the sole byproducts of this transformation are water and hydrogen gas. Experimental and computationalm echanistic studies indicatet hat the reactiont akes place through ac ombineda cceptorless dehydrogenation hydrogenautotransfermethodology.Multicomponent reactions are valuable sustainable processes for the construction of complex molecules in one pot from three or more substrates. This strategy merges severale lementary reaction steps, which leads to minimization of the amount of waste, and simplifies the workup and purifications teps. [1] Pyrroles represent prominent and important chemicalm otifs in medicinal, agro, and advanced materials chemistry.C lassical synthetic routes suffer from drawbacks mainly resultingf rom the generation of substantial amounts of waste produced during the multi-stepp re-functionalization of substrates or byproduct formation. [2] Accordingly,t here is ac ontinuous need to develop new catalytic systems that allow the direct and atom-economic conversion of renewable and readily available substrates to pyrroles.Alcohols can be obtained from renewable biomass resources and presentp romising sustainable feedstock chemicals. The utilization of alcohols as substrates in the synthesis of fine chemicals will hence contributen ot only to the reduction of toxic chemical waste but also to decrease CO 2 emissions by avoidingthe use of carbon fossil sources. [3] One of the key concepts for alcoholf unctionalization is hydrogen autotransfer (HA), which has become ap owerful tool for utilizing abundant alcohols as building blocks for environmentally benign CÀC and CÀNb ondf ormations, releasing water as the only byproduct (Scheme 1A). [4] Ar elatedc oncept is acceptorless dehydrogenation(AD), which permits the conversion of alcohols to car-Scheme1.Acceptorless dehydrogenation and hydrogen autotransfer catalysis.