Divergent Synthesis of α-Aroyloxy Ketones and Indenones: A Controlled Domino Radical Reaction for Di- A nd Trifunctionalization of Alkynes

Article abstract of DOI:10.1021/acs.joc.0c00967

Three different modes of aldehyde/alkyne assembly through a controlled radical reaction are devised. While a double C-H activation/annulation leads to indenones, a concurrent oxidation of both aldehydes and alkynes in the course of their connection offers

Full text of DOI:10.1021/acs.joc.0c00967

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Note
Divergent Synthesis of #-Aroyloxy Ketones and Indenones: A Controlled
Domino Radical Reaction for di- and tri-Functionalization of Alkynes
Farnaz Jafarpour, Meysam Azizzade, Yekta Golpazir-Sorkheh, Hamed Navid, and Saideh Rajai-Daryasarei
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.0c00967 • Publication Date (Web): 20 May 2020
Downloaded from pubs.acs.org on May 20, 2020
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Divergent Synthesis of α-Aroyloxy Ketones and Indenones: A Controlled
Domino Radical Reaction for di- and tri-Functionalization of Alkynes
Farnaz Jafarpour* Meysam Azizzade, Yekta Golpazir-Sorkheh, Hamed Navid and Saideh Rajai-
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Daryasarei
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School of Chemistry, College of Science, University of Tehran, P.O. Box 14155-6619, Tehran,
Iran. E-mail: Jafarpur@khayam.ut.ac.ir
O
O
O
Ar
Ar
R
O
TBHP
TBHP
O
+
Ar
PhCl
1/2 (2:1)
R = Ar
PhCl
1/2 (1:1)
R = Ar
Ar
1
2
Ar
DTBP
PhCl
dual oxidation/cross-coupling
Annulation
O
O
Ar
R = CO2H
Annulation/decarboxylative aroylation
diversity-oriented synthesis
no transition metals
wide functional group tollerance
TBHP as oxidant and initiator
ABSTRACT: Three different modes of aldehyde/alkyne assembly through a controlled radical
reaction is devised. While a double C-H activation/annulation leads to indenones, a concurrent
oxidation of both aldehydes and alkynes in the course of their connection offers aroyloxy ketones.
Besides two types of cascade reactions starting from identical materials, through a phenylpropiolic
acid substrate, a cascade three C-C bond formation via an uninterrupted C-H
functionalization/annulation/decarboxylative aroylation as a formidable challenge in radical
reactions, occurs to deliver 2-aroyl-3-aryl indenones.
Radical reactions serve as one of the most powerful and attractive tools for C-C bond formation
as a focal point for current synthetic method development.1 Within radical chemistry however,
complete control of product distribution to enable divergent synthesis of various valuable building
blocks and scaffolds is more challenging.2 Among the efforts to address this issue, the introduction
of a transition metal into the radical combination reactions has proven to be one of the most highly
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efficient strategies.3 The perspective of much of these works however, is from the viewpoint of
catalysis. We aim to score a controlled efficient divergent synthesis with a radical perspective
avoiding any metals.
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Over the past decade, transition-metal (TM) catalyzed functionalization of alkynes through the
addition of functionalities across a triple bond have emerged as a powerful tool for construction of
complicated building blocks. Particular intriguing transformations in this hot field include catalytic
coupling of alkynes and aldehydes towards heterocylces4 and carbocycles5 and also
hydrofunctionalizaion6 of alkynes towards vinyl ketones and allyl alcohols (Scheme 1A-1C).
Although the patterns of molecular scaffolds accessible by existing target oriented protocols are
broad, however all these reactions are limited to transition metals and also they do not share the
aim of accessing diversity. Diversity oriented synthetic methods that enable construction of
combinatorial matrices of molecular skeletons from the same precursors, are among the most
attractive synthetic tools.7
Annulation
R
Previous works:
O
R
O
R
R
heterocycles
(A)
O
R
R
R
R
carbocycles
R
O
R
O
R
O
R
(B)
(C)
+
R
R
R
R
Hydrofunctionalization
OH
O
R
R
R
R
O
O
(D)
OR3
R1
O
1- Ag2O (5 mol%)
100 °C, dioxane
2- m-CPBA (1.5 eq)
R2
OR3
+
R1 OH
O
O
R2
This work:
O
O
(E)
O
O
R
TBHP
PhCl
1/2 (2:1)
TBHP
Ar
+
Ar
PhCl
1/2 (1:1)
Ar
R = Ar
1
2
Ar
Ar
O
R = Ar
DTBP
PhCl
O
R = CO2H Ar
Scheme 1. Functionalization of alkynes
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Herein, we report that alkynes and aldehydes can have the potential to participate in both
annulation and aroylation/oxidation processes in presence of suitable promoters for radical-type
coupling reactions, via slight changes in reaction conditions (Scheme 1E). This protocol enables
branching cascades to generate a set of interesting small molecules highly diverse in skeletal
properties including α-aroyloxy ketones,8 2,3-diaryl indenones9 and aryl benzoyl indenones10 and
is one of the rare examples of incorporating skeletal diversity oriented synthesis in a radical
controlled reaction.
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Table 1. Screening divergent coupling of p-tolualdehyde and diphenylacetylenea
O
Ph
H
O
O
O
+
[O]/add
solvent
O
3a
Ph
Ph
2a
Ph
+
Me
H
Me
Me
1a
4a Ph
Ph
entry
[O]
additive solvent
Yield
(%)
3a
4a
1
2
3
H2O2
PhCl
PhCl
PhCl
PhCl
PhCl
DMSO
DCB
DCE
30 30
trace 15
nd 38
22 68
28 57
DTBP
K2S2O8
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
4
5b
6
10
15
5
5
7
8
10 10
9c
PhCl/H2O 40 10
10
10 TBHP Bu4NBr PhCl
11 TBHP CuBr PhCl
12 TBHP AgOAc PhCl
13d TBHP
PhCl
5
15 15
20 20
88 nd
aReaction conditions: aldehyde 1a (0.2 mmol), alkyne 2a (0.1 mmol), oxidant (4 eq), additive (0.2
b
c
eq), solvent (0.5 mL), 120 °C for 20h. TBHP (2 eq) was used. PhCl/H2O (1:1) was used.
dAldehyde 1a (0.1 mmol) was used.
In our survey, diphenylacetylene was initially combined with p-tolualdehyde (2 eq) in presence of
H2O2 where a 1:1 mixture of α-aroyloxy ketone 3a and indenone 4a were obtained (Table 1, entry
1). Optimizing the reaction with respect to oxidants, a commercial 70% solution of tert-butyl
hydroperoxide (TBHP) in H2O was found to be much more effective with a drastically increased
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yield and selectivity towards indenone product 4a (entries 2-4). Lowering the amount of oxidant
led to inferior results (entry 5). After several optimizations employing various additives and
solvents (see SI), fortunately we found that essentially equimolar amounts of alkyne and aldehyde
in chlorobenzene sufficed to provide switchable selectivity between the two cross-coupling paths
to afford aroyloxy ketone 3a as the sole product in 88% isolated yield (entries 7-13).
The results shown in Table 1 demonstrate that this approach has a great potential in the divergent
synthesis of α-aroyloxy ketones as prevalent structural motifs commonly found in natural products
and drug candidates8 as well as functionalized 2,3-disubstituted indenones widely found in
pharmaceuticals and bioactive products.11
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Recognizing the synthetic utility of this condition-controlled chemo-divergence, the substrate
scope for construction of α-aroyloxy ketones was first investigated. Traditional methods for
construction of these ubiquitous structural motifs include direct α-oxygenation of carbonyl
compounds employing various toxic metal oxidants or hypervalent iodine compounds.12 Very
recently, Sajiko and Cui performed a silver oxide catalyzed reaction of carboxylic acids and ynol
ethers for construction of α-carbonyloxy esters in two steps (Scheme 1D).13 Here a streamline
construction of α-aroyloxyketones via a one-step coupling of aldehydes and alkynes is achieved
excluding any metals, a strategy relying on the concurrent oxidation of both aldehydes and alkynes
in the course of their coupling, which is much less documented.14 As shown in the left section of
Table 2, a wide range of o-, m- and p- substituted aldehydes were fruitfully applied to this protocol
giving the desired products 3a-3k in good to excellent yields.
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Table 2. Substrate scope for divergent synthesis of indenones and α-aroyloxy ketonesa
5
6
7
8
H
O
Ph
O
Ph
O
+
O
TBHP (0.4 mmol)
PhCl (0.5 mL)
120 °C, 20 h
TBHP (0.4 mmol)
PhCl (0.5 mL)
120 °C, 20 h
Conditions B
Ar
Ar
Ar
Ph
Ph
O
H
3
4
1
2
Ph
Ph
Conditions A
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O
Ph
O
Ph
O
Ph
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O
O
O
Me
O
O
O
O
Ph
O
Ph
O
Ph
Ph
Ph
Ph
Ph
Ph
3a, 88%
3b
, 71%
O
3c
, 54%
Me
Me
MeO
Ph
Ph
Ph
O
4a, 68%
4c
, 86%
4b, 75%
4e, 57%
O
O
Ph
Ph
O
Ph
Ph
O
Cl
O
O
O
O
Ph
Cl
O
Ph
Cl
O
Ph
3d, 60%
3e, 71%
3f, 55%
MeO
F3C
F
Ph
Ph
4d, 59%
Ph
X
4f, 42%
O
Ph
Ph
O
O
Ph
Ph
O
O
Ph
Ph
O
O
OMe O
MeO
MeO
O
O
O
Ph
Ph
4j: X = Cl, 72%
4k: X = Br, 87%
4g: X = F, 83%
4h: X = Cl, 78%
4i: X = Br, 75%
X
3g, 64%
3h, 40%
3i, 53%
Me
Ph
O
Ph
Me
Ph
Cl
O
O
OH
OMe
O
O
O
O
O
O
MeO
Ph
Ph
Ph
Ph
Me2N
4m, 71%
MeO
3j, 84%
3k, 62%
Me
Me
Ph
Ph
S
Ph
4l, 63%
4n, 47%
Me
O
O
O
N
Ph
Ph
Ph
N
4p, 56% Ph
4o, 70% Ph
4q, 0% Ph
aConditions A: aldehyde 1a (0.1 mmol), alkyne 2a (0.1 mmol), TBHP (4 eq), in PhCl (0.5 mL) at
120 °C for 20h. Conditions B: aldehyde 1a (0.2 mmol), alkyne 2a (0.1 mmol), TBHP (4 eq), in
PhCl (0.5 mL) at 120 °C for 20h.
Benzaldehyde participated well in this cross-coupling resulting the desired product 3b in
reasonable yield. Although the fluoro group is the least reactive halogen in metal-catalyzed
reactions, the fluorinated aldehyde worked well with this metal-free protocol to afford the desired
product 3d in 60% yield. Fortunately, chloro groups in different substituted patterns were also
compatible with this process as synthetically interesting results capable of further
functionalizations (3e, 3f and 3i). Naphthaldehyde also worked well in this reaction to produce
the desired product 3j in promising yield. Unfortunately, nitro benzaldehyde was not tolerated
under the reaction conditions. Finally a methyl substituted diphenyl acetylene was satisfactorily
employed in the oxyacylation reaction to afford the desired product 3k in 62% yield.
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Next the generality of this divergent synthesis for construction of indenones was investigated (right
in Table 2). Methyl substituted aldehydes worked well under the optimized reaction condition to
afford the desired products 4a and 4b in high yields. With benzaldehyde, even superior result was
obtained (4c, 86% yield). More electron rich aldehydes bearing methoxy groups also participated
in this annulation reaction and provided the desired products albeit in lower yields (4d and 4n).
Trifluoromethyl substituent as a group with unique functional properties and wide applications in
organic synthesis and pharmaceutical science, also contributed well in this protocol to afford 4e in
57% yield. Intriguingly, susceptible bromo, chloro and fluoro groups were presereved in the course
of the reaction (4g-4k). Notably, hydroxyl group was also tolerated in this course, a significant
feature that eliminates the requirement of protection of hydroxyl groups and provides the option
of further functionalization (4l). Importantly, our lately developed procedure could also be readily
extended to unprecedented simple assembly of pyrrole 4o and pyridine 4p fused
cyclopentadienones.
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Intriguingly, when we tried to expand the alkyne scope to a phenylpropiolic acid, assembly of a
benzoyl phenyl substituted indenone with an absolute regioselectivity was realized using slightly
modified reaction conditions (Scheme 2). Employing some alkyl and alkoxy substituted aldehydes,
high yields of the desired products were collected (5a-5c). To the best of our knowledge, indenones
with such a substitution pattern are rare and less found in the literature.10 This origin offers a highly
selective cascade, three C-C bond formation and simultaneous incorporation of three
functionalities to
a
triple bond via an uninterrupted C-H functionalization/
annulation/decarboxylative aroylation strategy, which to the best of our knowledge is a formidable
challenge in radical reactions.15
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H
H
O
O
O
+
DTBP (0.3 mmol)
PhCl (0.5 mL)
120 °C, 16 h
Ar
Ar
CO2H
CO2
Ar
Ph
O
2b
1
5
Ph
O
O
O
O
O
Me
MeO
10
11
12
13
14
15
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17
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20
21
22
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30
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Ph
Ph
Ph
5c, 83%
5a, 73%
5b, 75%
Me
OMe
Scheme 2. Annulation/decarboxylative aroylation cascade
Some additional experiments were performed to elucidate the reaction mechanism (Scheme 3).
The reaction of benzaldehyde and diphenylacetylene were fully suppressed in presence of TEMPO
(2,2,6,6-tetramethyl-1-piperidinyl) (4eq) as a radical scavenger (equations 1 and 2). The result
supports a radical pathway for the reactions. Further control experiments were performed to gain
some insight to the details of aroyloxylation reaction. While, attempts to perform both the
annulation and aroyloxylation process on benzoic acid failed (3), peroxybenzoic acid participated
well in aroyloxylation reaction to afford the desired product 3b in 70% isolated yield (4). The
reaction of benzil and aldehyde 1c also failed to offer the desired product 3c which ruled out the
formation of this compound as a possible intermediate in the course of the reaction. The expected
product 3l reported previously to be obtained from the reaction of benzaldehyde and benzil,16 was
not observed under the standard reaction conditions, as well.
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O
O
TBHP (0.4 mmol)
PhCl (0.5 mL)
120 °C, 20 h
4c
(1)
(2)
+
Ph
+
Ph
N
O
0%
Ph
1a
(2 eq)
2a
(1 eq)
6, 42%
O
TEMPO (4 eq)
Ph
O
O
+
TBHP (0.4 mmol)
PhCl (0.5 mL)
120 °C, 20 h
TEMPO (4 eq)
O
2a (1eq)
Ph
3b, 0%
4c, 0%
1a (1 eq)
CO2H
O
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11
12
13
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46
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52
53
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58
59
60
TBHP (0.4 mmol)
PhCl (0.5 mL)
120 °C, 20 h
2a (1eq)
(3)
(4)
Ph
3b
+
+
0%
O
Ph
OH
O
+
TBHP (0.4 mmol)
PhCl (0.5 mL)
120 °C, 20 h
4c
2a (1eq)
3b
+
0%
70%
O
O
Ph
O
O
O
TBHP (0.4 mmol)
PhCl (0.5 mL)
120 °C, 20 h
(5)
Ph
O
MeO
1c (1 eq)
Ph
or
+
OMe
O
Ph
O
3l, 0%
Ph
3c, 0%
(1 eq)
MeO
Ph
O
Scheme 3. Control experiments
Refereeing to the above experiments a tentative mechanism for construction of α-aroyloxy ketone
may include a hydrogen abstraction from aldehyde by TBHP at first to form α-carbonyl radical A
which on further reaction with TBHP can be oxidized to the perester B (Scheme 4, path a). A
subsequent coupling of perester and diphenyl acetylene affords vinyl radical intermediate D which
upon oxidation with TBHP and further tautomerization, leads to α-aroyloxy ketone 3.17 On the
other hand, perior to the oxidation reaction, α-carbonyl radical A may react directly with alkyne
to afford vinyl radical E which will immediately undergo free-radical aromatic substitution
followed by oxidation via a single eletron transfer reaction. Final deprotonation of cationic
intermediate G under basic condition generates indenone 4. When phenylpropiolic acid is applied
as the substrate, intermolecular addition of α-carbonyl radical to the pregenerated indenone-2-
carboxylic acid (4, R = CO2H), furnishes radical intermediate H which on hydrogen abstraction,
results 2-aroylindenone 5 with high regioselectivity.
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O
O
O
OtBu
Ph
tBuO
path a
O
H
A
B
H2O
1
TBHP
TBHP
tBuO
+ H2O
Ph
Ph
O
O
HO
Ph
tBuOOH
2
O
O
3
O
Ph
R
O
Ph
C
D
10
11
12
13
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tBuO
O
O
O
Ph
R
path b
H
2
A
Ph
1
E
TBHP
R
tBuO + H2O
O
O
O
TBHP
SET
tBuO
or
R
R
+
HO
4
H
H
Ph
O
Ph
Ph
O
O
G
F
R = CO2H
O
Ar-C
O
O
O
TBHP
SET
tBuO
or
HO
Ar
CO2H
Ar
CO2H
+
Ar
5
H
I
Ph
Ph
Ph
- CO2
Scheme 4. Plausible reaction mechanisms
CONCLUSION
In conclusion we have uncovered a family of reactions leading to divergent synthesis of two classes
of biologically important α-aroyloxy ketone and indenone scaffolds from merger of identical
starting materials. This protocol is highlighted by controlled cascade di- and trifunctionalization
of
alkynes
rarely
achieved
in
radical
reactions
via
a
C-H
functionalization/annulation/decarboxylative aroylation track to generate indenones and their
aroyl derivatives. A concomitant oxidation/stitching of aldehyde/alkyne is also achieved via slight
changes in conditions to provide α-aroyloxy ketones. Based on the reaction intermediates detected,
plausible mechanisms for all sequences has been proposed.
EXPERIMENTAL SECTION
General Procedure for Synthesis of α-Aroyloxy Ketones from Alkynes and Aldehydes. A vial
equipped with a magnetic stirring bar was charged with internal alkyne (0.1 mmol, 1.0 equiv),
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aldehyde (0.1 mmol, 1.0 equiv), TBHP (0.4 mmol, 4.0 equiv), chlorobenzene (0.5 mL) and capped.
The resulting mixture was heated in an oil bath at 120 °C for 20 h. Removal of the solvent gave a
crude mixture which was purified by flash column chromatography (Hexane/EtOAc, 90:10) to
give the desired product.
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2-Oxo-1,2-diphenylethyl 4-methylbenzoate (3a).18 White solid, Yield 88% (29 mg); Rf = 0.52
(silica gel, Hexane /EtOAc 80:20); 1H NMR (400 MHz, CDCl3) δ 2.32 (s, 3H), 7.00 (s, 1H), 7.16
(d, J = 8.1 Hz, 2H), 7.29-7.36 (m, 5H), 7.42-7.51 (m, 3H), 7.89-7.97 (m, 4H); 13C{1H} NMR (100
MHz, CDCl3) δ 20.7, 76.7, 125.5, 127.6, 127.8, 128.1, 128.2, 128.9, 129.0, 132.4, 132.8, 133.7,
143.1, 165.1, 192.8; Anal. Calcd for C22H18O3: C, 79.98; H, 5.49. Found: C, 80.25; H, 5.60.
2-Oxo-1,2-diphenylethyl benzoate (3b).12d White solid, Yield 71% (22 mg); Rf = 0.51 (silica gel,
Hexane /EtOAc 80:20); 1H NMR (500 MHz, CDCl3) δ 7.10 (s, 1H), 7.36-7.47 (m, 7H), 7.54 (tt, J
= 7.5, 1.6 Hz, 1H), 7.56-7.61 (m, 3H), 8.01 (d, J = 7.2 Hz, 2H), 8.13 (d, J = 7.2 Hz, 2H); 13C{1H}
NMR (125 MHz, CDCl3) δ 77.9, 128.4, 128.7, 128.9, 129.1, 129.3, 129.7, 130.0, 133.4, 133.5,
133.7, 134.7, 166.0, 193.7; Anal. Calcd for C21H16O3: C, 79.73; H, 5.10. Found: C, 79.41; H, 4.98.
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2-Oxo-1,2-diphenylethyl 4-methoxybenzoate (3c).19 White solid, Yield 54% (19 mg); H NMR
(500 MHz, CDCl3) δ 3.87 (s, 3H), 6.93 (d, J = 8.7 Hz, 2H), 7.08 (s, 1H), 7.37-7.45 (m, 5H), 7.52-
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7.59 (m, 3H), 8.01-8.03 (m, 2H), 8.09 (d, J = 8.7 Hz, 2H); C{1H} NMR (125 MHz, CDCl3) δ
55.5, 77.7, 113.7, 121.8, 128.6, 128.7, 128.9 129.1, 129.2, 132.1, 133.4, 133.9, 134.8, 163.7, 165.7,
194.0; Anal. Calcd for C22H18O4: C, 76.29; H, 5.24. C, Found: 76.60; H, 5.36.
2-Oxo-1,2-diphenylethyl 4-fluorobenzoate (3d).20 White solid, Yield 60% (20 mg); Rf = 0.36
(silica gel, Hexane /EtOAc 90:10); 1H NMR (500 MHz, CDCl3) δ 7.10 (s, 1H), 7.12-7.14 (m, 2H),
7.39-7.48 (m, 5H), 7.53-7.61 (m, 3H), 8.00-8.03 (m, 2H), 8.14 (d, J = 8.7 Hz, 1H), 8.16 (d, J = 8.7
Hz, 1H); .Anal. Calcd for C21H15FO3: C, 75.44; H, 4.52. Found: C, 75.80; H, 4.68.
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2-Oxo-1,2-diphenylethyl 2,4-dichlorobenzoate (3e). White solid, Yield 71% (27 mg), mp 103-105
°C; Rf = 0.56 (silica gel, Hexane /EtOAc 80:20); 1H NMR (500 MHz, CDCl3) δ 7.13 (s, 1H), 7.34
(dd, J = 8.4, 2.1 Hz, 1H), 7.39-7.46 (m, 5H), 7.51 (d, J = 2.1 Hz, 1H), 7.53-7.60 (m, 3H), 8.01 (dd,
J = 8.4, 1.4 Hz, 2H), 8.05 (d, J = 8.5 Hz, 1H); 13C{1H} NMR (125 MHz, CDCl3) δ 78.5, 127.1,
127.2, 128.7, 128.8, 128.9, 129.2, 129.5, 131.1, 133.1, 133.2, 133.7, 134.4, 135.5, 138.8, 163.9,
193.2; EI-MS m/z (%) 384 (M•+, 1), 279 (7), 211 (5), 173 (51), 145 (5), 105 (100), 77 (8); Anal.
Calcd for C21H14Cl2O3: C, 65.47; H, 3.66. Found: C, 65.80; H, 3.81.
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2-Oxo-1,2-diphenylethyl 4-chlorobenzoate (3f). White solid; Yield 55% (19 mg); mp 110-112 °C;
Rf = 0.45 (silica gel, Hexane /EtOAc 95:5); 1H NMR (500 MHz, CDCl3) δ 7.10 (s, 1H), 7.38-7.45
(m, 7H), 7.54 (t, J = 7.5 Hz, 1H), 7.57-7.59 (m, 2H), 8.01 (d, J = 8.0 Hz, 2H), 8.07 (d, J = 8.5 Hz,
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2H); C{1H} NMR (125 MHz, CDCl3) δ 78.2, 128.6, 128.7, 128.7, 128.7, 128.8, 129.2, 129.5,
131.4, 133.5, 133.6, 134.6, 139.9, 165.2, 193.4; EI-MS m/z (%): 350 (M•+, 100), 195 (55), 211
(35), 111 (10); Anal. Calcd for C21H15ClO3: Elemental Analysis: C, 71.90; H, 4.31; Found: C,
71.58; H, 4.18.
2-Oxo-1,2-diphenylethyl 2,3,4-trimethoxybenzoate (3g). White solid, Yield 64% (26 mg); mp 130-
132 °C; Rf = 0.22 (silica gel, Hexane /EtOAc 80:20); 1H NMR (500 MHz, CDCl3) δ 3.89 (s, 3H),
3.93 (s, 6H), 6.73 (d, J = 8.8 Hz, 1H), 7.11 (s, 1H), 7.36-7.46 (m, 5H), 7.52-7.56 (m, 1H), 7.59 (d,
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J = 7.8 Hz, 2H), 7.79 (d, J = 8.9 Hz, 1H), 8.03 (d, J = 8.0 Hz, 2H); C{1H} NMR (125 MHz,
CDCl3) δ 56.1, 61.0, 61.9, 77.7, 106.9, 117.0, 127.6, 128.6, 128.7, 128.9, 129.0, 129.2, 133.4,
133.9, 134.9, 143.0, 155.2, 157.6, 164.7, 194.0; EI-MS m/z (%) 406 (M•+, 2), 195 (100), 152 (6),
105 (5); Anal. Calcd for C24H22O6: C, 70.93; H, 5.46. Found: C, 71.21; H, 5.57.
2-Oxo-1,2-diphenylethyl 3-methylbenzoate (3h). White solid; Yield 40% (13 mg); mp 98-100 °C;
Rf = 0.45 (silica gel, Hexane /EtOAc 95:5); 1H NMR (500 MHz, CDCl3) δ 2.40 (s, 3H), 7.11 (s,
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1H), 7.37-7.45 (m, 9H), 7.54 (t, J = 7.5 Hz, 1H), 7.59-7.62 (m, 2H), 7.95 (s, 1H), 8.02 (d, J = 8.0
Hz, 1H); 13C{1H} (125 MHz, CDCl3) δ 21.2, 77.8, 127.2, 128.3, 128.6, 128.7, 128.8, 129.1, 129.3,
130.4, 130.5, 133.5, 133.8, 134.2, 134.8, 138.7, 166.2, 193.8; EI-MS m/z (%): 330 (M•+, 100),
195 (60), 211 (40), 91 (10); Anal. Calcd for C22H18O3: Elemental Analysis: C, 79.98; H, 5.49;
Found: C, 80.22; H, 5.63.
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2-Oxo-1,2-diphenylethyl 3-chlorobenzoate (3i). White solid; Yield 53% (19 mg); mp 95-97 °C; Rf
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= 0.45 (silica gel, Hexane /EtOAc 95:5); H NMR (500 MHz, CDCl3) δ 7.12 (s, 1H), 7.39-7.47
(m, 7H), 7.55-7.60 (m, 4H), 8.00-8.04 (m, 2H), 8.11-8.12 (m, 1H); 13C{1H} (125 MHz, CDCl3) δ
78.3, 128.1, 128.7, 128.7, 128.8, 129.2, 129.5, 129.8, 130.0, 131.2, 133.4, 133.4, 133.6, 134.5,
134.5, 164.8, 193.3; EI-MS m/z (%): 350 (M•+,100), 195 (55), 211 (35), 111 (10); Anal. Calcd for
C21H15ClO3: Elemental Analysis: C, 71.90; H, 4.31; Found: C, 72.26; H, 4.48.
2-Oxo-1,2-diphenylethyl 1-naphthoate (3j). White solid, Yield 84% (31 mg); 1H NMR (500 MHz,
CDCl3) δ 7.23 (s, 1H), 7.37-7.48 (m, 5H), 7.50-7.58 (m, 3H), 7.59-7.65 (m, 3H), 7.89 (d, J = 8.2
Hz, 1H), 8.03-8.08 (m, 3H), 8.39 (dd, J = 7.3, 1.3 Hz, 1H), 8.98 (d, J = 8.7 Hz, 1H); 13C{1H} NMR
(125 MHz, CDCl3) δ 78.1, 124.5, 125.8, 126.2, 126.3, 127.8, 128.5, 128.6, 128.7, 128.9, 129.1
(2C), 129.3, 130.9, 131.5, 133.5, 133.7, 133.8 (2C), 134.9, 166.9, 193.9; Anal. Calcd for C25H18O3:
C, 81.95; H, 4.95. Found: C, 82.22; H, 5.04.
2-Oxo-1,2-di-p-tolylethyl 4-methylbenzoate (3k). White solid; Yield 62% (22 mg); mp 96-98 °C;
Rf = 0.35 (silica gel, Hexane /EtOAc 95:5); 1H NMR (500 MHz, CDCl3) δ 2.36 (s, 3H), 2.39 (s,
3H), 2.43 (s, 3H), 7.06 (s, 1H), 7.18-7.25 (m, 6H), 7.48 (d, J = 8.0 Hz, 2H), 7.93 (d, J = 8.0 Hz,
2H), 8.03 (d, J = 8.0 Hz, 2H); 13C{1H} (125 MHz, CDCl3) δ 21.3, 21.6, 21.7, 77.6, 126.8, 128.6,
128.9, 129.1, 129.3, 129.8, 130.0, 131.2, 132.2, 139.2, 143.9, 144.3, 166.1, 193.4; EI-MS m/z (%):
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358 (M•+,100), 239 (70), 135 (20); Anal. Calcd for C24H22O3: Elemental Analysis: C, 80.42; H,
6.19; Found: C, 80.75; H, 6.33.
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General Procedure for Synthesis of Indenones from Alkynes and Aldehydes. A vial equipped
with a magnetic stirring bar was charged with internal alkyne (0.1 mmol, 1.0 equiv), aldehyde (0.2
mmol, 2.0 equiv), TBHP (0.4 mmol, 4.0 equiv), chlorobenzene (0.5 mL) and capped. The resulting
mixture was heated in an oil bath at 120 °C for 20 h. Removal of the solvent gave a crude mixture
which was purified by flash column chromatography (Hexane/EtOAc, 95:5) to give the desired
product.
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5-Methyl-2,3-diphenyl-1H-inden-1-one (4a).21 Orange solid, Yield: 68% (20 mg); Rf = 0.41 (silica
gel, Hexane /EtOAc 95:5); 1H NMR (500 MHz, CDCl3) δ 2.36 (s, 3H), 6.95 (s, 1H), 7.09 (d, J =
7.2 Hz, 1H), 7.22-7.30 (m, 5H), 7.37-7.45 (m, 5H), 7.49 (d, J = 7.2 Hz, 1H); 13C{1H} NMR (125
MHz, CDCl3) δ 22.1, 122.5, 123.0, 127.6, 128.0, 128.4, 128.5, 128.8, 128.9, 129.1, 130.0, 130.9,
132.8, 132.9, 144.4, 145.7, 154.9, 196.1; EI-MS m/z (%) 296 (M•+, 100), 281 (53), 265 (16), 252
(48), 216 (14), 189 (12), 126 (14); Anal. Calcd for C22H16O: C, 89.16; H, 5.44. Found: C, 89.48;
H, 5.60.
7-Methyl-2,3-diphenyl-1H-inden-1-one (4b).22 Orange solid, Yield 75% (22 mg); Rf = 0.58 (silica
gel, Hexane /EtOAc 95:5); 1H NMR (500 MHz, CDCl3) δ 2.64 (s, 3H), 6.99 (d, J = 7.2 Hz, 1H),
7.08 (d, J = 7.8 Hz, 1H), 7.23-7.28 (m, 6H), 7.37-7.43 (m, 5H); 13C{1H} NMR (125 MHz, CDCl3)
δ 17.4, 119.2, 127.0, 127.6, 128.0, 128.6, 128.7, 129.0, 130.0, 130.9, 132.2, 132.4, 132.6, 132.9,
138.0, 145.7, 154.3, 197.6; Anal. Calcd for C22H16O: C, 89.16; H, 5.44. Found: C, 89.41; H, 5.56.
2,3-Diphenyl-1H-inden-1-one (4c).23 Orange solid; Yield 86% (24 mg); Rf = 0.43 (silica gel,
Hexane /EtOAc 95:5); 1H NMR (400 MHz, CDCl3) δ 7.05 (d, J = 7.2 Hz, 1H), 7.15-7.21 (m, 6H),
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7.26-7.33 (m, 6H), 7.50 (d, J = 7.4 Hz, 1H); C{1H} NMR (100 MHz, CDCl3) δ 120.2, 121.9,
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126.7, 127.0, 127.4, 127.5, 127.7, 127.8, 127.9, 128.2, 128.9, 129.7, 131.6, 132.4, 144.2, 154.3,
195.5; EI-MS m/z (%) 282 (M•+, 100), 265 (19), 252 (62), 126 (17); Anal. Calcd for C21H14O: C,
89.34; H, 5.00. Found: C, 89.62; H, 5.11.
5-Methoxy-2,3-diphenyl-1H-inden-1-one (4d).24 Orange solid, Yield 59% (19 mg); Rf = 0.44
(silica gel, Hexane /EtOAc 90:10); 1H NMR (500 MHz, CDCl3) δ 3.85 (s, 3H), 6.69 (dd, J = 7.9,
2.2 Hz, 1H), 6.72 (d, J = 2.2 Hz, 1H), 7.25-7.29 (m, 5H), 7.36-7.39 (m, 2H), 7.41-7.43 (m, 3H),
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7.57 (d, J = 7.9 Hz, 1H); C{1H} NMR (125 MHz, CDCl3) δ 55.8, 110.3, 110.5, 123.5, 124.9,
127.7, 128.0, 128.5, 128.8, 129.1, 130.0, 130.9, 132.7, 133.9, 147.9, 153.2, 164.4, 195.1; EI-MS
m/z (%) 312 (M•+, 100), 281(30), 268 (27), 252 (17), 239 (54), 135 (33), 120 (22); Anal. Calcd
for C22H16O2: C, 84.59; H, 5.16. Found: C, 84.88; H, 5.32.
2,3-Diphenyl-5-(trifluoromethyl)-1H-inden-1-one (4e).9h Orange-red solid, Yield 57% (20 mg),
mp 131-133 °C; Rf = 0.45 (silica gel, Hexane /EtOAc 95:5); 1H NMR (500 MHz, CDCl3) δ 7.28
(s, 5H), 7.34-7.41 (m, 3H), 7.46 (s, 3H), 7.61 (d, J = 7.5 Hz, 1H), 7.69 (d, J = 7.4 Hz, 1H); 13C{1H}
NMR (125 MHz, CDCl3) δ 117.6 (q, JC-F = 3.5 Hz), 122.7, 124.6 (q, JC-F = 271.0 Hz), 126.5 (q,
JC-F = 4.2 Hz), 128.1, 128.2, 128.3, 129.1, 129.7, 129.9, 130.1, 132.0, 133.4, 133.6, 135.1 (q, JC-F
= 32.1 Hz), 146.1, 154.6, 195.0; Anal. Calcd for C22H13F3O: C, 75.42; H, 3.74. Found: C, 75.73;
H, 3.86.
2,3-Diphenyl-1H-cyclopenta[a]naphthalen-1-one (4f).25 Orange solid, Yield 42% (14 mg); Rf =
0.42 (silica gel, Hexane /EtOAc 95:5); 1H NMR (500 MHz, DMSO-d6) δ 7.13-7.19 (m, 4H), 7.36-
7.44 (m, 3H), 7.51-7.63 (m, 5H), 7.74 (d, J = 7.6 Hz, 1H), 7.77 (d, J = 8.5 Hz, 1H), 8.02 (d, J =
8.2 Hz, 1H), 8.05 (d, J = 8.2 Hz, 1H); 13C{1H} NMR (125 MHz, DMSO-d6) δ 121.8, 123.1, 125.6,
126.3, 126.5, 127.0, 127.2, 128.4, 129.0, 129.1, 129.4, 129.8, 130.0, 130.8, 131.1, 133.1, 133.8,
134.8, 146.3, 155.2, 196.2; EI-MS m/z (%) 332 (M•+, 100), 316 (19), 303 (48), 282 (21), 255 (21),
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155 (21), 141 (22), 127 (19); Anal. Calcd for C25H16O: C, 90.33; H, 4.85. Found: C, 90.55; H,
4.94.
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5-Fluoro-2,3-diphenyl-1H-inden-1-one (4g). Orange solid, Yield 83% (25 mg), mp 132-134 °C;
Rf = 0.43 (silica gel, Hexane /EtOAc 95:5); 1H NMR (500 MHz, CDCl3) δ 6.87 (dd, J = 8.6, 2.3
Hz, 1H), 6.93 (ddd, J = 8.5, 8.4, 2.4 Hz, 1H), 7.25-7.45 (m, 10H), 7.58 (dd, J = 8.0, 5.1 Hz, 1H);
13C{1H} NMR (125 MHz, CDCl3) δ 110.2 (d, JC-F = 25.8 Hz), 114.4 (d, JC-F = 22.9 Hz), 124.8 (d,
JC-F = 9.8 Hz), 126.5 (d, JC-F = 3.2 Hz), 128.1, 128.2, 128.4, 129.0, 129.6, 130.0, 130.4, 132.2,
133.7, 148.6 (d, JC-F = 9.4 Hz), 153.1 (d, JC-F = 2.4 Hz), 166.5 (d, JC-F = 252.8 Hz), 194.7; Anal.
Calcd for C21H13FO: C, 83.98; H, 4.36. Found: C, 84.29; H, 4.49.
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5-Chloro-2,3-diphenyl-1H-inden-1-one (4h). Orange-red solid; Yield 78% (25 mg), mp 157-159
°C; Rf = 0.51 (silica gel, Hexane /EtOAc 95:5); 1H NMR (400 MHz, CDCl3) δ 7.05 (d, J = 1.7 Hz,
1H), 7.18-7.20 (m, 5H), 7.21 (d, J = 1.8 Hz, 1H), 7.27-7.31 (m, 2H), 7.34-7.38 (m, 3H), 7.45 (d, J
= 7.7 Hz, 1H); 13C{1H} NMR (100 MHz, CDCl3) δ 122.0, 123.9, 126.6, 128.1, 128.2, 128.4, 128.5,
129.0, 129.6, 130.0, 131.4, 132.2, 133.5, 139.7, 147.2, 154.0, 195.1; Anal. Calcd for C21H13ClO:
C, 79.62; H, 4.14. Found: C, 79.93; H, 4.27.
5-Bromo-2,3-diphenyl-1H-inden-1-one (4i).24 Orange solid, Yield 75% (27 mg), Rf = 0.50 (silica
gel, Hexane /EtOAc 95:5); 1H NMR (400 MHz, CDCl3) δ 7.19 (s, 6H), 7.27-7.31 (m, 2H), 7.34-
7.39 (m, 5H); 13C{1H} NMR (100 MHz, CDCl3) δ 124.1, 124.7, 128.1, 128.2, 128.3, 128.4, 129.0,
129.3, 129.6, 130.0, 130.2, 131.6, 132.2, 133.4, 147.3, 154.2, 195.3; Anal. Calcd for C21H13BrO:
C, 69.82; H, 3.63. Found: C, 70.15; H, 3.76.
7-Chloro-2,3-diphenyl-1H-inden-1-one (4j).22 Orange solid; Yield 72% (23 mg); Rf = 0.39 (silica
gel, Hexane /EtOAc 95:5); 1H NMR (500 MHz, CDCl3) δ 6.85 (d, J = 7.5 Hz, 1H), 7.25-7.43 (m,
10H), 7.55 (d, J = 8.3 Hz, 1H), 7.62 (d, J = 7.2 Hz, 1H); 13C{1H} NMR (125 MHz, CDCl3) δ 121.4,
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123.0, 127.3, 128.0, 128.1, 128.9, 129.3, 129.9, 130.0, 130.2, 130.6, 132.7, 133.0, 133.7, 133.8,
196.3; EI-MS m/z (%) 316 (M•+, 74), 281 (100), 252 (62), 176 (10), 126 (9); Anal. Calcd for
C21H13ClO: C, 79.62; H, 4.14. Found: C, 79.87; H, 4.23.
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7-Bromo-2,3-diphenyl-1H-inden-1-one (4k). Orange solid, Yield 87% (31 mg), mp 185-187 °C;
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Rf = 0.40 (silica gel, Hexane /EtOAc 95:5); H NMR (500 MHz, CDCl3) δ 6.74 (d, J = 7.2 Hz,
1H), 7.12-7.19 (m, 4H), 7.20-7.30 (m, 6H), 7.52 (d, J = 7.0 Hz, 1H), 7.65 (dd, J = 7.9, 1.3 Hz, 1H);
13C{1H} NMR (100 MHz, CDCl3) δ 121.4, 122.4 123.0, 127.9, 128.0, 128.1, 128.9, 129.3, 129.9,
130.0, 130.2, 130.6, 133.2, 133.3, 133.7, 135.0, 145.2, 154.7, 196.4; EI-MS m/z (%) 360 (M•+,
36), 295 (29), 281 (100), 252 (94), 126 (24), 84 (27); Anal. Calcd for C21H13BrO: C, 69.82; H,
3.63. Found: C, 69.50; H, 3.51.
7-Hydroxy-2,3-diphenyl-1H-inden-1-one (4l). Red solid, Yield 63% (19 mg), mp 90-92 °C; Rf =
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0.50 (silica gel, Hexane /EtOAc 90:10); H NMR (500 MHz, DMSO-d6) δ 6.57 (d, J = 7.0 Hz,
1H), 6.85 (d, J = 7.0 Hz, 1H), 7.16 (d, J = 7.0 Hz, 2H), 7.24-7.34 (m, 6H), 7.40-7.46 (m, 3H),
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10.51 (s, 1H); C{1H} NMR (125 MHz, DMSO-d6) δ 113.1, 114.2, 120.9, 128.0, 128.4, 128.9,
129.2, 129.5, 130.2, 131.4, 132.6, 132.9, 135.9, 146.6, 153.4, 155.7, 194.2; EI-MS m/z (%) 298
(M•+, 100), 281 (20), 253 (37), 240 (23); Anal. Calcd for C21H14O2: C, 84.54; H, 4.73. Found: C,
84.84; H, 4.82.
5-(Dimethylamino)-2,3-diphenyl-1H-inden-1-one (4m).26 Red solid; Yield 71% (23 mg), Rf = 0.20
(silica gel, Hexane /EtOAc 90:10); 1H NMR (500 MHz, DMSO-d6) δ 3.02 (s, 6H), 6.41 (s, 1H),
6.45 (d, J = 8.6 Hz, 1H), 7.17 (d, J = 7.3 Hz, 2H), 7.21-7.27 (m, 3H), 7.34-7.39 (m, 3H), 7.42-7.48
(m, 3H); 13C{1H} NMR (125 MHz, DMSO-d6) δ 106.7, 108.7, 116.8, 125.5, 128.0, 128.3, 128.9,
129.3, 129.5, 130.2, 131.7, 132.9, 134.1, 147.9, 152.2, 154.8, 193.9; Anal. Calcd for C23H19NO:
C, 84.89; H, 5.89; N, 4.30. Found: C, 84.55; H, 5.73; N, 4.06.
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5,6,7-Trimethoxy-2,3-diphenyl-1H-inden-1-one (4n). Red solid, Yield 47% (16 mg), mp 146-148
°C; Rf = 0.24 (silica gel (Hexane /EtOAc 90:10); 1H NMR (400 MHz, CDCl3) δ 3.78 (s, 3H), 3.79
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(s, 3H), 4.11 (s, 3H), 6.39 (s, 1H), 7.16 (s, 5H), 7.24-7.28 (m, 2H), 7.33-7.37 (m, 3H); C{1H}
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NMR (100 MHz, CDCl3) δ 55.5, 60.4, 61.3, 101.9, 111.9, 126.6, 126.9, 127.6, 127.8, 128.0, 128.9,
129.8, 131.7, 140.7, 141.9, 151.4, 156.3, 191.9; EI-MS m/z (%) 372 (M•+, 100), 357 (56), 329
(19), 215 (19), 195 (26); Anal. Calcd for C24H20O4: C, 77.40; H, 5.41. Found: C, 77.08; H, 5.27.
1-Methyl-4,5-diphenylcyclopenta[b]pyrrol-6(1H)-one (4o). Orange solid, Yield 70% (20 mg), mp
200-202 °C; Rf = 0.52 (silica gel, Hexane /EtOAc 90:10); 1H NMR (500 MHz, CDCl3) δ 2.95 (s,
3H), 6.36-6.40 (m, 1H), 6.65 (dd, J = 3.8, 2.1 Hz, 1H), 6.76 (s, 1H), 7.26-7.28 (m, 3H), 7.31-7.34
(m, 3H), 7.36-7.38 (m, 1H), 7.41 (d, J = 7.4 Hz, 1H), 7.58 (d, J = 7.1 Hz, 1H); 13C{1H} NMR (125
MHz, CDCl3) δ 35.0, 109.6, 112.9, 121.5, 122.5, 126.6, 127.6, 128.4, 129.0, 129.2, 131.1, 132.3,
133.2, 145.0, 146.3, 195.9; EI-MS m/z (%) 285 (M•+, 100), 269 (16), 257 (29), 241 (12), 215 (9);
Anal. Calcd for C20H15NO: C, 84.19; H, 5.30; N, 4.91. Found: C, 84.52; H, 5.41; N, 5.20.
6,7-Diphenyl-5H-cyclopenta[b]pyridin-5-one (4p). Orange solid, Yield 56% (16 mg), mp 164-166
°C; Rf = 0.25 (silica gel, Hexane /EtOAc 90:10); 1H NMR (500 MHz, CDCl3) δ 7.20 (dd, J = 7.2,
5.2 Hz, 1H), 7.33 (s, 5H), 7.39-7.42 (m, 3H), 7.62-7.65 (m, 2H), 7.81 (dd, J = 7.2, 1.6 Hz, 1H),
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8.56 (dd, J = 5.2, 1.6 Hz, 1H); C{1H} NMR (125 MHz, CDCl3) δ 122.5, 125.2, 128.2, 128.3,
128.4, 129.4, 129.8, 129.9, 130.1, 130.2, 130.7, 135.3, 152.1, 153.1, 166.8, 194.6; EI-MS m/z (%)
283 (M•+, 100), 254 (57), 226 (21), 127 (9); Anal. Calcd for C20H13NO: C, 84.78; H, 4.62; N,
4.94. Found: C, 85.10; H, 4.77; N, 5.17.
General Procedure for 2-Aroyl-3-phenylindenones from Phenylpropiolic Acid and
Aldehydes. A vial equipped with a magnetic stirring bar was charged with phenylpropiolic acid
(0.1 mmol, 1.0 equiv), aldehyde (0.2 mmol, 2.0 equiv), DTBP (0.3 mmol, 3.0 equiv),
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chlorobenzene (0.5 mL) and capped. The resulting mixture was heated in an oil bath at 120 °C for
16 h. Removal of the solvent gave a crude mixture which was purified by flash column
chromatography (Hexane/EtOAc, 90:10) to give the desired product.
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5-Methyl-2-(4-methylbenzoyl)-3-phenyl-1H-inden-1-one (5a). Yellow solid, Yield 73% (25 mg);
1H NMR (500 MHz, DMSO-d6) δ 2.31 (s, 3H), 2.38 (s, 3H), 7.20-7.24 (m, 3H), 7.29 (d, J = 7.0
Hz, 1H), 7.43-7.50 (m, 6H), 7.71 (d, J = 8.2 Hz, 2H); 13C{1H} NMR (125 MHz, DMSO-d6) δ 21.7,
22.0, 123.9, 124.7, 128.0, 128.4, 129.4, 129.7, 129.8, 131.0, 131.1, 131.4, 133.1, 134.4, 143.7,
145.1, 145.6, 160.1, 192.3, 193.4; Anal. Calcd for C24H18O2: C, 85.18; H, 5.36. Found: C, 85.50;
H, 5.49.
5-Isopropyl-2-(4-isopropylbenzoyl)-3-phenyl-1H-inden-1-one (5b). Yellow solid, Yield 75% (30
mg); 1H NMR (500 MHz, CDCl3) δ 1.23 (d, J = 6.9 Hz, 6H), 1.29 (d, J = 6.9 Hz, 6H), 2.91 (hep,
J = 6.9 Hz, 1H), 2.97 (hep, J = 6.9 Hz, 1H), 7.18-7.23 (m, 3H), 7.27 (d, J = 7.5 Hz, 1H), 7.39-7.43
(m, 3H), 7.51-7.55 (m, 2H), 7.57 (d, J = 7.5 Hz, 1H), 7.77 (d, J = 8.2 Hz, 2H); 13C{1H} NMR (125
MHz, CDCl3) δ 23.5, 23.7, 34.3, 34.8, 121.8, 123.8, 126.5, 127.8, 128.2, 128.6, 128.7, 129.8,
130.3, 131.6, 133.5, 134.9, 144.1, 155.1, 155.7, 160.6, 192.2, 193.4; Anal. Calcd for C28H26O2: C,
85.25; H, 6.64. Found: C, 85.59; H, 6.80.
5-Methoxy-2-(4-methoxybenzoyl)-3-phenyl-1H-inden-1-one (5c). Yellow solid, Yield 83% (31
mg); 1H NMR (500 MHz, DMSO-d6) δ 3.79 (s, 3H), 3.86 (s, 3H), 6.86 (d, J = 2.1 Hz, 1H), 6.94
(d, J = 9.0 Hz, 2H), 6.95 (d, J = 8.1 Hz, 1H), 7.42-7.49 (m, 5H), 7.56 (d, J = 8.1 Hz, 1H), 7.79 (d,
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J = 9.0 Hz, 2H); C{1H} NMR (125 MHz, DMSO-d6) δ 56.1, 56.5, 112.1, 112.9, 114.6, 122.8,
126.0, 128.4, 129.5, 129.8, 131.1, 131.3, 132.0, 134.4, 146.1, 157.4, 164.3, 164.8, 191.1, 192.4;
Anal. Calcd for C24H18O4: C, 77.82; H, 4.90. Found: C, 77.50; H, 4.77.
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2,2,6,6-Tetramethylpiperidin-1-yl benzoate (6).27 Colorless solid, Yield 42% (11 mg), mp 86-88
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°C; HRMS m/z (ESI) calcd for C16H24NO2 [M+H]+ m/z 262.1802, found 262.1797.
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ASSOCIATED CONTENT
Supporting Information
1
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Copies of H and C spectra of all synthesized compounds. This material is available free of
charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: jafarpur@khayam.ut.ac.ir
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
We acknowledge the University of Tehran for the financial support.
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