Copper‐Catalyzed Intermolecular Carboetherification of Unactivated Alkenes by Alkyl Nitriles and Alcohols

A three‐component carboetherification of unactivated alkenes has been developed allowing the rapid building of complexity from simple starting materials. A wide range of α‐substituted styrenes underwent smooth reactions with unactivated alkyl nitriles and alcohols to afford γ‐alkoxy alkyl nitriles with concomitant generation of a quaternary carbon center. A radical clock experiment provided clear‐cut evidence that the reaction proceeds through a tertiary alkyl radical intermediate.     

Copper‐Catalyzed Oxyboration of Unactivated Alkenes

The first regiodivergent oxyboration of unactivated terminal alkenes is reported, using copper alkoxide as a catalyst, bis(pinacolato)diboron [(Bpin)₂] as a boron source, and (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) as an oxygen source. The reaction is compatible with various functional groups. Two regioisomers are selectively produced by selecting the appropriate ligands on copper. The products may be used as a linchpin precursor for various other functionalizations, and net processes such as carbooxygenation, aminooxygenation, and dioxygenation of alkenes can be achieved after C?B bond transformations. Mechanistic studies indicate that the reaction involves the following steps: 1) Transmetalation between CuOtBu and (Bpin)₂ to generate a borylcopper species; 2) regiodivergent borylcupration of alkenes; 3) oxidation of the thus‐generated C?Cu bond to give an alkyl radical; 4) trapping of the resulting alkyl radical by TEMPO.     

Highly Enantioselective Copper‐Catalyzed Ring Opening of Oxabicyclic Alkenes with Grignard Reagents

A highly efficient copper‐catalyzed enantioselective ring opening of oxabicylic alkenes with Grignard reagents has been developed by using chiral spiro phosphine ligands. Excellent trans selectivities, good yields, and high enantioselectivities are obtained for a broad range of Grignard reagents under mild reaction conditions. The catalyst system shows an extraordinary activity and the TON of the reaction reaches 9000.     

Palladium(II)‐Catalyzed Enantioselective Azidation of Unactivated Alkenes

The first Pd‐catalyzed enantioselective azidation of unactivated alkenes has been established by using readily accessible 1‐azido‐1,2‐benziodoxol‐3(1H)‐one (ABX) as an azidating reagent, which affords a wide variety of structurally diverse 3‐N₃‐substituted piperidines in good yields with excellent enantioselectivity. The reaction features good functional‐group compatibility and mild reaction conditions. Notably, both an electrophilic azidating reagent and the sterically bulky chiral pyridinyl‐oxazoline (Pyox) ligand are crucial to the successful reaction.     

Efficient Copper‐Catalyzed Direct Intramolecular Aminotrifluoromethylation of Unactivated Alkenes with Diverse Nitrogen‐Based Nucleophiles

A mild, convenient, and step‐economical intramolecular aminotrifluoromethylation of unactivated alkenes with a variety of electronically distinct, nitrogen‐based nucleophiles in the presence of a simple copper salt catalyst, in the absence of extra ligands, is described. Many different nitrogen‐based nucleophiles (e.g., basic primary aliphatic and aromatic amines, sulfonamides, carbamates, and ureas) can be employed in this new aminotrifluoromethylation reaction. The aminotrifluoromethylation process allows straightforward access to diversely substituted CF₃‐containing pyrrolidines or indolines, in good to excellent yields, through a direct difunctionalization strategy from the respective acyclic starting materials. Mechanistic studies were conducted and a plausible mechanism was proposed.     

Synthesis of Spirocyclic Ethers by Enantioselective Copper‐Catalyzed Carboetherification of Alkenols

Spirocyclic ethers can be found in bioactive compounds. This copper‐catalyzed enantioselective alkene carboetherification provides 5,5‐, 5,6‐ and 6,6‐spirocyclic products containing fully substituted chiral carbon centers with up to 99 % enantiomeric excess. This reaction features the formation of two rings from acyclic substrates, 1,1‐disubstituted alkenols functionalized with either arenes, alkenes, or alkynes, and clearly constitutes a powerful way to synthesize chiral spirocyclic ethers.     

Nickel‐Catalyzed Asymmetric Reductive 1,2‐Carboamination of Unactivated Alkenes

Starting from diverse alkene‐tethered aryl iodides and O‐benzoyl‐hydroxylamines, the enantioselective reductive cross‐electrophilic 1,2‐carboamination of unactivated alkenes was achieved using a chiral pyrox/nickel complex as the catalyst. This mild, modular, and practical protocol provides rapid access to a variety of β‐chiral amines with an enantioenriched aryl‐substituted quaternary carbon center in good yields and with excellent enantioselectivities. This process reveals a complementary regioselectivity when compared to Pd and Cu catalysis.     

Enantioselective Synthesis of Allylboronates and Allylic Alcohols by Copper‐Catalyzed 1,6‐Boration

Chiral secondary allylboronates are obtained in high enantioselectivities and 1,6:1,4 ratios by the copper‐catalyzed 1,6‐boration of electron‐deficient dienes with bis(pinacolato)diboron (B₂(pin)₂). The reactions proceed efficiently using catalyst loadings as low as 0.0049 mol %. The allylboronates may be oxidized to the allylic alcohols, and can be used in stereoselective aldehyde allylborations. This process was applied to a concise synthesis of atorvastatin, in which the key 1,6‐boration was performed using only a 0.02 mol % catalyst loading.     

Copper‐Catalyzed Carbotrifluoromethylation of Unactivated Alkenes Driven by Trifluoromethylation of Alkyl Radicals

We report herein an unprecedented protocol for radical carbotrifluoromethylation of unactivated alkenes. With Cu(OTf)₂ as the catalyst, the reaction of unactivated alkenes, TMSCF₃ and activated alkyl chlorides at room temperature provides the corresponding carbotrifluoromethylation products in satisfactory yields. Directed by trifluoromethylation of alkyl radicals, the method exhibits an excellent regioselectivity that is opposite to those driven by CF₃ radical addition.     

Manganese‐Catalyzed Hydroarylation of Unactivated Alkenes

Transition‐metal‐catalyzed hydroarylation of unactivated alkenes with strategic use of remote coordinating functional groups has received significant attention recently to address the issues of both low reactivity and poor selectivity. The bidentate 8‐aminoquinoline amide group is the most successfully adopted in unactivated alkenes for Pd and Ni catalysis. We describe the first manganese‐catalyzed hydroarylation of unactivated alkenes bearing diverse simple functionalities with arylboronic acids. A series of δ‐ and γ‐arylated amides, ketones, pyridines, and amines was accessed with excellent regioselectivity and in high yields. Hydroalkenylation of unactivated alkenes was also shown to be applicable under this manganese‐catalysis regime. The method features earth‐abundant manganese catalysis, easily available substrates, broad functional‐group tolerance, and excellent regioselective control.     

Catalytic Enantioselective Functionalization of Unactivated Terminal Alkenes

Terminal alkenes are readily available functional groups which appear in α‐olefins produced by the chemical industry, and they appear in the products of many contemporary synthetic reactions. While the organic transformations that apply to alkenes are amongst the most studied reactions in all of chemical synthesis, the number of reactions that apply to nonactivated terminal alkenes in a catalytic enantioselective fashion is small in number. This Minireview highlights the cases where stereocontrol in catalytic reactions of 1‐alkenes is high enough to be useful for asymmetric synthesis.     

Construction of Quaternary Stereogenic Carbon Centers through Copper‐Catalyzed Enantioselective Allylic Alkylation of Azoles

Copper‐catalyzed enantioselective allylic alkylation of azoles with γ,γ‐disubstituted primary allylic phosphates was achieved using a new chiral N‐heterocyclic carbene ligand bearing a naphtholic hydroxy group. This reaction occurred with excellent branch regioselectivity and high enantioselectivity, thus forming a controlled all‐carbon quaternary stereogenic center at the position α to the heteroaromatic ring.     

Enantioselective Formation of Cyano‐Bearing All‐Carbon Quaternary Stereocenters: Desymmetrization by Copper‐Catalyzed N‐Arylation

The enantioselective construction of all‐carbon quaternary stereocenters is one of the most challenging fields in asymmetric synthesis. An asymmetric desymmetrization strategy offers an indirect and efficient method for the formation of all‐carbon stereocenters. An enantioselective formation of cyano‐bearing all‐carbon quaternary stereocenters in 1,2,3,4,‐tetrahydroquinolines and 2,3,4,5‐tetrahydro‐1H‐benzo[b]azepines by copper‐catalyzed desymmetric N‐arylation is demonstrated. The cyano group at the prochiral center plays a key role for the high enantioselectivity and works as an important functional group for further transformations. DFT studies provide a model which successfully accounts for the origin of enantioselectivity.     

Copper‐Catalyzed Regio‐ and Enantioselective Addition of Silicon Grignard Reagents to Alkenes Activated by Azaaryl Groups

A new application of silicon Grignard reagents in C(sp³)?Si bond formation is reported. With the aid of BF₃?OEt₂, these silicon nucleophiles add across alkenes activated by various azaaryl groups under copper catalysis. An enantioselective version employing benzoxazole‐activated alkenes as substrates and a CuI‐josiphos complex as catalyst has been developed, forming the C(sp3)?Si bond with good to high enantiomeric ratios (up to 97:3). The method expands the toolbox for “conjugate addition” type C(sp³)?Si bond formation.