Symmetrical and Unsymmetrical Coupling of Alkyl Halides Mediated by Grignard Reaction

A simple method for extending the carbon chain via the coupling of alkyl or aryl halides has been developed. The versatility of this reaction has been demonstrated by symmetrical and unsymmetrical coupling of alkyl, alkenyl or alkynyl halides.     

Cross‐Electrophile Coupling of Vinyl Halides with Alkyl Halides

An improved method for the reductive coupling of aryl and vinyl bromides with alkyl halides that gave high yields for a variety of substrates at room temperature with a low (2.5 to 0.5 mol %) catalyst loading is presented. Under the optimized conditions, difficult substrates, such as unhindered alkenyl bromides, can be coupled to give the desired olefins with minimal diene formation and good stereoretention. These improved conditions also worked well for aryl bromides. For example, a gram‐scale reaction was demonstrated with 0.5 mol % catalyst loading, whereas reactions at 10 mol % catalyst loading completed in as little as 20 minutes. Finally, a low‐cost single‐component pre‐catalyst, (bpy)NiI₂ (bpy=2,2′‐bipyridine) that is both air‐ and moisture‐stable over a period of months was introduced.     

Carbonylation of Tertiary Alkyl Halides Synthesis of Pivaloyl Halides

The carbonylation of tert-butyl halides in a two-phase system, RSO₃H/CCl₄, under carbon monoxide pressure affords the corresponding pivaloyl halides in good yields and selectivities.     

Manganese-Catalyzed Redox-Neutral Thiolation of Alkyl Halides with Thioformates

Transition metal-catalyzed C−S cross-coupling has emerged as an important strategy to furnish thioethers; however, the dominant utilization of noble metal catalysts as well as the construction of challenging C(sp³)−S bonds by transition metal-catalysis remain highly problematic. Earth-abundant manganese has gathered increasing interest as an attractive catalyst for new reaction development; nevertheless, C(sp³)−S cross-coupling reaction by manganese catalysis has not been reported. Herein, we disclose a highly efficient manganese-catalyzed redox-neutral thiolation of a broad range of alkyl halides with thioformates as practical sulfuration agents. Strategically, employing easily synthesized thioformates as thiyl radical precursors allows access to various aryl and alkyl thioethers in good to excellent yields. Notably, this redox-neutral method avoids the utilization of strong bases, external ligands, forcing reaction conditions, and stoichiometric manganese, thus presenting apparent advantages, such as broad substrate scope, excellent functional group compatibility, and mild reaction conditions. Finally, the utilities of this method are also illustrated by downstream transformations and late-stage thiolation of structurally complex natural products and pharmaceuticals.     

Perfluorooctanesulfonic Acid Catalyzed Friedel-Crafts Alkylation with Alkyl Halides

A New procedure to prepare superacid perfluorooctanesulfonic acid (POSA) is reported. POSA catalyzed Friedel-Crafts alkylation of aromatic compounds with alkyl halides in liquid-phase reactions. Alkylation gave higher total yields than the corresponding reactions with Nafion-H, without the need of any complex decomposition or work-up. The reactions do not need to be carried out under absolutely anhydrous condition. The catalyst POSA can be easily separated from the reaction mixture and reused or recovered. The reactivity of the alkylation reagents and the mechanism of the reaction are discussed.     

氢氧化铯促进下硒、端炔及卤代烃反应合成炔硒醚

DMF作溶剂, 4Å分子筛存在下, 将端炔、CsOH、硒粉在室温搅拌2 h, 然后加入溴代烃或二芳基碘盐, 在室温下搅拌20 h, 得炔硒醚, 收率约60%. 反应机理为端炔与氢氧化铯作用形成炔化铯, 然后元素硒进行C—Cs键插入形成炔硒化铯, 炔硒化铯对溴代烃或二芳基碘盐进行亲核取代得到相应的炔硒醚     

Reactions of O2 --Containing Supramolecules with Alkyl Halides

Formation of O₂ ^--containing supramolecules generated from the system 18-crown-6-KO₂ and electrochemically (tetraethylammonium superoxide) and the kinetics of the reactions of the generated O₂ ^- with alkyl halides in acetonitrile were studied conductometrically and UV-spectrophotometrically; the kinetic parameters of the processes were determined. The E2 mechanism was suggested for the reaction.     

Nickel-Catalyzed Electrochemical Reductive Relay Cross-Coupling of Alkyl Halides to Aryl Halides

A highly regioselective Ni-catalyzed electrochemical reductive relay cross-coupling between an aryl halide and an alkyl halide has been developed in an undivided cell. Various functional groups are tolerated under these mild reaction conditions, which provides an alternative approach for the synthesis of 1,1-diarylalkanes.     

Cobalt-Catalyzed Asymmetric Remote Borylation of Alkyl Halides

Enantioselective functionalization of racemic alkyl halides is an efficient strategy to assemble complex chiral molecules, but remains one of the biggest challenges in organic chemistry. The distant and selective activation of unreactive C−H bonds in alkyl halides has received growing interest as it enables rapid generation of molecular complexity from simple building blocks. Here, we reported a cobalt-catalyzed remote borylation of alkyl (pseudo)halides (alkyl−X, X=I, Br, Cl, OTs) with pinacolborane (HBpin) and presented a robust approach for the generation of valuable chiral secondary organoboronates from racemic alkyl halides. This migration borylation reaction is compatible with primary, secondary, and tertiary bromides, offering direct access to a broad range of alkylboronates. The extension of this catalytic system to the borylation of aryl halides was also demonstrated. Preliminary mechanistic studies revealed that this remote borylation involved a radical reaction pathway.     

Nickel-Catalyzed Direct Electrochemical Cross-Coupling between Aryl Halides and Activated Alkyl Halides

The electrochemical reduction of a mixture of aryl halides and activated alkyl halides in DMF in the presence of catalytic amount of NiBr(2)bipy leads to cross-coupling products in good to high yields. The method applies to the synthesis of alpha-aryl ketones, alpha-aryl esters, and allylated compounds from readily available organic halides. Optimization of the process has been obtained by slowly adding the most reactive organic halide (usually the activated alkyl halide) during the electrolysis which is best conducted at 70 degrees C when aryl bromides are involved.     

Reductions of Alkyl and Aryl Halides with Magnesium and Methanol

The combination of magnesium in methanol provides a convenient, efficient system for the selective hydrogenolysis of alkyl and aryl iodides and bromides. Vinyl bromides are also reduced if conjugated to an aromatic ring while only benzylic, allylic and naphthalenic chlorides are affected. Deuterium may be selectively introduced via utilization of methanol-d as solvent.     

A Convenient Synthesis of Sulfones Using Zinc Mediated Coupling Reaction of Sulfonyl Chlorides with Alkyl Halides in Aqueous Media

An efficient procedure for the preparation of sulfones has been developed through a simple reaction of aromatic sulfonyl chlorides with suitable alkyl halides mediated by commercial zinc powder in aqueous media at 0 °C ～ room temperature.     

Low-Temperature Reaction of Aurivillius Phases with Halides

Kijima et al. [T. Kijima, S. Kimura, Y. Kawahara, K. Ohe, M. Yada, and M. Machida, J. Solid State Chem. 146, 60 (1999)] recently reported a reaction between Bi₄Ti₃O₁₂ and LiI in the presence of iodine at 350°C. Their product was never obtained free of Bi₄Ti₃O₁₂, but their claim was that their product was Bi₄Ti₃O₁₂ intercalated with I and Li. We have repeated this reaction and found conditions under which the reaction goes to completion, i.e., Bi₄Ti₃O₁₂ is completely consumed. The dominant crystalline product is apparently identical to the product reported by Kijima et al. However, we conclude that no intercalation of Bi₄Ti₃O₁₂ has occurred. This dominant crystalline phase is in fact BiOI. The remainder of the product is poorly crystalline. Analogous reactions occur at low temperature using other halides such as NaCl and other Aurivillius phases such as Bi₂WO₆.     

A Stereoselective Route to (E)-Vinylic Selenides through the Palladium-Catalyzed Cross-Coupling Reaction of Selenovinylicdialkylboranes with Alkyl Halides

The reaction of selenoviylicdialkyboranes with alkyl halides takes place readily in the presence of Pd(PPh₃)₄ and sodium methoxide to afford (E)-vinylic selenides in excellent yields