α-Halocarbonyl compounds undergo β-hydrogen elimination to give conjugated olefins in the presence of a transition-metal catalyst. However, a copper/triamine catalyst system can induce the alkylative Mizoroki–Heck reaction of styrenes with tertiary-alkyl halides possessing a withdrawing group under very mild conditions. This reaction provides an efficient synthetic methodology for tertiary-alkylated styrenes.
In this communication, we established highly efficient Cu-catalyzed ARGET-ATRS (atom-transfer radical substitution) of alpha-bromocarbonyls with styrenes to produce tert-alkylated styrenes. The maximum TON was up to 12 000. Hünig's base was very important to regenerate active Cu. Moreover, a Cu-catalyzed C-C cleavage reaction via S2' and intermolecular C-H cyclization of α-bromoimide was found.
A highly efficient formal [3 + 2]-cycloaddition was established using a copper catalyst. The resulting dihydrofurans were subjected to oxidation followed by arylations to produce tetraarylfurans. In addition, the dihydrofuran can be converted to diaryldihydrothiophene by using Lawesson's reagent. This protocol will facilitate the synthesis of all different aryl-substituted furans and thiophenes.
Reactions of 2-bromoesters and styrenes underwent a [2+1] cycloaddition reaction, i.e., cyclopropanation, to produce donor-acceptor (D-A) cyclopropanes through a radical addition-ring closure process. In this reaction, the combination of copper(ii) complex and amines is found to be a good catalyst system to obtain cyclic compounds in high yields. This reaction provides an efficient protocol to synthesize D-A cyclopropanes, which are very important building blocks in organic synthesis.
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