AuI-catalyzed direct hydroamination/hydroarylation and double hydroamination of terminal alkynes

Article abstract of DOI:10.1002/ejoc.201000389

An efficient method for formal Markownikoff hydroamination/hydroarylation and double hydroamination of terminal alkynes has been developed. For example, treatment of terminal alkynes with amino-aromatics or diamines in the presence of 2-5 mol-% of Ph3PAuNTf2 in toluene at 100°C gave the corresponding products in excellent yields. The method was shown to be applicable to a broad range of substrates and, more importantly, unlike our previously reported method, a tethered hydroxy group in the alkyne is not necessary. The mechanism of the reaction is also discussed.

Full text of DOI:10.1002/ejoc.201000389

FULL PAPER
DOI: 10.1002/ejoc.201000389
AuI-Catalyzed Direct Hydroamination/Hydroarylation and Double
Hydroamination of Terminal Alkynes
Nitin T. Patil,*[a] Pediredla G. V. V. Lakshmi,[a] and Vipender Singh[a]
Keywords: Alkynes / Gold catalysts / Nucleophiles / Cyclization / Heterocycles
An efficient method for formal Markownikoff hydroamin-
ation/hydroarylation and double hydroamination of terminal
alkynes has been developed. For example, treatment of ter-
minal alkynes with amino-aromatics or diamines in the pres-
ence of 2–5 mol-% of Ph3PAuNTf2 in toluene at 100 °C gave
the corresponding products in excellent yields. The method
was shown to be applicable to a broad range of substrates
and, more importantly, unlike our previously reported
method, a tethered hydroxy group in the alkyne is not neces-
sary. The mechanism of the reaction is also discussed.
droamination/hydroarylation and double hydroamination
of alkynes. Yi and Yun reported the use of a cationic ruthe-
nium hydride complex as a catalyst for the formal hydro-
amination/hydroarylation of terminal alkynes that proceeds
with C–H activation.[12] Dixon and co-workers reported a
gold-catalyzed cyclization of alkynoic acids with amino-
aromatics involving a formal hydroamination/hydroaryl-
ation.[13] Recently, a CuI-catalyzed tandem hydroamination/
alkynylation of alkynes has been reported by Xu and Ham-
mond.[14]
We assumed that the amine X would attack an electro-
philically activated alkyne to generate an imine, which then
becomes a new electrophilic precursor capable of reacting
with a second tethered nucleophile (Nu = Ar or NH2) to
give a double addition product [Equation (2)]. A reaction
as envisioned could be considered as a hydroamination/hy-
droarylation (when Nu = Ar) and double hydroamination
(when Nu = NH2), which would provide access to a wide
variety of nitrogen-containing heterocycles.
Introduction
The addition of an N–H bond across an unactivated C–
C triple bond is one of the simplest and atom-economical[1]
synthetic transformations for the formation of C–N bonds.
Catalysts derived from both early and late transition
metals[2] as well as lanthanides[3] have shown significant ac-
tivity for the addition of N–H bonds across alkynes. These
processes[4] are potentially useful since imines/enamines that
are generated in situ can be converted into various hetero-
cycles[5] by cascade[6] design in one pot [Equation (1)].
(1)
Synthetic methods relying on π-acid catalysts have re-
cently been the focus of intense development.[7] In these
transformations, through the interaction of the alkyne with
a π-acidic metal, the electron density of the triple bond is
reduced, thereby rendering it electrophilic. A tethered nu-
cleophile may undergo addition followed by subsequent
transformations to produce heterocycles. Out of the various
types of reactions catalyzed by π-acids, double addition of
nucleophiles to triple bonds is very important from a syn-
thetic point of view. In this regard, reactions such as
hydroalkoxylation/hydroarylation,[8] double hydroalkoxyl-
ation,[9] double hydroarylation,[10] and hydroamination/
hydrophosphanation[11] of alkynes have been reported in
the literature. However, there are very few reports on hy-
(2)
Previously, we reported double hydroamination[15] and
hydroamination/hydroarylation[16] cascade reactions of ter-
minal alkynes bearing a hydroxy group in the proximity
(Figure 1, path a). A proximal hydroxy group proved to be
necessary for the reaction to occur; alkynes with no hydroxy
group in the tether (e.g., 1-octyne) failed to react. In this
paper, we report the Ph3PAuNTf2-catalyzed direct hydro-
amination/hydroarylation and double hydroamination of
terminal alkynes having no proximal hydroxy group (Fig-
ure 1, path b). The transformation shows a very broad sub-
[a] Organic Chemistry Division – II, Indian Institute of Chemical
Technology,
Hyderabad 500607, India
E-mail: nitin@iict.res.in
patilnitint@yahoo.com
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201000389.
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N. T. Patil, P. G. V. V. Lakshmi, V. Singh
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strate scope towards diversely substituted amino-aromatics only starting material 1a was recovered (Entry 11). On the
or diamines and terminal alkynes and, thus, provides ef- other hand, catalyst IPrAuNTf2 (II) produced 3a in 81%
ficient access to multi-substituted nitrogen-containing het- yield (Entry 12). Pleasingly, the Gagosz catalyst (III)
erocycles, such as pyrrolo[1,2-a]quinoxalines,[17] indolo[3,2- worked exceedingly well, to give 3a in 90% yield (Entry 13).
c]quinolines,[18] indolo[1,2-a]quinoxalines,[19] tetrahydro-4- When the catalyst loading was lowered (1 mol-%), a mar-
quinazolinones,[20] and benzo[4,5]imidazo[1,2-c]quinazol- ginal decrease in yield was observed (Entry 14).
ines;[21] members of this class of compounds are known to
exhibit interesting biological activities.
Table 1. Optimization studies for the reaction between 1a and 2a.[a]
Figure 1. Concept of intermolecular hydroamination/hydroaryl-
ation and double hydroamination of terminal alkynes.
Results and Discussion
Initial efforts were directed towards finding an appropri-
ate metal catalyst for the proposed reaction of 2-ami-
nophenylpyrrole (1a) with 1-octyne (2a) as model sub-
strates. Preliminary optimization studies revealed that the
use of a nonpolar, noncoordinating solvent such as toluene
was found to be the best.[22] Therefore, with toluene as sol-
vent, a series of π-acidic catalysts were screened, and the
results are outlined in Table 1. Based on our earlier re-
port,[15,16] the reaction was initially conducted by using
platinum catalysts, such as PtCl2, PtBr2 or PtCl4; however,
lower yields were obtained in all cases (Entries 1–3). The
[a] Reaction conditions: 1a (0.316 mmol), 2a (0.379 mmol), catalyst
(2 mol-%), toluene (2 mL), 100 °C. [b] Yield of isolated and chro-
matographically purified material. [c] 60–70% recovery of 1a. [d]
20–40% recovery of 1a. [e] Quantitative recovery of 1a. [f] 1 mol-
catalysts AgOTf and Cu(OTf)2 gave 3a in 20 and 40% % of catalyst was used.
yields, respectively (Entries 4 and 5). Next, we turned our
attention towards gold catalysts. A marginal increase in
During the course of the reaction, traces of Tf2NH could
yield (50%) was observed when AuCl was employed (En- be generated from Ph3PAuNTf2 either in the presence of 1a
try 6). A combination of Ph3PAuCl with various silver salts, or trace amount of water present in the reaction medium.
such as AgOTf (Entry 7), AgSbF6 (Entry 8), and AgBF4 A Brønsted acid thus formed might act as catalyst for the
(Entry 9) was examined; of these, the former catalytic sys- present transformation.[26] To test this, the reaction was
tem proved to be the best, giving 3a in 75% yield (Entry 7). conducted with 1a and 2a in the presence of 2 mol-%
No significant improvement in yield was observed when the Tf2NH (Entry 15); under these conditions, 1a was recovered
reaction mixture was heated for 48 h (compare Entries 10 rather than the product 3a, which was not obtained. This
and 7); in this case, 1a was recovered in 20% yield. This clearly indicates that the Ph3PAuNTf2 catalyst is responsible
observation can be explained on the basis of the instability for the reaction.
of Ph3PAuOTf at high temperature. Therefore, we planned
Inspired by the high degree of catalytic activity exhibited
to test the activity of thermally stable cationic AuI catalysts by the Gagosz catalyst, the scope of this transformation was
for the present transformation. To this end, thermally stable then explored under optimized conditions (Table 1, En-
AuI complexes, such as Ph3PAuBtz (I),[23] IPrAuNTf2 try 13).
(II),[24] and Ph3PAuNTf2 (III) (Gagosz catalyst),[25] were
The results are summarized in Table 2. From Entries 1–
prepared, and their catalytic activities were examined. Un- 6, it can be seen that a wide range of N-(2-aminophenyl)-
fortunately, the catalyst Ph3PAuBtz (I) did not work at all; pyrrole derivatives (bearing Me, OMe, COOMe, or Cl) 1b–
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AuI-Catalyzed Hydroamination and Hydroarylation
g reacted well with 1-octyne (2a) to give products 3b–g in the desired products 3i and 3j were obtained in 75 and 67%
moderate to high yields (65–89%). However, the reaction yields, respectively. Interestingly, the present catalytic sys-
of fluoro derivative 1h proved to be sluggish; the fluoro- tem was not appropriate for the reaction between N-(2-ami-
substituted pyrrolo[1,2-a]quinoxalines 3h was isolated in nophenyl)pyrrole and aromatic alkynes, such as phenyl-
only 48% yield, even after heating for 48 h (Entry 7). Next, acetylene (2d).[27] The use of AgOTf as catalyst was found
by keeping N-(2-aminophenyl)pyrrole (1a) as a substrate, a to be necessary to obtain the product in higher yields (En-
number of terminal alkynes were submitted to the reaction try 10). As exemplified in Entries 11 and 12, this method
conditions (Entries 8–16). For example, 4-phenyl-1-butyne is not applicable to aromatic alkynes having either strong
(2b) and propargyl alcohol (2c) reacted well with 1a, and electron-donating or -withdrawing groups. In the case of
Table 2. Ph3PAuNTf2-catalyzed hydroamination/hydroarylation of terminal alkynes.[a]
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Table 2. (Continued)
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AuI-Catalyzed Hydroamination and Hydroarylation
Table 2. (Continued)
[a] Reaction conditions: 1 (0.316 mmol), 2 (0.379 mmol), Ph3PAuNTf2 (2 mol-%), toluene (2 mL), 100 °C, 24 h. [b] Yield of isolated and
chromatographically purified material. [c] Reaction mixture was heated for 48 h. [d] AgOTf (10 mol-%) was used as catalyst. [e] 1a was
recovered when AgOTf (10 mol-%) and Ph3PAuNTf2 (2 mol-%) were used independently. [f] A combination of Ph3PAuCl and AgOTf
(5 mol-% each) was used. [g] 1r was recovered in nearly 15–20% yield. [h] 1s was recovered in ca. 60% yield.
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(p-methoxyphenyl)acetylene (2e), only 50% yield of 3l was alkynes, and the results are outlined in Table 3. From En-
obtained when AgOTf was used as catalyst (Entry 11); on tries 1–3 it can be seen that phenylacetylene (2d) reacted
the other hand, (p-nitrophenyl)acetylene was found to be well with 2-aminobenzamide (5a) and its methyl-substituted
inert under silver and gold catalysis (Entry 12). Free hy- derivatives 5b and 5c to furnish 6a–c in moderate to high
droxy or amino groups on the aromatic alkynes were toler- yields (70–85%). When halogen-containing substrates, such
ated well under the present reaction conditions. Thus, when as 5d, 5e, and 5f, were treated with 2d, the expected prod-
2g or 2h were treated with 1a, the corresponding products ucts 6d, 6e, and 6f were obtained in 90, 96, and 75% yields,
3n and 3o were obtained in 78 and 67% yields, respectively respectively (Entries 4–6). Other alkynes such as 2b and 2i
(Entries 13 and 14). Sterically hindered cyclohexylacetylene on reaction with 5a afforded 6g and 6h in 98 and 90%
(2i) gave 3p in 94% yield (Entry 15).
yields, respectively (Entries 7 and 8).
It is of interest to note that the catalyst system tolerates
the pyridine ring. The reaction between 1a and 2j under the
standard reaction conditions afforded pyridine-containing
compound 3q, albeit in 53% yield (Entry 16). When 2-(2-
aminophenyl)indoles 1i, 1j, and 1k were treated with 2d, the
expected products 3r, 3s, and 3t were obtained in 90, 92,
and 95% yields, respectively (Entries 17, 18, and 19). Next,
we checked the reactivity of various N-(2-aminophenyl)-
indoles 1l–q with 2d. It has been found that groups such as
Cl, OR and NO2 were well tolerated and, thus, indolo[1,2-a]-
quinoxalines 3u–z were obtained in good to excellent yields
(Entries 20–25). The reaction could also be performed with
other (2-aminophenyl)arenes in which the pyrrole or indole
moiety was exchanged for a different aromatic ring, such as
an electron-rich benzene ring. For example, the reaction of
1r with 2d and 2a gave the corresponding product 3aa and
3ab in 75 and 72% yields, respectively, as single regioiso-
mers (Entries 26, 27). When (2-aminophenyl)arene 1s,
which does not contain an electron-donating group, was
used, the reaction was found to be sluggish, and 3ac was
isolated in only 30% yield (Entry 28). It should be noted
that the present reaction is limited to terminal alkynes; in-
ternal alkynes are not viable substrates.
Table 3. Ph3PAuNTf2-catalyzed double hydroamination of terminal
alkynes.[a]
[a] Reaction conditions:
5
(0.316 mmol),
2
(0.379 mmol),
Ph3PAuNTf2 (5 mol-%), toluene (2 mL), 100 °C, 24 h. [b] Yield of
isolated and chromatographically purified material. [c] AgOTf
(20 mol-%) was used.
We were pleased to find that not only 2-aminobenz-
amides 5 but also 2-(2-aminophenyl)benzimidazole (7)
worked well for the transformation (Scheme 2). The reac-
tion of 7 with 2a and 2d under the standard conditions gave
benzo[4,5]imidazo[1,2-c]quinazolines 8a and 8b in 94 and
80% yields, respectively.
Having established a procedure for hydroamination/hy-
droarylation of terminal alkynes, we next explored the one-
pot cascade reaction between symmetrical diamines and al-
kynes (Scheme 1). Pleasingly, diamines 4a and 4b, on reac-
tion with 2d under the standard conditions, gave indolo[3,2-
c]quinolines 3r and 3s in 79 and 70% yields, respectively.[28]
It is worth mentioning that this multicatalytic[29] process,
catalyzed by a single metal catalyst, involves the formation
of one C–C bond and two C–N bonds.
Scheme 2. Reaction between 2-(2-aminophenyl)benzimidazole and
2a/2d.
A mechanistic hypothesis based on π-activation cata-
lyzed by Ph3PAuNTf2 is shown in Figure 2, with substrates
1a and 2a as an example. First, coordination of the alkyne
to AuI might take place to generate Au-coordinated alkyne
Scheme 1. Ph3PAuNTf2-catalyzed one-pot synthesis of indolo-
quinolines from 4 and 2d.
Stimulated by the unique reactivity exhibited by the Ga- 9. The formed intermediate 9 would react with 1a to form
gosz catalyst for hydroamination/hydroarylation of alkynes, Au-coordinated imine 10, which might be in equilibrium
we next turned our attention towards double hydroamin- with enamine 10Ј or 10ЈЈ. A series of events such as a Fri-
ation reactions. Under the established conditions, several 2- del–Craft-type reaction, protonation and regeneration of
aminobenzamides were treated with aromatic or aliphatic Au catalyst might then occur to afford product 3a. In short,
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AuI-Catalyzed Hydroamination and Hydroarylation
the proposed mechanism involves
a tandem hydro-
amination/hydroarylation. Alternative mechanisms involv-
ing tandem hydroarylation/hydroamination were ruled out
based on the following facts: (1) A control experiment per-
formed with 1a and 2a did not show the existence of 2-
vinylpyrrole 11; the presence of starting materials and prod-
uct 3a were the only detectable species (Scheme 3); (2) the
reaction between N-phenylpyrrole 12 and 2a, under the
standard conditions, did not give product 13 – instead, de-
composition of 12 was observed (Scheme 4).
Scheme 5. Reaction between N-(2-aminophenyl)pyrrole (1a) and
acetophenone.
A crossover experiment (Scheme 6) was conducted by
treating 1a (0.126 mmol) with a 1:1 mixture of 2b/2a-d
(90%) (1 equiv. each) in the presence of 2 mol-%
Ph3PAuNTf2 at 100 °C in toluene. The reaction afforded a
45:55 mixture of 3i/3a-d (90% deuterium content) in 92%
yield. The unequal ratio of 3i/3a-d could arise from a small
difference in the rates of reactivity between the differentially
substituted alkynes. The observation that the crossover
product was not obtained clearly supports the mechanism
proposed in Figure 2.
Figure 2. Plausible mechanism exemplified with 1a and 2a.
Scheme 6. Crossover experiment.
A significant rate enhancement was observed when the
reactions were conducted under microwave conditions.[30]
Representative examples are described in Table 4. Reactions
of 1a with 2a in the presence of 2 mol-% of Ph3PAuNTf2
under microwave conditions (T = 150 °C, P = 90–110 W)
afforded 3a in 93% yield (Entry 1).[31] It is interesting to
note that 1a reacted with 2d in the presence of Ph3PAuNTf2
Scheme 3. Reaction between 1a and 2a under standard conditions.
Table 4. Ph3PAuNTf2-catalyzed hydroamination/hydroarylation
and double hydroamination of terminal alkynes under microwave
conditions.[a]
Scheme 4. Reaction between N-phenylpyrrole 12 and 1-octyne (2a).
Our proposed mechanism is entirely different to that re-
ported by Yi and Yun.[12] They treated amino-aromatics
with terminal alkynes in the presence of Ru3(CO)12 and
HBF4·OEt2 in benzene at 90–95 °C and proposed a mecha-
nism involving an intramolecular migratory insertion of
amine and subsequent α-pyrrole sp2 C–H bond activation
and cyclization via an unsaturated cationic ruthenium acet-
ylide complex. Due to the strong alkynophilicity of Au cata-
lysts, such C–H bond activation is unlikely to occur in the
present case.
To obtain further insight into the mechanism, a reaction
between 1a and acetophenone was conducted in the pres-
ence of 2 mol-% Ph3PAuNTf2 in toluene at 100 °C for 12 h.
Product 3a was obtained in 95% yield, which clearly
showed the intermediacy of the imine under the present re-
action conditions (Scheme 5).
[a] Amino-aromatics 1a/5a/7 (0.316 mmol), alkynes 2 (0.379 mmol),
Ph3PAuNTf2 (2 mol-%), toluene (2 mL), microwaves (m.w.),
150 °C, P = 90–110 W, 15 min (Biotage, Initiator Eight, single-
mode reactor). [b] Yield of purified product.
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N. T. Patil, P. G. V. V. Lakshmi, V. Singh
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27.1, 24.2, 22.5, 13.9 ppm. IR (film): νmax = 3360, 3040, 2943, 2930,
˜
to afford exclusively the desired product 3k in 91% yield
(Entry 2). This is in contrast to our previous results
(Table 2, Entry 10), wherein the use of AgOTf as a catalyst
was required. The observed difference in the case of the
microwave-assisted reaction could be attributed to the
faster reaction rate compared with conventional heating,
which suppressed the formation of the undesired prod-
uct.[27] The reaction of 2d and 2b with 5a gave 6a and 6g
in 89 and 98% yield, respectively (Entries 3 and 4). This
microwave-assisted AuI-catalyzed transformation can be
successfully extended to 2-(2-aminophenyl)benzimidazole
(7), thus leading to the formation of the corresponding
benzo[4,5]imidazo[1,2-c]quinazolines 8a and 8b in 88% and
90% yields, respectively (Entries 5 and 6).
2860, 1708, 1615, 1600, 1520, 1460, 1423, 1365, 1160, 970, 850,
740, 725, 704 cm–1. HRMS: calcd. for C18H25N2 [M+ + H]
269.2018; found 269.2022.
4-Hexyl-4,8-dimethyl-4,5-dihydropyrrolo[1,2-a]quinoxaline
(3b):
Yield: 78 mg (87%); viscous liquid; Rf = 0.63 (hexane/EtOAc =
1
90:10). H NMR (400 MHz, CDCl3): δ = 7.04 (s, 2 H), 6.68 (d, J
= 6.8 Hz, 1 H), 6.52 (d, J = 8.3 Hz, 1 H), 6.18 (t, J = 3.0 Hz, 1 H),
5.85 (dd, J = 3.0, 1.5 Hz, 1 H), 2.29 (s, 3 H), 1.45 (s, 3 H), 1.29–
1.20 (m, 10 H), 0.84 (t, J = 6.8 Hz, 3 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 132.8, 125.0, 115.3, 115.0, 113.5, 109.6, 102.8, 101.3,
53.9, 41.6, 31.7, 29.5, 26.9, 24.2, 22.5, 20.8, 13.9 ppm. IR (film):
ν
max = 3350, 3103, 3022, 2955, 2929, 2856, 1660, 1623, 1597, 1519,
˜
1482, 1419, 1375, 1334, 1285, 1032, 857, 806, 773, 706, 697 cm–1.
HRMS: calcd. for C19H27N2 [M+ + H] 283.2174; found 283.2170.
8-Chloro-4-hexyl-4-methyl-4,5-dihydropyrrolo[1,2-a]quinoxaline
(3c): Yield: 79 mg (83%); thick liquid; Rf = 0.54 (hexane/EtOAc =
90:10). 1H NMR (300 MHz, CDCl3): δ = 7.21 (d, J = 1.8 Hz, 1 H),
7.02 (dd, J = 2.8, 1.3 Hz, 1 H), 6.86 (dd, J = 8.3, 2.3 Hz, 1 H), 6.56
(d, J = 8.3 Hz, 1 H), 6.23 (t, J = 3.2 Hz, 1 H), 5.90 (dd, J = 3.2,
1.5 Hz, 1 H), 3.72 (br. s, 1 H), 1.47 (s, 3 H), 1.24–1.20 (m, 10 H),
0.84 (t, J = 6.6 Hz, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
135.9, 133.9, 133.3, 124.2, 115.9, 114.5, 113.7, 110.3, 103.4, 101.9,
Conclusions
We have developed an efficient Ph3PAuNTf2-catalyzed
direct double hydroamination and hydroamination/hydro-
arylation of terminal alkynes. Unlike our previously re-
ported methods, tethered hydroxy groups on the alkynes
are not necessary, which thereby enlarges the scope of the
reaction. These approaches provide a wide range of multi-
substituted pyrrolo[1,2-a]quinoxalines, indolo[3,2-c]quinol-
ines, indolo[1,2-a]quinoxalines, tetrahydro-4-quinazol-
inones, and benzo[4,5]imidazo[1,2-c]quinazolines from eas-
ily available starting materials. The catalyst loading is rela-
tively low in most cases and the procedure is operationally
simple. Furthermore, we have described a Ph3PAuNTf2-cat-
alyzed one-pot cascade process for the synthesis of indol-
oquinolines starting directly from symmetrical 2-[2-(2-ami-
nophenyl)-1-ethynyl]anilines and terminal alkynes.
54.0, 41.9, 31.6, 29.4, 27.0, 24.1, 22.5, 13.9 ppm. IR (film): ν
=
˜
max
3350, 3080, 2960, 2958, 2938, 2860, 1611, 1493, 1460, 1380, 1092,
1039, 848, 750, 692, 610 cm–1. HRMS: calcd. for C18H24ClN2 [M+
+ H] 303.1628; found 303.1615.
7,9-Dichloro-4-hexyl-4-methyl-4,5-dihydropyrrolo[1,2-a]quinoxaline
(3d): Yield: 72 mg (75%); viscous liquid; Rf = 0.57 (hexane/EtOAc
1
= 90:10). H NMR (300 MHz, CDCl3): δ = 7.85 (d, J = 1.5 Hz, 1
H), 6.83 (d, J = 2.3 Hz, 1 H), 6.67 (d, J = 2.1 Hz, 1 H), 6.19 (t, J
= 3.4 Hz, 1 H), 5.88 (d, J = 2.1 Hz, 1 H), 3.90 (br. s, 1 H), 1.46 (s,
3 H), 1.31–1.21 (m, 10 H), 0.85 (t, J = 6.8 Hz, 3 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 139.2, 134.8, 132.0, 122.3, 122.0, 121.1,
118.9, 114.1, 109.3, 102.6, 53.6, 40.6, 31.7, 29.4, 25.9, 24.2, 22.6,
14.1 ppm. IR (film): ν
= 3353, 3098, 2963, 2943, 2920, 2874,
˜
max
1600, 1518, 1490, 1450, 1328, 1050, 887, 844, 750, 707, 690,
605 cm–1. HRMS: calcd. for C18H23Cl2N2 [M+ + H] 337.1238;
found 337.1227.
Methyl 4-Hexyl-4-methyl-4,5-dihydropyrrolo[1,2-a]quinoxaline-8-
carboxylate (3e): Yield: 74 mg (72%); light-yellow solid; m.p. 118–
120 °C; Rf = 0.45 (hexane/EtOAc = 90:10). 1H NMR (300 MHz,
CDCl3): δ = 7.91 (d, J = 2.2 Hz, 1 H), 7.60 (dd, J = 8.3, 2.2 Hz, 1
H), 7.17 (dd, J = 3.0, 1.5 Hz, 1 H), 6.60 (d, J = 8.3 Hz, 1 H), 6.23
(t, J = 3.7 Hz, 1 H); 5.89 (dd, J = 3.0, 1.5 Hz, 1 H), 4.09 (br. s, 1
H), 3.88 (s, 3 H), 1.51 (s, 3 H), 1.48–1.19 (m, 10 H), 0.83 (t, J =
6.8 Hz, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 166.9, 139.7,
132.5, 126.9, 123.8, 119.5, 115.7, 113.9, 110.4, 103.5, 54.6, 51.8,
Experimental Section
General Procedure for Ph3PAuNTf2/AgOTf-Catalyzed Hydroamin-
ation/Hydroarylation of Terminal Alkynes: See Table 2. To a screw-
cap vial containing a stir bar, were added aromatic amine 1
(0.316 mmol), alkyne 2 (0.379 mmol), and catalyst Ph3PAuNTf2
(2 mol-% with respect to 1) or AgOTf (10 mol-% with respect to
1a) in toluene (2 mL). The reaction vial was fitted with a cap, evac-
uated and filled with nitrogen. The reaction vial was heated with
stirring at 100 °C for the specified time. The reaction mixture was
cooled to ambient temperature, diluted with ethyl acetate and fil-
tered through a plug of silica gel. The filtrate was concentrated,
and the residue was purified by silica gel column chromatography
with hexane/ethyl acetate as an eluent to afford analytically pure
product 3.
43.3, 31.7, 29.4, 28.1, 24.2, 22.5, 14.0 ppm. IR (KBr): νmax = 3328,
˜
3070, 3050, 2960, 2943, 2850, 1910, 1745, 1603, 1480, 1479, 1463,
1250, 1080, 1050, 977, 845, 775, 742 cm–1. HRMS: calcd. for
C20H27N2O2 [M+ + H] 327.2073; found 327.2063.
4-Hexyl-4,6-dimethyl-4,5-dihydropyrrolo[1,2-a]quinoxaline (3f):
1
Yield: 58 mg (65%); liquid; Rf = 0.72 (hexane/EtOAc = 90:10). H
4-Hexyl-4-methyl-4,5-dihydropyrrolo[1,2-a]quinoxaline (3a): Yield: NMR (300 MHz, CDCl3): δ = 7.21 (dd, J = 3.0, 1.5 Hz, 1 H), 6.80
1
76 mg (90%); liquid; Rf = 0.62 (hexane/EtOAc = 90:10). H NMR
(t, J = 7.5 Hz, 1 H), 6.60 (d, J = 7.5 Hz, 1 H), 6.52 (d, J = 7.5 Hz,
(400 MHz, CDCl3): δ = 7.26–7.24 (m, 1 H), 7.09–7.08 (m, 1 H), 1 H), 6.18 (t, J = 3.0 Hz, 1 H), 5.87 (dd, J = 3.0, 1.5 Hz, 1 H), 3.64
6.90 (dt, J = 8.1, 1.6 Hz, 1 H), 6.75 (dt, J = 8.1, 1.6 Hz, 1 H), 6.64
(d, J = 7.2 Hz, 1 H), 6.23 (t, J = 3.2 Hz, 1 H), 5.90 (dd, J = 3.2,
(br. s, 1 H), 2.60 (s, 3 H), 1.44 (s, 3 H), 1.29–1.19 (m, 10 H), 0.84
(t, J = 6.8 Hz, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 137.2,
1.6 Hz, 1 H), 1.51 (s, 3 H), 1.46–1.24 (m, 10 H), 0.87 (t, J = 6.8 Hz, 125.7, 124.5, 123.2, 118.5, 114.1, 108.7, 101.7, 53.3, 40.2, 31.8, 29.6,
3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 135.2, 131.2, 124.6,
25.9, 24.3, 22.7, 21.6, 14.2 ppm. IR (film): νmax = 3350, 3095, 3054,
˜
118.6, 115.3, 114.4, 113.6, 109.9, 109.7, 102.9, 54.1, 41.9, 31.7, 29.4,
2956, 2929, 2855, 1597, 1502, 1491, 1415, 1376, 1297, 1164, 1093,
4726
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 4719–4731

AuI-Catalyzed Hydroamination and Hydroarylation
886, 771, 707, 701, 611 cm–1. HRMS: calcd. for C19H27N2 [M+
H] 283.2174; found 283.2180.
+
= 90:10). 1H NMR (300 MHz, CDCl3): δ = 7.22–7.15 (m, 3 H),
7.08 (s, 1 H), 6.86 (dt, J = 7.5, 1.5 Hz, 1 H), 6.75–6.64 (m, 4 H),
6.22 (t, J = 3.1 Hz, 1 H), 5.89–5.88 (m, 1 H), 4.16 (br. s, 1 H), 3.70
(s, 3 H), 1.82 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 158.3,
137.9, 134.5, 133.1, 126.9, 125.8, 124.6, 119.7, 116.1, 114.6, 114.2,
4-Hexyl-4-methyl-4,5-dihydropyrrolo[1,2-a]quinoxalin-7-yl Methyl
Ether (3g): Yield: 84 mg (89%); light-yellow solid; m.p. 118–120 °C;
1
Rf = 0.48 (hexane/EtOAc = 90:10). H NMR (300 MHz, CDCl3):
113.4, 109.9, 105.5, 56.7, 55.1, 28.9 ppm. IR (film): ν
= 3328,
˜
max
δ = 7.12 (d, J = 8.3 Hz, 1 H), 6.98 (dd, J = 3.0, 1.5 Hz, 1 H), 6.28–
6.24 (m, 1 H), 6.17 (dd, J = 6.8, 3.0 Hz, 2 H), 5.84 (dd, J = 3.7,
1.5 Hz, 1 H), 3.74 (s, 3 H), 3.63 (br. s, 1 H), 1.46 (s, 3 H), 1.33–
1.21 (m, 10 H), 0.84 (t, J = 6.8 Hz, 3 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 157.1, 136.5, 130.9, 119.4, 115.0, 113.2, 109.5, 103.3,
102.5, 101.2, 55.2, 54.2, 42.2, 31.8, 29.6, 27.4, 24.3, 22.6, 14.2 ppm.
3054, 2959, 1707, 1627, 1480, 1432, 1240, 1030, 774, 743, 692,
608 cm–1. HRMS: calcd. for C19H19N2O [M+ + H] 291.1497; found
291.1493.
3-(4-Methyl-4,5-dihydropyrrolo[1,2-a]quinoxalin-4-yl)phenol (3n):
1
Yield: 68 mg (78%); liquid; Rf = 0.24 (hexane/EtOAc = 90:10). H
NMR (300 MHz, CDCl3): δ = 7.16 (dd, J = 7.7, 1.1 Hz, 1 H), 7.06
(dd, J = 2.8, 1.3 Hz, 1 H), 6.99 (t, J = 7.9 Hz, 1 H), 6.81 (dt, J =
7.5, 1.1 Hz, 1 H), 6.75–6.59 (m, 4 H), 6.49 (dd, J = 8.1, 2.4 Hz, 1
H), 6.22 (t, J = 3.2 Hz, 1 H), 5.96–5.94 (m, 1 H), 1.78 (s, 3 H) ppm.
13C NMR (75 MHz, [D6]DMSO): δ = 156.7, 148.7, 136.1, 132.5,
128.4, 124.6, 124.3, 117.4, 116.1, 115.1, 114.1, 113.9, 113.1, 112.9,
IR (KBr): ν
= 3347, 3012, 3002, 2979, 1609, 1583, 1510, 1472,
˜
max
1462, 1334, 1248, 1179, 1031, 829, 751, 743, 704, 691 cm–1. HRMS:
calcd. for C19H27N2O [M+ + H] 299.2123; found 299.2132.
8-Fluoro-4-hexyl-4-methyl-4,5-dihydropyrrolo[1,2-a]quinoxaline
(3h): Yield: 43 mg (48%); viscous liquid; Rf = 0.68 (hexane/EtOAc
= 90:10). 1H NMR (300 MHz, CDCl3): δ = 7.41 (dd, J = 8.8,
4.9 Hz, 1 H), 6.43–6.33 (m, 3 H), 6.01 (d, J = 2.9 Hz, 1 H), 5.78
(d, J = 3.9 Hz, 1 H), 3.65 (br. s, 1 H), 1.43 (s, 3 H), 1.29–1.21 (m,
10 H), 0.85 (t, J = 6.8 Hz, 3 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 158.4, 132.8, 128.3, 124.6, 121.3, 115.2, 115.0, 113.5, 109.7,
104.4, 102.9, 102.2, 101.8, 54.3, 42.2, 31.6, 29.4, 27.2, 24.2, 22.5,
109.5, 103.6, 55.9, 29.2 ppm. IR (film): ν
= 3369, 3358, 3057,
˜
max
2958, 1907, 1598, 1497, 1458, 1220, 1054, 810, 750, 648 cm–1
.
HRMS: calcd. for C18H17N2O [M+ + H] 277.1341; found 277.1331.
3-(4-Methyl-4,5-dihydropyrrolo[1,2-a]quinoxalin-4-yl)aniline (3o):
Yield: 60 mg (67%); yellow solid; m.p. 120–122 °C; Rf = 0.43 (hex-
1
ane/EtOAc = 85:15). H NMR (300 MHz, CDCl3): δ = 7.26–7.16
13.9 ppm. IR (film): ν
= 3356, 3049, 2957, 2928, 2856, 1705,
˜
max
(m, 1 H), 7.08–7.07 (m, 1 H), 6.96 (t, J = 7.7 Hz, 1 H), 6.85 (dt, J
= 7.5, 1.3 Hz, 1 H), 6.77–6.64 (m, 3 H), 6.48 (s, 1 H), 6.38 (d, J =
7.7 Hz, 1 H), 6.23 (t, J = 3.0 Hz, 1 H), 5.94 (d, J = 2.0 Hz, 1 H),
3.48 (br. s, 3 H), 1.81 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 147.7, 146.0, 135.2, 132.9, 129.3, 129.0, 124.6, 119.0, 115.8,
115.6, 114.5, 114.1, 113.7, 113.0, 109.8, 104.5, 56.7, 29.2 ppm. IR
1622, 1525, 1493, 1467, 1377, 1278, 1159, 1104, 996, 883, 770,
630 cm–1. HRMS: calcd. for C18H24FN2 [M+ + H] 287.1924; found
287.1911.
4-Methyl-4-phenethyl-4,5-dihydropyrrolo[1,2-a]quinoxaline (3i):
1
Yield: 68 mg (75%); liquid; Rf = 0.48 (hexane/EtOAc = 90:10). H
NMR (300 MHz, CDCl3): δ = 7.25–7.13 (m, 3 H), 7.12–7.02 (m, 4
H), 6.87 (dt, J = 7.5, 1.5 Hz, 1 H), 6.73 (dt, J = 7.5, 1.5 Hz, 1 H),
6.56 (dd, J = 7.5, 1.5 Hz, 1 H), 6.22 (t, J = 3.7 Hz, 1 H), 5.95 (dd,
J = 3.0, 1.5 Hz, 1 H), 2.69–2.57 (m, 2 H), 2.19–2.05 (m, 1 H), 1.98–
1.88 (m, 1 H), 1.55 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ
= 142.0, 132.8, 128.8, 128.3, 128.2, 125.7, 124.7, 118.7, 118.1, 115.4,
114.4, 113.8, 109.9, 103.1, 54.3, 43.9, 31.0, 27.7 ppm. IR (film):
(KBr): νmax = 3399, 3280, 3100, 1699, 1607, 1550, 1495, 1440, 1350,
˜
1210, 1050, 852, 750, 703 cm–1. HRMS: calcd. for C18H18N3 [M+
+ H] 276.1501; found 276.1501.
4-Cyclohexyl-4-methyl-4,5-dihydropyrrolo[1,2-a]quinoxaline (3p):
Yield: 79 mg (94%); viscous liquid; Rf = 0.69 (hexane/EtOAc =
1
90:10). H NMR (300 MHz, CDCl3): δ = 7.21–7.18 (m, 1 H), 7.05
(s, 1 H), 6.85 (t, J = 7.7 Hz, 1 H), 6.68 (t, J = 7.5 Hz, 1 H), 6.58
(d, J = 7.7 Hz, 1 H), 6.19 (t, J = 2.8 Hz, 1 H), 5.86 (d, J = 1.8 Hz,
1 H), 3.86 (br. s, 1 H), 1.78–1.59 (m, 5 H), 1.46 (s, 3 H), 1.14–0.84
(m, 6 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 135.3, 132.6,
124.5, 117.9, 114.5, 114.1, 113.9, 113.4, 109.4, 104.2, 56.4, 47.1,
ν
max = 3359, 3040, 2949, 2927, 2860, 1708, 1612, 1600, 1490, 1473,
˜
1336, 770, 739, 690 cm–1. HRMS: calcd. for C20H21N2 [M+ + H]
289.1705; found 289.1716.
(4-Methyl-4,5-dihydropyrrolo[1,2-a]quinoxalin-4-yl)methanol (3j):
Yield: 45 mg (67%); white solid; m.p. 138–140 °C; Rf = 0.33 (hex-
ane/EtOAc = 90:10). H NMR (500 MHz, CDCl3): δ = 7.23 (t, J
= 7.7 Hz, 1 H), 7.10 (s, 1 H), 6.89 (t, J = 7.7 Hz, 1 H), 6.75 (t, J =
7.7 Hz, 1 H), 6.68 (d, J = 7.7 Hz, 1 H), 6.23 (t, J = 2.8 Hz, 1 H),
5.97 (d, J = 1.9 Hz, 1 H), 3.55 (ABq, J = 10.6 Hz, 2 H), 1.53 (s, 3
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 134.6, 124.8, 118.9,
115.8, 114.4, 114.1, 113.9, 113.8, 110.1, 104.1, 67.9, 54.9, 23.7 ppm.
35.4, 27.6, 26.9, 26.4, 26.2, 23.5 ppm. IR (film): νmax = 3356, 3057,
˜
1
2953, 2930, 2850, 1708, 1640, 1600, 1495, 1472, 1303, 1049, 745,
705, 430 cm–1. HRMS: calcd. for C18H23N2 [M+ + H] 267.1861;
found 267.1863.
4-Methyl-4-(2-pyridyl)-4,5-dihydropyrrolo[1,2-a]quinoxaline (3q):
Yield: 44 mg (53%); white solid; m.p. 70–72 °C; Rf = 0.27 (hexane/
EtOAc = 90:10). 1H NMR (300 MHz, CDCl3): δ = 8.49 (d, J =
4.5 Hz, 1 H), 7.48–7.36 (m, 2 H), 7.17–7.16 (m, 2 H), 7.01–6.96 (m,
1 H), 6.89–6.77 (m, 3 H), 6.33 (t, J = 3.0 Hz, 1 H), 6.21 (dd, J =
3.7, 1.5 Hz, 1 H), 5.29 (br. s, 1 H), 1.88 (s, 3 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 148.7, 145.4, 136.4, 129.9, 127.8, 125.2,
124.6, 121.8, 120.7, 119.2, 116.4, 114.3, 110.0, 107.6, 105.7, 57.8,
IR (KBr): ν
= 3356, 3335, 3020, 2960, 2800, 1998, 1620, 1600,
˜
max
1493, 1456, 1290, 1052, 850, 740, 430 cm–1. HRMS: calcd. for
C13H13N2O [M+ – H] 213.1028; found 213.1039.
4-Methyl-4-phenyl-4,5-dihydropyrrolo[1,2-a]quinoxaline (3k): Yield:
80 mg (97%); viscous liquid; Rf = 0.48 (hexane/EtOAc = 90:10).
1H NMR (300 MHz, CDCl3): δ = 7.27–7.15 (m, 5 H), 7.13–7.07
(m, 2 H), 6.86 (dt, J = 7.5, 1.5 Hz, 1 H), 6.74–6.65 (m, 2 H), 6.23
(t, J = 3.0 Hz, 1 H), 5.94 (dd, J = 3.0, 1.5 Hz, 1 H), 1.85 (s, 3 H)
ppm. 13C NMR (75 MHz, CDCl3): δ = 132.9, 128.1, 126.8, 125.6,
124.6, 119.2, 115.7, 114.1, 109.9, 104.5, 56.8, 29.3 ppm. IR (film):
28.2 ppm. IR (KBr): ν
= 3340, 3080, 3057, 2959, 1612, 1598,
˜
max
1448, 1430, 1426, 1050, 1016, 749, 740, 704 cm–1. HRMS: calcd.
for C17H15N3Na [M+ + Na] 284.1164; found 284.1154.
6-Methyl-6-phenyl-6,11-dihydro-5H-indolo[3,2-c]quinoline (3r):
Yield: 88 mg (90%); pale-yellow solid; m.p. 98–100 °C; Rf = 0.46
(hexane/EtOAc = 90:10). 1H NMR (400 MHz, CDCl3): δ = 8.12
(br. s, 1 H), 7.61 (d, J = 7.3 Hz, 2 H), 7.29–7.23 (m, 3 H), 7.19 (t,
J = 7.3 Hz, 2 H), 7.03–6.95 (m, 2 H), 6.88 (d, J = 8.0 Hz, 1 H),
6.83 (t, J = 7.3 Hz, 1 H), 6.64 (t, J = 7.3 Hz, 1 H), 6.48 (d, J =
8.0 Hz, 1 H), 2.07 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
ν
max = 3320, 3100, 2942, 1918, 1643, 1605, 1489, 1459, 1320, 1229,
˜
1058, 850, 740, 704 cm–1. HRMS: calcd. for C18H17N2 [M+ + H]
261.1392; found 261.1402.
4-(4-Methoxyphenyl)-4-methyl-4,5-dihydropyrrolo[1,2-a]quinoxaline
(3l): Yield: 46 mg (50%); viscous liquid; Rf = 0.31 (hexane/EtOAc
Eur. J. Org. Chem. 2010, 4719–4731
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4727

N. T. Patil, P. G. V. V. Lakshmi, V. Singh
FULL PAPER
147.9, 142.5, 137.1, 130.2, 128.6, 128.1, 126.9, 126.5, 125.6, 121.8,
120.0, 119.9, 119.3, 117.1, 114.2, 113.3, 110.9, 59.1, 29.0 ppm. IR
126.6, 126.5, 125.6, 125.5, 120.6, 118.6, 116.6, 112.4, 112.0, 110.9,
70.3, 57.2, 28.4 ppm. IR (film): ν
= 3471, 3375, 3209, 3001,
˜
max
(KBr): νmax = 3409, 3053, 3022, 2965, 2922, 1623, 1607, 1573, 1509,
2935, 2840, 1619, 1580, 1504, 1439, 1388, 1256, 1092, 1056, 978,
˜
1460, 1319, 1135, 1027, 921, 844, 704, 697, 607, 465 cm–1. HRMS: 924, 741, 698 cm–1. HRMS: calcd. for C29H25N2O [M+ + H]
calcd. for C22H19N2 [M+ + H] 311.1548; found 311.1535.
417.1967; found 417.1979.
2,6,8-Trimethyl-6-phenyl-6,11-dihydro-5H-indolo[3,2-c]quinoline
(3s): Yield: 98 mg (92%); white solid; m.p. 208–210 °C; Rf = 0.53
(hexane/EtOAc = 90:10). 1H NMR (500 MHz, CDCl3): δ = 8.01
(br. s, 1 H), 7.55 (d, J = 7.9 Hz, 2 H), 7.25 (t, J = 7.0 Hz, 2 H),
7.16 (t, J = 7.0 Hz, 1 H), 7.10 (d, J = 7.9 Hz, 1 H), 6.97 (s, 1 H),
6.82 (d, J = 7.9 Hz, 1 H), 6.76 (d, J = 7.9 Hz, 1 H), 6.71 (s, 1 H),
6.38 (d, J = 7.9 Hz, 1 H), 2.24 (s, 3 H), 2.23 (s, 3 H), 2.05 (s, 3 H)
ppm. 13C NMR (75 MHz, CDCl3): δ = 147.1, 141.0, 135.4, 129.4,
129.0, 128.0, 126.7, 126.3, 123.3, 120.5, 119.1, 113.9, 113.7, 113.3,
6-Methyl-9-nitro-6-phenyl-5,6-dihydroindolo[1,2-a]quinoxaline (3x):
Yield: 81 mg (72%); orange solid; m.p. 212–213 °C; Rf = 0.37 (hex-
ane/EtOAc = 90:10). H NMR (500 MHz, CDCl3): δ = 8.52 (s, 1
H), 8.13 (d, J = 8.7 Hz, 1 H), 7.98 (d, J = 8.7 Hz, 1 H), 7.77 (d, J
= 7.8 Hz, 1 H), 7.32 (d, J = 8.7 Hz, 2 H), 7.27–7.24 (m, 2 H), 7.19–
7.15 (m, 1 H), 7.03 (t, J = 7.8 Hz, 1 H), 6.95–6.90 (m, 1 H), 6.88–
6.84 (m, 1 H), 6.50 (s, 1 H), 4.36 (br. s, 1 H), 1.95 (s, 3 H) ppm.
13C NMR (75 MHz, CDCl3): δ = 145.1, 143.9, 142.1, 136.6, 130.0,
128.9, 128.4, 127.5, 125.8, 125.5, 120.1, 117.8, 117.7, 117.1, 116.9,
1
110.5, 61.7, 29.6, 28.9, 21.5 ppm. IR (KBr): ν
= 3227, 3049,
˜
max
116.5, 111.4, 105.5, 100.5, 57.5, 28.7 ppm. IR (KBr): ν
= 3359,
˜
max
2921, 2916, 1616, 1556, 1515, 1445, 1310, 1216, 1028, 795,
632 cm–1. HRMS: calcd. for C24H23N2 [M+ + H] 339.1861; found
339.1877.
3024, 2922, 2853, 1619, 1599, 1509, 1462, 1343, 1313, 1072, 886,
744, 458 cm–1. HRMS: calcd. for C22H18N3O2 [M+ + H] 356.1399;
found 356.1394.
2,8-Dichloro-6-methyl-6-phenyl-6,11-dihydro-5H-indolo[3,2-c]-
quinoline (3t): Yield: 114 mg (95%); pale-yellow solid; m.p. 120–
122 °C; Rf = 0.46 (hexane/EtOAc = 90:10). 1H NMR (500 MHz,
CDCl3): δ = 8.10 (br. s, 1 H), 7.49 (d, J = 8.8 Hz, 2 H), 7.25 (t, J
= 7.0 Hz, 2 H), 7.19–7.12 (m, 3 H), 6.96–6.89 (m, 2 H), 6.79 (s, 1
H), 6.38 (s, 1 H), 2.01 (s, 3 H) ppm. 13C NMR (100 MHz, [D6]-
DMSO): δ = 149.7, 148.8, 142.5, 135.8, 131.1, 128.1, 127.9, 126.5,
125.7, 123.7, 121.3, 120.7, 119.1, 117.8, 114.3, 113.9, 113.0, 112.7,
2,6-Dimethyl-6-phenyl-5,6-dihydroindolo[1,2-a]quinoxaline (3y):
Yield: 77 mg (75%); white solid; m.p. 118–120 °C; Rf = 0.33 (hex-
ane/EtOAc = 90:10). H NMR (500 MHz, CDCl3): δ = 7.95 (d, J
= 8.3 Hz, 1 H), 7.59–7.55 (m, 2 H), 7.31–7.07 (m, 7 H), 6.72–6.65
(m, 2 H), 6.34 (s, 1 H), 4.09 (br. s, 1 H), 2.33 (s, 3 H), 1.89 (s, 3 H)
ppm. 13C NMR (75 MHz, CDCl3): δ = 144.8, 141.4, 133.9, 133.3,
129.5, 128.1, 127.7, 127.3, 127.0, 125.9, 124.5, 122.3, 120.9, 120.7,
1
117.4, 116.6, 111.7, 98.9, 57.7, 28.9, 21.2 ppm. IR (KBr): ν
=
˜
max
58.2, 29.1 ppm. IR (KBr): ν
= 3391, 2921, 1605, 1567, 1506,
˜
max
3350, 3067, 2950, 1689, 1604, 1480, 1432, 1305, 1050, 1016, 849,
743, 707 cm–1. HRMS: calcd. for C23H21N2 [M+ + H] 325.1705;
found 325.1704.
1462, 1371, 1295, 1180, 1068, 943, 857, 797, 766, 703, 594 cm–1.
HRMS: calcd. for C22H15Cl2N2 [M+ – H] 377.0612; found
377.0626.
2-Chloro-6-methyl-6-phenyl-5,6-dihydroindolo[1,2-a]quinoxaline
(3z): Yield: 73 mg (70%); liquid; Rf = 0.59 (hexane/EtOAc = 90:10).
1H NMR (300 MHz, CDCl3): δ = 7.90 (d, J = 8.3 Hz, 1 H), 7.75
(d, J = 2.6 Hz, 1 H), 7.56 (d, J = 7.5 Hz, 1 H), 7.29–7.04 (m, 7 H),
6.86 (dd, J = 8.3, 2.2 Hz, 1 H), 6.68–6.65 (d, J = 8.3 Hz, 1 H), 6.35
(s, 1 H), 1.89 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 144.3,
140.8, 134.4, 133.9, 129.6, 128.3, 127.3, 125.8, 124.6, 123.7, 122.8,
121.3, 121.2, 117.3, 116.8, 111.5, 110.9, 99.6, 57.7, 28.9 ppm. IR
6-Methyl-6-phenyl-5,6-dihydroindolo[1,2-a]quinoxaline (3u): Yield:
94 mg (96%); pale-yellow solid; m.p. 76–78 °C; Rf = 0.59 (hexane/
EtOAc = 90:10). 1H NMR (300 MHz, CDCl3): δ = 7.95 (d, J =
7.5 Hz, 1 H), 7.79 (dd, J = 7.5, 1.5 Hz, 1 H), 7.56 (d, J = 6.8 Hz,
1 H), 7.33–7.29 (m, 2 H), 7.22–7.09 (m, 5 H), 6.94–6.84 (m, 2 H),
6.77 (dd, J = 7.5, 2.2 Hz, 1 H), 6.32 (s, 1 H), 1.92 (s, 3 H) ppm.
13C NMR (75 MHz, CDCl3): δ = 140.4, 136.3, 131.7, 131.2, 129.7,
128.8, 128.6, 128.5, 128.0, 124.8, 122.1, 120.9, 120.0, 116.3, 110.7,
(film): νmax = 3365, 3057, 2924, 2853, 1594, 1561, 1500, 1455, 1415,
˜
103.0, 59.3, 20.2 ppm. IR (KBr): ν
= 3444, 3360, 3054, 2916,
˜
max
1362, 1296, 1232, 1090, 1026, 861, 806, 769, 746, 578 cm–1. HRMS:
calcd. for C22H18ClN2 [M+ + H] 345.1159; found 345.1150.
1624, 1603, 1515, 1459, 1332, 1213, 1130, 1009, 884, 827, 762, 746,
617 cm–1. HRMS: calcd. for C22H19N2 [M+ + H] 311.1548; found
311.1536.
9-Methoxy-6-methyl-6-phenyl-5,6-dihydrophenanthridine (3aa):
1
Yield: 71 mg (75%); liquid; Rf = 0.61 (hexane/EtOAc = 80:20). H
8-Methoxy-6-methyl-6-phenyl-5,6-dihydroindolo[1,2-a]quinoxaline
(3v): Yield: 105 mg (98%); pale-yellow solid; m.p. 130–132 °C; Rf
NMR (300 MHz, CDCl3): δ = 7.60 (dd, J = 8.3, 1.5 Hz, 1 H), 7.48–
7.45 (m, 2 H), 7.27–7.15 (m, 4 H), 7.04 (dt, J = 7.5, 1.5 Hz, 1 H),
6.77–6.74 (m, 1 H), 6.73 (s, 1 H), 6.66–6.62 (m, 1 H), 6.57 (dd, J
= 8.3, 1.5 Hz, 1 H), 3.82 (s, 3 H), 1.81 (s, 3 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 158.6, 147.5, 143.3, 132.7, 131.9, 130.1,
129.0, 128.4, 128.1, 127.8, 126.8, 123.2, 118.5, 115.1, 112.5, 107.4,
1
= 0.59 (hexane/EtOAc = 90:10). H NMR (300 MHz, CDCl3): δ =
7.76 (dd, J = 7.5, 1.5 Hz, 1 H), 7.56 (d, J = 8.3 Hz, 1 H), 7.31–7.29
(m, 2 H), 7.22–7.08 (m, 4 H), 6.94–6.82 (m, 2 H), 6.78 (dd, J = 7.5,
1.5 Hz, 1 H), 6.55 (d, J = 8.3 Hz, 1 H), 6.49 (s, 1 H), 3.94 (s, 3 H),
1.91 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 153.3, 145.0,
136.3, 128.5, 128.2, 128.0, 127.1, 126.0, 125.6, 124.2, 123.3, 119.8,
116.9, 116.5, 105.3, 104.0, 100.9, 95.9, 64.5, 55.4, 29.2 ppm. IR
59.1, 55.1, 28.7 ppm. IR (film): ν
= 3332, 3053, 2959, 2928,
˜
max
1888, 1605, 1493, 1453, 1411, 1371, 1318, 1283, 1224, 1144, 1076,
1026, 855, 757, 696 cm–1. HRMS: calcd. for C21H20NO [M+ + H]
302.1545; found 302.1551.
(KBr): νmax = 3360, 3056, 2927, 2836, 1599, 1577, 1557, 1436, 1361,
˜
1254, 1184, 1085, 990, 761, 642 cm–1. HRMS: calcd. for
C23H21N2O [M+ + H] 341.1654; found 341.1655.
6-Hexyl-6-methyl-5,6-dihydro-9-phenanthridinyl Methyl Ether (3ab):
1
9-(Benzyloxy)-6-methyl-6-phenyl-5,6-dihydroindolo[1,2-a]quin- Yield: 70 mg (72%); liquid; Rf = 0.69 (hexane/EtOAc = 80:20). H
oxaline (3w): Yield: 98 mg (75%); thick liquid; Rf = 0.51 (hexane/
EtOAc = 90:10). H NMR (500 MHz, [D6]DMSO): δ = 7.83–7.79
NMR (300 MHz, CDCl3): δ = 7.59 (d, J = 8.3 Hz, 1 H), 7.21–7.20
(m, 1 H), 7.08–7.01 (m, 2 H), 6.76–6.70 (m, 2 H), 6.53 (d, J =
7.5 Hz, 1 H), 3.86 (s, 3 H), 1.49 (s, 3 H), 1.38–1.21 (m, 10 H), 0.85
1
(m, 1 H), 7.66–7.62 (m, 1 H), 7.46–7.41 (m, 2 H), 7.36–7.24 (m, 5
H), 7.17–7.04 (m, 4 H), 6.99–6.93 (m, 1 H), 6.89–6.85 (m, 2 H), (t, J = 6.8 Hz, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 158.4,
6.81–6.73 (m, 1 H), 6.34–6.32 (m, 1 H), 5.11–5.07 (m, 2 H), 1.88
(s, 3 H) ppm. 13C NMR (100 MHz, [D6]DMSO): δ = 153.3, 141.3,
137.1, 136.9, 131.3, 129.7, 128.8, 128.5, 127.9, 127.6, 127.3, 127.2,
143.8, 132.5, 132.0, 128.9, 125.2, 123.1, 120.6, 118.1, 114.9, 112.6,
107.4, 55.7, 55.2, 41.9, 31.7, 29.5, 28.1, 24.1, 22.5, 14.0 ppm. IR
(film): νmax = 3369, 2928, 2856, 1710, 1608, 1498, 1458, 1421, 1376,
˜
4728
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 4719–4731

AuI-Catalyzed Hydroamination and Hydroarylation
1304, 1216, 1172, 1039, 863, 812, 747, 628 cm–1. HRMS: calcd. for
C21H28NO [M+ + H] 310.2171; found 310.2182.
(CHCl3/MeOH = 95:05). 1H NMR (300 MHz, [D6]DMSO): δ =
8.81 (br. s, 1 H), 7.85 (br. s, 1 H), 7.46 (d, J = 7.4 Hz, 2 H), 7.26
(t, J = 7.2 Hz, 2 H), 7.16 (t, J = 7.2 Hz, 1 H), 7.06 (t, J = 7.7 Hz,
1 H), 6.75 (d, J = 8.3 Hz, 1 H), 6.53 (d, J = 7.7 Hz, 1 H); 1.62 (s,
3 H) ppm. 13C NMR (75 MHz, [D6]DMSO): δ = 161.3, 149.8,
147.0, 132.9, 128.5, 128.0, 127.7, 127.1, 125.0, 119.9, 113.8, 111.8,
6-Methyl-6-phenyl-5,6-dihydrophenanthridine (3ac): Yield: 26 mg
(30 %); liquid; Rf = 0.71 (hexane/EtOAc = 80:20). 1H NMR
(300 MHz, CDCl3): δ = 7.78–7.75 (m, 2 H), 7.42–7.34 (m, 5 H),
7.30–7.22 (m, 3 H), 7.17–7.09 (m, 2 H), 6.76 (dd, J = 7.7, 1.0 Hz,
1 H), 1.95 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 149.0,
139.8, 139.2, 132.9, 131.6, 130.0, 129.0, 128.9, 128.6, 128.4, 128.0,
69.3, 30.5 ppm. IR (KBr): ν
= 3391, 3198, 3063, 2921, 1665,
˜
max
1602, 1562, 1492, 1458, 1380, 1358, 1200, 1125, 1029, 926, 856,
794, 704, 581 cm–1. HRMS: calcd. for C15H14ClN2O [M+ + H]
273.0795; found 273.0785.
127.7, 126.9, 126.4, 123.6, 119.7, 56.7, 26.4 ppm. IR (film): ν
=
˜
max
3373, 3057, 2923, 1951, 1810, 1684, 1634, 1592, 1473, 1438, 1365,
1289, 1208, 1077, 742, 695, 574 cm–1. HRMS: calcd. for C20H18N
[M+ + H] 272.1439; found 272.1427.
5-Fluoro-2-methyl-2-phenyl-1,2,3,4-tetrahydro-4-quinazolinone (6e):
Yield: 78 mg (96 %); white solid; m.p. 216–218 °C; Rf = 0.52
(CHCl3/MeOH = 95:05). 1H NMR (500 MHz, [D6]DMSO): δ =
8.44 (br. s, 1 H), 7.47 (m, 3 H), 7.24 (t, J = 7.2 Hz, 2 H), 7.15 (t,
J = 7.2 Hz, 1 H), 7.07 (m, 1 H), 6.56 (d, J = 7.8 Hz, 1 H), 6.20 (t,
J = 8.5 Hz, 1 H), 1.68 (s, 3 H) ppm. 13C NMR (75 MHz, [D6]-
DMSO): δ = 163.8, 161.1, 160.4, 149.5, 147.1, 134.1, 133.9, 131.4,
131.2, 128.0, 127.1, 125.0, 111.6, 110.4, 104.4, 104.1, 101.7, 101.4,
General Procedure for the Ph3PAuNTf2-Catalyzed One-Pot Synthe-
sis of Indoloquinolines 3 from 4 and 2d: See Scheme 1. A solution
of aromatic amine 4 (0.316 mmol) in toluene (2 mL) was treated
with alkyne 2d (0.379 mmol) in the presence of Ph3PAuNTf2
(2 mol-% with respect to 4) according to the procedure described
for 1, to afford 3.
69.8, 30.4 ppm. IR (KBr): ν
= 3399, 3186, 3055, 2926, 1666,
˜
max
General Procedure for the Ph3PAuNTf2-Catalyzed Double Hydro-
amination of Terminal Alkynes: See Table 3 and Scheme 2. A solu-
tion of 2-aminobenzamide 5 or 2-(2-aminophenyl)benzimidazole 7
(0.316 mmol) in toluene (2 mL) was treated with alkyne 2
(0.379 mmol) in the presence of Ph3PAuNTf2 (2–5 mol-% with re-
spect to 5/7), according to the procedure described for the synthesis
of 3 from 1, to give analytically pure 6 and 8.
1625, 1569, 1449, 1371, 1317, 1224, 1205, 1146, 1044, 1028, 799,
783, 750 cm–1. HRMS: calcd. for C15H14FN2O [M+ + H] 257.1090;
found 257.1099.
6-Bromo-2-methyl-2-phenyl-1,2,3,4-tetrahydro-4-quinazolinone (6f):
Yield: 75 mg (75 %); yellow solid; m.p. 178–180 °C; Rf = 0.63
(CHCl3/MeOH = 95:05). 1H NMR (300 MHz, [D6]DMSO): δ =
8.83 (br. s, 1 H), 7.69 (br. s, 1 H), 7.57 (d, J = 2.3 Hz, 1 H), 7.47
(d, J = 7.6 Hz, 2 H), 7.25 (t, J = 7.2 Hz, 3 H), 7.16 (t, J = 7.2 Hz,
1 H), 6.73 (d, J = 8.7 Hz, 1 H), 1.67 (s, 3 H) ppm. 13C NMR
(75 MHz, [D6]DMSO): δ = 162.5, 147.1, 146.2, 135.7, 129.2, 128.0,
2-Methyl-2-phenyl-1,2,3,4-tetrahydro-4-quinazolinone (6a): Yield:
64 mg (85 %); yellow solid; m.p. 214–215 °C (ref.[32] m.p. 225–
1
229 °C); Rf = 0.59 (CHCl3/MeOH = 95:05). H NMR (300 MHz,
[D6]DMSO): δ = 8.63 (br. s, 1 H), 7.50 (dd, J = 7.2, 1.7 Hz, 3 H),
7.38 (br. s, 1 H), 7.23 (t, J = 7.2 Hz, 2 H), 7.14 (t, J = 7.3 Hz, 2
H), 6.75 (d, J = 7.9 Hz, 1 H), 6.55 (t, J = 6.9 Hz, 1 H), 1.68 (s, 3
H) ppm. 13C NMR (75 MHz, [D6]DMSO): δ = 163.7, 147.6, 147.1,
133.2, 127.8, 127.2, 126.9, 125.1, 116.7, 114.9, 114.2, 70.1,
127.2, 125.0, 118.5, 116.7, 107.8, 70.2, 30.4 ppm. IR (KBr): ν
=
˜
max
3300, 3156, 3049, 2968, 1901, 1690, 1604, 1545, 1480, 1456, 1050,
749, 658, 448 cm–1. HRMS: calcd. for C15H14BrN2O [M+ + H]
317.0290; found 317.0282.
2-Methyl-2-phenethyl-1,2,3,4-tetrahydro-4-quinazolinone (6g):
Yield: 82 mg (98 %); white solid; m.p. 148–150 °C; Rf = 0.66
(CHCl3/MeOH = 95:05). 1H NMR (500 MHz, [D6]DMSO): δ =
7.77 (s, 1 H), 7.65 (d, J = 7.3 Hz, 1 H), 7.19 (t, J = 7.3 Hz, 2 H),
7.15 (d, J = 7.3 Hz, 2 H), 7.09 (t, J = 7.3 Hz, 1 H), 6.63–6.59 (m,
2 H), 6.14 (br. s, 1 H), 2.79–2.68 (m, 2 H), 2.03–1.91 (m, 2 H), 1.47
(s, 3 H) ppm. 13C NMR (75 MHz, [D6]DMSO): δ = 163.1, 147.1,
141.9, 133.2, 128.3, 128.1, 127.1, 125.6, 116.2, 114.1, 113.5, 68.9,
30.6 ppm. IR (KBr): ν
= 3406, 3180, 3050, 3022, 2993, 2936,
˜
max
2908, 1667, 1614, 1560, 1493, 1445, 1382, 1217, 1151, 1028, 946,
807, 776, 747, 703, 561 cm–1. HRMS: calcd. for C15H15N2O [M+
H] 239.1184; found 239.1188.
+
2,7-Dimethyl-2-phenyl-1,2,3,4-tetrahydro-4-quinazolinone (6b):
Yield: 56 mg (70 %); white solid; m.p. 194–196 °C; Rf = 0.65
(CHCl3/MeOH = 95:05). 1H NMR (300 MHz, [D6]DMSO): δ =
8.39 (br. s, 1 H), 7.54 (d, J = 7.3 Hz, 2 H), 7.43 (d, J = 7.9 Hz, 1
H), 7.23 (t, J = 7.2 Hz, 2 H), 7.13 (t, J = 7.2 Hz, 1 H), 6.54 (s, 1
H), 6.37 (d, J = 7.7 Hz, 1 H), 2.23 (s, 3 H), 1.69 (s, 3 H) ppm. 13C
NMR (75 MHz, [D6]DMSO): δ = 163.9, 147.7, 147.1, 143.2, 127.9,
127.2, 126.9, 125.1, 118.1, 114.2, 112.7, 70.1, 30.7, 21.3 ppm. IR
43.1, 29.8, 28.0 ppm. IR (KBr): ν
= 3278, 3172, 3023, 2969,
˜
max
2916, 1644, 1612, 1581, 1511, 1486, 1393, 1155, 1031, 753,
700 cm–1. HRMS: calcd. for C17H19N2O [M+ + H] 267.1497; found
267.1508.
2-Cyclohexyl-2-methyl-1,2,3,4-tetrahydro-4-quinazolinone (6h):
Yield: 69 mg (90 %); yellow solid; m.p. 166–168 °C; Rf = 0.63
(CHCl3/MeOH = 95:05). 1H NMR (500 MHz, [D6]DMSO): δ =
7.60 (d, J = 8.3 Hz, 1 H), 7.38 (br. s, 1 H), 7.12 (t, J = 7.2 Hz, 1
H), 6.61 (d, J = 8.3 Hz, 1 H), 6.56 (t, J = 7.2 Hz, 1 H), 5.94 (br. s,
1 H), 1.86–1.72 (m, 5 H), 1.64–1.57 (m, 2 H), 1.36 (s, 3 H), 1.19–
1.02 (m, 4 H) ppm. 13C NMR (75 MHz, [D6]DMSO): δ = 162.8,
146.9, 133.1, 126.9, 115.6, 113.5, 113.4, 71.1, 47.8, 30.6, 26.6, 26.3,
(KBr): νmax = 3405, 3168, 3055, 3022, 2983, 2918, 1666, 1620, 1553,
˜
1488, 1446, 1359, 1278, 1212, 1026, 816, 777, 699, 550, 468 cm–1.
HRMS: calcd. for C16H17N2O [M+ + H] 253.1341; found 253.1349.
2,6,8-Trimethyl-2-phenyl-1,2,3,4-tetrahydro-4-quinazolinone (6c):
Yield: 70 mg (83%); pale-yellow solid; m.p. 188–190 °C; Rf = 0.56
(CHCl3/MeOH = 95:05). 1H NMR (300 MHz, [D6]DMSO): δ =
8.67 (br. s, 1 H), 7.46 (d, J = 7.5 Hz, 2 H), 7.24–7.20 (m, 3 H), 7.13
(t, J = 7.2 Hz, 1 H), 6.89 (s, 1 H), 6.44 (br. s, 1 H), 2.20 (s, 3 H),
2.10 (s, 3 H), 1.70 (s, 3 H) ppm. 13C NMR (75 MHz, [D6]DMSO):
δ = 164.3, 147.8, 134.9, 127.8, 126.9, 125.3, 125.0, 124.9, 115.6,
25.9, 25.8, 24.7 ppm. IR (KBr): ν
= 3336, 3183, 3049, 3022,
˜
max
2927, 2852, 1634, 1608, 1577, 1506, 1485, 1448, 1330, 1273, 1150,
1047, 803, 769, 752, 594 cm–1. HRMS: calcd. for C15H21N2O [M+
+ H] 245.1654; found 245.1651.
70.1, 30.4, 19.9, 17.1 ppm. IR (KBr): ν
= 3392, 3150, 3080,
˜
max
2960, 2925, 2910, 1927, 1685, 1600, 1550, 1480, 1446, 1350, 1050,
850, 748, 707 cm–1. HRMS: calcd. for C17H19N2O [M+ + H]
267.1497; found 267.1496.
6-Hexyl-6-methyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazoline
(8a): Yield: 95 mg (94%); thick liquid; Rf = 0.45 (hexane/EtOAc =
70:30). H NMR (300 MHz, [D6]DMSO): δ = 7.87 (d, J = 7.7 Hz,
1
5-Chloro-2-methyl-2-phenyl-1,2,3,4-tetrahydro-4-quinazolinone (6d):
Yield: 77 mg (90%); pale-yellow solid; m.p. 196–197 °C; Rf = 0.63
1 H), 7.67–7.60 (m, 2 H), 7.24–7.14 (m, 3 H), 6.90 (s, 1 H), 6.78
(d, J = 8.1 Hz, 1 H), 6.72 (t, J = 7.5 Hz, 1 H), 1.85 (s, 3 H), 1.49–
Eur. J. Org. Chem. 2010, 4719–4731
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4729

N. T. Patil, P. G. V. V. Lakshmi, V. Singh
FULL PAPER
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22.9, 21.8, 13.7 ppm. IR (film): ν
= 3356, 3093, 2956, 2927,
˜
max
[4]
2855, 1612, 1600, 1480, 1449, 1310, 1050, 855, 748 cm–1. HRMS:
calcd. for C21H26N3 [M+ + H] 320.2127; found 320.2133.
6-Methyl-6-phenyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazoline
(8b): Yield: 79 mg (80%); pale-yellow solid; m.p. 148–150 °C (ref.[33]
m.p. 148 °C); Rf = 0.52 (hexane/EtOAc = 70:30). 1H NMR
(300 MHz, [D6]DMSO): δ = 8.03 (d, J = 7.7 Hz, 1 H), 7.65–7.55
(m, 4 H), 7.38–7.36 (m, 2 H), 7.18 (dt, J = 7.3, 1.3 Hz, 1 H), 7.10
(t, J = 7.3 Hz, 1 H), 6.90–6.77 (m, 3 H), 6.45–6.42 (m, 1 H), 2.17
(s, 3 H) ppm. 13C NMR (75 MHz, [D6]DMSO): δ = 147.6, 143.8,
143.3, 143.0, 132.9, 131.5, 128.4, 125.7, 124.6, 122.0, 121.8, 118.8,
[5]
118.2, 114.6, 111.9, 111.6, 74.8, 26.5 ppm. IR (KBr): ν
= 3226,
˜
max
3055, 3022, 2927, 1614, 1588, 1532, 1449, 1477, 1372, 1309, 1270,
1168, 1026, 800, 746, 695 cm–1. HRMS: calcd. for C21H18N3 [M+
+ H] 312.1501; found 312.1497.
General Procedure for the Ph3PAuNTf2-Catalyzed Hydroamination/
Hydroarylation and Double Hydroamination of Terminal Alkynes
under Microwave-Assisted Conditions: A solution of the amino-aro-
matic 1, 5 or 7 (0.316 mmol), alkyne 2 (0.379 mmol) and
Ph3PAuNTf2 (2 mol-%) in toluene (2 mL) was sealed under nitro-
gen in a reaction vial and irradiated in a microwave reactor
(Biotage, initiator 8, single-mode reactor) at 150 °C for 15 min. On
cooling the reaction mixture to ambient temperature, the solvent
was removed in vacuo, and the black residue was purified by col-
umn chromatography (silica gel; EtOAc/hexane, 90:10) to afford
pyrrolo[1,2-a]quinoxalines 3/tetrahydro-4-quinazolinones 6/benzo-
[4,5]imidazo[1,2-c]quinazolines 8.
[6]
[7]
Supporting Information (see footnote on the first page of this arti-
cle): Preparation of starting materials and copies of 1H and 13C
NMR spectra of all newly synthesized products.
Acknowledgments
We gratefully acknowledge financial support by the Council of Sci-
entific and Industrial Research, India. N. T. P. is grateful to Dr. J. S.
Yadav, Director, Indian Institute of Chemical Technology, and Dr.
V. V. N. Reddy, Head, Org-II Division, for their support and en-
couragement.
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Received: March 22, 2010
Published Online: July 13, 2010
Eur. J. Org. Chem. 2010, 4719–4731
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4731