Facile Synthesis and Palladium‐Catalyzed Cross‐Coupling Reactions of 2,3‐Bis(pinacolatoboryl)‐1,3‐butadiene

Treatment of 1,1‐bis(pinacolatoboryl)ethene with an excess of 1‐bromo‐1‐lithioethene gave 2,3‐bis(pinacolatoboryl)‐1,3‐butadiene in high yield. Palladium‐catalyzed cross‐coupling of the resulting diborylbutadiene with aryl iodides took place smoothly in the presence of a catalytic amount of Pd(OAc)₂/PPh₃ and aqueous KOH to give 2,3‐diaryl‐1,3‐butadienes in good yields. The coupling reaction with commercially available 4‐acetoxyphenylmethyl chloride under the same conditions followed by hydrolysis of the acetyl groups gave anolignan B in a one‐pot manner. A variety of [3]‐ to [6]dendralenes were synthesized by palladium‐catalyzed coupling of the diene or 1,1‐bis(pinacolato)borylethene with alkenyl or dienyl halides, respectively, in good yields.     

Copper‐Catalyzed Intermolecular Trifluoromethylazidation of Alkenes: Convenient Access to CF3‐Containing Alkyl Azides

A novel copper‐catalyzed intermolecular trifluoromethylazidation of alkenes has been developed under mild reaction conditions. A variety of CF₃‐containing organoazides were directly synthesized from a wide range of olefins, including activated and unactivated alkenes, and the resulting products can be easily transformed into the corresponding CF₃‐containing amine derivatives.     

A Cobalt‐Catalyzed Alkene Hydroboration with Pinacolborane

An extremely efficient cobalt catalyst for the hydroboration of both vinylarenes and aliphatic α‐olefins with pinacolborane is described, providing the anti‐Markovnikov products with excellent regio‐ and chemoselectivity, broad functional‐group tolerance, and high turnover numbers (up to 19 800). The alkene hydroboration route is further extended to a two‐step, one‐pot hydroboration and cross‐coupling of alkylboronates with aryl chlorides.     

Copper‐Catalyzed Cross‐Coupling of Boronic Esters with Aryl Iodides and Application to the Carboboration of Alkynes and Allenes

Copper‐catalyzed Suzuki–Miyaura‐type cross‐coupling and carboboration processes are reported. The cross‐couplings function well with a variety of substituted aryl iodides and aryl boronic esters and allows for orthogonal reactivity compared to palladium‐catalyzed processes. The carboboration method includes both alkynes and allenes and provides access to highly substituted and stereodefined vinyl boronic esters. The alkyne carboboration method is highlighted in the simple one‐pot synthesis of Tamoxifen.     

Nickel‐Catalyzed Csp2Csp3 Bond Formation by CarbonFluorine Activation

We report herein a general catalytic method for Csp²?Csp³ bond formation through C?F activation. The process uses an inexpensive nickel complex with either diorganozinc or alkylzinc halide reagents, including those with β‐hydrogen atoms. A variety of fluorine substitution patterns and functional groups can be readily incorporated. Sequential reactions involving different precatalysts and coupling partners permit the synthesis of densely functionalized fluorinated building blocks.     

Iron‐Catalyzed 1,2‐Addition of Perfluoroalkyl Iodides to Alkynes and Alkenes

Iron catalysis has been developed for the intermolecular 1,2‐addition of perfluoroalkyl iodides to alkynes and alkenes. The catalysis has a wide substrate scope and high functional‐group tolerance. A variety of perfluoroalkyl iodides including CF₃I can be employed. The resulting perfluoroalkylated alkyl and alkenyl iodides can be further functionalized by cross‐coupling reactions. This methodology provides a straightforward and streamlined access to perfluoroalkylated organic molecules.     

A mild benzannulation through directed cycloaddition reactions

Simple as ABC: Alkynyl borane cycloadditions can be substrate-directed to assemble aromatic difluoroboranes within an extremely mild and efficient reaction manifold compared to that of traditional methods (see scheme). The aromatic boranes are readily transformed into a range of useful products.     

Copper‐Catalyzed Enantioselective 1,6‐Boration of para‐Quinone Methides and Efficient Transformation of gem‐Diarylmethine Boronates to Triarylmethanes

Presented is the first enantioselective copper‐catalyzed 1,6‐conjugate addition of bis(pinacolato)diboron to para‐quinone methides. The reaction proceeds with excellent yields and good to excellent enantioselectivities, and provides an attractive approach to the construction of optically active gem‐diarylmehtine boronic esters. Additionally, the subsequent conversion of the derived potassium trifluoroborates into triarylmethanes with highly enantiospecificity was realized.     

Palladium(0)‐Catalyzed Cross‐Coupling of Potassium (Z)‐2‐Chloroalk‐1‐enyl Trifluoroborates: A Chemo‐ and Stereoselective Access to (Z)‐Chloroolefins and Trisubstituted Alkenes

Original and ambivalent : We describe the preparation of a series of new potassium trifluoroborates 1 , and the study of their behaviour in a Pd⁰‐catalyzed cross‐coupling reaction. We found that compounds 1 are endowed with original properties as they behave as nucleophilic cross‐coupling partners chemoselectively, but also as ambivalent synthons. The usefulness of this methodology has been successfully illustrated by the first total synthesis of an N‐acyl spermidine.

     

Rhodium‐Catalyzed Transnitrilation of Aryl Boronic Acids with Dimethylmalononitrile

An efficient transnitrilation of aryl boronic acids with dimethylmalononitrile (DMMN) is described. This rhodium‐catalyzed electrophilic cyanation presents a novel approach to prepare aryl nitriles by using a carbon‐bound cyanating reagent which undergoes cross‐coupling with the aryl boronic acid. The reaction expands the degree of functional‐group compatibility exhibited by the transnitrilation of aryl Grignard and aryllithium reagents. A variety of aryl boronic acid derivatives and dialkylmalononitriles were amenable to the transnitrilation.     

A Copper(I)‐Catalyzed Enantioselective γ‐Boryl Substitution of Trifluoromethyl‐Substituted Alkenes: Synthesis of Enantioenriched γ,γ‐gem‐Difluoroallylboronates

The first catalytic enantioselective γ‐boryl substitution of CF₃‐substituted alkenes is reported. A series of CF₃‐substituted alkenes was treated with a diboron reagent in the presence of a copper(I)/Josiphos catalyst to afford the corresponding optically active γ,γ‐gem‐difluoroallylboronates in high enantioselectivity. The thus obtained products could be readily converted into the corresponding difluoromethylene‐containing homoallylic alcohols using highly stereospecific allylation reactions.     

Nickel‐Catalyzed Cross‐Coupling of Functionalized Difluoromethyl Bromides and Chlorides with Aryl Boronic Acids: A General Method for Difluoroalkylated Arenes

Transition‐metal‐catalyzed difluoroalkylation of aromatics remains challenging despite the importance of difluoroalkylated arenes in medicinal chemistry. Herein, the first successful example of nickel‐catalyzed difluoroalkylation of aryl boronic acids is described. The reaction allows access to a variety of functionalized difluoromethyl bromides and chlorides, and paves the way to highly cost‐efficient synthesis of a wide range of difluoroalkylated arenes. The notable features of this protocol are its high generality, excellent functional‐group compatibility, low‐cost nickel‐catalyst, and practicality for gram‐scale production, thus providing a facile method for applications in drug discovery and development.     

Amidyl Radicals by Oxidation of α‐Amido‐oxy Acids: Transition‐Metal‐Free Amidofluorination of Unactivated Alkenes

A three‐component transition‐metal‐free amidofluorination of unactivated alkenes and styrenes is presented. α‐Amido‐oxy acids are introduced as efficient and easily accessible amidyl radical precursors that are oxidized by a photoexcited organic sensitizer (Mes‐Acr‐Me) to the corresponding carboxyl radical. Sequential CO₂ and aldehyde/ketone fragmentation leads to an N‐centered radical that adds to an alkene. Commercial Selectfluor is used to trap the adduct radical through fluorine‐atom transfer. The transformation features by high functional‐group tolerance, broad substrate scope, and practical mild conditions. Mechanistic studies support the radical nature of the cascade.     

Pd‐Catalyzed Difluoromethylation of Vinyl Bromides,Triflates, Tosylates,and Nonaflates

Pd‐catalyzed difluoromethylation of di‐, tri‐ or tetra‐substituted vinyl bromides, triflates, tosylates and nonaflates under mild conditions is described. The reaction tolerates a wide range of functional groups, such as bromide, chloride, fluoride, ester, amine, nitrile, and protected carbonyl, thus providing a general route for the preparation of difluoromethylated alkenes.     

Enantioselective Palladium‐Catalyzed Oxidative β,β‐Fluoroarylation of α,β‐Unsaturated Carbonyl Derivatives

The site‐selective palladium‐catalyzed three‐component coupling of deactivated alkenes, arylboronic acids, and N‐fluorobenzenesulfonimide is disclosed herein. The developed methodology establishes a general, modular, and step‐economical approach to the stereoselective β‐fluorination of α,β‐unsaturated systems.     

Stereospecific Couplings of Secondary and Tertiary Boronic Esters

This Minireview highlights advances in the Suzuki–Miyaura cross‐coupling of secondary boron reagents for the creation of C? C bonds with control of stereochemistry. It also includes non‐transition‐metal coupling of secondary and tertiary boronic esters to electron‐rich aromatics.