Difunctionalization Of Alkenes Research Articles

Halogenation of Alkenes Using Three‐Component Reactions: A Decade of Development

AbstractAlkenes are valuable feedstocks in organic synthesis. One effective method for synthesizing organic halides with functional groups in close proximity involves the direct difunctionalization of alkenes via three‐component reactions. This approach not only reduces the number of steps involved in the synthesis process, but also minimizes waste generation and enables the formation of complex molecules from simple starting materials. In this review, we mainly discuss decade developments (2013‐2023) in two categories: (1) halogenation via three‐membered ring intermediates, involving haliranium, thiiranium,seleniranium, aziridinium and epoxide species; (2) halogenation via a radical pathway. Reactions with I2, BiI3, NaI, Bu4N+[I(O2CAr)2]−, NIS, NBS, NCS, DBH, BsNMeBr, HBr, HCl, KI, NH4I, I2O5, Et3N ⋅ 3HF, Selectfluor, CuI, CuBr, CuCl, LiCl, KBr, NaCl, SOCl2, Py ⋅ 9HF, NFSI, TBSCl et al have been recorded and how the added reagents work will be discussed. We hope this review will do help for future research in this area.

Ligand control of regioselectivity in palladium-catalyzed heteroannulation reactions of 1,3-Dienes

Olefin carbofunctionalization reactions are indispensable tools for constructing diverse, functionalized scaffolds from simple starting materials. However, achieving precise control over regioselectivity in intermolecular reactions remains a formidable challenge. Here, we demonstrate that using PAd2nBu as a ligand enables regioselective heteroannulation of o-bromoanilines with branched 1,3-dienes through ligand control. This approach provides regiodivergent access to 3-substituted indolines, showcasing excellent regioselectivity and reactivity across a range of functionalized substrates. To gain further insights into the origin of selectivity control, we employ a data-driven strategy, developing a linear regression model using calculated parameters for phosphorus ligands. This model identifies four key parameters governing regioselectivity in this transformation, paving the way for future methodology development. Additionally, density functional theory calculations elucidate key selectivity-determining transition structures along the reaction pathway, corroborating our experimental observations and establishing a solid foundation for future advancements in regioselective olefin difunctionalization reactions.

Visible-light-induced four-component difunctionalization of alkenes to construct phosphorodithioate-containing quinoxalin-2(1H)-ones

A facile visible-light-induced 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) catalyzed four-component reaction of alkenes, quinoxalin-2(1H)-ones, P4S10 and alcohols has been developed at room temperature. This tandem reaction provides an efficient strategy for the construction of various phosphorodithioate-containing quinoxalin-2(1H)-ones with moderate to good yields by using air (dioxygen) as the green oxidant. Experimental studies revealed a radical process was involved in this photochemical reaction.

Red-light-mediated copper-catalyzed photoredox catalysis promotes regioselectivity switch in the difunctionalization of alkenes

Controlling regioselectivity during difunctionalization of alkenes remains a significant challenge, particularly when the installation of both functional groups involves radical processes. In this aspect, methodologies to install trifluoromethane (−CF3) via difunctionalization have been explored, due to the importance of this moiety in the pharmaceutical sectors; however, these existing reports are limited, most of which affording only the corresponding β-trifluoromethylated products. The main reason for this limitation arises from the fact that −CF3 group served as an initiator in those reactions and predominantly preferred to be installed at the terminal (β) position of an alkene. On the contrary, functionalization of the −CF3 group at the internal (α) position of alkenes would provide valuable products, but a meticulous approach is necessary to win this regioselectivity switch. Intrigued by this challenge, we here develop an efficient and regioselective strategy where the −CF3 group is installed at the α-position of an alkene. Molecular complexity is achieved via the simultaneous insertion of a sulfonyl fragment (−SO2R) at the β-position. A precisely regulated sequence of radical generation using red light-mediated photocatalysis facilitates this regioselective switch from the terminal (β) position to the internal (α) position. Furthermore, this approach demonstrates broad substrate scope and industrial potential for the synthesis of pharmaceuticals under mild reaction conditions.

Enantioselective Ni-Catalyzed 1,2-Borylalkynylation of Unactivated Alkenes.

Enantioselective three-component difunctionalization of alkenes with boron reagents represents an attractive strategy for assembling three-dimensional chiral organoboron compounds. However, regio- and enantiocontrol comprise the pivot challenges in these transformations, which predominantly require the use of activated conjugated alkenes. Herein, by utilizing various carbonyl directing groups, including amides, sulfinamides, ketones, and esters, we succeed in realizing a nickel-catalyzed 1,2-borylalkynylation of unactivated alkenes to enable the simultaneous incorporation of a boron entity and an sp-fragment across the double bond. The products contain boryl, alkynyl, and carbonyl functional groups with orthogonal synthetic reactivities, offering three handles for further derivatization to access valuable intermediates. The utility of this ligand-enabled asymmetric protocol has been highlighted through the late-stage decoration of drug-relevant molecules.

Photoredox Ring Opening 1,2-Alkylarylation of Alkenes with Sulfonium Salts Toward Thioether-Substituted Oxindoles.

A novel strategy for the difunctionalization of electron-deficient alkenes with aryl sulfonium salts to access remote sulfur-containing oxindole derivatives by using in situ-formed copper(I)-based complexes as a photoredox catalyst is presented. This method enables the generation of the C(sp3)-centered radicals through site selective cleavage of the C-S bond of aryl sulfonium salts under mild conditions. Moreover, the oxidation reactions of desired products provide a new strategy for the preparation of sulfoxide or sulfone-containing compounds. Importantly, this approach can be easily applied to late-stage modification of pharmaceuticals molecules.

Mechanochemistry Drives Alkene Difunctionalization via Radical Ligand Transfer and Electron Catalysis.

A general and modular protocol is reported for olefin difunctionalization through mechanochemistry, facilitated by cooperative radical ligand transfer (RLT) and electron catalysis. Utilizing mechanochemical force and catalytic amounts of 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO), ferric nitrate can leverage nitryl radicals, transfer nitrooxy-functional group via RLT, and mediate an electron catalysis cycle under room temperature. A diverse range of activated and unactivated alkenes exhibited chemo- and regioselective 1,2-nitronitrooxylation under solvent-free or solvent-less conditions, showcasing excellent functional group tolerance. Mechanistic studies indicated a significant impact of mechanochemistry and highlighted the radical nature of this nitrative difunctionalization process.

Regioselective difunctionalization of alkenes with CF2FG Moieties

The organofluorine chemistry field has steadily increased over the years. In particular, the difunctionalization of unsaturated compounds is an efficient pathway toward the formation of regioselective and highly functionalized aliphatic compounds. This review depicts the recent advances made for simultaneously forming C−FG1 and C−CF2FG2 on alkenes (FG = functional group) by catalysis. This review highlights approaches involving transition metal-catalyzed transformations and one electron manifold.

Synthesis of Biindene Derivatives via Pd-Catalyzed Alkene Difunctionalization Reactions.

The palladium-catalyzed cross-coupling of 2-allylphenyl triflate and related electrophiles with substituted indenes affords biindene derivatives in moderate to good yields with high selectivity for thermodynamically preferred alkene isomers. The transformations involve alkene nucleopalladation with indenyl anions, and we also demonstrate that 2-allylphenyl triflates can be transformed to indenes under similar conditions. The scope of this transformation, along with the mechanism of formation of both indene and biindene products, is described.

Copper-Catalyzed Asymmetric Aminative Difunctionalization of Alkenes with Azodicarboxylates

Copper-Catalyzed Asymmetric Aminative Difunctionalization of Alkenes with Azodicarboxylates

Visible‐Light‐Induced Three‐Component Alkylpyridylation of Alkenes Enabled by Electron Donor‐Acceptor Complex

Visible‐light‐induced difunctionalization of alkenes is a powerful strategy for constructing complex molecules. Herein, we disclose a three‐component 1,2‐alkylpyridylation of alkenes under mild and photosensitizers‐free conditions. UV‐vis absorption spectroscopy studies and NMR titration experiments indicate that the formation of an EDA complex between 4‐alkyl‐DHPs and 4‐cyanopyridines. Primary, secondary, and tertiary C(sp3)‐centered radicals were formed by homolytic cleavage of 4‐alkyl‐DHPs. Gram‐scale synthesis and late‐stage functionalization of medicinally relevant molecules showed the synthetic potential of our methodology.

Light-induced perfluoroalkylative carbonylation of unactivated alkenes with a recyclable photocatalyst

The development of heterogeneous catalysis difunctionalization of olefins is of great significance because it can save costs in the industry. Here, we report the perfluoroalkyl carbonylation reaction of inactive olefins catalyzed by titanium dioxide under light, obtaining β-perfluoroalkylamide compounds. The catalyst has high activity and wide functional group tolerance and can maintain high activity after multiple cycles. This catalyst reduces the use of precious metals, avoids ligands, and can easily be separated from the reaction mixtures.

Construction of β-Oximino Phosphorodithioates via (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl-Promoted Difunctionalization of Alkenes with tert-Butyl Nitrite, P4S10, and Alcohols.

A (2,2,6,6-tetramethylpiperidin-1-yl)oxyl-mediated difunctionalization of alkenes with tert-butyl nitrite, P4S10, and alcohols has been developed for the synthesis of β-oximino phosphorodithioates. The reaction goes through a radical pathway with the successive installation of phosphorodithioate and an oxime group. This four-component protocol offers a practical approach to constructing a variety of β-oximino phosphorodithioates in moderate to good yields with favorable functional group tolerance.

Nickel-catalysed enantioselective alkene dicarbofunctionalization enabled by photochemical aliphatic C–H bond activation

The development of novel strategies to rapidly construct complex chiral molecules from readily available feedstocks is a long-term pursuit in the chemistry community. Radical-mediated alkene difunctionalizations represent an excellent platform towards this goal. However, asymmetric versions remain highly challenging, and more importantly, examples featuring simple hydrocarbons as reaction partners are elusive. Here we report an asymmetric three-component alkene dicarbofunctionalization capitalizing on the direct activation of C(sp3)–H bonds through the combination of photocatalysed hydrogen atom transfer and nickel catalysis. This protocol provides an efficient platform for installing two vicinal carbon–carbon bonds across alkenes in an atom-economic fashion, providing a wide array of high-value chiral α-aryl/alkenyl carbonyls and phosphonates, as well as 1,1-diarylalkanes from ubiquitous alkane, ether and alcohol feedstocks. This method exhibits operational simplicity, broad substrate scope and excellent regioselectivity, chemoselectivity and enantioselectivity. The compatibility with bioactive motifs and expedient synthesis of pharmaceutically relevant molecules highlight the synthetic potential of this protocol.

Copper‐Catalyzed Cyanoalkylation and Trifluoromethylthiolation of Styrene Derivatives via a Visible‐Light‐Promoted Cross‐Coupling

AbstractTransition‐metal catalyzed difunctionalization of olefins has attracted considerable attention as a method to construct carbon‐carbon and carbon‐hetero bonds. Herein, the copper‐catalyzed three‐component radical cross‐coupling of oxime esters, styrenes and AgSCF3 through a visible‐light‐promoted iminyl radical‐mediated carbon‐carbon bond cleavage strategy has been described. Utilizing low‐cost copper salt as both photosensitizers and cross‐couplers, this protocol delivers diverse target products, providing a supplementary approach for cyanoalkylation and trifluoromethylthiolation of drug molecules.

Copper-Catalyzed 1,2-Sulfonyletherification of 1,3-Dienes.

A selective three-component 1,2-sulfonyl etherification of aryl 1,3-dienes enabled by copper catalysis to afford biologically interesting alkenyl 1,2-sulfone ether derivatives through C-S and C-O bond formation is described. The protocol proceeds with the sulfonyl chloride and alcohols under simple, mild, and base-free conditions, providing a straightforward route to sulfonylated allyl ether compounds with broad functional group tolerance and excellent chemo- and regioselectivity. Mechanistic studies indicate that the selective alkene difunctionalization includes a key copper-mediated single-electron transfer process.

Photoredox-Catalyzed Acylchlorination of α-CF3 Alkenes with Acyl Chloride and Application as Masked Access to β-CF3-enones.

We disclose a photocatalytic strategy that simultaneously addresses the construction of trifluoromethylated quaternary carbon centers and the preparation of β-CF3-enones through radical difunctionalization of α-CF3 alkenes with acyl chlorides. This method is characterized by its broad functional group compatibility, high efficiency, and atom economy. The versatility of this transformation is poised to broaden the applications of α-CF3 alkenes, providing new pathways for the rapid assembly of structurally diverse fluorinated compounds.

The Difunctionalization of Alkenes Completed by DMTSM and CF3SO2Na without Metal Catalysts

AbstractThe electrophilic thiolation of alkenes initiated by DMTSM and the addition of CF3SO2Na in one pot has been developed. This reaction also can be extended to ArSO2Na. This protocol features a good substrate scope, simple procedures, and mild reaction conditions and affords the desired products in moderate yields without metal catalysts.

Harnessing charge relocation: A novel approach for the remote difunctionalization of alkenes

Harnessing charge relocation: A novel approach for the remote difunctionalization of alkenes

Confinement Effect in Metal-Organic Framework Cu3(BTC)2 for Enhancing Shape Selectivity of Radical Difunctionalization of Alkenes.

The radical difunctionalization of alkenes plays a vital role in pharmacy, but the conventional homogeneous catalytic systems are challenging in selectivity and sustainability to afford the target molecules. Herein, the famous readily available metal-organic framework (MOF), Cu3(BTC)2, has been applied to cyano-trifluoromethylation of alkenes as a high-performance and recyclable heterogeneous catalyst, which possesses copper(II) active sites residing in funnel-like cavities. Under mild conditions, styrene derivatives and various unactivated olefins could be smoothly transformed into the corresponding cyano-trifluoromethylation products. Moreover, the transformation brought about by the active copper center in confined environments achieved regio- and shape selectivity. To understand the enhanced selectivity, the activation manner of the MOF catalyst was studied with control catalytic experiments such as FT-IR and UV-vis absorption spectroscopy of substrate-incorporated Cu3(BTC)2, which elucidated that the catalyst underwent a radical transformation with the intermediates confined in the MOF cavity, and the confinement effect endowed the method with pronounced selectivities.