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Concerted nucleophilic substitution, known as SN2 reaction, is a fundamental organic transformation used in synthesis to introduce new functional groups and construct carbon–carbon and carbon–heteroatom bonds1. SN2 reactions typically involve backside attack of a nucleophile to the σ* orbital of a C(sp3)–X bond (X = halogen or other leaving group), resulting in complete inversion of a stereocentre2. By contrast, the corresponding stereoinvertive nucleophilic substitution on electronically unbiased sp2 vinyl electrophiles, namely concerted SNV(σ) reaction, is much rarer, and so far limited to carefully designed substrates mostly in ring-forming processes3,4. Here we show that concerted SNV reactions can be accelerated by a proposed strain-release mechanism in metallated complexes, leading to the development of a general and stereospecific alkenylidene homologation of diverse organoboronates. This method enables the iterative incorporation of multiple alkenylidene units, giving cross-conjugated polyenes that are challenging to prepare otherwise. Further application to the synthesis of bioactive compounds containing multi-substituted alkenes is also demonstrated. Computational studies suggest an unusual SN2-like concerted pathway promoted by diminishing steric strain in the square planar transition state, which explains the high efficiency and stereoinversive feature of this metallate SNV reaction.We report an SNV reaction, a rare nucleophilic substitution that involves electronically unbiased vinyl electrophiles, which allows the synthesis of cross-conjugated polyenes and bioactive compounds with multi-substituted alkenes. [ABSTRACT FROM AUTHOR]

Since the discovery of the palladium/norbornene (Pd/NBE)‐catalyzed ortho amination in 2013, escaping the limitation of only yielding tertiary anilines has been a long‐standing challenge. Here, we describe that, by carefully choosing the phosphine ligand and NBE mediator, the installation of a N‐mono‐alkylamino group becomes feasible. The reaction tolerates a wide range of aryl iodide substrates and various N‐mono‐tertiary alkylamine‐derived electrophiles. Both ipso alkenylation and alkynylation can be realized. The synthetic utility of this method is exemplified by the formation of primary amino group via selective deprotection and streamlined access to N‐heterocycles. Preliminary success of installing a bulky N‐secondary alkylamino group and a mechanistic understanding of the decomposition pathways of mono N‐alkylamine electrophiles have been obtained. [ABSTRACT FROM AUTHOR]

Carbon-hydrogen (C-H) and carbon-carbon (C-C) bonds are the main constituents of organic matter. Recent advances in C-H functionalization technology have vastly expanded our toolbox for organic synthesis.sup.1. By contrast, C-C activation methods that enable editing of the molecular skeleton remain limited.sup.2-7. Several methods have been proposed for catalytic C-C activation, particularly with ketone substrates, that are typically promoted by using either ring-strain release as a thermodynamic driving force.sup.4,6 or directing groups.sup.5,7 to control the reaction outcome. Although effective, these strategies require substrates that contain highly strained ketones or a preinstalled directing group, or are limited to more specialist substrate classes.sup.5. Here we report a general C-C activation mode driven by aromatization of a pre-aromatic intermediate formed in situ. This reaction is suitable for various ketone substrates, is catalysed by an iridium/phosphine combination and is promoted by a hydrazine reagent and 1,3-dienes. Specifically, the acyl group is removed from the ketone and transformed to a pyrazole, and the resulting alkyl fragment undergoes various transformations. These include the deacetylation of methyl ketones, carbenoid-free formal homologation of aliphatic linear ketones and deconstructive pyrazole synthesis from cyclic ketones. Given that ketones are prevalent in feedstock chemicals, natural products and pharmaceuticals, these transformations could offer strategic bond disconnections in the synthesis of complex bioactive molecules. Aromatization-driven C-C bond activation through iridium/phosphine catalysis enables deacylative transformations in various ketone substrates., Author(s): Yan Xu [sup.1] , Xiaotian Qi [sup.2] , Pengfei Zheng [sup.1] [sup.3] , Carlo C. Berti [sup.1] , Peng Liu [sup.2] , Guangbin Dong [sup.1] Author Affiliations: (1) Department [...]