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Rh(I)-catalyzed cycloisomerizations of bicyclo[1.1.0]butanes provide a fruitful approach to cyclopropane-fused heterocycles. Products and stereochemical outcome are highly dependent on catalyst. The triphenylphosphine (PPh₃) ligand provides pyrrolidines, placing substituentsantito the cyclopropyl group. The 1,2-bis(diphenylphosphino)ethane (dppe) ligand yields azepanes with substituentssynto the cyclopropyl group. In this work, quantum mechanical DFT calculations pinpoint a reversal of regio- and diastereoselectivity, suggesting a concerted (double) C−C bond cleavage and rhodium carbenoid formation, driven by strain-release. The ligand-influenced cleavage step determines the regioselectivity of carbometalation and product formation, and suggests new applications of bicyclobutanes.

Reactions that lead to destruction of aromatic ring systems often require harsh conditions and, thus, take place with poor selectivities. Selective partial dearomatization of fused arenes is even more challenging but can be a strategic approach to creating versatile, complex polycyclic frameworks. Herein we describe a general organophotoredox approach for the chemo- and regioselective dearomatization of structurally diverse polycyclic aromatics, including quinolines, isoquinolines, quinoxalines, naphthalenes, anthracenes and phenanthrenes. The success of the method for chemoselective oxidative rupture of aromatic moieties relies on precise manipulation of the electronic nature of the fused polycyclic arenes. Mechanistic studies show that the addition of a hydrogen atom transfer (HAT) agent helps favor the dearomatization pathway over the more thermodynamically downhill aromatization pathway. We show that this strategy can be applied to rapid synthesis of biologically valued targets and late-stage skeletal remodeling en route to complex structures.

An unusual diastereodivergent stereoselective allylation reaction is presented. It consists of a palladium‐catalyzed allylation reaction of an organocatalytically generated amino isobenzofulvene, where the diastereoselectivity is controlled by the electronic properties of a monodentate, achiral ligand on palladium. One major diastereoisomer is formed using triarylphosphines substituted with neutral or electron‐donating substituents of the aryl group, while those with electron‐withdrawing substituents favor the other diastereoisomer. The diastereoselectivity correlates with the Taft inductive parameter of substituents on the triarylphosphine ligand on palladium. The synergistic reaction involves both a catalytic secondary amine catalyst for the indene‐aldehyde activation and the monodentate phosphine ligands on palladium, affording a highly enantioselective reaction with up to 98 % enantiomeric excess. Based on computational investigations, the role of the monodentate phosphine ligand on the diastereoselectivity is discussed.

We report herein a rare example of enantiodivergent aldehyde addition with β‐alkenyl allylic boronates via chiral Brønsted acid catalysis. 2,6‐Di‐9‐anthracenyl‐substituted chiral phosphoric acid‐catalyzed asymmetric allylation using β‐vinyl substituted allylic boronate gave alcohols withRabsolute configuration. The sense of asymmetric induction of the catalyst in these reactions is opposite to those in prior reports. Moreover, in the presence of the same acid catalyst, the reactions with β‐2‐propenyl substituted allylic boronate generated homoallylic alcohol products withSabsolute configuration. Unusual substrate‐catalyst C−H⋅⋅⋅π interactions in the favoured reaction transition state were identified as the origins of observed enantiodivergence through DFT computational studies.

We report asymmetric bioinspired total syntheses of the fungal metabolites emeriones A–C via stereoselective oxidations of two bicyclo[4.2.0]octadiene diastereomers. The central bicyclic scaffolds are prepared in an 8π/6π electrocyclization cascade of a stereodefined pentaene, which contains the fully assembled side chains of the emeriones. The anti‐aldol side chain is made using a Paterson‐aldol addition, and the epoxide of the dioxabicyclo[3.1.0]hexane side chain via ring‐closure onto an oxidized acetal. Our work has enabled the structural revision of emerione C, and resulted in the synthesis of a “missing” family member, which we call emerione D. DFT calculations identified two methyl groups that govern torquoselectivity in the 8π/6π cascade.

Silanes are important in chemistry and material science. The self‐redistribution of HSiCl₃is an industrial process to prepare SiH₄, which is widely used in electronics and automobile industries. However, selective silane cross‐redistribution to prepare advanced silanes is challenging. We now report an enthalpy‐driven silane cross‐redistribution to access bis‐silanes that contain two different types of Si−H bonds in the same molecule. Compared with entropy‐driven reactions, the enthalpy‐driven reaction shows high regioselectivity, broad substrate scope (62 examples) and high atom economy. Our combined experimental and computational study indicates that the reaction proceeds through a Ni⁰‐Ni^II‐Ni^IVcatalytic cycle.

The electrochemical generation of vinyl carbocations from alkenyl boronic esters and boronates is reported. Using easy‐to‐handle nucleophilic fluoride reagents, these intermediates are trapped to form fully substituted vinyl fluorides. Mechanistic studies support the formation of dicoordinated carbocations through sequential single‐electron oxidation events. Notably, this electrochemical fluorination features fast reaction times and Lewis acid‐free conditions. This transformation provides a complementary method to access vinyl fluorides with simple fluoride salts such as TBAF.

Herein, we leverage the Ni‐catalyzed enantioselective reductive dicarbofunctionalization of internal alkenes with alkyl iodides to enable the synthesis of chiral pyrrolidinones bearing vicinal stereogenic centers. The application of newly developed^1‐NapQuinim is critical for formation of two contiguous stereocenters in high yield, enantioselectivity, and diastereoselectivity. This catalytic system also improves both the yield and enantioselectivity in the synthesis of α,α‐dialkylated γ‐lactams. Computational studies reveal that the enantiodetermining step proceeds with a carbamoyl‐Ni^Iintermediate that is reduced by the Mn reductant prior to intramolecular migratory insertion. The presence of thet‐butyl group of the Quinim ligand leads to an unfavorable distortion of the substrate in the TS that leads to the minor enantiomer. Calculations also support an improvement in enantioselectivity with^1‐NapQuinim compared to^p‐tolQuinim.

A strategy to control the diastereoselectivity of bond formation at a prochiral attached‐ring bridgehead is reported. An unusual stereodivergent Michael reaction relies on basic vs. Lewis acidic conditions and non‐covalent interactions to controlre‐ vs.si‐ facial selectivity en route to fully substituted attached‐rings. This divergency reflects differential engagement of one rotational isomer of the attached‐ring system. The successful synthesis of anerythrosubtarget diastereomer ultimately leads to a short formal synthesis of merrilactone A.