65487-87-8Relevant academic research and scientific papers
Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis
Zhou, Min-Jie,Zhang, Lei,Liu, Guixia,Xu, Chen,Huang, Zheng
supporting information, p. 16470 - 16485 (2021/10/20)
The value of catalytic dehydrogenation of aliphatics (CDA) in organic synthesis has remained largely underexplored. Known homogeneous CDA systems often require the use of sacrificial hydrogen acceptors (or oxidants), precious metal catalysts, and harsh reaction conditions, thus limiting most existing methods to dehydrogenation of non- or low-functionalized alkanes. Here we describe a visible-light-driven, dual-catalyst system consisting of inexpensive organophotoredox and base-metal catalysts for room-temperature, acceptorless-CDA (Al-CDA). Initiated by photoexited 2-chloroanthraquinone, the process involves H atom transfer (HAT) of aliphatics to form alkyl radicals, which then react with cobaloxime to produce olefins and H2. This operationally simple method enables direct dehydrogenation of readily available chemical feedstocks to diversely functionalized olefins. For example, we demonstrate, for the first time, the oxidant-free desaturation of thioethers and amides to alkenyl sulfides and enamides, respectively. Moreover, the system's exceptional site selectivity and functional group tolerance are illustrated by late-stage dehydrogenation and synthesis of 14 biologically relevant molecules and pharmaceutical ingredients. Mechanistic studies have revealed a dual HAT process and provided insights into the origin of reactivity and site selectivity.
Catalytic Intramolecular Wittig Reaction Based on a Phosphine/Phosphine Oxide Catalytic Cycle for the Synthesis of Heterocycles
Wang, Long,Sun, Mei,Ding, Ming-Wu
, p. 2568 - 2578 (2017/05/19)
The catalytic intramolecular Wittig reactions of carbonyl-containing bromides are reported. The R3PO byproducts participate in the catalytic cycle; therefore, the Wittig reaction can be accomplished with only a catalytic amount of organophosphorus reagent. The reaction has also been applied to the efficient and selective synthesis of isoquinolin-1(2H)-ones, indoles, 2,3-dihydro-1H-2-benzazepin-1-ones, benzofurans, and 1,2-dihydroquinolines with a catalytic amount of phosphine oxide (0.1 equiv.) and a tetramethyldisiloxane/titanium isopropoxide [TMDS/Ti(OiPr)4] reductant system (yields: 35–88 %).
Palladium(II)/polyoxometalate-catalyzed direct alkenylation of benzofurans under atmospheric dioxygen
Huang, Qiufeng,Ke, Shaojia,Qiu, Lin,Zhang, Xiaofeng,Lin, Shen
, p. 1531 - 1534 (2014/06/24)
An efficient and selective C2 alkenylation of benzofurans was performed by using Pd(OAc)2 combined with a catalytic amount of 11-molybdovanadophosphoric acid (H4PMo11VO40) under an atmosphere of dioxygen. N-Acetylglycine (Ac-Gly-OH) was observed to be an effective additive for the olefination reaction. A tolerant POM: The efficient and selective direct alkenylation of benzofurans is achieved by using palladium acetate combined with 11-molybdovanadophosphoric acid. The transformation is performed under an atmosphere of dioxygen. Functional groups such as ethoxy, cyano, chloro, bromo, and ester are tolerated under the reaction conditions, and N-acetylglycine (Ac-Gly-OH) appears to be an effective additive for this reaction. 1 atm=101.3 kPa.
p-Toluenesulfonic acid-promoted selective functionalization of unsymmetrical arylalkynes: a regioselective access to various arylketones and heterocycles
Jacubert, Maud,Provot, Olivier,Peyrat, Jean-Fran?ois,Hamze, Abdallah,Brion, Jean-Daniel,Alami, Mouad
experimental part, p. 3775 - 3787 (2010/07/04)
Regioselective hydration of a wide range of internal alkynes has been afforded in high to good yields by using PTSA in EtOH. The scope of the reaction of alkynes has been delineated. Arylaliphatic alkynes and diarylalkynes were regioselectively hydrated in good to excellent yields and short reaction times when the reaction was achieved under microwave irradiation. Moreover, diarylalkynes, arylenynes as well as diaryldiynes bearing a methoxy- or a thiomethyl substituent on the ortho position underwent a regioselective 5-endo-dig-cyclization to give a variety of 2-aryl- and 2-styrylbenzofuran or benzothiphene derivatives. We believe that, this new environmentally metal-free procedure combined to microwave irradiation would be in importance in the search of green laboratory-scale synthesis.
2-substituted benzo[b]furans from (E)-1,2-dichlorovinyl ethers and organoboron reagents: Scope and mechanistic investigations into the one-pot Suzuki coupling/direct arylation
Geary, Laina M.,Hultin, Philip G.
supporting information; experimental part, p. 5563 - 5573 (2010/12/29)
2-Substituted benzo[b]furans can easily be assembled from simple phenols, boronic acids or other organoboron reagents, and trichloroethylene. The overall process requires only two synthetic steps, with the key step being a one-pot sequential Suzuki cross-coupling/direct arylation reaction. The method tolerates many useful functional groups and does not require the installation of any other activating functionality. The modular nature of the process permits the rapid synthesis of many analogues using essentially the same chemistry, of particular value in drug development. Results of kinetic isotope effect studies and investigations into the regioselectivity of the process indicate that the direct arylation step most likely does not involve an electrophilic palladation. The most likely mechanism lies somewhere on the continuum between a C-H bond metathesis and an assisted palladation or concerted metallation-deprotonation pathway. A very efficient modular approach to the construction of benzo[b]furans using trichloroethylene as a scaffold is described. This method gives easy access to highlysubstituted heterocycles in only two synthetic operations, and is especially suitable for rapid construction of compound libraries.
Modular construction of 2-substituted benzo[b]furans from 1,2-Dichlorovinyl ethers
Geary, Laina M.,Hultin, Philip G.
supporting information; experimental part, p. 5478 - 5481 (2010/02/27)
"Chemical Equation Presented" (E)-1,2-Dichlorovinyl ethers and amides are easily accessible from trichloroethylene via nucleophilic addition across in situ synthesized dlchloroacetylene. A one-pot, sequential Suzukl-Miyaura coupling/intramolecular direct
3-Zinciobenzofuran and 3-zincioindole: Versatile tools for the construction of conjugated structures containing multiple benzoheterole units
Nakamura, Masaharu,Ilies, Laurean,Otsubo, Saika,Nakamura, Eiichi
, p. 944 - 947 (2007/10/03)
(Chemical Equation Presented) Closing the ring: Thermally stable but reactive 3-zinciobenzofurans and indoles were synthesized by metalative cyclization of 2-ynyl phenols or anilines. Furthermore, a variety of extended π-conjugated molecules were obtained by Pd-catalyzed cross-coupling reactions of these heterocycles with mono- or polyhalo-substituted arenes and alkenes (R2Haln; see scheme; Bn = benzyl).
2,3-Disubstituted benzofuran and indole by copper-mediated C-C bond extension reaction of 3-zinciobenzoheterole
Nakamura, Masaharu,Ilies, Laurean,Otsubo, Saika,Nakamura, Eiichi
, p. 2803 - 2805 (2007/10/03)
A metalative 5-endo-dig cyclization reaction of 2-ynylphenoles or anilines effected by BuLi and ZnCl2 produces 3-zinciobenzoheteroles in excellent yield. These intermediates have been transmetalated to the corresponding cuprates and allowed to react with electrophiles to produce a variety of 2,3-disubstituted benzofurans and indoles.
Deprotonation of benzylic ethers using a hindered phosphazene base. A synthesis of benzofurans from Ortho-substituted benzaldehydes
Kraus, George A.,Zhang, Ning,Verkade, John G.,Nagarajan, Muthukaman,Kisanga, Philip B.
, p. 2409 - 2410 (2007/10/03)
(equation presented) The hindered nonionic phosphazene base P4-t-Bu efficiently deprotonates o-arylmethoxy benzaldehydes, leading to a direct synthesis of benzofurans. Strong ionic bases such as LDA, LiTMP, and KH failed.
General synthesis of polysubstituted benzo[b]furans
Katritzky, Alan R.,Fali, Clara N.,Li, Jianqing
, p. 8205 - 8209 (2007/10/03)
2-(Benzotriazol-1-ylmethyl)furans 4a-c, on treatment with n-BuLi followed by various α,β-unsaturated ketones and aldehydes, gave the adducts 6a-f which underwent intramolecular cyclization to form substituted benzo[b]furans 10a-f. Lithiation and subsequen
