Primary Alkyl Bromides Research Articles

Barbier-Negishi Coupling of Secondary Alkyl Bromides with Aryl and Alkenyl Triflates and Nonaflates.

A mild and practical Barbier-Negishi coupling of secondary alkyl bromides with aryl and alkenyl triflates and nonaflates has been developed. This challenging reaction was enabled by the use of a very bulky imidazole-based phosphine ligand, which resulted in good yields as well as good chemo- and site selectivities for a broad range of substrates at room temperature and under non-aqueous conditions. This reaction was extended to primary alkyl bromides by using an analogous pyrazole-based ligand.

Barbier–Negishi Coupling of Secondary Alkyl Bromides with Aryl and Alkenyl Triflates and Nonaflates

AbstractA mild and practical Barbier–Negishi coupling of secondary alkyl bromides with aryl and alkenyl triflates and nonaflates has been developed. This challenging reaction was enabled by the use of a very bulky imidazole‐based phosphine ligand, which resulted in good yields as well as good chemo‐ and site selectivities for a broad range of substrates at room temperature and under non‐aqueous conditions. This reaction was extended to primary alkyl bromides by using an analogous pyrazole‐based ligand.

Remote alkylation of N-(quinolin-8-yl)benzamides with alkyl bromides via ruthenium(ii)-catalyzed C-H bond activation.

A ruthenium(ii) catalyzed remote C-5 alkylation of the quinoline ring of N-(quinolin-8-yl)benzamides with alkyl bromides via C-H bond activation is described. Various substituted N-(quinolin-8-yl)benzamides reacted with tertiary or secondary or primary alkyl bromides giving the alkylated products in good to moderate yields. Herein, the ruthenium catalyzed remote C-5 alkylation is effected via aromatic C-H bond activation as a key step. It has been proved by the deuterium labelling studies and mechanistic investigations.

Irradiation-Induced Heck Reaction of Unactivated Alkyl Halides at Room Temperature.

The palladium-catalyzed Mizoroki-Heck reaction is arguably one of the most significant carbon-carbon bond-construction reactions to be discovered in the last 50 years, with a tremendous number of applications in the production of chemicals. This Nobel-Prize-winning transformation has yet to overcome the obstacle of its general application in a range of alkyl electrophiles, especially tertiary alkyl halides that possess eliminable β-hydrogen atoms. Whereas most palladium-catalyzed cross-coupling reactions utilize the ground-state reactivity of palladium complexes under thermal conditions and generally apply a single ligand system, we report that the palladium-catalyzed Heck reaction proceeds smoothly at room temperature with a variety of tertiary, secondary, and primary alkyl bromides upon irradiation with blue light-emitting diodes in the presence of a dual phosphine ligand system. We rationalize that this unprecedented transformation is achieved by utilizing the photoexcited-state reactivity of the palladium complex to enhance oxidative addition and suppress undesired β-hydride elimination.

Visible-Light-Driven Palladium-Catalyzed Radical Alkylation of C-H Bonds with Unactivated Alkyl Bromides.

Reported herein is a novel visible-light photoredox system with Pd(PPh3 )4 as the sole catalyst for the realization of the first direct cross-coupling of C(sp3 )-H bonds in N-aryl tetrahydroisoquinolines with unactivated alkyl bromides. Moreover, intra- and intermolecular alkylations of heteroarenes were also developed under mild reaction conditions. A variety of tertiary, secondary, and primary alkyl bromides undergo reaction to generate C(sp3 )-C(sp3 ) and C(sp2 )-C(sp3 ) bonds in moderate to excellent yields. These redox-neutral reactions feature broad substrate scope (>60 examples), good functional-group tolerance, and facile generation of quaternary centers. Mechanistic studies indicate that the simple palladium complex acts as the visible-light photocatalyst and radicals are involved in the process.

Visible‐Light‐Driven Palladium‐Catalyzed Radical Alkylation of C−H Bonds with Unactivated Alkyl Bromides

AbstractReported herein is a novel visible‐light photoredox system with Pd(PPh3)4 as the sole catalyst for the realization of the first direct cross‐coupling of C(sp3)−H bonds in N‐aryl tetrahydroisoquinolines with unactivated alkyl bromides. Moreover, intra‐ and intermolecular alkylations of heteroarenes were also developed under mild reaction conditions. A variety of tertiary, secondary, and primary alkyl bromides undergo reaction to generate C(sp3)−C(sp3) and C(sp2)−C(sp3) bonds in moderate to excellent yields. These redox‐neutral reactions feature broad substrate scope (>60 examples), good functional‐group tolerance, and facile generation of quaternary centers. Mechanistic studies indicate that the simple palladium complex acts as the visible‐light photocatalyst and radicals are involved in the process.

Sulfonamidation of halogen-substituted electrophiles with N-(2,2,2-trichloroethyl)arenesulfonamides

Reactions of N-(2,2,2-trichloroethyl)arenesulfonamides with primary alkyl bromides and iodides, allyl bromide, chloroacetonitrile, and benzyl chloride in acetonitrile on heating in the presence of potassium carbonate gave the corresponding N-alkyl-N-(2,2,2-trichloroethyl)arenesulfonamides.

Iron-Catalyzed Heck-Type Alkenylation of Functionalized Alkyl Bromides

The ability of iron to controllably generate alkyl radicals from alkyl halides as a key step in atom transfer radical polymerization (ATRP) has been adapted to facilitate a formal Heck cross-coupling between styrenes and functionalized alkyl bromides. A simple FeCl2 catalyst in a coordinating solvent gave excellent activity without the need for expensive ligands. Tertiary, secondary, and even primary alkyl bromides are tolerated to give the products in moderate to good yields (up to 94% yield). The easily accessible reagents and operational simplicity make this reaction a method of choice for the alkenylation of alkyl halides, especially for functionalized tertiary alkyl halides, which are difficult to target by classic palladium-catalyzed Heck reactions because of the competing β-hydride elimination.

Nickel-Catalyzed Reductive Conjugate Addition of Primary Alkyl Bromides to Enones To Form Silyl Enol Ethers.

Conjugate addition of organometallic reagents to enones to form silyl enol ether products is a versatile method to difunctionalize activated olefins, but the organometallic reagents required can be limiting. The reductive cross-electrophile coupling of unhindered primary alkyl bromides with enones and chlorosilanes to form silyl enol ether products is catalyzed by a nickel-complexed ortho-brominated terpyridine ligand. The conditions are compatible with a variety of cyclic/acyclic enones and functional groups.

Ionic iron(III) complexes bearing a dialkylbenzimidazolium cation: Efficient catalysts for magnesium‐mediated cross‐couplings of aryl phosphates with alkyl bromides

A series of ionic iron(III) complexes of general formula [HLn][FeX4] (HL1 = 1,3‐dibenzylbenzimidazolium cation, X = Cl, 1; HL1, X = Br, 2; HL2 = 1,3‐dibutylbenzimidazolium cation, X = Br, 3; HL3 = 1,3‐bis(diphenylmethyl)benzimidazolium cation, X = Br, 4) were easily prepared in high yields by the direct reaction of FeX3 with 1 equiv. of [HLn]X under mild conditions. All of them were characterized using elemental analysis, Raman spectroscopy and electrospray ionization mass spectrometry, and X‐ray crystallography for 1 and 4. In the presence of magnesium turnings and LiCl, these air‐ and moisture‐insensitive complexes showed high catalytic activities in direct cross‐couplings of aryl phosphates with primary and secondary alkyl bromides with broad substrate scope, wherein complex 4 was the most effective.

ChemInform Abstract: Nickel‐Catalyzed Reductive Amidation of Unactivated Alkyl Bromides.

AbstractA user‐friendly, Ni‐catalyzed reductive amidation of unactivated primary, secondary, and tertiary alkyl bromides with isocyanates is described.

Intermolecular Photocatalyzed Heck‐like Coupling of Unactivated Alkyl Bromides by a Dinuclear Gold Complex

A practical protocol for a photocatalyzed alkyl-Heck-like reaction of unactivated alkyl bromides and different alkenes promoted by dinuclear gold photoredox catalysis in the presence of an inorganic base is reported. Primary, secondary, and tertiary unactivated alkyl bromides with β-hydrogen can be applied. Esters, aldehydes, ketones, nitriles, alcohols, heterocycles, alkynes, alkenes, ethers, and halogen moieties are all well tolerated. In addition to 1,1-diarylalkenes, silylenolethers and enamides can also be applied, which further increases the synthetic potential of the reaction. The mild reaction conditions, broad substrate scope, and an excellent functional-group tolerance deliver an ideal tool for synthetic chemists that can even be used for challenging late-stage modifications of complex natural products.

Photoinduced Charge-Transfer State of 4-Carbazolyl-3-(trifluoromethyl)benzoic Acid: Photophysical Property and Application to Reduction of Carbon-Halogen Bonds as a Sensitizer.

The photoinduced persistent intramolecular charge-transfer state of 4-carbazolyl-3-(trifluoromethyl)benzoic acid was confirmed. It showed a higher catalytic activity in terms of yield and selectivity in the photochemical reduction of alkyl halides compared to the parent carbazole. Even unactivated primary alkyl bromides could be reduced by this photocatalyst. The high catalytic activity is rationalized by considering the slower backward single-electron transfer owing to the spatial separation of the donor and acceptor subunits.

Nickel‐Catalyzed Reductive Amidation of Unactivated Alkyl Bromides

AbstractA user‐friendly, nickel‐catalyzed reductive amidation of unactivated primary, secondary, and tertiary alkyl bromides with isocyanates is described. This catalytic strategy offers an efficient synthesis of a wide range of aliphatic amides under mild conditions and with an excellent chemoselectivity profile while avoiding the use of stoichiometric and sensitive organometallic reagents.

Nickel-Catalyzed Reductive Amidation of Unactivated Alkyl Bromides.

A user-friendly, nickel-catalyzed reductive amidation of unactivated primary, secondary, and tertiary alkyl bromides with isocyanates is described. This catalytic strategy offers an efficient synthesis of a wide range of aliphatic amides under mild conditions and with an excellent chemoselectivity profile while avoiding the use of stoichiometric and sensitive organometallic reagents.

ChemInform Abstract: Copper‐Catalyzed Arylation of Alkyl Halides with Arylaluminum Reagents.

We report a Cu-catalyzed coupling between triarylaluminum reagents and alkyl halides to form arylalkanes. The reaction proceeds in the presence of N,N,N',N'-tetramethyl-o-phenylenediamine (NN-1) as a ligand in combination with CuI as a catalyst. This catalyst system enables the coupling of primary alkyl iodides and bromides with electron-neutral and electron-rich triarylaluminum reagents and affords the cross-coupled products in good to excellent yields.

Ni-catalyzed direct carboxylation of unactivated alkyl electrophiles with carbon dioxide

The Ni-catalyzed direct reductive carboxylation of unactivated primary alkyl bromides bearing β-hydrogens with carbon dioxide under atmospheric pressure is highlighted. This reaction exhibits excellent functional group compatibility and represents an attractive and operationally-simple method for the synthesis of valuable carboxylic acids from readily available alkyl bromides and carbon dioxide.

Cu(i)-catalyzed multicomponent cascade reactions of terminal alkynes, unactivated primary alkyl bromides, CO2 and NaN3

We have developed a mild, robust, and multicomponent cascade reaction for the synthesis of triazolo-fused dihydrooxazinones from terminal alkynes, unactivated primary alkyl bromides, carbon dioxide and sodium azide.

Design and Synthesis of Triblock Copolymers for Creating Complex Secondary Structures by Orthogonal Self-Assembly

We herein report the synthesis and characterization of ABC-type triblock copolymers containing two complementary association motifs and investigate their folding into well-defined polymeric nanoparticles under diluted conditions via intramolecular orthogonal hydrogen bonding. The precursor ABC-type triblock copolymers are prepared via reversible addition–fragmentation chain transfer (RAFT) polymerization bearing primary alkyl bromide on A, protected alkyne on B, and protected hydroxyl pendant groups on the C units. The dithioester groups of the RAFT polymers are quantitatively removed by radical-induced reduction before the side-chain functionalization. The complementary motifs, i.e., Hamilton wedge (HW, A block), benzene-1,3,5-tricarboxamide (BTA, B block), and cyanuric acid (CA, C block), are incorporated into the linear triblock copolymers side chains via postfunctionalization. The self-assembly processes of the HW and CA supramolecular motifs are followed by nuclear magnetic resonance (1H NMR) spectro...

Copper-catalyzed arylation of alkyl halides with arylaluminum reagents.

We report a Cu-catalyzed coupling between triarylaluminum reagents and alkyl halides to form arylalkanes. The reaction proceeds in the presence of N,N,N’,N’-tetramethyl-o-phenylenediamine (NN-1) as a ligand in combination with CuI as a catalyst. This catalyst system enables the coupling of primary alkyl iodides and bromides with electron-neutral and electron-rich triarylaluminum reagents and affords the cross-coupled products in good to excellent yields.