a Reaction condition A: 1a (0.4 mmol),2a (0.6 mmol), Catalyst (8 mol %), Ag Salt (0.6 mmol) and
Additive (0.8 mmol) in solvent (3 mL) at 80 oC under
argon for 12 h. b Isolated yield.c 90 oC.d 100 oC. DCE:
1,2-dichloroethane. HFIP: 1,1,1,3,3,3-hexafluoro-2-propanol.
With the optimal reaction conditions established, we first explored the
substrate versatility of N -nitrosoanilines and iodonium ylides,
respectively (Scheme 2). Generally, all the reactions could proceed
smoothly in moderate to excellent yields. By first,N -nitrosoanilines 1a -1t with various
substituents installed on the para , meta or orthoposition of the benzene ring as well as N atom were examined with2a , and smoothly transformed into the desired compounds3aa -3ta in 25-80% yields. Introducing halogens (F,
Cl, Br), electron-donating substituents (OCH3 and
CH3) and electron-withdrawing substituents
(CF3, NO2 and
CO2CH3) at the para position of the
benzene ring afforded the corresponding products3ba -3ia in moderate to good yields. When
CH3 and OCH3 were placed at 3-position
of the benzene ring, 3ja and 3ka were offered in 53%
and 54% yield, respectively, superior to 3la with a
CF3 substituent. Moreover, O -fluorosubstitutedN -nitroaniline 1m was also tolerated under the standard
condition A. It was worth mentioning that the substituent on the
nitrogen atom was not limited to a methyl, but could be favorably
extended to Et (3na , 67%), n -Bu (3oa , 57%),
Bn (3pa , 49%), and even p -Methylphenyl (3qa ,
30%). More importantly, this transformation was also compatible withN -nitroso-tetrahydroquinoline independent of electronic factors
(3ra -3ta ), which greatly broaden its application
scope. Then, iodonium ylides were
also investigated. A variety of iodonium ylides
(2b -2i ) smoothly reacted with 1a to afford
the desired products 3ab -3ai in moderate to good
yields. For example, iodonium ylides bearing a methyl, dimethyl or
phenyl at R2 position could be well delivered to the
desired products 3ab , 3ac and 3ae in 67%,
69% and 56% yields, respectively. Besides, 4-F, 4-Cl, 4-Br and
4-CH3 phenyl substituted substrates were favored to
provide 3af -3ai in 42%-72% yields. What’s more,
five-membered iodine ylide (2d ) was converted to 3adat a high yield of 72%.
Scheme 2. Substrate Scope for3 a,b
a Reaction condition A: 1 (0.4 mmol),2 (0.6 mmol), [Cp*RhCl2]2(8 mol %), AgBF4 (0.6 mmol) and PivOH (0.8 mmol) in
acetone (3 mL) at 90 oC under argon for 12 h.b Isolated yield.
After constructing a preliminary knowledge of the optimal reaction
conditions and substrates diversity, we were further intrigued by the
structure of 3aa , because the carbonyl group of its
tetrahydrocarbazol-4-one possibly acted as a new directing group to
selectively catalyze cross dehydrogenative coupling (CDC) reaction
between the C5 -position of 3aa and
other (hetero)arenes. To verify our idea, we chose 3aa (0.2
mmol) and 4a (0.4 mmol) as template substrates and treated them
with [Cp*IrCl2]2 (5 mol %),
AgSbF6 (20 mol %), PivOH (0.2 mmol) and
Ag2O (0.6 mmol) in 1,2-dichloroethane (DCE) at 130oC under argon for 24 h. To our delight, the desired
product 5a could be attained in 37% isolated yield (Table 2,
entry 1), and its exact structure has been verified by the1H and 13C NMR spectroscopy, mass
spectrometry data and X-ray crystallographic analysis (see Figure S2 in
the Supporting Information). The detailed reaction condition
optimization was shown in Table 2. Finally, we treated 3aa (0.2
mmol) and 4a (0.4 mmol) in the presence of
[Cp*IrCl2]2 (5 mol %) and
AgSbF6 (20 mol %) as catalysts, AgOPiv (0.6 mmol) and
PivOH (0.2 mmol) as additives in 2 mL of dioxane where 5a was
obtained in 76% isolated yield at 100 oC under argon
for 24 h (Table 2, entry 8).
Table 2. Optimization of Reaction Condition
Ba