635305-48-5

Usage

Uses

Used in Organic Synthesis:
2-(4-Methyl-2-thienyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 4-Methyl-2-thienylboronic acid pinacol ester, and 4-Methyl-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)thiophene are used as reagents for cross-coupling reactions, enabling the efficient formation of carbon-carbon bonds in organic synthesis.
Used in Pharmaceutical Research:
In the pharmaceutical industry, 4-Methyl-2-thienylboronic acid pinacol ester serves as an important intermediate in the synthesis of pharmaceuticals and agrochemicals, acting as a building block for more complex molecules with potential therapeutic applications.
Used in the Preparation of Biaryl Compounds:
4-Methyl-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)thiophene, as a boronic acid derivative, is utilized in the preparation of biaryl compounds, which are key structural motifs in various biologically active molecules and pharmaceutical agents.
These three chemicals are essential tools in the field of organic chemistry, providing chemists with the means to create complex molecular structures with potential applications in various industries, including pharmaceuticals, agrochemicals, and materials science.

Upstream product

• 53119-60-1 2-bromo-4-methylthiophene 
• 61676-62-8 2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane 
• 76-09-5 2,3-dimethyl-2,3-butane diol 
• 162607-15-0 (4-methyl-2-thienyl)boronic acid 
• 616-44-4 3-Methylthiophene 
• 22092-92-8 diisopropopylaminoborane 
• 73183-34-3 bis(pinacol)diborane 
• 25015-63-8 4,4,5,5-tetramethyl-[1,3,2]-dioxaboralane 

Downstream Products

• 1357566-22-3 tris(4-(4-methylthiophen-2-yl)phenyl)amine 
• 1402883-53-7 2-amino-3-methyl-6-((1S,2R)-2-(4-(4-methylthiophen-2-yl)-phenyl)cyclopropyl)pyrimidin-4(3H)-one hydrochloride 
• 1332448-56-2 2,8-dimethyl-5-(3-(4-methylthiophen-2-yl)phenyl)-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole 
• 1332448-03-9 C₂₄H₂₄N₂S 

Relevant academic research and scientific papers

Remarkably Efficient Iridium Catalysts for Directed C(sp2)-H and C(sp3)-H Borylation of Diverse Classes of Substrates

Here we describe the discovery of a new class of C-H borylation catalysts and their use for regioselective C-H borylation of aromatic, heteroaromatic, and aliphatic systems. The new catalysts have Ir-C(thienyl) or Ir-C(furyl) anionic ligands instead of the diamine-type neutral chelating ligands used in the standard C-H borylation conditions. It is reported that the employment of these newly discovered catalysts show excellent reactivity and ortho-selectivity for diverse classes of aromatic substrates with high isolated yields. Moreover, the catalysts proved to be efficient for a wide number of aliphatic substrates for selective C(sp3)-H bond borylations. Heterocyclic molecules are selectively borylated using the inherently elevated reactivity of the C-H bonds. A number of late-stage C-H functionalization have been described using the same catalysts. Furthermore, we show that one of the catalysts could be used even in open air for the C(sp2)-H and C(sp3)-H borylations enabling the method more general. Preliminary mechanistic studies suggest that the active catalytic intermediate is the Ir(bis)boryl complex, and the attached ligand acts as bidentate ligand. Collectively, this study underlines the discovery of new class of C-H borylation catalysts that should find wide application in the context of C-H functionalization chemistry.

Manganese-Catalyzed C(sp2)-H Borylation of Furan and Thiophene Derivatives

Aryl boronic esters are bench-stable, platform building-blocks that can be accessed through metal-catalyzed aryl C(sp2)-H borylation reactions. C(sp2)-H bond functionalization reactions using rare- and precious-metal catalysts are well established, and while examples utilizing Earth-abundant alternatives have emerged, manganese catalysis remains lacking. The manganese-catalyzed C-H borylation of furan and thiophene derivatives is reported alongside an in situ activation method providing facile access to the active manganese hydride species. Mechanistic investigations showed that blue light irradiation directly affected catalysis by action at the metal center, that C(sp2)-H bond borylation occurs through a C-H metallation pathway, and that the reversible coordination of pinacolborane to the catalyst gave a manganese borohydride complex, which was as an off-cycle resting state.

Iron-catalysed C(sp2)-H borylation enabled by carboxylate activation

Arene C(sp2)-H bond borylation reactions provide rapid and efficient routes to synthetically versatile boronic esters. While iridium catalysts are well established for this reaction, the discovery and development of methods using Earth-abundant alternatives is limited to just a few examples. Applying an in situ catalyst activation method using air-stable and easily handed reagents, the iron-catalysed C(sp2)-H borylation reactions of furans and thiophenes under blue light irradiation have been developed. Key reaction intermediates have been prepared and characterised, and suggest two mechanistic pathways are in action involving both C-H metallation and the formation of an iron boryl species.

Iridium-Catalyzed Silylation of Five-Membered Heteroarenes: High Sterically Derived Selectivity from a Pyridyl-Imidazoline Ligand

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.

Isodesmic C-H Borylation: Perspectives and Proof of Concept of Transfer Borylation Catalysis

The potential advantages of using arylboronic esters as boron sources in C-H borylation are discussed. The concept is showcased using commercially available 2-mercaptopyridine as a metal-free catalyst for the transfer borylation of heteroarenes using arylboronates as borylation agents. The catalysis shows a unique functional group tolerance among C-H borylation reactions, tolerating notably terminal alkene and alkyne functional groups. The mechanistic investigation is also described.

Iridium/N-heterocyclic carbene-catalyzed C-H borylation of arenes by diisopropylaminoborane

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.

Iron-catalyzed C-H borylation of arenes

Well-defined iron bis(diphosphine) complexes are active catalysts for the dehydrogenative C-H borylation of aromatic and heteroaromatic derivatives with pinacolborane. The corresponding borylated compounds were isolated in moderate to good yields (25-73%) with a 5 mol% catalyst loading under UV irradiation (350 nm) at room temperature. Stoichiometric reactivity studies and isolation of an original trans-hydrido(boryl)iron complex, Fe(H)(Bpin)(dmpe)2, allowed us to propose a mechanism showing the role of some key catalytic species.

C-H bond activation/borylation of furans and thiophenes catalyzed by a half-sandwich iron N-heterocyclic carbene complex

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.

Iridium-catalyzed borylation of thiophenes: versatile, synthetic elaboration founded on selective C-H functionalization

Iridium-catalyzed borylation has been applied to various substituted thiophenes to synthesize poly-functionalized thiophenes in good to excellent yields. Apart from common functionalities compatible with iridium-catalyzed borylations, additional functional group tolerance to acyl (COMe) and trimethylsilyl (TMS) groups was also observed. High regioselectivities were observed in borylation of 3- and 2,5-di-substituted thiophenes. Electrophilic aromatic C-H/C-Si bromination on thiophene boronate esters is shown to take place without breaking the C-B bond, and one-pot C-H borylation/Suzuki-Miyaura cross-coupling has been accomplished on 2- and 3-borylated thiophenes.

Solution-phase microwave-assisted synthesis of unsubstituted and modified α-quinque- and sexithiophenes

The facile synthesis of poorly soluble unsubstituted and modified α-quinque- and sexithiophenes under microwave irradiation in the liquid phase is described. The use of microwave irradiation allowed these compounds to be prepared in a few minutes and at high yields by means of the Suzuki cross-coupling reaction. Unsubstituted sexithiophene was obtained in 10 min via the one-pot borylation/Suzuki reaction, purified according to a very simple procedure, and isolated in 84% yield. The efficient synthesis of two new methylated quinque- and sexithiophenes displaying liquid crystalline properties is reported. A new microwave-assisted methodology for the conversion of aldehyde-terminated quinque- and sexithiophenes into the corresponding cyano derivatives is also described. The use of microwaves was extended to the Sonogashira coupling reaction and found to be very effective in the preparation of a quinquethiophene containing acetylenic spacers. The electronic and optical characterization of this compound is reported and discussed in relation to that of unsubstituted quinquethiophene.