885692-91-1Relevant articles and documents
Iridium-Catalyzed Silylation of Five-Membered Heteroarenes: High Sterically Derived Selectivity from a Pyridyl-Imidazoline Ligand
Hartwig, John F.,Karmel, Caleb,Kharitonova, Elena V.,Rubel, Camille Z.
supporting information, p. 6074 - 6081 (2020/02/25)
The steric effects of substituents on five-membered rings are less pronounced than those on six-membered rings because of the difference in bond angles. Thus, the regioselectivities of reactions of five-membered heteroarenes that occur with selectivities dictated by steric effects, such as the borylation of C?H bonds, have been poor in many cases. We report that the silylation of five-membered-ring heteroarenes occurs with high sterically derived regioselectivity when catalyzed by the combination of [Ir(cod)(OMe)]2 (cod=1,5-cyclooctadiene) and a phenanthroline ligand or a new pyridyl-imidazoline ligand that further increases the regioselectivity. The silylation reactions with these catalysts produce high yields of heteroarylsilanes from functionalization at the most sterically accessible C?H bonds of these rings under conditions that the borylation of C?H bonds with previously reported catalysts formed mixtures of products or products that are unstable. The heteroarylsilane products undergo cross-coupling reactions and substitution reactions with ipso selectivity to generate heteroarenes that bear halogen, aryl, and perfluoroalkyl substituents.
Iridium/N-heterocyclic carbene-catalyzed C-H borylation of arenes by diisopropylaminoborane
Tobisu, Mamoru,Igarashi, Takuya,Chatani, Naoto
supporting information, p. 654 - 661 (2016/07/06)
Catalytic C-H borylation of arenes has been widely used in organic synthesis because it allows the introduction of a versatile boron functionality directly onto simple, unfunctionalized arenes. We report herein the use of diisopropylaminoborane as a boron source in C-H borylation of arenes. An iridium(I) complex with 1,3-dicyclohexylimidazol-2-ylidene is found to efficiently catalyze the borylation of arenes and heteroarenes. The resulting aminoborylated products can be converted to the corresponding boronic acid derivatives simply by treatment with suitable diols or diamines.
C-H bond activation/borylation of furans and thiophenes catalyzed by a half-sandwich iron N-heterocyclic carbene complex
Hatanaka, Tsubasa,Ohki, Yasuhiro,Tatsumi, Kazuyuki
supporting information; experimental part, p. 1657 - 1666 (2011/08/05)
A coordinatively unsaturated iron-methyl complex having an N-heterocyclic carbene ligand, [Cp*Fe-(LMe)Me] (1; Cp *=η5-C5Me5, L Me=1,3,4,5-tetramethyl-imidazol-2-ylidene), is synthesized from the reaction of [Cp*Fe(TMEDA)Cl] (TMEDA=N,N,N',N'- tetramethylethylenediamine) with methyllithium and LMe. Complex 1 is found to activate the C-H bonds of furan, thiophene, and benzene, giving rise to aryl complexes, [Cp*Fe(LMe)-(aryl)] (aryl=2-furyl (2), 2-thienyl (3), phenyl (4)). The C-H bond cleavage reactions are applied to the dehydrogenative coupling of furans or thiophenes with pinacolborane (HBpin) in the presence of tert-butylethylene and a catalytic amount of 1 (10 mol% to HBpin). The borylation of the furan/thiophene or 2-substituted furans/thiophenes occurs exclusively at the 2-or 5-positions, respectively, whereas that of 3-substituted furans/thiophenes takes place mainly at the 5-position and gives a mixture of regioisomers. Treatment of 2 with 2 equiv of HBpin results in the quantitative formation of 2-boryl-furan and the borohydride complex [Cp *Fe(LMe)(H2Bpin)] (5). Heating a solution of 5 in the presence of tert-butylethylene led to the formation of an alkyl complex [Cp*Fe-(LMe)CH2CH2tBu] (6), which was found to cleave the C-H bond of furan to produce 2. On the basis of these results, a possible catalytic cycle is proposed.
