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 (3e –3g ) 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 3j –3p 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
(3q –3v , 65–74%). Furthermore, more
sterically-hindered, multi-substituted substrates were also successfully
employed in this process, affording 3y –3aj 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 products3ao –3aq were obtained in 60–68% yields.