65487-87-8Relevant articles and documents
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.
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.
