The regioselective copper-catalyzedaddition of sp³ C-H bonds adjacent to an oxygen atom to various alkynes has been accomplished under mild reactions conditions in the presence of tert-butyl hydroperoxide to give the corresponding alkenylated products. C-Hactivation - copper - addition reactions - alkynes - tert-butyl hydroperoxide
Radical C(sp<sup>3</sup>)–H alkenylation, alkynylation and allylation of ethers and amides enabled by photocatalysis
作者:Subhasis Paul、Joyram Guin
DOI:10.1039/c7gc00840f
日期:——
enables selective incorporation of alkenyl, alkynyl and allyl functional groups into the C(sp3)–H bond under green reaction conditions is developed. The process is based on the catalytic formation of α-alkoxyl/α-amidyl radicals via the homolytic activation of the C(sp3)–H bond of ethers/amides with a catalytic amount of diarylketone in the presence of a household fluorescent light bulb. This simple reaction
quantum dots (QDs) can activate α-C-H bond of THF via forming QDs/THF conjugates. Under visible light irradiation, the resultant alkoxyalkyl radical directly engages in radical cross-coupling with α-amino radical from amino C-H bonds or radicaladdition with alkene or phenylacetylene, respectively. In contrast to stoichiometric oxidant or hydrogenatom transfer reagents required in previous studies, the
Phenylglyoxylic Acid: An Efficient Initiator for the Photochemical Hydrogen Atom Transfer C−H Functionalization of Heterocycles
作者:Giorgos N. Papadopoulos、Maroula G. Kokotou、Nikoleta Spiliopoulou、Nikolaos F. Nikitas、Errika Voutyritsa、Dimitrios I. Tzaras、Nikolaos Kaplaneris、Christoforos G. Kokotos
DOI:10.1002/cssc.202001892
日期:2020.11.20
C−H functionalization at the α‐position of heterocycles has become a rapidly growing area of research. Herein, a cheap and efficient photochemical method was developed for the C−H functionalization of heterocycles. Phenylglyoxylic acid (PhCOCOOH) could behave as an alternative to metal‐based catalysts and organic dyes and provided a very general and wide array of photochemical C−H alkylation, alkenylation
(THF) and unactivated alkenes via a dehydrogenative coupling of C(sp [3])−H and C(sp [2])−H bonds, yielding α-functionalized cyclic ethers. The reaction exhibited excellent E/Z selectivity and good to excellent yields (51%–88%). We also hypothesized for a β-H elimination route which confirmed the radicalpathway of intermediate (E) for ether alkenylation/functionalization. This methodology can be employed