Herein we describe an efficient distal
ipso-migration of O- and S-containing
heteroaryls and the
radical heteroarylation of unactivated alkenes. The migration is triggered
by various fluoroalkyl radicals, leading to valuable multifunctionalized
ketones. The comparisons of migratory aptitude for O-/S-containing heteroaryls are comprehensively investigated.
The origin of the chemoselective migration could be partially attributed
to the discrepancy in the energy level of the LUMO of each heteroaryl
group.
We report the first demonstrations of intra- and intermolecular acyclic nitronate olefin cycloaddition (ANOC) reactions that enable the highly efficient syntheses of isoxazolines bearing various functional groups. This general approach...
The mechanisms of transition-metal-catalyzed cyclopropenes involved reactions are complicated since diversified active intermediates could be potentially formed. Herein, computational studies were performed to gain mechanistic insights into the Rh(I)-and Rh 2 (II)-catalyzed regioselective ring-opening of allylic cyclopropenecarboxylate (1) and further rearrangement to form Δ β,γ butenolides. For the Rh(I)-catalyzed ring-opening of cyclopropene moiety of 1, an unusual oxidative addition of CÀ C σ bond of the three-membered ring onto Rh(I) to form the intermediate with a CÀ Rh σ bond and a π…Rh interaction is proposed. While, for the Rh 2 (II)-catalyzed reaction, it is more feasible for the cyclopropene moiety of 1 to convert to the Rh 2 (II) vinyl carbene intermediate. Despite the formation of different key intermediates for the Rh(I) and Rh 2 (II)-catalyzed ring-opening reactions, the subsequent intramolecular nucleophilic cyclization to form furan derivatives is similar. In addition, the origins of different regioselectivities for the Rh(I) and Rh 2 (II)catalyzed reactions are revealed.
Summary of main observation and conclusionIt could be proposed that gold(I)‐catalyzed reactions of ynamides with benzofurazan N‐oxides might proceed through either O‐attack or N‐attack to afford α‐oxo or α‐imino Au(I)‐carbenoid intermediates. Computational studies were performed to predict that benzofurazan N‐oxides are ready to undergo the chemoselective N‐attack to the Au(I)‐activated ynamides to generate the α‐imino Au(I)‐carbenoid intermediate. Experimental studies were carried out to confirm the computational results and the 7‐nitroindole derivatives were synthesized in a concise and efficient manner. The unfavored O‐attack for benzofurazan N‐oxides, which is in contrast to nitrones and pyridine/quinoline N‐oxides, in the Au(I)‐catalyzed reactions with ynamides is rationalized.
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