Difunctionalization reactions of C−C -bonds have the potential to streamline access to molecules that would otherwise be difficult to prepare. However, the development of such reactions is challenging because C−C -bonds are typically unreactive.Exploiting the high ring-strain energy of polycyclic carbocycles is a common strategy to weaken and facilitate the reaction of C−C -bonds, but there are limited examples of highly strained C−C -bonds being used in difunctionalization reactions. We demonstrate that highly strained bicyclo[1.1.0]butyl boronate complexes (strain energy: ca. 65 kcal/mol), which were prepared by reacting boronic esters with bicyclo[1.1.0]butyl lithium, react with electrophiles to achieve the diastereoselective difunctionalization of the strained central C−C -bond of the bicyclo[1.1.0]butyl unit. The reaction shows broad substrate scope, with a range of different electrophiles and boronic esters being successfully employed to form a diverse set of 1,1,3-trisubstituted cyclobutanes (>50 examples) with high diastereoselectivity. The high diastereoselectivity observed has been rationalized based on a combination of experimental data and DFT calculations, which suggests that separate concerted and stepwise reaction mechanisms are operating depending upon the migrating substituent and electrophile used. This material is available free of charge via the Internet at http://pubs.acs.org.

Here we report ap alladium-catalysed difunctionalisation of unsaturated CÀCb onds with acid chlorides.F ormally,t he C À COCl bond of an acid chloride is cleaved and added, with complete atom economy,a cross either strained alkenes or atethered alkyne to generate new acid chlorides.The transformation does not require exogenous carbon monoxide, operates under mild conditions,shows agood functional group tolerance,a nd gives the isolated products with excellent stereoselectivity.T he intermolecular reaction tolerates both aryl-and alkenyl-substituted acid chlorides and is successful when carboxylic acids are transformed to the acid chloride in situ. The reaction also shows an example of temperaturedependent stereodivergence which,t ogether with plausible mechanistic pathways, is investigated by DFT calculations. Moreover,w es how that benzofurans can be formed in an intramolecular variant of the reaction. Finally,derivatisation of the products from the intermolecular reaction provides ahighly stereoselective approach for the synthesis of tetrasubstituted cyclopentanes.

We describe a general strategy for the intermolecular synthesis of polysubstituted cyclopentenones using palladium catalysis. Overall, this reaction is achieved via a molecular shuffling process involving an alkyne, an α,β-unsaturated acid chloride, which serves as both the alkene and carbon monoxide source, and a hydrosilane to create three new C–C bonds. This new carbon monoxide-free pathway delivers the products with excellent yields. Furthermore, the regioselectivity is complementary to conventional methods for cyclopentenone synthesis. In addition, a set of regio- and chemodivergent reactions are presented to emphasize the synthetic potential of this novel strategy.

Hydroformylation, a reaction which installs both a C-H bond and an aldehyde group across an unsaturated substrate, is one of the most important catalytic reactions both in industry and academia. Given the synthetic importance of creating new C-C bonds, the development of carboformylation reactions, wherein a new C-C bond is formed instead of a C-H bond, would bear enormous synthetic potential to rapidly increase molecular complexity in the synthesis of valuable aldehydes. However, the demanding complexity inherent in a fourcomponent reaction, utilizing an exogenous CO source, has made the development of a direct carboformylation reaction a formidable challenge. Here, we describe a palladium catalysed strategy which uses readily available aroyl chlorides as a carbon electrophile and CO source, in tandem with a sterically congested hydrosilane, to perform a stereoselective carboformylation of alkynes. An extension of this protocol to four chemodivergent carbonylations further highlights the creative opportunity offered by this strategy in carbonylation chemistry.Carbonylation reactions using carbon monoxide (CO) constitute an industrial core technology. They provide a direct and atom-economic strategy to convert, on a multimillion ton-scale per year, bulk chemicals to various carbonyl-containing compounds and their derivatives, which are essential commodity products in daily life [1][2][3][4] . Due to the importance of these reactions in preparative chemistry, intense academic and industrial research has been dedicated to the development of more environmentally benign and robust catalyst systems as well as highly chemo-, regio-and stereoselective carbonylation reactions [5][6][7][8][9][10][11][12][13][14] . The seminal discovery of transition-metal

<p>Hydroformylation, a reaction which installs both a C–H bond and an aldehyde group across an unsaturated substrate, is one of the most important catalytic reactions both in industry and academia. Given the synthetic importance of creating new C–C bonds, and the widespread academic and industrial impact of <i>hydroformylation</i>, the development of <i>carboformylation</i> reactions, wherein a new C–C bond is formed instead of a C–H bond, would bear enormous synthetic potential to rapidly increase molecular complexity in the synthesis of valuable aldehydes. However, the demanding complexity inherent in a four-component reaction, utilizing an exogenous CO source, has made the development of a direct carboformylation reaction a formidable challenge. Here, we describe a molecular shuffling strategy featuring the use of readily available aroyl chlorides as a carbon electrophile and CO source, in tandem with a sterically congested hydrosilane, to perform a stereoselective carboformylation of alkynes under palladium catalysis. An extension of this protocol to four chemodivergent carbonylations further highlights the creative opportunity offered by this molecular shuffling strategy in carbonylation chemistry.</p>