2132-84-5Relevant academic research and scientific papers
Transition Metal-Free sp3?sp3 Carbon-Carbon Coupling between Benzylboronic Esters and Alkyl Bromides
Barker, Timothy J.,Russell, Richard W.
, p. 2782 - 2784 (2021/06/25)
A transition metal-free coupling reaction of benzylboronic esters and alkyl halides has been developed. Both alkyl bromides and alkyl iodides were found to be competent substrates with the nucleophilic boronate intermediate generated from the combination of benzylboronic ester and an alkyllithium. Good chemoselectivity was observed for the reaction with the alkyl bromide in substrates with a second electrophile present. Both secondary and tertiary benzylboronic esters were effective nucleophiles in the reaction with primary alkyl halides. Mechanistic observations are consistent with a radical mechanism.
Reductive activation and hydrofunctionalization of olefins by multiphoton tandem photoredox catalysis
Czyz, Milena L.,Taylor, Mitchell S.,Horngren, Tyra H.,Polyzos, Anastasios
, p. 5472 - 5480 (2021/06/01)
The conversion of olefin feedstocks to architecturally complex alkanes represents an important strategy in the expedient generation of valuable molecules for the chemical and life sciences. Synthetic approaches are reliant on the electrophilic activation of unactivated olefins, necessitating functionalization with nucleophiles. However, the reductive functionalization of unactivated and less activated olefins with electrophiles remains an ongoing challenge in synthetic chemistry. Here, we report the nucleophilic activation of inert styrenes through a photoinduced direct single electron reduction to the corresponding nucleophilic radical anion. Central to this approach is the multiphoton tandem photoredox cycle of the iridium photocatalyst [Ir(ppy)2(dtbbpy)] PF6, which triggers in situ formation of a high-energy photoreductant that selectively reduces styrene olefinic π bonds to radical anions without stoichiometric reductants or dissolving metals. This mild strategy enables the chemoselective reduction and hydrofunctionalization of styrenes to furnish valuable alkane and tertiary alcohol derivatives. Mechanistic studies support the formation of a styrene olefinic radical anion intermediate and a Birch-type reduction involving two sequential single electron transfers. Overall, this complementary mode of olefin activation achieves the hydrofunctionalization of less activated alkenes with electrophiles, adding value to abundant olefins as valuable building blocks in modern synthetic protocols.
Copper-catalyzed alkyl-alkyl cross-coupling reactions using hydrocarbon additives: Efficiency of catalyst and roles of additives
Iwasaki, Takanori,Imanishi, Reiko,Shimizu, Ryohei,Kuniyasu, Hitoshi,Terao, Jun,Kambe, Nobuaki
, p. 8522 - 8532 (2015/01/08)
Cross-coupling of alkyl halides with alkyl Grignard reagents proceeds with extremely high TONs of up to 1230000 using a Cu/unsaturated hydrocarbon catalytic system. Alkyl fluorides, chlorides, bromides, and tosylates are all suitable electrophiles, and a TOF as high as 31200 h-1 was attained using an alkyl iodide. Side reactions of this catalytic system, i.e., reduction, dehydrohalogenation (elimination), and the homocoupling of alkyl halides, occur in the absence of additives. It appears that the reaction involves the β-hydrogen elimination of alkylcopper intermediates, giving rise to olefins and Cu-H species, and that this process triggers both side reactions and the degradation of the Cu catalyst. The formed Cu-H promotes the reduction of alkyl halides to give alkanes and Cu-X or the generation of Cu(0), probably by disproportionation, which can oxidatively add to alkyl halides to yield olefins and, in some cases, homocoupling products. Unsaturated hydrocarbon additives such as 1,3-butadiene and phenylpropyne play important roles in achieving highly efficient cross-coupling by suppressing β-hydrogen elimination, which inhibits both the degradation of the Cu catalyst and undesirable side reactions.
Replacing conventional carbon nucleophiles with electrophiles: Nickel-catalyzed reductive alkylation of aryl bromides and chlorides
Everson, Daniel A.,Jones, Brittany A.,Weix, Daniel J.
supporting information; experimental part, p. 6146 - 6159 (2012/05/07)
A general method is presented for the synthesis of alkylated arenes by the chemoselective combination of two electrophilic carbons. Under the optimized conditions, a variety of aryl and vinyl bromides are reductively coupled with alkyl bromides in high yields. Under similar conditions, activated aryl chlorides can also be coupled with bromoalkanes. The protocols are highly functional-group tolerant (-OH, -NHTs, -OAc, -OTs, -OTf, -COMe, -NHBoc, -NHCbz, -CN, -SO2Me), and the reactions are assembled on the benchtop with no special precautions to exclude air or moisture. The reaction displays different chemoselectivity than conventional cross-coupling reactions, such as the Suzuki-Miyaura, Stille, and Hiyama-Denmark reactions. Substrates bearing both an electrophilic and nucleophilic carbon result in selective coupling at the electrophilic carbon (R-X) and no reaction at the nucleophilic carbon (R-[M]) for organoboron (-Bpin), organotin (-SnMe3), and organosilicon (-SiMe2OH) containing organic halides (X-R-[M]). A Hammett study showed a linear correlation of σ and σ(-) parameters with the relative rate of reaction of substituted aryl bromides with bromoalkanes. The small ρ values for these correlations (1.2-1.7) indicate that oxidative addition of the bromoarene is not the turnover-frequency determining step. The rate of reaction has a positive dependence on the concentration of alkyl bromide and catalyst, no dependence upon the amount of zinc (reducing agent), and an inverse dependence upon aryl halide concentration. These results and studies with an organic reductant (TDAE) argue against the intermediacy of organozinc reagents.
Nickel-catalyzed reductive cross-coupling of aryl halides with alkyl halides
Everson, Daniel A.,Shrestha, Ruja,Weix, Daniel J.
supporting information; experimental part, p. 920 - 921 (2010/03/31)
(Chemical Equation Presented) The direct reductive cross-coupling of alkyl halides with aryl halides is described. The transformation is efficient (equimolar amounts of the starting materials are used), generally high-yielding (all but one between 55 and 88% yield), highly functional-group-tolerant [OH, NHBoc, NHCbz, Bpin, C(O)Me, CO2Et, and CN are all tolerated], and easy to perform (uses only benchtop-stable reagents, tolerates small amounts of water and oxygen, changes color when complete, and uses filtration workup). The reaction appears to avoid the formation of intermediate organomanganese species, and a synergistic effect was found when a mixture of two ligands was employed.
Equilibria of isomeric transformations and relations between thermodynamic properties of secondary alkylbenzenes
Pimerzin, A. A.,Nesterova, T. N.,Rozhnov, A. M.
, p. 641 - 648 (2007/10/02)
Equilibria of mutual transformations of monoamylbenzenes and diamylbenzenes (AmB), monohexylbenzenes (HxB), monoheptylbenzenes (HpB), and monodecylbenzenes (DB) have been studied in the liquid state over the range 273 to 423 K in the presence of 3 to 9 mass per cent of AlCl3.Values of ΔfH0m and ΔfS0m for the reactions studied have been calculated from the temperature dependences of the equilibrium constants.Below are given the reactions and the corresponding values for ΔfH0m/(kJ.mol-1) and ΔfS0m/(J.K-1.mol-1): 3-AmB=2-AmB, -(0.16 +/- 0.08), (8.45 +/- 0.23); 3-HxB=2-HxB, -(0.30 +/- 0.07), (3.85 +/- 0.21); 3-HpB=2-HpB, -(0.21 +/- 0.07), (3.52 +/- 0.22); 3-DB=2-DB, -(0.23 +/- 0.14), (3.51 +/- 0.43); 4-HpB=3-HpB, (0.02 +/- 0.41), (7.57 +/- 1.29); 4-DB=3-DB, (0.09 +/- 0.41), (1.69 +/- 1.28); 5-DB=4-DB, -(0.01 +/- 0.09), (0.18 +/- 0.25).For para-to-meta transformations of diamylbenzenes the average molar reaction enthalpy is -(0.26 +/- 0.46)kJ.mol-1 and the intrinsic change of molar entropy is -(0.99 +/- 1.2)J.K-1.mol-1.It is shown that for the calculation of enthalpies of formation of secondary alkylbenzenes correlations can be used which do not take into account the position of the phenyl substituent on the aliphatic hydrocarbon chain.The calculation of enthalpies of formation of normal and secondary alkylbenzenes in the liquid state at 298.15 K is made on the basis of experimental and literature values.
Nuclear Heptylation of Benzene and Naphthalene and Cyclopentylation of Toluene
Badr, M. Z. A.,El-Naggar, G. M.,Aly, M. M.,Fahmy, A. M.
, p. 961 - 964 (2007/10/02)
Thermal decomposition of 1-, 2-, 3- and 4-heptyltoluene-p-sulphonates in the presence of aromatic substrates like benzene or naphthalene at 130-35 deg, affords differently substituted α- and β-isomers in the case of naphthalene.Skeletal isomerisation of the alkyl group is observed where different isomeric 1-, 2-, 3- and 4-heptyl-aromatics are obtained.Also thermal decomposition of cyclopentylmethane sulphonate in the presence of toluene at 130-35 deg, furnishes the corresponding o-, m- and p-substituted toluenes.The isomers have been identified and estimated quantitatively by GLC.
