24840-05-9Relevant academic research and scientific papers
Selective Construction of C?C and C=C Bonds by Manganese Catalyzed Coupling of Alcohols with Phosphorus Ylides
Liu, Xin,Werner, Thomas
supporting information, p. 1096 - 1104 (2020/12/31)
Herein, we report the manganese catalyzed coupling of alcohols with phosphorus ylides. The selectivity in the coupling of primary alcohols with phosphorus ylides to form carbon-carbon single (C?C) and carbon-carbon double (C=C) bonds can be controlled by the ligands. In the conversion of more challenging secondary alcohols with phosphorus ylides the selectivity towards the formation of C?C vs. C=C bonds can be controlled by the reaction conditions, namely the amount of base. The scope and limitations of the coupling reactions were thoroughly evaluated by the conversion of 21 alcohols and 15 ylides. Notably, compared to existing methods, which are based on precious metal complexes as catalysts, the present catalytic system is based on earth abundant manganese catalysts. The reaction can also be performed in a sequential one-pot reaction generating the phosphorus ylide in situ followed manganese catalyzed C?C and C=C bond formation. Mechanistic studies suggest that the C?C bond was generated via a borrowing hydrogen pathway and the C=C bond formation followed an acceptorless dehydrogenative coupling pathway. (Figure presented.).
Skeletally Tunable Seven-Membered-Ring Fused Pyrroles
Andreou, Dimitrios,Essien, Nsikak B.,Pubill-Ulldemolins, Cristina,Terzidis, Michael A.,Papadopoulos, Athanasios N.,Kostakis, George E.,Lykakis, Ioannis N.
supporting information, p. 6685 - 6690 (2021/09/11)
We describe a copper-mediated method that enables the synthesis of seven-membered-ring fused pyrroles (7-mrFPs). The protocol proceeds via an in situ spiro-intermediate ring expansion and tolerates a library of 7-mrFP derivatives with a broad range of functional groups in a simple step with tangible parameters and substrate adaptations. These rare 7-mrFPs are now accessible on a millimolar scale, and selected examples exhibit high antioxidant activity.
1,3-Diphenyldisiloxane Enables Additive-Free Redox Recycling Reactions and Catalysis with Triphenylphosphine
Buonomo, Joseph A.,Cole, Malcolm S.,Eiden, Carter G.,Aldrich, Courtney C.
, p. 3583 - 3594 (2020/09/15)
The recently reported chemoselective reduction of phosphine oxides with 1,3-diphenyldisiloxane (DPDS) has opened up the possibility of additive-free phosphine oxide reductions in catalytic systems. Herein we disclose the use of this new reducing agent as an enabler of phosphorus redox recycling in Wittig, Staudinger, and alcohol substitution reactions. DPDS was successfully utilized in ambient-temperature additive-free redox recycling variants of the Wittig olefination, Appel halogenation, and Staudinger reduction. Triphenylphosphine-promoted catalytic recycling reactions were also facilitated by DPDS. Additive-free triphenylphosphine-promoted catalytic Staudinger reductions could even be performed at ambient temperature due to the rapid nature of phosphinimine reduction, for which we characterized kinetic and thermodynamic parameters. These results demonstrate the utility of DPDS as an excellent reducing agent for the development of phosphorus redox recycling reactions.
Systematic Study on the Catalytic Arsa-Wittig Reaction
Inaba, Ryoto,Kawashima, Ikuo,Fujii, Toshiki,Yumura, Takashi,Imoto, Hiroaki,Naka, Kensuke
, p. 13400 - 13407 (2020/09/21)
Efficient catalytic arsa-Wittig reactions have been developed by using 1-phenylarsolane as a catalyst. A wide array of aldehydes was converted to the corresponding olefins in high yields with moderate to excellent E stereoselectivity in the presence of a catalytic amount of 1-phenylarsolane. Moreover, density functional theory calculations were carried out to afford insight into the E/Z selectivity.
An aerobic and green C-H cyanation of terminal alkynes
Si, Yi-Xin,Zhang, Song-Lin,Zhu, Peng-Fei
supporting information, p. 9216 - 9220 (2020/12/03)
This study describes a benign C-H cyanation of terminal alkynes with α-cyanoesters serving as a nontoxic cyanide source. In situ generation of the key copper cyanide intermediate is proposed by a sequence of α-C-H oxidation and copper-mediated β-carbon elimination of α-cyanoesters, releasing the α-ketoester byproduct observed experimentally. The ensuing reaction of copper cyanide with terminal alkynes delivers preferentially cyanoalkynes and surpasses the possible Glaser type dimerization of terminal alkynes or the undesired accumulation of HCN under protic conditions. The presence of the co-oxidant K2S2O8 is crucial to this selectivity, probably by promoting oxidative transmetalation and the resulting formation of the Cu(iii)(acetylide)(CN) intermediate. All the reagents and salts used are commercially available, cheap and nontoxic, avoiding the use of highly toxic cyanide salts typically required in cyanation studies. The scope of this reaction is demonstrated with a set of alkynes and α-cyanoesters. The application of this method to late-stage functionalization of the terminal alkyne group in an estrone derivative is also feasible, showing its practical value for drug design.
Metal-free dehydrosulfurization of thioamides to nitriles under visible light
Xu, Tianxiao,Cao, Tianpeng,Feng, Qingyuan,Huang, Shenlin,Liao, Saihu
supporting information, p. 5151 - 5153 (2020/05/26)
A visible light-mediated, metal-free dehydrosulfurization reaction of thioamides to nitriles is described. This reaction features high yields, mild reaction conditions, and the use of a cheap organic dye as the photoredox catalyst and air as the oxidant.
Phosphetane oxides as redox cycling catalysts in the catalytic wittig reaction at room temperature
Longwitz, Lars,Spannenberg, Anke,Werner, Thomas
, p. 9237 - 9244 (2019/10/08)
Recently, phosphorus redox cycling has gained significant importance for a number of transformations originally requiring the use of stoichiometric amounts of phosphorus reagents. While these methodologies have several benefits, high catalyst loadings (≥10 mol percent) and harsh reaction conditions (T ≥ 100 °C) often limit their versatility and applicability. Herein, we report differently substituted phosphetane oxides as efficient catalysts for the catalytic Wittig reaction. The phosphetane scaffold is easy to modify, and a number of catalysts can be obtained in a simple two-step synthesis. The activity in the Wittig reaction significantly surpasses previously reported phospholane-based catalysts and the reaction can be conducted with catalyst loadings as low as 1.0 mol percent even at room temperature. Furthermore, a Br?nsted acid additive is no longer required to achieve high yields at these mild conditions. A methyl-substituted phosphetane oxide was employed to synthesize 25 different alkenes with yields of up to 97percent. The methodology has a good functional group tolerance and the reaction can be performed starting with alkyl chlorides, bromides, or iodides. Additionally, it was possible to use poly(methylhydrosiloxane) as the terminal reductant in the catalytic Wittig reaction employing 2-MeTHF as a renewable solvent. The intermediates of the Wittig reaction were analyzed by 31P NMR spectroscopy, and in situ NMR experiments confirmed phosphane oxide as the resting state of the catalyst. Further kinetic investigations revealed a striking influence of the base on the rate of phosphane oxide reduction.
Water as a Hydrogenating Agent: Stereodivergent Pd-Catalyzed Semihydrogenation of Alkynes
Zhao, Chuan-Qi,Chen, Yue-Gang,Qiu, Hui,Wei, Lei,Fang, Ping,Mei, Tian-Sheng
, p. 1412 - 1416 (2019/03/07)
Palladium-catalyzed transfer semihydrogenation of alkynes using H2O as the hydrogen source and Mn as the reducing reagent is developed, affording cis- and trans-alkenes selectively under mild conditions. In addition, this method provides an efficient way to access various cis-1,2-dideuterioalkenes and trans-1,2-dideuterioalkenes by using D2O instead of H2O.
E- and Z-, di- and tri-substituted alkenyl nitriles through catalytic cross-metathesis
Mu, Yucheng,Nguyen, Thach T.,Koh, Ming Joo,Schrock, Richard R.,Hoveyda, Amir H.
, p. 478 - 487 (2019/04/08)
Nitriles are found in many bioactive compounds, and are among the most versatile functional groups in organic chemistry. Despite many notable recent advances, however, there are no approaches that may be used for the preparation of di- or tri-substituted alkenyl nitriles. Related approaches that are broad in scope and can deliver the desired products in high stereoisomeric purity are especially scarce. Here, we describe the development of several efficient catalytic cross-metathesis strategies, which provide direct access to a considerable range of Z- or E-di-substituted cyano-substituted alkenes or their corresponding tri-substituted variants. Depending on the reaction type, a molybdenum-based monoaryloxide pyrrolide or chloride (MAC) complex may be the optimal choice. The utility of the approach, enhanced by an easy to apply protocol for utilization of substrates bearing an alcohol or a carboxylic acid moiety, is highlighted in the context of applications to the synthesis of biologically active compounds.
Allyl-Nickel Catalysis Enables Carbonyl Dehydrogenation and Oxidative Cycloalkenylation of Ketones
Huang, David,Szewczyk, Suzanne M.,Zhang, Pengpeng,Newhouse, Timothy R.
supporting information, p. 5669 - 5674 (2019/04/26)
We herein disclose the first report of a first-row transition metal-catalyzed α,β-dehydrogenation of carbonyl compounds using allyl-nickel catalysis. This development overcomes several limitations of previously reported allyl-palladium-catalyzed oxidation, and is further leveraged for the development of an oxidative cycloalkenylation reaction that provides access to bicycloalkenones with fused, bridged, and spirocyclic ring systems using unactivated ketone and alkene precursors.
