Condensation of α-aroylketene dithioacetals and 2- hydroxyarylaldehydes results in facile synthesis of a combinatorial library of 3-aroylcoumarins

Article abstract of DOI:10.1021/jo061372e

A facile, convenient, efficient, and high yielding synthesis of a combinatorial library of 3-aroylcoumarins has been developed by the condensation of easily available α-aroylketene dithioacetals (AKDTAs) and 2-hydroxybenzaldehydes (salicylaldehydes)/2-hydroxy-1-naphthaldehyde in the presence of catalytic amount of piperidine in THF reflux. The condensation of ferrocene derived α-aroylketene dithioacetal and 2-hydroxybenzaldehyde furnished coumarin installed on a ferrocene platform.

Full text of DOI:10.1021/jo061372e

Condensation of r-Aroylketene Dithioacetals and
2-Hydroxyarylaldehydes Results in Facile Synthesis of a
Combinatorial Library of 3-Aroylcoumarins#
H. Surya Prakash Rao* and S. Sivakumar
Department of Chemistry, Pondicherry UniVersity, Pondicherry 605 014, India
hspr@yahoo.com
ReceiVed July 2, 2006
A facile, convenient, efficient, and high yielding synthesis of a combinatorial library of 3-aroylcoumarins
has been developed by the condensation of easily available R-aroylketene dithioacetals (AKDTAs) and
2-hydroxybenzaldehydes (salicylaldehydes)/2-hydroxy-1-naphthaldehyde in the presence of catalytic
amount of piperidine in THF reflux. The condensation of ferrocene derived R-aroylketene dithioacetal
and 2-hydroxybenzaldehyde furnished coumarin installed on a ferrocene platform.
Introduction
and Wittig8 condensation reactions. To make these classical
reactions efficacious, several variations in terms of catalyst and
reaction conditions have been introduced.9 In recent years
versatile coumarin syntheses could be achieved through organo-
palladium intermediates.10 A few combinatorial library syntheses
of derivatives of this important scaffold have been developed,
principally to test their utility as drug candidates.11 In continu-
ation of our interest in polarized keteneacetals,12 we now report
a conceptually novel route for the synthesis of 3-aroylcoumarins
starting from a readily available R-aroylketene dithioacetals
(AKDTAs) 1 and the 2-hydroxybenzaldehydes (salicylalde-
The coumarins (2H-chromen-2-ones, 2H-1-benzopyran-2-
ones) are among the best-known oxygen heterocycles, well
represented as a structural motif in numerous natural products.1
Several coumarins have found application in technological2 and
therapeutic3 fields. Naturally, there has been a continuous effort
to develop new, convenient, and versatile syntheses of coumarins
with defined structural features. Classical routes to coumarins
incorporate Pechmann,4 Knoevenagel,5 Perkin,6 Reformatsky,7
* To whom correspondence should be addressed. E-mail: hspr@yahoo.com.
Fax: +91 413 2655987.
# Ketene Acetal Chemistry: Part 4; see ref 12c.
(6) Johnson, J. R. Org. React. 1942, 1, 210-266.
(7) Shriner, R. L. Org. React. 1942, 1, 1-37.
(1) (a) Murray, R. D. H.; Mendez. J.; Brown, S. A. in The Natural
Coumarins: Occurrence, Chemistry and Biochemistry; John Wiley and
Sons: New York, 1982. (b) Hepworth, J. D. In ComprehensiVe Heterocyclic
Chemistry; Katritzky, A. R., Rees, C. W., Eds.; Pergamon: New York,
1984; Vol. 3, pp 799-810. (c) Hepworth, J. D.; Gabbutt, C. D.; Heron, B.
M. In ComprehensiVe Heterocyclic Chemistry-II; Katritzky, A. R., Rees,
C. W., Scriven, E. F. V., Eds.; Pergamon: New York, 1996; Vol. 5, pp
417-434.
(8) (a) Narasimhan, N. S.; Mali, R. S.; Barve, M. V. Synthesis, 1979,
906-909. (b) Harayama, T.; Nakatsuka, K.; Katsuro, K.; Nishioka, H.;
Murakami, K.; Fuji, M. Chem. Express 1993, 8, 245-248. (c) Yavari, I.;
Hekmat-Shoar, R.; Zonouzi, A. Tetrahedron Lett. 1998, 39, 2391-2392.
(9) For examples see (a) Dittmer, D. C.; Li, Q.; Avilov, D. V. J. Org.
Chem. 2005, 70, 4682-4686. (b) Alexander, V. M.; Bhat, R. P.; Samant,
S. D. Tetrahedron Lett. 2005, 46, 6957-6959.
(2) (a) Perfumery: Clark, G. S. Perfum. FlaVor. 1995, 20, 23-34. (b)
Fluorescent chemo-sensors: Chen, C.-T.; Huang, W.-P. J. Am. Chem. Soc.
2002, 124, 6246-6247. (c) Laser, technology: Sekar, N. Colourage 2003,
50, 55-56. (d) Fluorescent indicators: Brun, M. P.; Bischoff, L.; Garbay,
C. Angew. Chem., Int. Ed. 2004, 43, 3432-3436.
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Y. Science 2000, 287, 1992-1995. (b) Jia, C.; Lu, W.; Oyamada, J.;
Kitamura, T.; Matsuda, K.; Irie, M.; Fujiwara, Y. J. Am. Chem. Soc. 2000,
122, 7252-7263. (c) Jia, C.; Piao, D.; Kitamura, T.; Fujiwara, Y. J. Org.
Chem. 2000, 65, 7516-7522. (d) Selles, P.; Mueller, U. Org. Lett. 2004,
6, 277-279. (e) Li, K.; Zeng, Y. Neuenswander, B.; Tunge, J. A. J. Org.
Chem. 2005, 70, 6515-6518. (f) Aoki, S.; Amamoto, C.; Oyamada, J.;
Kitamura, T. Tetrahedron 2005, 61, 9291-9297.
(3) (a) O’Kennedy, R., Thornes, R. D., Eds.; in Coumarins: Biology,
Applications and Mode of Action; Wiley: Chichester, U.K. 1997. (b) Chem.
Weekly 2001, 159-150.
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H.; Duisberg, C. Chem. Ber. 1884, 17, 929. (c) Russel, A.; Fyre, J. R. Org.
Synth. 1941, 21, 22-26. (d) Sethna, S.; Phadke, R. Org. React. 1953, 7,
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10.1021/jo061372e CCC: $33.50 © 2006 American Chemical Society
Published on Web 10/11/2006
J. Org. Chem. 2006, 71, 8715-8723
8715

Rao and Sivakumar
SCHEME 1 a
hydes) 2. Some of the 3-aroylcoumarins-target molecules of the
present study-were shown to be efficient triplet sensitizers.13
Moreover, 3-aroylcoumarins are good Michael acceptors, amen-
able to further synthetic transformations.14
The AKDTAs 1 are three carbon synthons, employed
extensively for the synthesis of a wide variety of heterocyclic
compounds.15 They also serve as intermediates for benzo- and
heteroaromatic annulations, en route to the synthesis of complex
heterocycles.16 They are essentially masked â-ketoesters 3 with
reactivity difference emanating from respective structural
features. When required, the ester functionality in 1 can be
unmasked through simple hydrolysis.17 In several reactions the
AKDTAs 1 behave as R,â-unsaturated carbonyl compounds,
where in, depending on the nucleophile, either 1,2- or 1,4-
addition takes place.16
a Reagents and conditions: (i) piperidine 10 mol %, THF reflux, 12-48
h, 74-95%.
TABLE 1. Synthesis of 3-Benzoylcoumarin 4a from 1a (1 mmol)
and 2a (1 mmol) Using Different Bases/Conditions
The AKDTAs 1 are polarized alkenes wherein polarization
flows from two electron-donating alkylsulfanyl groups on C-1
to the electron-withdrawing carbonyl group on C-2. While C-1
in 1 exhibits electrophilic characteristics, the C-2 shows
nucleophilic characteristics. We reasoned that condensation
reaction of 1 with the 2-hydroxybenzaldehydes (salicylalde-
hydes) 2, molecules having nucleophilic oxygen and electro-
philic carbonyl carbon, could result in two-component conden-
sation, and subsequent hydrolysis and dehydration could lead
to 3-aroylcoumarins. A wide variety of AKDTAs 1 are easily
available and the unknown ones can be prepared readily from
substituted acetophenones, carbon disulfide, and an alkylating
agent in a single-pot operation.18 Similarly, a wide variety of
2-hydroxybenzaldehydes 2 can be prepared from corresponding
phenols via the Reimer-Tiemann reaction.19 With leads available
in both the aromatic rings, condensation of the AKDTAs 1 with
the 2-hydroxybenzaldehydes 2 could lead to the synthesis of a
combinatorial library of 3-aroylcoumarins.
entry
base (equiv)
piperidine (1.0)
piperidine (0.1)
piperidine (1.0)
pyrrolidine (1.1)
morpholine (0.1 or 1.1)
DBU or Et3N or DABCO
(0.1 or 1.1)
NaH (1.0)
K2CO3 or NaOH (aq, 1.1),
TBAB (0.05)
solventa
yield %
1
2
3
4
5
6
THF
THF
97b
94c
EtOH
THF
THF
THF
d
25e
27e
no reaction
7
8
THF/DMF (10:1)
DCM
19e
no reaction
9
basic alumina or
KF/neutral alumina
neatf
no reactiong
a All solution-phase reactions were conducted at reflux temperature of
the solvent used. b After 8 h reflux. c Based on the recovered 1a (5%) after
48 h reflux. d Anticipated coumarin 4a did not form, instead the reaction
furnished the chalcone 16a (vide infra). e After 48 h reflux; yield based on
recovered 1a. f The reaction was conducted under microwave irradiation
(2.45 GHz; 370 W, 2 min). g Extensive decomposition of 1a took place.
took place smoothly in the presence of piperidine in THF reflux
to result in the formation of 3-benzoylcoumarin20 4a in 97%
yield (Scheme 1; entry 1, Table 1). The condensation of 1a
with 2a to generate coumarin 4a was investigated under a variety
of conditions (base, solvent, etc.), as a test case, to optimize
the yield, and the results are gathered in Table 1. The
condensation took place even with a catalytic amount of
piperidine (10 mol %; entry 2). Though the condensation
reaction with a catalytic amount of piperidine was clean, it took
a longer time (48 h) and about 5% of 1a remained as such. On
the other hand, the reaction was relatively fast (8 h) when 1
equiv of piperidine was employed. The reaction did not take
place when piperidine in EtOH was used (entry 3). The other
secondary amines, pyrrolidine (entry 4) and morpholine (entry
5), gave only poor yield of the desired product 4a. The reaction
Results and Discussion
Indeed, condensation of the AKDTA, 3,3-bis(methylsulfanyl)-
1-phenyl-2-propen-1-one 1a with 2-hydroxybenzaldehyde 2a
(13) Specht, D. P.; Martic, P. A.; Farid, S. Tetrahedron 1982, 38, 1203-
1211.
(14) (a) Sastry, V. D. N.; Seshadri, T. R. Proc. Ind. Acad. Sci. 1942,
16A, 29-35; Chem. Abstr. 1943, 37, 880. (b) Yamashita, M.; Okuyama,
K.; Kawajiri, T.; Takada, A.; Inagaki, Y.; Nakano, H.; Tomiyama, M.;
Ohnaka, A.; Teryama, I.; Kawasaki, I.; Ohta, S. Tetrahedron 2002, 58,
1497-1505. (c) Nemeryuk, M. P.; Dimitrova, V. D.; Anisimova, O. S.;
Sedov, A. L.; Soloveva, N. P.; Traven, V. F. Chem. Heterocycl. Comp.
2003, 39, 1454-1464.
(15) (a) Dieter, R. K. Tetrahedron, 1986, 42, 3029-3096. (b) Junjappa,
H.; Ila, H.; Asokan, C. V. Tetrahedron, 1990, 46, 5423-5506.
(16) (a) Ila, H.; Junjappa, H.; Mahanta, P. K. In Progress in Heterocyclic
Chemistry; Gribble, G. W., Gilchrist, T. L., Eds.; Pergamon Press: Oxford,
U.K., 2001; Vol. 13, Chapter 1, 1-24. (b) Panda, K.; Suresh, J. R.; Ila, H.;
Junjappa, H. J. Org. Chem. 2003, 68, 3498-3506.
(17) Shahak, I.; Sasson, Y. Tetrahedron. Lett. 1973, 43, 4207-4210.
(18) (a) Thuillier, J.; Vialle, J. Bull. Soc. Chim. Fr. 1959, 1398-1401;
Chem Abstr. 1960, 54, 12110. (b) Thuillier, J.; Vialle, J. Bull. Soc. Chim.
Fr. 1962, 2182-2186; Chem Abstr. 1963, 59, 2786.
(19) (a) Wynberg, H. Chem. ReV. 1960, 60, 169-164. (b) Wynberg, H.;
Meijer, E. W. Org. React. 1982, 28, 1-36. (c) Wynberg, H. The Riemer-
Tiemann Reaction. In ComprehensiVe Organic Synthesis; Trost, B. M.,
Fleming, I., Eds.; Pergamon: Oxford, 1991; Vol. 2, 269-775.
(20) (a) Ghosal, S. C. Q. J. Ind. Chem. Soc. 1926, 3, 105-109; Chem.
Abstr. 1927, 21, 3187. (b) Buu-Hoi, N. P.; Saint-Ruf, G.; Loc., T. B.; Xuong,
N. D. J. Chem. Soc. 1957, 2593-2596. (c) Andreichikov, Yu. S.;
Tokmakova, T. N. J. Org. Chem. USSR (Eng. Transl.) 1987, 23, 796-
800; Chem. Abstr. 1988, 108, 150236. (d) Nemeryuk, M. P.; Dimitrova,
V. D.; Sedov, A. L.; Anisimova, O. S.; Traven, V. F. Chem. Heterocycl.
Comp. 2000, 36, 874-875. (e) Nemeryuk, M. P.; Dimitrova, V. D.; Sedov,
A. L.; Anisimova, O. S.; Traven, V. F. Chem. Heterocycl. Comp. 2002,
38, 249-250.
8716 J. Org. Chem., Vol. 71, No. 23, 2006

Condensation of R-Aroylketene Dithioacetals
TABLE 2. Synthesis of 3-Aroylcoumarins from AKDTAs and 2-Hydroxyarylaldehydes in Piperidine (Catalytic) and THF Reflux
SCHEME 2 a
did not take place when non-nuclophilic tert-amine bases such
as 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU), 1,4-diazabicyclo-
[2,2,2]octane (DABCO) or triethylamine (TEA) was employed
either in catalytic or in stoichiometric quantities (entry 6). Yield
of the desired product was poor when the strong base NaH was
employed (entry 7). There was no condensation when the two-
phase reaction was conducted with a mild base (aq K2CO3) or
a strong base (aq NaOH) under the biphasic conditions (DCM,
H2O) in the presence of a catalytic amount of tetrabutylammo-
nium bromide (TBAB; entry 8). The microwave mediated
heating under neat conditions by adsorbing the two reactants
on basic alumina or 5% KF on neutral alumina led to extensive
decomposition of the reaction mixture (entry 9). Thus, it is clear
from the aforementioned experiments that the best yield of
coumarin 4a could be obtained by employing piperidine as base
and THF as solvent.
To test generality of the condensation and to realize synthesis
of a small combinatorial library of 3-aroylcoumarins, three
AKDTAs 1a-c were reacted with four 2-hydroxybenzaldehydes
2a-d to furnish twelve coumarins 4a-l in good yields (Scheme
1 and Table 2) by using piperidine (10 mol %) as base in THF
reflux. All the coumarins 4a-l were characterized by analytical
and spectral data.21 The 1H NMR spectra of the coumarins 4a-l
displayed a characteristic singlet for the olefinic hydrogen at
about δ 8.0. Condensation of three AKDTAs 1a-c with
a Reagents and conditions. (i) piperidine 10 mol %, THF reflux, 12-36
h, 80-89%.
2-hydroxy-1-naphthaldehyde 5 furnished 2-aroyl-3H-benzo[f]-
chromen-3-ones 6a-c in good yields (Scheme 2).14c,20 The 1H
NMR spectra of the coumarins 6a-c displayed a singlet for
the C-1 olefinic hydrogen at about δ 8.8 and doublet for the
C-10 peri-hydrogen in the bay region at δ 8.2.
Since the 3-aroylcoumarin derivatives exhibit characteristics
of triplet sensitizers, particularly when there is extended
conjugation to aromatic rings, we next planned the synthesis
of the 3-aroylcoumarins incorporating naphthalene ring or
biphenyl group in the aroyl portion of the target coumarins.
Following the procedure described above, we have conducted
the condensation of the AKDTAs 7, 9,22 and 11 with 2-hy-
droxybenzaldehyde 2a to furnish the 3-aroylcoumarins 8, 10,
and 12 in good yields (Scheme 3). The coumarins 8, 10, and
12 were characterized on the basis of spectral data which
matched well with the parent molecules 4. The AKDTAs 7 and
11 were prepared from the corresponding aryl methyl ketones,
carbon disulfide, and dimethyl sulfate. The 1H NMR spectrum
(21) Some of the 3-aroylcoumarins prepared in this study are known
compounds. See refs 13, 14c, and 20; however, see Experimental Section
for complete spectral data for all the products prepared in this study.
(22) Datta, A.; Poornachand, D.; Ila, H.; Junjappa, H. Tetrahedron 1989,
45, 7631-7640.
J. Org. Chem, Vol. 71, No. 23, 2006 8717

Rao and Sivakumar
SCHEME 3 a
SCHEME 5
SCHEME 6 a
a Reagents and conditions: (i) piperidine 10 mol %, 2-hydroxybenzal-
dehyde 1 equiv, THF reflux, 10-24 h, 69-92%.
SCHEME 4 a
aReagents and conditions: (i) piperidine, EtOH reflux, 10 h, 82-90%.
by neighboring group effect of oxygen would furnish coumarins
4 in a multistep process. Even though product formation can
be explained by concerted cycloaddition involving 1 and enolate
form of 2, in view of the polar nature of 1 and the requirement
to dearomatize 2 before cycloaddition, the concerted process is
unlikely.
When the reaction of the AKDTA 1a with 2-hydroxyben-
zaldehyde 2a was conducted in ethanol reflux instead of in THF
reflux, the reaction furnished known chalcone23 16a in 90%
yield, instead of coumarin 4a (entry 3, Table 1 and Scheme 6).
Similarly, the reaction of 1b with 2a furnished chalcone24 16b
instead of coumarin 4b. Evidently, in ethanol reflux 1a was
reverting to acetophenone before aldol condensation with
2-hydroxybenzaldehyde 2a.25
a Reagents and conditions: (i) (a) CS2, t-BuONa, THF, 0 °C, 90 min;
(b) Me2SO4, 0 °C, 90 min, 67%; (ii) piperidine 10 mol %, 2-hydroxyben-
zaldehyde, THF reflux, 9 h, 85%.
of the coumarin, 3-(1-naphthylcarbonyl)-2H-2-chromenone 8
displayed a singlet for the C-4 olefinic hydrogen at δ 8.2 in
tandem with other coumarins, whereas the C-8′ peri-hydrogen
in the naphthalene ring shifted to downfield and it appeared at
δ 8.52 (cf. δ 8.44 for C-8-H in 7) indicating that the C-8′ peri-
hydrogen is having CH-O type hydrogen bonding interactions
with the oxygen of the carbonyl group. Similarly, the 1H NMR
spectrum of 3-(2-naphthylcarbonyl)-2H-2-chromenone 10 dis-
played a singlet for the C-1′ peri-hydrogen at δ 8.56 (cf. δ 8.40
for C-1-H in 9).
Conclusions
From this investigation we have shown that facile synthesis
of 3-aroylcoumarins can be achieved under mild conditions from
easily available AKDTAs and 2-hydroxybenzaldehydes. The
condensation reaction works well with a catalytic amount of
piperidine in THF reflux. This scheme offers a good scope for
the synthesis of a wide variety of 3-aroylcoumarins. Considering
that the aroylacetic esters, which are traditional reacting partners
for 2-hydroxybenzaldehydes in the 3-aroylcoumarin syntheses
are difficult to prepare,26 present procedure is a significant
As a next attempt, we have installed coumarin motif on the
ferrocene platform following the method presently developed.
The ferrocene based AKDTA 13 was smoothly transformed into
coumarin 3-η5-ferrocenoyl-2H-2-chromenone 14 by condensa-
tion with 2-hydroxybenzaldehyde 2a in the presence of a
1
catalytic amount of piperidine (Scheme 4). The H NMR and
13C NMR spectral data of the coumarin portion of 14 matched
well with the parent coumarins 4. The AKDTA 13 was prepared
from acetyl ferrocene 15 by reaction with carbon disulfide and
sodium tert-butoxide followed by alkylation with dimethyl
sulfate.
(23) William, E. T.; Cheng-I, M. L. J. Am. Chem. Soc. 1973, 95, 4426-
4428.
(24) Le Fevre, C. G; Le Fevre, R. J. W.; Pearson, J. J. Chem. Soc. 1934,
37-43.
(25) (a) Ireland, R. E.; Marshall, J. A. J. Am. Chem. Soc. 1959, 81, 6336-
6337. (b) Apparao, S.; Rahman, A.; Ila, H.; Junjappa, H. Tetrahedron Lett.
1982, 23, 971-974.
(26) (a) Hauser, C. R.; Hudson, B. E., Jr. Org. React. 1942, 1, 266-
289. (b) Schaefer, J. P.; Bloomfield, J. J. Org. React. 1967, 15, 1.(c)
Shiosaki, K.; Fels, G.; Rapoport, H. J. Org. Chem. 1981, 46, 3230-3234.
(d) Katritzky, A. R.; Wang, Z.; Wang, M.; Wilkerson, C. R.; Hall, C. D.;
Akhmedov, N. G. J. Org. Chem. 2004, 69, 6617-6622.
A possible mechanism for the formation of coumarins 4 from
the AKDTAs 1 and the 2-hydroxybenzaldehydes 2 is given in
Scheme 5. Conjugate addition (Michael reaction) of the anion
generated from 2 to 1 would result in enolate anion, which
participates in subsequent intramolecular aldol condensation.
Dehydration followed by hydrolysis of the thioacetal assisted
8718 J. Org. Chem., Vol. 71, No. 23, 2006

Condensation of R-Aroylketene Dithioacetals
improvement over existing methods. We are now concentrating
on the synthesis of some 3-aroylcoumarins with tailored
properties.
Experimental Section
1-Biphenyl-4-yl-3,3-bismethylsulfanyl-2-propen-1-one 11. Fol-
lowing the general procedure described above, the reaction of
4-phenylacetophenone (1.75 g, 9.0 mmol), carbon disulfide (0.66
mL, 11 mmol), sodium tert-butoxide (3.0 g, 31 mmol), and freshly
distilled dimethyl sulfate (1.0 mL, 10.8 mmol) furnished 1.75 g of
1-biphenyl-4-yl-3,3-bismethylsulfanyl-2-propen-1-one 11 in 65%
yield as light yellow colored crystals after recrystallization: mp
112-114 °C (ethanol) (lit.18a 122 °C. UV λmax (MeOH): 356 nm
(log ꢀ ) 3.75), 287 nm (log ꢀ ) 3.6). IR (KBr) 2971, 1612, 1474,
1237, 755 cm-1. 1H NMR (300 MHz, CDCl3): δ 7.99 (d, J ) 8.7
Hz, 2H), 7.35-7.70 (m, 7H), 6.81 (s, 1H), 2.58 (s, 3H), 2.54 (s,
3H). 13C NMR (75 MHz, CDCl3): δ 185.1, 166.4, 144.4, 140.1,
138.0, 128.8, 128.3, 127.9, 127.2, 127.1, 109.4, 17.4, 15.0. Anal.
Calcd for C17H16OS2: C, 67.96; H, 5.37. Found: C, 67.96; H, 5.35.
General Procedure for the Preparation of 1-Aryl-3,3-bis-
(methylsulfanyl)-2-propen-1-ones. To a stirred suspension of
freshly prepared sodium tert-butoxide (3.0 g, 31 mmol) in dry THF
(7 mL) at 0 °C a solution of aryl ketones (9.0 mmol) and carbon
disulfide (84 mg, 0.66 mL, 11 mmol) in dry THF (10 mL) was
added through a pressure equalizer funnel, and the mixture was
vigorously stirred at 0 °C for 90 min. Appearance of reddish solid
in the reaction medium indicated the formation of disodium salt of
1-aryl-3,3-bissulfanyl-2-propen-1-ones. To this suspension, a solu-
tion of dimethyl sulfate (1.2 mL, 10.8 mmol) in dry THF (5 mL)
was carefully added dropwise during 10 min at 0 °C, and the
reaction mixture was allowed to stir at 0 °C for 90 min. After
completion of the reaction (TLC; hexanes/EtOAc ) 8:2), the
mixture was transferred into a 100 mL beaker containing 50 g of
crushed ice, and the contents of the beaker were stirred well. A
light yellow colored solid formed, was filtered, and was washed
with water (20 mL × 3). The crude solid was recrystallized from
5% DCM in hexanes or EtOH. Physical, spectral, and analytical
data of the hitherto unknown AKDTAs are subsequently given.
3,3-Bis(methylsulfanyl)-1-η5-ferrocenyl-2-propen-1-one 13. Fol-
lowing the general procedure described above, the reaction of
acetylferrocene (2 g, 9.0 mmol), carbon disulfide (0.64 mL, 10.8
mmol), sodium tert-butoxide (3.05 g, 31.05 mmol), and freshly
distilled dimethyl sulfate (1.0 mL, 10.8 mmol) furnished 1.84 g of
3,3-bis(methylsulfanyl)-1-η5-ferrocenyl-2-propen-1-one 13 in 67%
yield as brown powder after recrystallization: mp 112-115 °C
(ethanol). UV λmax (MeOH): 483 nm (log ꢀ ) 3.01), 392 nm (log
ꢀ ) 3.03), 295 nm (log ꢀ ) 2.91), 240 nm (log ꢀ ) 3.02). IR
3,3-Bis(methylsulfanyl)-1-(1-naphthyl)-2-propen-1-one 7. Fol-
lowing the general procedure described above, the reaction of
1-acetylnaphthalene (1.53 g, 9.0 mmol) with carbon disulfide (0.64
mL, 10.8 mmol), sodium tert-butoxide (3.1 g, 31.2 mmol) and
freshly distilled dimethyl sulfate (1.0 mL, 10.8 mmol) furnished
1.47 g of 3,3-bis(methylsulfanyl)-1-(1-naphthyl)-2-propen-1-one 7
in 60% yield as light yellow colored crystals after recrystalliza-
tion: mp 98-102 °C (ethanol). UV λmax (MeOH): 350 nm (log ꢀ
) 4.6), 281 nm (log ꢀ ) 4.33). IR (KBr) 3053, 1608, 1505, 1478,
1236, 1187, 783 cm-1. 1H NMR (300 MHz, CDCl3): δ 8.44 (d, J
) 9.0 Hz, 1H), 7.42-7.95 (m, 6H), 6.54 (s, 1H,), 2.55 (s, 3H),
2.48 (s, 3H). 13C NMR (75 MHz, CDCl3): δ 189.4, 166.1, 139.9,
133.7, 130.8, 130.1, 128.2, 126.9, 126.1, 125.9, 125.8, 124.6, 113.5,
17.2, 14.9. Anal. Calcd for C15H14OS2: C, 65.66; H, 5.14. Found:
C, 65.23; H, 5.14.
1
(KBr): 2984, 1600, 1482, 1375, 1243, 1093, 761, 624 cm-1. H
NMR (300 MHz, CDCl3): δ 6.35 (s, 1H), 4.78 (br s, 2H), 4.45 (br
s, 2H), 4.13 (br s, 5H), 2.52 (br s, 6H). 13C NMR (75 MHz,
CDCl3): δ 189.8, 161.4, 111.8, 82.0, 72.1, 70.3, 69.5, 17.2, 15.4.
Anal. Calcd for C15H16OS2Fe: C, 54.22; H, 4.85. Found: C, 54.19;
H, 4.91.
General Procedure for the Preparation of 3-Aroyl Cou-
marins: To a stirred solution of 2-hydroxyarylaldehydes (2a-e,
2.2 mmol) and 1-aryl-3,3-bis(methylsulfanyl)-2-propen-1-ones (1a-
c, 2.2 mmol) in dry THF (15 mL), piperidine (19 mg, 22 µL, 0.22
mmol) in dry THF (5 mL) was added dropwise over 5 min at room
temperature under a blanket of dry nitrogen. The reaction mixture
was heated at reflux in a preheated oil bath (80 °C) for 12-15 h
for completion of the reaction (TLC; hexanes/EtOAc ) 8:2). The
reaction mixture was then diluted with dichloromethane (25 mL),
and the organic solution was washed sequentially with water (3 ×
25 mL) and brine (2 × 10 mL) and dried over anhydrous Na2SO4.
Evaporation of the solvent under reduced pressure resulted in crude
3-aroylcoumarins as gummy liquid. The crude product was
subjected to column chromatography on SiO2 (25 g; 15 cm × 1
cm) using increasing amounts of ethyl acetate in hexanes as eluent.
Evaporation of the pooled fractions having the required 3-aroyl-
coumarins resulted in free flowing solids. Analytical samples were
obtained by crystallization from EtOH or DCM/hexanes. In some
reactions, a small amount (e5%) of AKDTAs were recovered from
the reaction mixture. In cases where AKDTAs were recovered,
yields of the coumarins have been computed on the basis of
recovered starting material.
3,3-Bis(methylsulfanyl)-1-(2-naphthyl)-2-propen-1-one 9. Fol-
lowing the general procedure described above, the reaction of
2-acetylnaphthalene (1.5 g, 9.0 mmol), carbon disulfide (0.65 mL,
11 mmol), sodium tert-butoxide (3.0 g, 31.0 mmol), and freshly
distilled dimethyl sulfate (1.0 mL, 10.8 mmol) furnished 1.74 g of
3,3-bis(methylsulfanyl)-1-(2-naphthyl)-2-propen-1-one 9 in 70%
yield as light yellow colored crystals after recrystallization: mp
79-81 °C (5% DCM in hexanes). UV λmax (MeOH): 356 nm (log
ꢀ ) 4.19), 258 nm (log ꢀ ) 4.01). IR (KBr): 2915, 1609, 1480,
1426, 1256, 1183, 790, 567 cm-1. 1H NMR (300 MHz, CDCl3): δ
8.40 (s, 1H), 7.51-8.03 (m, 6H), 6.91 (s, 1H), 2.60 (s, 3H), 2.54
(s, 3H). 13C NMR (75 MHz, CDCl3): δ 185.5, 166.4, 136.7, 134.9,
132.6, 129.3, 128.4, 128.3, 127.8, 127.7, 126.5, 124.3, 109.6, 17.4,
15.1. Anal. Calcd for C15H14OS2: C, 65.66; H, 5.14. Found: C,
65.64; H, 5.07.
J. Org. Chem, Vol. 71, No. 23, 2006 8719

Rao and Sivakumar
3-Benzoyl-2H-2-chromenone 4a. Following the general procedure
described previously, the reaction of 2-hydroxybezaldehyde (sali-
cyladehyde) 2a (268 mg, 2.2 mmol), 3,3-bis(methylsulfanyl)-1-
phenyl-2-propen-1-one 1a (500 mg, 2.2 mmol), and peperidine (19
mg, 0.22 mmol) furnished 533 mg of 3-benzoyl-2H-2-chromenone
4a in 94% yield as colorless crystals after column purification and
recrystallization: mp 134-136 °C (ethanol) (lit.13 137-139 °C).
UV λmax (MeOH): 290 nm (log ꢀ ) 3.98), 253 nm (log ꢀ ) 3.82).
IR (KBr): 3063, 1719, 1607, 1243, 755 cm-1. 1H NMR (300 MHz,
CDCl3): δ 8.08 (s, 1H), 7.88 (d, J ) 8.1 Hz, 2H), 7.51-7.69 (m,
3H), 7.49 (d, J ) 8.1 Hz, 2H), 7.32-7.49 (m, 2H). 13C NMR (75
MHz, CDCl3): δ 191.6 158.4, 154.7, 145.4, 136.2, 133.8, 133.6,
129.5, 129.2, 128.6, 126.9, 124.9, 118.1, 116.0.
7.28-7.64 (m, 6H), 2.43 (s, 3H). 13C NMR (75 MHz, CDCl3): δ
191.8, 152.9, 145.5, 136.3, 134.8, 134.7, 133.7, 129.6, 128.8, 128.6,
126.9, 117.9, 116.6, 115.4, 20.7. Anal. Calcd for C17H12O3: C,
77.26; H, 4.58. Found: C, 77.35; H, 4.55.
6-Methyl-3-(4-methylbenzoyl)-2H-2-chromenone 4e. Following
the general procedure described above, the reaction of 2-hydroxy-
5-methylbenzaldehyde 2b (285 mg, 2.1 mmol), 1-(4-methylphenyl)-
3,3-bis(methylsulfanyl)-2-propen-1-one 1b (500 mg, 2.1 mmol), and
peperidine (18 mg, 0.2 mmol) furnished 467 mg of 6-methyl-3-
(4-methylbenzoyl)-2H-2-chromenone 4e in 80% yield as colorless
crystals after column purification: mp 158-160 °C (5% DCM in
hexanes). UV (MeOH): λmax 334 nm (log ꢀ ) 3.59), 290 nm (log
ꢀ ) 4.00). IR (KBr): 3061, 2917, 1715, 1651, 1605, 1252, 781
1
cm-1. H NMR (300 MHz, CDCl3): δ 7.99 (s, 1H), 7.78 (d, J )
3-(4-Methylbenzoyl)-2H-2-chromenone 4b. Following the general
procedure described above, the reaction of 2-hydroxybenzaldehyde
2a (256 mg, 2.1 mmol), 1-(4-methylphenyl)-3,3-bis(methylsulfa-
nyl)-2-propen-1-one 1b (500 mg, 2.1 mmol), and peperidine (18
mg, 0.2 mmol) furnished 498 mg of 3-(4-methylbenzoyl)-2H-2-
chromenone 4b in 90% yield as colorless crystals after column
purification and recrystallization: mp 132-134 °C (5% DCM in
hexanes) (lit.20c 133-134 °C). UV (MeOH): λmax 288 nm (log ꢀ
7.8 Hz, 2H), 7.25-7.46 (m, 5H), 2.43 (s, 6H). 13C NMR (75 MHz,
CDCl3): δ 191.4, 158.9, 152.9, 145.1, 144.8, 134.7, 134.6, 133.72,
129.8, 129.3, 128.8, 127.2, 117.9, 116.6, 21.8, 20.7. Anal. Calcd
for C18H14O3: C, 77.68; H, 5.07. Found: C, 77.62; H, 5.13.
1
) 4.08). IR (KBr): 3075, 1713, 1606, 1241, 762 cm-1. H NMR
(300 MHz, CDCl3): δ 8.05 (s, 1H), 7.78 (d, J ) 8.4 Hz, 2H),
7.55-7.68 (m, 2H), 7.31-7.43 (m, 2H), 7.27 (d, J ) 8.4 Hz, 2H),
2.43 (s, 3H). 13C NMR (75 MHz, CDCl3): δ 191.2, 158.3, 155.1,
145.0, 144.9, 133.6, 133.5, 129.8, 129.3, 129.1, 126.9, 124.9, 118.2,
116.9. 21.9.
3-(4-Chlorobenzoyl)-6-methyl-2H-2-chromenone 4f. Following
the general procedure described above, the reaction of 2-hydroxy-
5-methylbenzaldehyde 2b (258 mg, 1.9 mmol), 1-(4-chlorophenyl)-
3,3-bis(methylsulfanyl)-2-propen-1-one 1c (500 mg, 1.9 mmol), and
peperidine (17 mg, 0.2 mmol) furnished 520 mg of 3-(4-chloroben-
zoyl)-6-methyl-2H-2-chromenone 4f in 92% yield as colorless
crystals after column purification: mp above 200 °C (ethanol). UV
(MeOH): λmax 336 nm (log ꢀ ) 3.69), 291 nm (log ꢀ ) 4.08). IR
1
(KBr): 3062, 2917, 1713, 1675, 1605, 1243, 765 cm-1; H NMR
3-(4-Chlorobenzoyl)-2H-2-chromenone 4c. Following the general
procedure described above, the reaction of 2-hydroxybenzaldehyde
2a (232 mg, 1.9 mmol), 1-(4-chlorophenyl)-3,3-bis(methylsulfanyl)-
2-propen-1-one 1c (500 mg, 1.9 mmol), and peperidine (18 mg,
0.2 mmol) furnished 512 mg of 3-(4-chlorobenzoyl)-2H-2-chrome-
none 4c in 95% yield as colorless crystals after column purification
and recrystallization: mp above 200 °C (5% DCM in hexanes).
UV (MeOH): λmax 289 nm(log ꢀ ) 4.10). IR (KBr): 3059, 1713,
1656, 1608, 1237, 754 cm-1. 1H NMR (300 MHz, CDCl3): δ 8.33
(s, 1H), 7.87 (d, J ) 8.4 Hz, 2H), 7.79 (d, J ) 7.3 Hz, 1H), 7.68
(t, J ) 7.3 Hz, 1H), 7.50 (d, J ) 8.4 Hz, 2H), 7.35-7.43 (m, 2H).
13C NMR (75 MHz, CDCl3): δ 189.8, 157.5, 154.1, 145.5, 138.9,
134.4, 133.2, 130.7, 129.5, 128.4, 125.8, 124.5, 117.9, 116.0. Anal.
Calcd for C16H9O3Cl: C, 67.50; H, 3.19. Found: C, 67.52; H, 3.16.
3-Benzoyl-6-methyl-2H-2-chromenone 4d. Following the general
(300 MHz, CDCl3): δ 8.08 (s, 1H), 7.81 (d, J ) 8.4 Hz, 2H),
7.48-7.31 (m, 5H), 2.44 (s, 3H). 13C NMR (75 MHz, CDCl3): δ
190.2, 158.2, 152.4, 145.5, 139.6, 134.5, 134.4, 134.2, 130.4, 128.5,
128.4, 125.7, 117.3, 116.1, 20.2. Anal. Calcd for C17H11O3Cl: C,
68.35; H, 3.71. Found: C, 68.41; H, 3.81.
3-Benzoyl-6-methoxy-2H-2-chromenone 4g. Following the gen-
eral procedure described above, the reaction of 2-hydroxy-5-
methoxybenzaldehyde 2c (335 mg, 2.2 mmol), 3,3-bis(methylsul-
fanyl)-1-phenyl-2-propen-1-one 1a (500 mg, 2.2 mmol) and
peperidine (19 mg, 0. 22 mmol) furnished 579 mg of 3-benzoyl-
6-methoxy-2H-2-chromenone 4 g in 94% yield as colorless crystals
after column purification: mp 160-162 °C (5% DCM in hexanes).
UV (MeOH): λmax 362 nm (log ꢀ ) 3.77), 289 nm (log ꢀ ) 4.21),
248 nm (log ꢀ ) 4.2). IR (KBr): 3082, 2934, 1710, 1650, 1603,
1
1249, 686 cm-1. H NMR (300 MHz, CDCl3): δ 8.01 (s, 1H),
procedure described above, the reaction of 2-hydroxy-5-methyl-
benzaldehyde 2b (299 mg, 2.2 mmol), 3,3-bis(methylsulfanyl)-1-
phenyl-2-propen-1-one 1a (500 mg, 2.2 mmol), and peperidine (19
mg, 0.22 mmol) furnished 464 mg of 3-benzoyl-6-methyl-2H-2-
chromenone 4d in 80% yield after column purification as colorless
crystals: mp 174 °C (5% DCM in hexanes) (lit.20a 174 °C). UV
(MeOH): λmax 341 nm (log ꢀ ) 3.65), 292 nm (log ꢀ ) 4.03). IR
7.86 (d, J ) 8.4 Hz, 2H), 7.15-7.65 (m, 6H), 3.74 (s, 3H). 13C
NMR (75 MHz, CDCl3): δ 191.7, 158.7, 156.3, 149.2, 145.2, 136.2,
133.7, 129.7, 128.5, 127.7, 121.7, 118.4, 117.9, 110.6, 55.9.
1
(KBr): 3090, 2993, 1721, 1656, 1605, 1248, 686 cm-1. H NMR
(300 MHz, CDCl3): δ 8.03 (s, 1H), 7.88 (d, J ) 7.8 Hz, 2H),
8720 J. Org. Chem., Vol. 71, No. 23, 2006

Condensation of R-Aroylketene Dithioacetals
6-Methoxy-3-(4-methylbenzoyl)-2H-2-chromenone 4h. Following
the general procedure described above, the reaction of 2-hydroxy-
5-methoxybenzaldehyde 2c (320 mg, 2.1 mmol), 1-(4-methylphe-
nyl)-3,3-bis(methylsulfanyl)-2-propen-1-one 1b (500 mg, 2.1mmol),
and peperidine (18 mg, 0.21 mmol) furnished 456 mg of 6-methoxy-
3-(4-methylbenzoyl)-2H-2-chromenone 4h in 74% yield as colorless
crystals after column purification and recrystallization: mp 174-
176 °C (ethanol). UV (MeOH): λmax 361 nm (log ꢀ ) 3.64), 287
nm (log ꢀ ) 4.20). IR (KBr): 3079, 2963, 1710, 1650, 1569, 1256,
crystals after column purification and recrystallization: mp above
200 °C (ethanol). UV (MeOH): λmax 334 nm (log ꢀ ) 3.51), 383
nm (log ꢀ ) 3.97). IR (KBr): 3104, 2993, 1725, 1650, 1606, 1287,
1
775 cm-1. H NMR (300 MHz, CDCl3): δ 7.92 (s, 1H), 7.74 (d,
J ) 8.1 Hz, 2H), 7.54-7.58 (m, 2H), 7.34 (d, J ) 8.1 Hz, 2H),
7.26 (d, J ) 8.4 Hz, 1H), 2.49 (s, 3H). 13C NMR (75 MHz,
CDCl3): δ 190.4, 157.5, 153.2, 144.9, 143.2, 133.5, 133.2, 130.2,
129.8, 129.4, 128.9, 128.1, 119.4, 118.4, 21.9. Anal. Calcd for
C17H11O3Cl: C, 68.35; H, 3.71. Found: C, 68.47; H, 3.76.
1
748 cm-1.; H NMR (300 MHz, CDCl3): δ 8.00 (s, 1H), 7.78 (d,
J ) 8.1 Hz, 2H), 7.21-7.37 (m, 5H), 3.86 (s, 3H), 2.43 (s, 3H).
13C NMR (75 MHz, CDCl3): δ 191.3, 158.7, 156.3, 149.2, 144.9,
144.8, 133.6, 129.8, 129.3, 127.5, 121.5, 118.5, 117.9, 110.5, 55.9,
21.8. Anal. Calcd for C18H14O4: C, 73.46; H, 4.79. Found: C,
73.41; H, 4.76.
6-Chloro-3-(4-chlorobenzoyl)-2H-2-chromenone 4l. Following
the general procedure described above, the reaction of 5-chloro-
2-hydroxybenzaldehyde 2d (297 mg, 1.9 mmol), 1-(4-chlorophe-
nyl)-3,3-bis(methylsulfanyl)-2-propen-1-one 1c (500 mg, 1.9 mmol),
and peperidine (18 mg, 0.2 mmol) furnished 513 mg of 6-chloro-
3-(4-chlorobenzoyl)-2H-2-chromenone 4l in 85% yield as colorless
crystals after column purification and recrystallization: mp above
200 °C (ethanol). UV (MeOH): λmax 286 nm (log ꢀ ) 4.22), 238
nm (log ꢀ ) 4.15). IR (KBr): 3050, 2993, 1725, 1635, 1243, 765
cm-1. 1H NMR (300 MHz, DMSO): δ 8.37 (s, 1H), 7.95 (dd, J )
8.1, 2.1 Hz, 2H), 7.94 (br s, 1H), 7.74 (dd, J ) 8.7, 1.8 Hz, 1H),
7.58 (br d, J ) 8.1 Hz, 2H), 7.50 (d, J ) 8.7 Hz, 1H). 13C NMR
(75 MHz, DMSO): δ 190.2, 157.5, 152.8, 144.4, 138.9, 134.6,
133.0, 131.3, 128.7, 128.6, 128.5, 126.9, 119.6, 118.2. Anal. Calcd
for C16H8O3Cl2: C, 60.22; H, 2.52. Found: C, 59.98; H, 2.50.
3-(4-Chlorobenzoyl)-6-methoxy-2H-2-chromenone 4i. Following
the general procedure described above, the reaction of 2-hydroxy-
5-methoxybenzaldehyde 2c (289 mg, 1.9 mmol), 1-(4-chlorophe-
nyl)-3,3-bis(methylsulfanyl)-2-propen-1-one 1c (500 mg, 1.9 mmol)
and peperidine (17 mg, 0.2 mmol) furnished 554 mg of 3-(4-
chlorobenzoyl)-6-methoxy-2H-2-chromenone 4i in 93% yield as
colorless crystals after column purification and recrystallization:
mp above 200 °C (ethanol). UV (MeOH): λmax 350 nm (log ꢀ )
3.68), 287 nm (log ꢀ ) 4.17), 256 nm (log ꢀ ) 4.22). IR (KBr):
1
3123, 2940, 1706, 1625, 1581, 1262, 780 cm-1. H NMR (300
MHz, CDCl3): δ 8.10 (s, 1H), 7.82 (d, J ) 8.4 Hz, 2H), 7.22-
7.49 (m, 5H), 3.87 (s, 3H). 13C NMR (75 MHz, CDCl3): δ 190.1,
157.8, 155.9, 148.7, 145.4, 134.1, 130.4, 128.4, 128.5, 125.7, 121.6,
117.9, 117.4, 110.3, 55.4. Anal. Calcd for C17H11O4Cl: C, 64.88;
H, 3.52. Found: C, 64.38; H, 3.75.
2-Benzoyl-3H-benzo[f]chromen-3-one 6a. Following the general
procedure described above, the reaction of 2-hydroxy-1-naphthal-
dehyde 5 (343 mg, 2.2 mmol), 3,3-bis(methylsulfanyl)-1-phenyl-
2-propen-1-one 1a (500 mg, 2.2 mmol), and peperidine (19 mg,
0.22 mmol) furnished 587 mg of 2-benzoyl-3H-benzo[f]chromen-
3-one 6a in 89% yield as colorless crystals after column purification
and recrystallization: mp above 200 °C (ethanol) (lit.20c 216-217
°C). UV (MeOH): λmax 372 nm (log ꢀ ) 4.03), 256 nm (log ꢀ )
4.22), 230 nm (log ꢀ ) 4.60). IR (KBr): 3102, 2959, 1700, 1654,
3-Benzoyl-6-chloro-2H-2-chromenone 4j. Following the general
procedure described above, the reaction of 5-chloro-2-hydroxy-
benzaldehyde 2d (344 mg, 2.2 mmol), 3,3-bis(methylsulfanyl)-1-
phenyl-2-propen-1-one 1a (500 mg, 2.2 mmol), and peperidine (19
mg, 0.22 mmol) furnished 549 mg of 3-benzoyl-6-chloro-2H-2-
chromenone 4j in 88% yield as colorless crystals after column
purification and recrystallization: mp 162-164 °C (ethanol) (lit.20b
163 °C). UV (MeOH): λmax 336 nm (log ꢀ ) 3.96), 284 nm (log
ꢀ ) 4.33). IR (KBr): 3050, 1725, 1635, 1237, 683 cm-1. 1H NMR
(300 MHz, CDCl3): δ 7.95 (s, 1H), 7.82 (d, J ) 8.4 Hz, 2H),
7.53-7.62 (m, 2H), 7.46 (d, J ) 8.4 Hz, 2H), 7.43 (br s, 1H), 7.33
(t, J ) 8.4 Hz, 1H). 13C NMR (75 MHz, CDCl3): δ 190.6, 157.3,
153.2, 143.5, 136.0, 133.9, 133.2, 130.2, 129.6, 128.6, 126.7, 128.2,
119.3, 118.4. Anal. Calcd for C16H9O3Cl: C, 67.50; H, 3.36.
Found: C, 67.45; H, 3.36.
1
12 1262, 752 cm-1. H NMR (300 MHz, CDCl3): δ 8.89 (s, H),
8.24 (d, J ) 8.4 Hz, 1H), 8.08 (d, J ) 9.3 Hz, 1H), 7.89-7.94 (m,
3H), 7.7 (t, J ) 7.3 Hz, 1H), 7.57-7.65 (m, 2H), 7.45-7.51 (m,
3H). 13C NMR (75 MHz, CDCl3): δ 191.9, 158.4, 155.4, 141.7,
136.5, 135.3, 133.6, 130.3, 129.6, 129.4, 129.2, 128.9, 128.5, 126.5,
125.4, 121.5, 116.7, 112.6.
2-(4-Methylbenzoyl)-3H-benzo[f]chromen-3-one 6b. Following
the general procedure described above, the reaction of 2-hydroxy-
1-naphthaldehyde 5 (327 mg, 2.1 1 mmol), 1-(4-methylphenyl)-
3,3-bis(methylsulfanyl)-2-propen-1-one 1b (500 mg, 2.1 mmol), and
peperidine (18 mg, 0.21 mmol) furnished 527 mg of 2-(4-
methylbenzoyl)-3H-benzo[f]chromen-3-one 6b in 80% yield as
colorless crystals after column purification and recrystallization:
mp 190-192 °C (ethanol) (lit.20c 190-191 °C) (toluene). UV
(MeOH): λmax 370 nm (log ꢀ ) 3.86), 258 nm (log ꢀ ) 4.08). IR
6-Chloro-3-(4-methylbenzoyl)-2H-2-chromenone 4k. Following
the general procedure described above, the reaction of 5-chloro-
2-hydroxybenzaldehyde 2d (329 mg, 2.1 mmol), 1-(4-methylphe-
nyl)-3,3-bis(methylsulfanyl)-2-propen-1-one 1b (500 mg, 2.1 mmol),
and peperidine (18 mg, 0.2 mmol) furnished 575 mg of 6-chloro-
3-(4-methylbenzoyl)-2H-2-chromenone 4k in 92% yield as colorless
1
(KBr): 3065, 2950, 1706, 1656, 1562, 1256, 780 cm-1. H NMR
(400 MHz, CDCl3): δ 8.89 (s, 1H), 8.25 (d, J ) 8.8 Hz, 1H), 8.11
J. Org. Chem, Vol. 71, No. 23, 2006 8721

Rao and Sivakumar
(d, J ) 9.3 Hz, 1H), 7.94 (d, J ) 8.3 Hz, 1H), 7.83 (d, J ) 8.3 Hz,
2H), 7.71 (br t, J ) 7.3 Hz, 1H), 7.61 (br t, J ) 7.8 Hz, 1H), 7.51
(d, J ) 9.3 Hz, 1H), 7.29 (d, J ) 8.3 Hz, 2H), 2.40 (s, 3H). 13C
NMR (100 MHz, CDCl3): δ 191.6, 158.6, 155.27, 144.8, 141.4,
135.2, 133.8, 130.3, 129.8, 129.4, 129.3, 129.2, 128.9, 126.5, 125.6,
121.5, 116.7, 112.7, 21.8.
δ 188.9, 156.3, 139.4, 134.5, 133.9, 131.2, 130.5, 128.5, 128.2,
127.9 (×2), 127.1, 127.0, 126.5, 125.5, 123.1, 120.6, 120.3, 118.3,
115.3. HRMS (ESI+): calcd for C20H12O3 (MH+), 301.0786; found,
301.0784.
3-(Biphenyl-4-yl-carbonyl)-2H-2-chromenone 12. Following the
general procedure described above, the reaction of 2-hydroxyben-
zaldehyde 2a (244 mg, 2.0 mmol), 1-biphenyl-4-yl-3,3-bis-meth-
ylsulfanyl-2-propen-1-one 11 (500 mg, 1.66 mmol), and peperidine
(18 mg, 0.2 mmol) furnished 374 mg of 3-(biphenyl-4-yl-carbonyl)-
2H-2-chromenone 12 in 69% yield as light yellow powder after
column purification and recrystallization: mp above 200 °C
(ethanol). UV (MeOH): λmax 353 nm (log ꢀ ) 2.91), 302 nm (log
ꢀ ) 2.89), 244 nm (log ꢀ ) 2.98). IR (KBr): 1713, 1659, 1603,
2-(4-Chlorobenzoyl)-3H-benzo[f]chromen-3-one 6c. Following
the general procedure described above, the reaction of 2-hydroxy-
1-naphthaldehyde 5 (296 mg, 1.9 mmol), 1-(4-chlorophenyl)-3,3-
bis(methylsulfanyl)-2-propen-1-one 1c (500 mg, 1.9 mmol), and
peperidine (18 mg, 0.2 mmol) furnished 539 mg of 2-(4-chloroben-
zoyl)-3H-benzo[f]chromen-3-one 6c in 85% yield as colorless
crystals after column purification and recrystallization: mp above
200 °C, (ethanol) (lit.20c 232-233 °C) (toluene). UV (MeOH): λmax
374 nm (log ꢀ ) 3.90), 260 nm (log ꢀ ) 4.12). IR (KBr): 3020,
1450, 1264, 1241, 918, 749, 692 cm-1 1H NMR (300 MHz,
.
1
1706, 1656, 1562, 1256, 780 cm-1. H NMR (400 MHz, CDCl3):
CDCl3): δ 8.04 (s, 1H), 7.89 (d, J ) 7.5 Hz, 2H), 7.62 (d, J ) 7.8
Hz, 2H), 7.22-7.64 (m, 9H). 13C NMR (100 MHz, CDCl3): δ
192.2, 154.7, 146.6, 145.4, 134.7, 134.8, 133.6, 130.2, 129.2, 128.9
(× 2), 128.3, 127.3, 127.2, 127.2, 124.9, 118.2, 116.9. HRMS
(ESI+): calcd for C22H14O3 (MH+), 327.0643; found, 327.0652.
δ 8.97 (s, 1H), 8.28 (d, J ) 8.3 Hz, 1H), 8.13 (d, J ) 8.8 Hz, 1H),
7.96 (d, J ) 8.3 Hz, 1H), 7.86 (d, J ) 8.8 Hz, 2H), 7.75 (t, J ) 7.3
Hz, 1H), 7.63 (t, J ) 7.9 Hz, 1H), 7.52 (d, J ) 9.3 Hz, 1H), 7.47
(d, J ) 8.8 Hz, 2H). 13C NMR (100 MHz, CDCl3) δ 190.9, 158.7,
155.6, 142.5, 140.2, 135.7, 134.9, 130.9, 130.3, 129.4, 129.3, 129.1,
128.9, 126.6, 124.8, 121.5, 116.7, 112.7.
3-(1-Naphthylcarbonyl)-2H-2-chromenone 8. Following the gen-
eral procedure described above, the reaction of 2-hydroxybenzal-
dehyde 2a (267 mg, 2.1mmol), 3,3-bis(methylsulfanyl)-1-(1-
naphthyl)-2-propen-1-one 7 (500 mg, 1.8 mmol), and peperidine
(18 mg, 0.2 mmol) furnished (437 mg) of 3-(1-naphthylcarbonyl)-
2H-2-chromenone 8 in 80% yield as colorless crystals after column
purification and recrystallization: mp above 200 °C (5% DCM in
hexanes). UV (MeOH): λmax 383 nm (log ꢀ ) 2.98), 302 nm (log
ꢀ ) 2.87), 245 nm (log ꢀ ) 2.95). IR (KBr): 1719, 1652, 1564,
1233, 1195, 911, 786, 755 cm-1; 1H NMR (400 MHz, DMSO-D6/
CDCl3; 1:9): δ 8.55 (d, J ) 8.8 Hz, 1H), 8.20 (s, 1H), 8.03 (d, J
) 8.0 Hz, 1H), 7.91 (d, J ) 8.0 Hz, 1H), 7.73, (d, J ) 6.8 Hz,
1H), 7.50-7.65 (m, 4H), 7.49 (t, J ) 7.4 Hz, 1H), 7.38 (d, J ) 8.3
Hz, 1H), 7.33 (t, J ) 7.3 Hz, 1H). 13C NMR (100 MHz, DMSO-
D6/CDCl3; 9:1): δ 193.1, 158.0, 154.9, 146.7, 134.5, 133.9, 133.8,
133.3, 130.6, 129.6, 129.5, 128.5, 128.1, 127.5, 126.7, 125.4, 124.9,
124.3, 118.2, 116.9. HRMS (ESI+): calcd for C20H12O3 (MH+),
301.0786; found, 301.0774.
3-η5-Ferrocenoyl-2H-2-chromenone 14. Following the general
procedure described previously, the reaction of 2-hydroxybenzal-
dehyde 2a (219 mg, 1.8 mmol), 3,3-bis(methylsulfanyl)-1-η5-
ferrocenyl-2-propen-1-one 13 (500 mg, 1.5 mmol), and peperidine
(16 mg, 0.19 mmol) furnished 484 mg of 3-η5-ferrocenoyl-2H-2-
chromenone 14 in 85% yield of a brownish red powder after column
purification: mp above 200 °C (ethanol). UV (CHCl3): λmax 498
nm (log ꢀ ) 2.77), 359 nm (log ꢀ ) 2.96), 304 nm (log ꢀ ) 2.96),
262 nm (log ꢀ ) 2.93). IR (KBr): 1643, 1588, 1458, 1336, 1186,
748 cm-1. 1H NMR (400 MHz, CDCl3): δ 7.97 (s, 1H), 7.63 (t, J
) 8.3 Hz, 1H), 7.60 (d, J ) 8.34 Hz, 1H), 7.40 (d, J ) 8.3 Hz,
1H), 7.35 (t, J ) 7.8 Hz, 1H), 4.86 (br s, 2H), 4.64 (br s, 2H), 4.29
(s, 5H). 13C NMR (100 MHz, CDCl3): δ 194.0, 158.0, 154.4, 141.8,
133.1, 128.8, 128.0, 124.8, 118.0, 116.9, 82.04, 73.4, 70.9, 70.5.
HRMS (ESI+): calcd for C20H14O3Fe (MH+), 359.0292; found,
359.0272.
(E)-3-(2-Hydroxyphenyl)-1-phenyl-2-propen-1-one 16a. Follow-
ing the general procedure described above, the reaction of 2-hy-
droxybenzaldehyde 2a (268 mg, 2.2 mmol), 3,3-bis(methylsulfanyl)-
1-phenyl-2-propen-1-one 1a (500 mg, 2.20 mmol), and peperidine
(18 mg, 0.2 mmol) in ethanol reflux furnished 443 mg of 3-benzoyl-
2H-2-chromenone 16a in 90% yield as a light yellow solid: mp
151-153 °C (ethanol) (lit.24 153 °C). UV (MeOH): λmax 353 nm
(log ꢀ ) 3.70), 299 nm (log ꢀ ) 3.8), 267 nm (log ꢀ ) 3.64). IR
3-(2-Naphthylcarbonyl)-2H-2-chromenone 10. Following the
general procedure described previously, the reaction of 2-hydroxy-
benzaldehyde 2a (267 mg, 2.1mmol), 3,3-bis(methylsulfanyl)-1-
(2-naphthyl)-2-propen-1-one 9 (500 mg, 1.8 mmol), and peperidine
(18 mg, 0.2 mmol) furnished (503 mg) of 3-(2-naphthylcarbonyl)-
2H-2-chromenone 10 in 92% yield as colorless crystals after column
purification and recrystallization: mp above 200 °C (ethanol). UV
(MeOH): λmax 407 nm (log ꢀ ) 3.04), 311 nm (log ꢀ ) 2.87), 242
nm (log ꢀ ) 2.95). IR (KBr): 1643, 1588, 1458, 1336, 1186, 748,
1
(KBr): 3203, 3063, 2994, 1638, 1594, 1556, 1243, 755 cm-1. H
NMR (300 MHz, CDCl3): δ 9.54 (br s, 1H), 8.11 (d, J ) 15.6 Hz,
1H), 8.01 (br d, J ) 6.9 Hz, 2H), 7.71 (d, J ) 15.6 Hz, 1H), 7.30-
7.60 (m, 4H), 7.23 (br t, J ) 8.4 Hz, 1H), 6.96 (d, J ) 7.2 Hz,
1
cm-1. H NMR (60 MHz, CCl4 + CDCl3; 5:1): δ 8.56 (s, 1H)
6.85-8.17 (m, 11H). 13C NMR (100 MHz, DMSO/CDCl3; 1:5):
8722 J. Org. Chem., Vol. 71, No. 23, 2006

Condensation of R-Aroylketene Dithioacetals
1
1H), 6.87 (t, J ) 7.2 Hz, 1H). 13C NMR (75 MHz, CDCl3/DMSO,
7:2): δ 190.8, 157.0, 140.9, 138.1, 132.0, 131.1, 129,1, 128.1,
128.0, 121.7, 121.5, 119.2, 116.1.
1243, 755 cm-1. H NMR (400 MHz, acetone-D6): δ 9.47 (br s,
1H), 8.14 (d, J ) 15.6 Hz, 1H), 8.05 (br d, J ) 9.3 Hz, 2H), 7.85
(br d, J ) 15.6 Hz, 1H), 7.67 (br d, J ) 7.8 Hz, 1H), 7.34 (d, J )
8.3 Hz, 2H), 7.24 (t, J ) 7.8 Hz, 1H), 6.84-6.99 (m, 2H), 2.4 (s,
3H). 13C NMR (75 MHz, acetone-D6): δ 189.9, 157.9, 144.1, 140.1,
136.9, 132.4, 130.1, 129.7, 129.3, 122.9, 122.4, 120.7, 116.9, 21.5.
Acknowledgment. H.S.P.R. thanks UGC, UGC-SAP, CSIR,
and DST-FIST for financial assistance. We thank Prof. A.
Srikrishna, IISc, Bangalore, SIF, IISc, Bangalore and SAIC, IIT,
Chennai for recording spectra.
(E)-3-(2-Hydroxyphenyl)-1-(4-methylphenyl)-2-propen-1-one 16b.
Following the procedure described above, the reaction of 2-hy-
droxybenzaldehyde 2a (256 mg, 2.1 mmol), 3,3-bis(methylsulfanyl)-
1-(4-methylphenyl)-2-propen-1-one 1b (500 mg, 2.1 mmol), and
peperidine (18 mg, 0.2 mmol) in ethanol reflux furnished 409 mg
of (E)-3-(2-hydroxyphenyl)-1-(4-methylphenyl)-2-propen-1-one 16b
in 82% yield as light yellow colored powder after column
purification: mp 157-158 °C (ethanol) (lit.25 158-159 °C). UV
(MeOH): λmax 353 nm (log ꢀ ) 3.70), 299 nm (log ꢀ ) 3.8), 267
(log ꢀ ) 3.64) nm. IR (KBr): 3203, 3063, 2994, 1638, 1594, 1556,
Supporting Information Available: General experimental
details, 1H and 13C NMR spectra for compounds 4a-l, 6a-c, and
7-14 are given in this section. This material is available free of
charge via the Internet at http://pubs.acs.org.
JO061372E
J. Org. Chem, Vol. 71, No. 23, 2006 8723