Iridium-Catalyzed Asymmetric Difunctionalization of C-C σ-Bonds Enabled by Ring-Strained Boronate Complexes

Lewis Acid Catalyzed Divergent Reaction of Bicyclo[1.1.0]Butanes With Quinones for the Synthesis of Diverse Polycyclic Molecules

Bicyclo[1.1.0]butanes (BCBs) are highly strained hydrocarbons with unique structural properties and intrinsic reactivity, making them valuable building blocks for constructing complex molecular architectures. Herein, we report the Lewis acid-catalyzed divergent reactions of BCBs with quinones, yielding a diverse array of polycyclic molecules. Using Sc(OTf)₃ as a catalyst, pyrazole-substituted BCBs efficiently undergo formal (3 + 2) cycloaddition reactions with quinones, producing highly substituted bicyclo[2.1.1]hexanes featuring a caged framework. Monosubstituted BCB ketones undergo a sequential cascade involving Alder-ene reaction, 4π electrocyclic ring-opening, and [4 + 2] cycloaddition reaction, yielding fused benzoxepines efficiently. Disubstituted BCB esters, ketones, and amides undergo a tandem isomerization and (3 + 2) cycloaddition process, stereoselectively yielding tetrahydrocyclobuta[b]benzofuran products. Notably, strong Lewis acids such as SnCl₄ and BiBr₃ directly participate in the ring-opening reactions of monosubstituted BCB ketones, generating halogenated cyclobutane derivatives. Additionally, the synthetic potential of these approaches has been further highlighted through scale-up experiments and a range of transformations. This study demonstrates the tunability of reaction pathways based on the diverse substitution patterns of BCBs, providing efficient methods for the synthesis of a range of polycyclic compounds.

Borylated strain rings synthesis via photorearrangements enabled by energy transfer catalysis

Borylated carbocycles occupy a pivotal position as essential components in synthetic chemistry, drug discovery, and materials science. Herein, we present a photorearrangement that uniquely involves a boron atom enabled by energy transfer catalysis under visible light conditions. The boron functional group could be translocated through energy transfer mechanism and valuable borylated cyclopropane scaffolds could be generated smoothly. Furthermore, we showcase a 1,5-HAT (hydrogen atom transfer)/cyclization reaction, which is also enhanced by energy transfer catalysis excited by visible light. This method enables the synthesis of borylated cyclobutane frameworks. These boron-involved photorearrangement and cyclization reactions represent two techniques for synthesizing highly desirable borylated strained ring structures, which offering avenues for the synthesis of complex organic molecules with medicinal and material science applications.

Generation and Use of Bicyclo[1.1.0]butyllithium under Continuous Flow Conditions

The bicyclo[1.1.0]butyl scaffold has emerged as a valuable bioisostere in drug discovery programs. Here, we present a streamlined approach for the generation of bicyclo[1.1.0]butyllithium and its functionalization with various classes of electrophiles in a one-flow process, eliminating the need for intermediate isolation. In comparison to traditional batch processes, the flow method allows the use of a single organolithium reagent instead of two and operates at significantly higher temperatures (0 °C versus -78 °C), enhancing both practicality and scalability.

Copper-Catalyzed Cross-Coupling of Bicyclobutanes with Triftosylhydrazone Leading to Skipped Dienes

Here, we report a protocol for the synthesis of skipped dienes through the cross-coupling of bicyclo[1.1.0]butanes with trifluoromethyl triftosylhydrazones. The reaction is run using TpBr3Cu(NCMe) as a catalyst to give access to a library of trifluoromethylated skipped dienes (32 examples, ≤98% yield) with excellent E/Z selectivity under mild and operationally safe conditions. The presented methods proved to be compatible with various functionalized bicyclo[1.1.0]butanes and triftosylhydrazones.

Facile Synthesis of Housanes by an Unexpected Strategy

Rigid bicyclic hydrocarbons have emerged as important building blocks in the drug discovery industry. Despite progress in this general area, bicyclo[2.1.0]pentanes (housanes) are an understudied class of molecules. Herein we report an unconventional synthesis of borylated housanes. Our method features a broad scope and high diastereoselectivities in the synthesis of versatile intermediates. The route involves a strain-release diboration of bicyclo[1.1.0]butane and intramolecular deborylative alkylation. The versatility of the bridgehead boronic ester was demonstrated in several functionalizations. Lastly, the mechanism of the reaction was investigated, and an unusual stereospecific and diastereoselective ring expansion was uncovered.

Diverse Synthesis of Arene-Fused [n.1.1]-Bridged Molecules via Catalytic Cycloaddition and Rearrangement Reactions

Although great advancement has been made in synthesis of 3D bridged bicyclic[n.1.1]-bioisosteres, facile construction of 2D/3D merged molecules incorporating bridged rings, as novel chemical space in drug discovery, remains a significant challenge. Herein a collective, selective, and diversity-oriented approach for up to 6 types of 2D/3D polycyclic scaffolds featuring bicyclo[n.1.1] substructure is reported. A boronyl radical-catalyzed [2σ+2π] cycloaddition between bicyclo[1.1.0]butanes and ortho-quinone methides afforded spirocyclic compounds containing a bicyclo[2.1.1]hexanes unit, which were used as intermediates for synthesis of three types of 2D/3D scaffolds via judiciously controlled Lewis acid-catalyzed rearrangements. The reaction and rearrangement of para-quinone methides worked analogously and provided another two polycyclic scaffolds.

Solvent-Dependent Divergent Cyclization of Bicyclo[1.1.0]butanes

Bicyclo[1.1.0]butanes (BCBs) have recently garnered significant research interest as versatile precursors for synthesizing potential [n.1.1] bioisosteres and multi-functionalized cyclobutanes in a straightforward and atom-economical manner. Here, we report a solvent-dependent divergent cyclization of BCBs that provides highly diastereospecific decorated cyclobutanes and oxygen-containing bicyclo[3.1.1]heptanes (BCHeps), which serve as bioisosteres of meta-substituted arenes. Additionally, an unprecedented 1,2-difunctionalization reaction mode for BCBs was explored, thus expanding the chemical space of arene bioisosteres and highly functionalized cyclobutanes.

Stereoselective Radical Acylfluoroalkylation of Bicyclobutanes via N-Heterocyclic Carbene Catalysis

Cyclobutanes are prominent structural components in natural products and drug molecules. With the advent of strain-release-driven synthesis, ring-opening reactions of bicyclo[1.1.0]butanes (BCBs) provide an attractive pathway to construct these three-dimensional structures. However, the stereoselective difunctionalization of the central C-C σ-bonds remains challenging. Reported herein is a covalent-based organocatalytic strategy that exploits radical NHC catalysis to achieve diastereoselective acylfluoroalkylation of BCBs under mild conditions. The Breslow enolate acts as a single electron donor and provides an NHC-bound ketyl radical with appropriate steric hindrance, which effectively distinguishes between the two faces of transient cyclobutyl radicals. This operationally simple method tolerates various fluoroalkyl reagents and common functional groups, providing a straightforward access to polysubstituted cyclobutanes (75 examples, up to >19 : 1 d.r.). The combined experimental and theoretical investigations of this organocatalytic system confirm the formation of the NHC-derived radical and provide an understanding of how stereoselective radical-radical coupling occurs.

Ring Expansion toward Fused Diazabicyclo[3.1.1]heptanes through Lewis Acid Catalyzed Highly Selective C-C/C-N Bond Cross-Exchange Reaction between Bicyclobutanes and Diaziridines

The synthesis of bicyclic scaffolds has garnered considerable interest in drug discovery because of their ability to mimic benzene bioisosteres. Herein, we introduce a new approach that utilizes a Lewis acid (Sc(OTf)3)-catalyzed σ-bond cross-exchange reaction between the C-C bond of bicyclobutanes and the C-N bond of diaziridines to produce multifunctionalized and medicinally interesting azabicyclo[3.1.1]heptane derivatives. The reaction proceeds well with different bicyclobutanes and a broad range of aryl- as well as alkenyl-, but also alkyl-substituted diaziridines (up to 98 % yield). Conducting a scale-up experiment and exploring the synthetic transformations of the cycloadducts emphasized the practical application of the synthesis. Furthermore, a zinc-based chiral Lewis acid catalytic system was developed for the enantioselective version of this reaction (up to 96 % ee).

Asymmetric synthesis of atropisomers featuring cyclobutane boronic esters facilitated by ring-strained B-ate complexes

The strain-release-driven reactions of bicyclo[1.1.0]butanes (BCBs) have received significant attention from chemists. Notably, 1,2-migratory reactions enabled by BCB-derived B-ate complexes effectively complement the reactions initiated by common BCBs. The desired products are particularly valuable for late-stage transformations due to the presence of the C-B bond. However, asymmetric reactions mediated by BCB-derived boronate complexes have progressed slowly. In this study, we develop an asymmetric synthesis of atropisomers featuring cis-cyclobutane boronic esters facilitated by 1,2-carbon or boron migration of ring-strained B-ate complexes, achieving high enantioselectivity. The reaction is compatible with various aryl, alkenyl, alkyl boronic esters and B2pin2, and shows good compatibility with natural product derivatives. Mechanistic studies are conducted to understand stereoselective control in the dynamic kinetic asymmetric transformations (DYKATs). The target products can undergo a series of transformations, further demonstrating the practicality of this methodology.

Visible Light Promoted de Mayo Type Reaction of Bicyclo[1.1.0]butanes

We reported herein a visible light mediated de Mayo-type reaction between 1,3-diketones and BCB. The reaction proceeds through a [2π+2σ] cycloaddition and retro-aldol sequence, producing cis-difunctionalized cyclobutanes in high yields with good regio- and diastereoselectivity.

Enantioselective dearomative formal (3+3) cycloadditions of bicyclobutanes with aromatic azomethine imines: access to fused 2,3-diazabicyclo[3.1.1]heptanes

Although cycloadditions of bicyclobutanes (BCBs) have emerged as a reliable approach for producing bicyclo[n.1.1]alkanes such as azabicyclo[3.1.1]heptanes (aza-BCHeps), serving as saturated bioisosteres of arenes, the catalytic asymmetric variant remains underdeveloped and presents challenges. Herein, we developed several Lewis acid-catalyzed systems for the challenging dearomative (3+3) cycloaddition of BCBs and aromatic azomethine imines. This resulted in fused 2,3-diazabicyclo[3.1.1]heptanes, introducing a novel chemical space for the caged hydrocarbons. Moreover, an asymmetric Lewis acid catalysis strategy was devised for the (3+3) cycloadditions of BCBs and N-iminoisoquinolinium ylides, forming chiral diaza-BCHeps with up to 99% yield and 97% ee. This study showcases a unique instance of asymmetric (3+3) cycloaddition facilitated by the creation of a chiral environment via the activation of BCBs.

Zinc-Catalyzed Enantioselective Formal (3+2) Cycloadditions of Bicyclobutanes with Imines: Catalytic Asymmetric Synthesis of Azabicyclo[2.1.1]hexanes

The cycloaddition reaction involving bicyclo[1.1.0]butanes (BCBs) offers a versatile and efficient synthetic platform for producing C(sp3)-rich rigid bridged ring scaffolds, which act as phenyl bioisosteres. However, there is a scarcity of catalytic asymmetric cycloadditions of BCBs to fulfill the need for enantioenriched saturated bicycles in drug design and development. In this study, an efficient synthesis of valuable azabicyclo[2.1.1]hexanes (aza-BCHs) by an enantioselective zinc-catalyzed (3+2) cycloadditions of BCBs with imines is reported. The reaction proceeds effectively with a novel type of BCB that incorporates a 2-acyl imidazole group and a diverse array of alkynyl- and aryl-substituted imines. The target aza-BCHs, which consist of α-chiral amine fragments and two quaternary carbon centers, are efficiently synthesized with up to 94 % and 96.5:3.5 er under mild conditions. Experimental and computational studies reveal that the reaction follows a concerted nucleophilic ring-opening mechanism of BCBs with imines. This mechanism is distinct from previous studies on Lewis acid-catalyzed cycloadditions of BCBs.

Merging Organocatalysis with 1,2-Boronate Rearrangement: A Lewis Base-Catalyzed Asymmetric Multicomponent Reaction

Catalytic asymmetric multicomponent 1,2-boronate rearrangements provide a practical approach for synthesizing highly valuable enantioenriched boronic esters. When applied to alkenyl or heteroaryl boronates, these reactions have relied mainly on transition-metal catalysis. Herein, we present an organocatalytic, Lewis base-catalyzed asymmetric multicomponent 1,2-boronate rearrangement, involving indoles, boronic esters, and Morita-Baylis-Hillman carbonates, leading to enantioenriched, highly substituted indole and indoline derivatives. Using cinchona alkaloid-based catalysts, high selectivity has been achieved, enabling expansion of the chemical space around pharmaceutically relevant indole and indoline derivatives.

Enantioselective formal (3 + 3) cycloaddition of bicyclobutanes with nitrones enabled by asymmetric Lewis acid catalysis

The absence of catalytic asymmetric methods for synthesizing chiral (hetero)bicyclo[n.1.1]alkanes has hindered their application in new drug discovery. Here we demonstrate the achievability of an asymmetric polar cycloaddition of bicyclo[1.1.0]butane using a chiral Lewis acid catalyst and a bidentate chelating bicyclo[1.1.0]butane substrate, as exemplified by the current enantioselective formal (3 + 3) cycloaddition of bicyclo[1.1.0]butanes with nitrones. In addition to the diverse bicyclo[1.1.0]butanes incorporating an acyl imidazole group or an acyl pyrazole moiety, a wide array of nitrones are compatible with this Lewis acid catalysis, successfully assembling two congested quaternary carbon centers and a chiral aza-trisubstituted carbon center in the pharmaceutically important hetero-bicyclo[3.1.1]heptane product with up to 99% yield and >99% ee.

Chemoselective and Stereoselective Allylation of Bis(alkenyl)boronates

Bis(alkenyl)boronates react with optically active Ir(π-allyl) species in a process that involves allylation of the more substituted olefin and 1,2-metalate shift of the less substituted olefin. The method constructs valuable enantioenriched tertiary allylic boronic esters with high chemoselectivity, enantioselectivity and diastereoselectivity. Allylic functionalization reactions transform the 1,3-stereodiad to 1,5- and 1,6-stereochemical relationships.

Palladium-Catalyzed Ligand-Controlled Switchable Hetero-(5 + 3)/Enantioselective [2σ+2σ] Cycloadditions of Bicyclobutanes with Vinyl Oxiranes

For nearly 60 years, significant research efforts have been focused on developing strategies for the cycloaddition of bicyclobutanes (BCBs). However, higher-order cycloaddition and catalytic asymmetric cycloaddition of BCBs have been long-standing formidable challenges. Here, we report Pd-catalyzed ligand-controlled, tunable cycloadditions for the divergent synthesis of bridged bicyclic frameworks. The dppb ligand facilitates the formal (5+3) cycloaddition of BCBs and vinyl oxiranes, yielding valuable eight-membered ethers with bridged bicyclic scaffolds in 100% regioselectivity. The Cy-DPEphos ligand promotes selective hetero-[2σ+2σ] cycloadditions to access pharmacologically important 2-oxabicyclo[3.1.1]heptane (O-BCHeps). Furthermore, the corresponding catalytic asymmetric synthesis of O-BCHeps with 94-99% ee has been achieved using chiral (S)-DTBM-Segphos, representing the first catalytic asymmetric cross-dimerization of two strained rings. The obtained O-BCHeps are promising bioisosteres for ortho-substituted benzenes.

PolyBorylated Alkenes as Energy-Transfer Reactive Groups: Access to Multi-Borylated Cyclobutanes Combined with Hydrogen Atom Transfer Event

While polyborylated alkenes are being recognized for their elevated status as highly valuable reagents in modern organic synthesis, allowing efficient access to a diverse array of transformations, including the formation of C-C and C-heteroatom bonds, their potential as energy-transfer reactive groups has remained unexplored. Yet, this potential holds the key to generating elusive polyborylated biradical species, which can be captured by olefins, thereby leading to the construction of new highly-borylated scaffolds. Herein, we report a designed energy-transfer strategy for photosensitized [2+2]-cycloadditions of poly-borylated alkenes with various olefins enabling the regioselective synthesis of diverse poly-borylated cyclobutane motifs, including the 1,1-di-, 1,1,2-tri-, and 1,1,2,2-tetra-borylated cyclobutanes. In fact, these compounds belong to a family that presently lacks efficient synthetic pathways. Interestingly, when α-methylstyrene was used, the reaction involves an interesting 1,5-hydrogen atom transfer (HAT). Mechanistic deuterium-labeling studies have provided insight into the outcome of 1,5-hydrogen atom transfer process. In addition, the polyborylated cyclobutanes are then demonstrated to be useful in selective oxidation processes resulting in the formation of cyclobutanones and γ-lactones.

Simultaneous Stereoinvertive and Stereoselective C(sp3)-C(sp3) Cross-Coupling of Boronic Esters and Allylic Carbonates

With increasing interest in constructing more three-dimensional entities, there has been growing interest in cross-coupling reactions that forge C(sp3)-C(sp3) bonds, which leads to additional challenges as it is not just a more difficult bond to construct but issues of stereocontrol also arise. Herein, we report the stereocontrolled cross-coupling of enantioenriched boronic esters with racemic allylic carbonates enabled by iridium catalysis, leading to the formation of C(sp3)-C(sp3) bonds with single or vicinal stereogenic centers. The method shows broad substrate scope, enabling primary, secondary, and even tertiary boronic esters to be employed, and can be used to prepare any of the four possible stereoisomers of a coupled product with vicinal chiral centers. The new method, which combines the simultaneous enantiospecific reaction of a chiral nucleophile with the enantioselective reaction of a chiral electrophile in a single process, offers a solution for stereodivergent cross-coupling of two C(sp3) fragments.

Eu(OTf)3 -Catalyzed Formal Dipolar [4π+2σ] Cycloaddition of Bicyclo-[1.1.0]butanes with Nitrones: Access to Polysubstituted 2-Oxa-3-azabicyclo[3.1.1]heptanes

Herein, we have synthesized multifunctionalized 2-oxa-3-azabicyclo[3.1.1]heptanes, which are considered potential bioisosteres for meta-substituted arenes, through Eu(OTf)3 -catalyzed formal dipolar [4π+2σ] cycloaddition of bicyclo[1.1.0]butanes with nitrones. This methodology represents the initial instance of fabricating bicyclo[3.1.1]heptanes adorned with multiple heteroatoms. The protocol exhibits both mild reaction conditions and a good tolerance for various functional groups. Computational density functional theory calculations support that the reaction mechanism likely involves a nucleophilic addition of nitrones to bicyclo[1.1.0]butanes, succeeded by an intramolecular cyclization. The synthetic utility of this novel protocol has been demonstrated in the concise synthesis of the analogue of Rupatadine.

Photoredox-Catalyzed Alkylarylation of N-Aryl Bicyclobutyl Amides with α-Carbonyl Alkyl Bromides: Access to 3-Spirocyclobutyl Oxindoles

A visible-light-induced radical alkylarylation of N-aryl bicyclobutyl amides with α-carbonyl alkyl bromides for the synthesis of functionalized 3-spirocyclobutyl oxindoles is described in which β-selective radical addition of the alkyl radical to N-aryl bicyclobutyl amides forms a key radical intermediate followed by interception with intrinsic arene functional group. This approach can be applicable to a wide range of α-carbonyl alkyl bromides, including primary, secondary, and tertiary α-bromoalkyl esters, ketones, nitriles, and nitro compounds.

Strain-enabled radical spirocyclization cascades: rapid access to spirocyclobutyl lactones and - lactams

Spirocyclobutane derivatives have gained significant attention in drug discovery programs due to their broad spectrum of biological activities and clinical applications. Ring-strain in organic molecules is a powerful tool to promote reactivity by releasing strain energy, allowing the construction of complex molecules selectively and efficiently. Herein, we report the first strain-enabled radical spirocyclization cascades for the synthesis of functionalized spirocyclobutyl lactones and - lactams, which are finding increasing applications in medicinal chemistry. The reaction of interelement compounds with bicyclobutane (BCB) allyl esters and - amides proceeds with high chemoselectivity under simple, catalyst-free conditions using blue light irradiation. The reaction has been successfully extended to synthesize bis-spirocycles. To introduce a more diverse set of functional groups, we have developed a dual photoredox/nickel catalytic system capable of mediating the carbosulfonylation of BCB allyl amides. The reaction shows broad applicability across various (hetero)aryl halides, aryl sulfinates, and BCB allyl amides, operates under mild conditions and demonstrates excellent functional group compatibility. The functional groups introduced during the cascade reactions served as versatile handles for further synthetic elaboration.

Double Strain-Release [2π+2σ]-Photocycloaddition

In pursuit of potent pharmaceutical candidates and to further improve their chemical traits, small ring systems can serve as a potential starting point. Small ring units have the additional merit of loaded strain at their core, making them suitable reactants as they can capitalize on this intrinsic driving force. With the introduction of cyclobutenone as a strained precursor to ketene, the photocycloaddition with another strained unit, bicyclo[1.1.0]butane (BCB), enables the reactivity of both π-units in the transient ketene. This double strain-release driven [2π+2σ]-photocycloaddition promotes the synthesis of diverse heterobicyclo[2.1.1]hexane units, a pharmaceutically relevant bioisostere. The effective reactivity under catalyst-free conditions with a high functional group tolerance defines its synthetic utility. Experimental mechanistic studies and density functional theory (DFT) calculations suggest that the [2π+2σ]-photocycloaddition takes place via a triplet mechanism.

Iridium/Acid Dual-Catalyzed Enantioselective Aza-ene-type Allylic Alkylation of Nitro Ketene Aminals with Racemic Allylic Alcohols

The enantioselective allylic alkylation of nitro ketene aminals with racemic allylic alcohols was realized by iridium/acid dual catalysis. An allyl group was installed on the α-position of nitro ketene aminals in a branched-selective manner in high efficiency with excellent enantioselectivities (93-99% ee). The protocol was applied to the late-stage modification of neonicotinoid insecticides, which directly furnished a novel neonicotinoid analogue with good insecticidal activity against Aphis craccivora (LC50 = 6.40 mg/L). On the basis of the control experiment, an aza-ene-type allylic alkylation reaction mechanism was proposed.

Asymmetric Synthesis of Chiral 1,2-Bis(Boronic) Esters Featuring Acyclic, Non-Adjacent 1,3-Stereocenters

The construction of acyclic, non-adjacent 1,3-stereogenic centers, prevalent motifs in drugs and bioactive molecules, has been a long-standing synthetic challenge due to acyclic nucleophiles being distant from the chiral environment. In this study, we successfully synthesized highly valuable 1,2-bis(boronic) esters featuring acyclic and nonadjacent 1,3-stereocenters. Notably, this reaction selectively produces migratory coupling products rather than alternative deborylative allylation or direct allylation byproducts. This approach introduces a new activation mode for selective transformations of gem-diborylmethane in asymmetric catalysis. Additionally, we found that other gem-diborylalkanes, previously challenging due to steric hindrance, also successfully participated in this reaction. The incorporation of 1,2-bis(boryl)alkenes facilitated the diversification of the alkenyl and two boron moieties in our target compounds, thereby enabling access to a broad array of versatile molecules. DFT calculations were performed to elucidate the reaction mechanism and shed light on the factors responsible for the observed excellent enantioselectivity and diastereoselectivity. These were determined to arise from ligand-substrate steric repulsions in the syn-addition transition state.

Photochemical α-selective radical ring-opening reactions of 1,3-disubstituted acyl bicyclobutanes with alkyl halides: modular access to functionalized cyclobutenes

Although ring-opening reactions of bicyclobutanes bearing electron-withdrawing groups, typically with β-selectivity, have evolved as a powerful platform for synthesis of cyclobutanes, their application in the synthesis of cyclobutenes remains underdeveloped. Here, a novel visible light induced α-selective radical ring-opening reaction of 1,3-disubstituted acyl bicyclobutanes with alkyl radical precursors for the synthesis of functionalized cyclobutenes is described. In particular, primary, secondary, and tertiary alkyl halides are all suitable substrates for this photocatalytic transformation, providing ready access to cyclobutenes with a single all-carbon quaternary center, or with two contiguous centers under mild reaction conditions.

syn-Selective Difunctionalization of Bicyclobutanes Enabled by Photoredox-Mediated C-S σ-Bond Scission

Given the importance of cyclic frameworks in molecular scaffolds and drug discovery, it is intriguing to precisely forge and manipulate ring systems in synthetic chemistry. In this field, the intermolecular synthesis of densely substituted cyclobutanes with precise diastereocontrol under simple reaction conditions remains a challenge. Herein, a photoredox strategy for the difunctionalization of bicyclo[1.1.0]butanes (BCBs) under high regio- and syn-selectivity is disclosed. C-S σ-bond cleavage of partially unsaturated sulfur-containing bifunctional reagents in an overall strain-release-driven process enables the thio-alkynylation, -alkenylation, and -allylation of BCBs under mild conditions and demonstrates the generality of this protocol. Mechanistic studies suggest that the intermediacy of cyclic distonic radical cations might be key for the efficient scission of C-S σ-bonds and the origin of diastereoselectivity.