A mesoporous silica (SBA‐15)‐supported pyrimidine‐substituted N‐heterocyclic carbene iridium complex was prepared and used as a catalyst for both environmentally friendly N‐alkylation of amines and ...β‐alkylation of secondary alcohols with primary alcohols. The structure of the supported iridium catalyst was characterized by Fourier transform infrared (FT‐IR), 13C and 29Si solid‐state nuclear magnetic resonance (NMR), small‐angle X‐ray scattering (SAXS), transmission electron microscopy (TEM), iridium K‐edge X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS) spectroscopic analyses which demonstrated that the coordination environment of the iridium centre and the 3‐dimensional‐hexagonal pore structure of SBA‐15 were retained after the immobilization. The catalyst was found to be highly efficient for both kinds of reaction on a wide range of substrates under mild conditions. Moreover, the supported iridium catalyst was obviously superior to the unsupported one in the N‐alkylation of aniline and β‐alkylation of 1‐phenylethanol with benzyl alcohol as substrate, which indicated that not only the iridium complex moiety but also the support material contributed to the catalytic activity of the supported iridium catalyst in these reactions. The supported iridium catalyst can be easily recycled by simple washing without chemical treatment, and exhibited excellent recycling performance without notable decrease in catalytic efficiency even after twelve test cycles for N‐alkylation of aniline with benzyl alcohol, nine cycles for N‐alkylation of different amines with different alcohols, and eight cycles for β‐alkylation of 1‐phenylethanol with benzyl alcohol, respectively.
Herein, we report the NHC-Ru catalyst system that realizes the chemo-selective transformation of ketones with methanol. By simply changing the base, a broad range of structurally diverse ketones, ...could be selectively and efficiently converted to the corresponding β-methylated secondary alcohols or secondary alcohols. Remarkably, this catalytic system was very effective for the synthesis of bio-related molecules and deuterated alcohols, as well as the three-component coupling between methyl ketones, primary alcohols, and methanol. The reaction mechanism was further revealed by experiment and DFT mechanistic investigations.
The base-controlled chemo-selective transformation ketones with methanol by the NHC-Ru complex is presented. Display omitted
•Catalytic conversion of alkynes to secondary alcohols by FePC with NaBH4.•1-phenylethanol derivatives formed following the addition and elimination mechanism.•Examining anticancer activity by ...binding of the product with protein kinase b.•Determine the highest chemical stability of compound 1 by DFT calculations.
1-Phenyl ethanol derivatives are well-known classes of drug molecules that play an important role as effective substitute analogs to anticancer and antiviral agents. In this work, phenylacetylene was selected as a simple alkyne in the presence of iron (II) phthalocyanine with NaBH4 as a catalyst. This reaction has been proven that it is a significantly efficient catalyzed conversion of terminal and internal alkynes to 1-phenyl ethanol derivatives as secondary alcohols followed by the addition and elimination mechanism. However, such drug design by compiling the redox reaction and its sequence essentially requires exact stoichiometry of iron phthalocyanine to alkynes. The products were characterized using flash column chromatography with an eluent ratio of PE: EA (5: 1 / V: V), gas chromatography, 1H, and 13C NMR spectroscopy. The potential of the synthesized compounds to bind to protein kinase B was investigated through molecular docking to dig out their probable anticancer activity. Compound 7 (1-(4-bromophenyl) ethan-1-ol) exhibited the highest binding potential. However, the binding potential of all the compounds was less than the standard parent compound. In addition, the density functional theory (DFT) studies of the compounds were also applied which revealed that compound 1 might have the highest chemical stability.
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•Electrooxidation of 2,3-butanediol is highly sensitive towards the surface structure of the electrode.•Partially oxidized acetoin and fully oxidized diacetyl are formed with ...different selectivites on the different Pt surfaces.•CC bond cleavage occurs only on the Pt(100) surface forming the catalyst poison CO.•Modification of Pt(100) with an ionic liquid suppresses the CC bond cleavage and increases the selectivity towards acetoin.
In heterogeneous catalysis, ionic liquids (ILs) are used as chemical modifiers to control selectivity. In our work, we aim to apply the same concept to electrocatalytic systems. As a model reaction, we studied the electrooxidation of 2,3-butanediol on the low-index Pt(111), Pt(100) and Pt(110) surfaces in an acidic environment. We used the IL 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (C2C1ImOTf) dissolved in an aqueous electrolyte as a catalyst modifier. The reaction mechanisms were investigated by electrochemical infrared reflection absorption spectroscopy (EC-IRRAS). The oxidation of 2,3-butanediol is highly structure dependent. On all three surfaces, the two products formed are acetoin and diacetyl, i.e. either one or two alcohol functionalities are oxidized. However, we observe distinct features on the different surfaces with respect to activity, potential window of oxidation, and selectivity. Only the Pt(100) surface is active towards CC bond cleavage. The latter reaction leads to the formation of COads and poisoning of the catalyst. Modification of this surface by addition of the IL leads to an increase of the selectivity for acetoin from 51 % to 78 % (at 1.1 VRHE). In addition, CC bond cleavage is suppressed, no CO is formed, and the surface remains active for the target reaction. We attribute these effects to the reversible and structure dependent adsorption of the OTf− anions on the Pt surfaces and additional interionic interactions. Our results demonstrate the potential of ILs to control selectivity in electrocatalytic reactions.
The alkylation of ketones or secondary alcohols using alcohols as alkylating agents via hydrogen borrowing strategy presents a powerful method for the synthesis of ɑ‐alkylated ketones. In this ...review, we summarize the progress catalyzed by Ir, Pd, Rh, Ru, Mn, Fe, Co, Ni, and Cu catalysts for the α‐alkylation of ketones with alcohols and cross‐coupling of secondary alcohols with alcohols from 2017 to 2021. A wide range of ketones (aromatic and aliphatic ketones) and alcohols (benzylic and aliphatic primary alcohols, aromatic and aliphatic secondary alcohols, alkenyl alcohols, and diols) are well tolerated. Furthermore, we also discuss current challenges and propose perspectives on the coming development in this filed. The objective of the present review is to give an overview on recent advances for α‐alkylation of ketones with alcohols and β‐alkylation of secondary alcohols with alcohols. Finally, we hope that this review will give inspirations on alkylation of ketones or secondary alcohols with alcohols.
A tandem photo- and biocatalytic dynamic kinetic resolution of secondary alcohols and amines was achieved employing a commercially available lipase, Candida antarctica lipase B (CALB), and a ...heteroleptic copper complex. The process is an example of using copper-based photocatalysis to promote hydrogen atom transfer (HAT) processes employing thiyl radicals. Screening of 48 complexes and 5 disulfides identified Cu(dtbbpy)(DPEPhos)BF4 and (Ph3SiS)2 as an optimal catalyst system to promote the HAT process. The catalytic system represents a general system for radical-mediated racemization applicable to both aliphatic and aromatic alcohols and amines (18 examples, 60 → 97% yield, 76 → 99% ee).
Ethanol is one of the most promising renewable resources for producing key industrial commodities. Herein, we present the direct conversion of ethanol to either primary or secondary alcohols, or to ...hydrocarbons, using ruthenium PNP pincer complexes (RPNP)RuHXCO (R = iPr, Ph, Cy, tBu; X = Cl, H–BH3) as catalysts. Using phenyl-substituted phosphines leads to the selective production of secondary alcohols over primary alcohols. Hence, employing (PhPNP)RuH(Cl)CO (Ru-1) as a catalyst in ethanol, containing 20 mol % of NaOtBu, at 115 °C leads to 89% selective production of the secondary alcohols. A yield of 12% of 2-butanol, and in total 22% of secondary alcohols, was achieved. In addition, minor amounts of 2-butenes/butane (≤5%) were observed. On the contrary, when using bulky phosphine substituents, such as t-butyl, the selectivity completely shifts toward primary alcohols. Thus, using ( tBuPNP)RuH(Cl)CO (Ru-5) leads to >99% selectivity of 1-butanol (13% yield) over secondary alcohols at 115 °C. The catalytic system is highly competitive for producing 1-butanol with 22% yield obtained at 130 °C. Our methodology unveils the potential for developing methods to use bulk bio-alcohols to selectively produce primary or secondary alcohols and hydrocarbons under mild conditions.
A available and robust NN-manganese(I) complex has been developed that can efficiently catalyze the transfer dehydrogenative of a broad range of secondary alcohols to ketones with high TON of 2250.
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•Manganese-promoted efficient transfer dehydrogenative oxidation of a wide range of (hetero)aromatic-, cycloalkyl and aliphatic-containing alcohols is reported.•This protocol provides an attractive and sustainable alternative for producing aromatic and aliphatic ketones.•Experimental and DFT studies indicate that this catalytic system follows an outer-sphere bifunctional mechanism.•The NN-bidentate complex Mn1 outperforms its tridentate NNN-Mn analogues due to the configuration and steric hindrance of catalysts.
Two types of non-phosphine based manganese(I) complexes, NN-manganese carbonyl complexes (Mn1 – Mn5) and NNN/S-pincer complexes (Mn6 – Mn10), have been assessed as catalysts for the transfer dehydrogenative (TDH) oxidation of secondary alcohols to afford ketones. Among them, Mn1, in combination with KBH4, proved the most effective and robust catalyst allowing (hetero)aromatic-, cycloalkyl and aliphatic--containing alcohols to be efficiently converted to their corresponding ketones with particularly high values of TON achievable (TON up to 2550). Furthermore, on the basis of experimental and DFT studies, an outer-sphere bifunctional mechanism for this Mn-catalyzed TDH is proposed. Density functional theory (DFT) computations suggest that the NN-bidentate complex Mn1 outperforms its tridentate NNN-Mn analogues due to the configuration and steric hindrance of catalysts. More importantly, this Mn-based catalytic TDH protocol using acetone as an inexpensive hydrogen acceptor offers an attractive and sustainable alternative for producing aromatic and aliphatic ketones.
A cobalt‐catalyzed addition of hydrosilanes to unsaturated carbon‐oxygen bonds has been developed, relying on complexes featuring easily accessible and inexpensive PNP‐type pincer ligands. A wide ...range of heterocyclic, aliphatic, and aromatic ketones, including those containing both electron‐donating and electron‐withdrawing substituents, were transformed into silyl ethers or secondary alcohols with high yields. An important feature of this protocol is that silanes can act as both the substrates and activators, eliminating the need for external additives such as strong bases.
Base‐free hydrosilylation of ketones mediated by cobalt complexes bearing triazine‐based PNP pincer‐type ligands is reported. As a result, access to versatile silyl ethers or alcohols is provided efficiently under mild conditions. In addition, the employment of hydrosilanes as reagents and activators of the pre‐catalysts minimizes the need for any external additives in favor of sustainability aspects.
The enantioselective oxidation of secondary alcohols represents a valuable approach for the synthesis of optically pure compounds. Flavoprotein oxidases can catalyse such selective transformations by ...merely using oxygen as electron acceptor. While many flavoprotein oxidases preferably act on primary alcohols, the FAD-containing alcohol oxidase from Phanerochaete chrysosporium was found to be able to perform kinetic resolutions of several secondary alcohols. By selective oxidation of the (S)-alcohols, the (R)-alcohols were obtained in high enantiopurity. In silico docking studies were carried out in order to substantiate the observed (S)-selectivity. Several hydrophobic and aromatic residues in the substrate binding site create a cavity in which the substrates can comfortably undergo van der Waals and pi-stacking interactions. Consequently, oxidation of the secondary alcohols is restricted to one of the two enantiomers. This study has uncovered the ability of an FAD-containing alcohol oxidase, that is known for oxidizing small primary alcohols, to perform enantioselective oxidations of various secondary alcohols.
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