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optimized condition 25% conversion for this highly challeng-
ing substrate was attained (Table 3, entry 17), increasing the
catalyst loading to 1 mol% with 8 equivalents of ammonium
formate resulted in an improved yield of 55% with excellent
selectivity (Table 3, entry 18). It is worth mentioning that, in
general, our catalytic system provided a highly chemoselective
route for the reduction of nitroarenes containing other reduci-
ble functional groups, such as carbonyl, nitrile, and carboxylic
acid. In a separate experiment, it was also found that the trans-
fer hydrogenation of acetophenone with HCOONH4 under the
optimized reaction conditions resulted in only 7% of 1-phenyl-
ethanol after 24 h. This result clearly demonstrates the origin
of high chemoselectivity observed in the reduction of nitroar-
enes containing other reducible groups, such as carbonyl
(Table 3, entries 11 and 12). Notably, the present catalytic
system also offered promising results for the regioselective re-
duction of dinitrobenzenes; this recently received considerable
attention as a challenging substrate in regioselective hydroge-
nation reactions.[31] As illustrated in entries 19 and 21 of
Table 3, ortho- and para-dinitrobenzenes gave excellent con-
versions and regioselectivities to the corresponding nitroani-
line derivatives with as little as 0.5 mol% of catalyst and 4–
8 equivalents of HCOONH4. It is important to note that, in the
case of O-dinitrobenzene, when the amount of HCOONH4 was
increased from four to eight equivalents, the regioselectivity
completely shifted toward the formation of 1,2-diaminoben-
zene, albeit with low conversion (Table 3, entry 20). The pres-
ent system was compatible when nitrophenol or nitrobenzyl
alcohol derivatives were used as substrates, showing excellent
conversions and selectivities with 0.5–1 mol% of Mag-IL-Pd
catalyst and 4–8 equivalents of HCOONH4 within 15–20 h
(Table 3, entries 22–26).
the Mag-IL-Pd catalyst was to conduct organic reactions in
water as the most environmentally acceptable solvent, we next
tried to accomplish the direct formylation of nitroarenes in
neat water. To the best of our knowledge, there have not been
any reports on the direct, one-pot synthesis of formanilides
from nitroarenes in water as a solvent. Interestingly, our pre-
liminary investigation revealed that, when 0.5 mol% of catalyst
and 0.5 mL of pure formic acid (as both reducing and formylat-
ing agents instead of ammonium formate) were used in water
at 908C, the selectivity of the reaction of nitrobenzene was
almost completely shifted toward the formation of N-phenyl-
formamide rather than aniline (Table 2, entry 17). Encouraged
by this observation, we next investigated the impact of lower
temperature, as well as catalyst and formic acid loading, on
the selective synthesis of N-phenylformamide to find the best
reaction conditions. As seen in Table 2, entries 18 and 19,
when the amount of formic acid was decreased to 30 equiva-
lents an excellent conversion and selectivity for N-phenylfor-
mamide could be obtained. However, a lower amount of
formic acid (10 equiv) was inadequate for completion of the re-
action. The reduction of nitrobenzene was also determined in
neat formic acid (in the absence of water as a reaction solvent)
under otherwise optimized reaction conditions. Neither aniline
nor N-phenylformamide formed owing to strong deactivation
and aggregation of palladium species to form palladium black,
which strongly suppressed the catalyst activity, as evidenced
by changes in the color of the reaction mixture. This observa-
tion clearly highlights the important role of water in these re-
actions. Although the reaction could be conducted at 708C by
employing 30 equivalents of formic acid, the yield of N-formy-
laniline was significantly inferior, even after 24 h (Table 2,
entry 20). In addition, the direct reductive N-formylation of ni-
trobenzene to form N-phenylformamide was unsuccessful at
room temperature, even in the presence of an excess of formic
acid (Table 2, entry 21). On the other hand, the reaction also
reached completion within 24 h with as little as 0.25 mol% cat-
alyst, giving 97% yield of N-phenylformamide with excellent
selectivity (Table 2, entry 23). A combination of HCOONH4
(2 equiv) with formic acid (10 equiv) was also tested under oth-
erwise identical reaction conditions for comparative purposes.
The observed selectivity of the process toward the formation
of N-phenylformamide remarkably dropped (below 61%) with
the production of a considerable amount of aniline (39%)
under the investigated conditions (Table 2 entry 24).
Encouraged by these interesting results for the catalytic
transfer hydrogenation of nitroarenes with Mag-IL-Pd catalyst,
in the next stage of this research we turned our attention to
direct, one-pot reductive N-formylation of nitroarenes to give
the corresponding formanilides by using the present magneti-
cally separable nanocatalyst. Formanilides are one of the most
important classes of organic molecules and have been exten-
sively used as biologically active materials, precursors for the
synthesis of fungicides and herbicides, and as Lewis bases in
catalysis.[32] The conventional approach for the synthesis of for-
manilides requires two-step catalytic reactions, including the
reduction of a nitro compound to the corresponding aniline
and then condensation of the aniline with formic acid. Because
one-pot synthetic reactions of formanilides are favored from
economic and environmental viewpoints, in recent years much
attention has been directed toward the synthesis of formani-
lides from nitro compounds.[33] It has been previously reported
that the use of ammonium formate in an aprotic solvent, such
as acetonitrile, could serve as a formylating reagent of ani-
lines[34] or result in the direct reductive formylation of nitro
compounds.[35] Comparatively, we have also found that a satis-
factory conversion of nitrobenzene to formanilide with
HCOONH4 (6 equiv) could be achieved in acetonitrile at reflux
within 24 h by using Mag-IL-Pd catalyst (0.5 mol%; Table 2,
entry 16). However, because the major objective of designing
Having optimized the reaction conditions for the reductive
N-formylation of nitrobenzene (Table 2, entry 23), we then ex-
plored the performance of our system in the reductive formy-
lation of various nitroarenes containing other functional
groups in water. As seen in Table 4, nitroarenes containing
either electron-donating or -withdrawing substituents, such as
F, CN, CH3, COCH3, and OH, at para or meta positions gave ex-
cellent yields of the corresponding N-arylformamides with ex-
cellent selectivities by using as little as 0.25 mol% of catalyst
(Table 4, entries 1–7). In the case of sterically hindered O-sub-
stituted nitroarenes, the conversions were quantitative and
moderate selectivities were obtained (owing to the formation
of the corresponding aniline; Table 4, entries 8 and 9). It is im-
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