a Reaction conditions: 1a (0.20 mmol),2a (0.40 mmol), rongalite (equiv as stated), solvent (2.0 mL), T (as stated), 3 h, under Ar. b Isolated yields based on 1a . c Bu4NF (1.0 equiv) was added. d Bu4NCl (1.0 equiv) was added. e Bu4NBr (1.0 equiv) was added.f Diphenyliodonium tetrafluoroborate2a’ was used in place of 2a .
Following that, the scope of substrates appropriate for this cross-coupling reaction using ideal conditions was explored and the suitability of several diaryliodonium salts was demonstrated (Scheme 3). Substrates bearing alkyl (products 3b and 3c ), alkoxy (3d ), halogen (3e3g ) and electron-withdrawing (3h and 3i ) substituents at thepara -site of the benzene ring were basically compatible with this process and gave the corresponding products in considerable results (70–82%). Additionally, meta -substituted diaryliodonium salts containing electron-neutral, electron-donating, and electron-withdrawing groups gave products 3j3p in good yields (69–85%). Notably, C(sp2)-F, C(sp2)-Cl and C(sp2)-Br groups were discovered to be unreactive using the current reaction circumstances, implying that halogen-based substituents could be exploited for further elaborations. Althoughortho -substituted substrates appeared to be rigid, moderate to good yields of the corresponding products could still be achieved (3q3v , 65–74%). Furthermore, more sterically-hindered, multi-substituted substrates were also successfully employed in this process, affording 3y3aj in significant yields (59–82%). Polyfluorinated diaryliodonium salts also performed smoothly with CF3-alkenes, yielding products3ak and 3al in 63% and 55% yields, respectively. Bulkier substrates based on naphthalene and biphenyl skeletons participated in this reaction to give 3am and 3an in 60–68% yields. Notably, a series of cyclic diaryliodonium salts was assessed and products3ao3aq were obtained in 60–68% yields.