Metal-free, one-pot oxidative conversion of aldehydes to primary thioamides in aqueous media

Article abstract of DOI:10.1080/00397911.2013.808350

One-pot tandem reactions of a variety of aldehydes with aqueous ammonia, molecular iodine, and O,O-diethyl dithiophosphoric acid readily afford the corresponding primary thioamides. This is an inexpensive, practical, and metal-free way of accessing various thioamides from aldehydes in aqueous media. The pure products are obtained simply by filtration followed by successive washing with aqueous sodium thiosulfate and water. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications for the following free supplemental resource(s): Full experimental and spectral details.]

Full text of DOI:10.1080/00397911.2013.808350

This article was downloaded by: [Michigan State University]
On: 26 November 2013, At: 03:56
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An
International Journal for Rapid
Communication of Synthetic Organic
Chemistry
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/lsyc20
Metal-Free, One-Pot Oxidative
Conversion of Aldehydes to Primary
Thioamides in Aqueous Media
Arvind K. Yadav a , Vishnu P. Srivastava a & Lal Dhar S. Yadav a
a Green Synthesis Laboratory, Department of Chemistry , University
of Allahabad , Allahabad , India
Published online: 20 Nov 2013.
To cite this article: Arvind K. Yadav , Vishnu P. Srivastava & Lal Dhar S. Yadav (2014) Metal-Free,
One-Pot Oxidative Conversion of Aldehydes to Primary Thioamides in Aqueous Media, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
44:3, 408-416, DOI: 10.1080/00397911.2013.808350
To link to this article: http://dx.doi.org/10.1080/00397911.2013.808350
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or
howsoever caused arising directly or indirectly in connection with, in relation to or arising
out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &

Conditions of access and use can be found at http://www.tandfonline.com/page/terms-
and-conditions

Synthetic Communications1, 44: 408–416, 2014
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2013.808350
METAL-FREE, ONE-POT OXIDATIVE CONVERSION
OF ALDEHYDES TO PRIMARY THIOAMIDES IN
AQUEOUS MEDIA
Arvind K. Yadav, Vishnu P. Srivastava, and Lal Dhar S. Yadav
Green Synthesis Laboratory, Department of Chemistry, University of
Allahabad, Allahabad, India
GRAPHICAL ABSTRACT
Abstract One-pot tandem reactions of a variety of aldehydes with aqueous ammonia,
molecular iodine, and O,O-diethyl dithiophosphoric acid readily afford the corresponding
primary thioamides. This is an inexpensive, practical, and metal-free way of accessing
various thioamides from aldehydes in aqueous media. The pure products are obtained simply
by filtration followed by successive washing with aqueous sodium thiosulfate and water.
[Supplementary materials are available for this article. Go to the publisher’s online
edition of Synthetic Communications1 for the following free supplemental resource(s):
Full experimental and spectral details.]
Keywords Aldehydes; deoxygenation; green chemistry; nitriles; O,O-diethyl dithio-
phosphopric acid; thioamides
INTRODUCTION
Thioamides and their derivatives have attracted considerable attention because
of their utility in the synthesis of a variety of biologically and pharmaceutically
relevant heterocycles such as thiazoles and thiazolines,[1] betaines,[2] mesoionic
rhodanines,[3] and other hetrocycles.[4] In particular, they are useful building blocks
in the Hantzsch thiazole synthesis for the preparation of a wide variety of
substrates.[5] Some thioamide derivatives have been reported to exhibit potent activity
against parasitic nematodes,[6] antitubercular activity,[7] iminosupressive activity,
DHODH inhibitory properties,[8] and opioid activity at m- and d-recepters.[9] A series
of thioamides has also been found to possess strong HIV-1 reverse transcriptase
Received April 17, 2013.
Address correspondence to Lal Dhar S. Yadav, Green Synthesis Laboratory, Department of
Chemistry, University of Allahabad, Allahabad 211002, India. E-mail: ldsyadav@hotmail.com
408

ALDEHYDES TO PRIMARY THIOAMIDES
409
Scheme 1. One-pot oxidative conversion of aldehydes to thioamides.
inhibitory action.[10] Thioamides are used in rubber vulcanization and as boosters or
as inhibitors of metal corrosion.[11]
Many methods have been reported in the literature for the preparation of
primary thioamides. These methods include (i) conversion of aldehydes to oximes
and then to thioamides using reagents such as PSCl3,[12] (NH4)2S with TiCl3OTf-
[bmim]Br,[13] and O,O-diethyl dithiophosphoric acid;[14] (ii) conversion of amides to
thioamides using Lawesson’s reagents,[15] (NH4)2S in Tf2O at ꢀ40 ꢁC,[16] P4S10
[17]
and PSCl3;[18] (iii) conversion of nitriles to thioamides using alkali metal hydrogen
sulfide or (NH4)2S under pressure in a closed reactor or using (P4S11)Na2;[19] (iv)
condensation of aldehydes and amines in the presence of S=Na2S at high temper-
ature (120 ꢁC),[20] and carboxylic acids and amines in the presence of ammonium
phosphorodithioate.[21]
To the best of our knowledge, only one method is known for the one-pot
conversion of aldehydes to primary thioamides without oximation.[19b] However, this
method suffers from several drawbacks: the reaction is performed in a sealed vessel
(under pressure), requires high temperature (160–180 ꢁC), gives poor yields (36–
46%) of primary thioamides, and limited examples (only four) are available. In view
of overcoming these drawbacks and filling the gap in the literature for a convenient
one-pot synthesis of primary thioamides from aldehydes without oximation, we
hypothesized that aldehydes could be converted to the corresponding primary thioa-
mides through nitriles in a one-pot procedure as depicted in Scheme 1. To realize this
hypothesis, we required reagents that would efficiently convert aldehydes to nitriles
and in turn to primary thioamides (RCHO!RCN!RCSNH2) without interfering
[22]
with each other. For the first step (RCHO!RCN), we selected aqueous NH3=I2
and for the second step (RCN!CSNH2), O,O-diethyl dithiophosphoric acid (2)
was picked up, which has been previously used by us in various deoxygenative
sulfurization–cyclization reactions.[23] To our delight, these reagents worked well
for the envisaged one-pot conversion of aldehydes 1 to the corresponding thioamides
3 in aqueous media (Scheme 1).
RESULTS AND DISCUSSION
We started our study with the model reaction of aldehyde 1a, iodine, aqueous
ammonia, and O,O-diethyl dithiophosphoric acid (2) in aqueous media. The reaction
mixture was stirred at rt for 30 min followed by stirring at 90 ꢁC for 2 h to afford
the desired primary thioamide 3a in 85% isolated yield (Table 1, entry 1). Although
water qualifies as an efficient green solvent for the present reaction, we also
performed the reaction in various organic solvents for comparison purposes.
Obviously, among the tested solvents, water was the best not only in view of the
environmental concerns but also in terms of the yield and reaction time (Table 1).

410
A. K. YADAV, V. P. SRIVASTAVA, AND L. D. S. YADAV
Table 1. One-pot conversion of benzaldehydes to thiobenzamides in various solventsa
Entry
Solvent
Temp. (ꢁC)b
Time (h)c
Conv. (%)d
Select. (%)e
Yield (%)f
1
2
H2O
H2O
90
2
2
2
3
3
3
4
4
4
3
91
91
83
84
85
80
75
69
70
86
97
96
98
97
96
98
98
98
96
97
85
84
78
78
78
76
70
65
64
80
Reflux
75
90
3
H2O
4
Dioxane
Dioxane
THF
5
Reflux
Reflux
Reflux
90
6
7
DCE
8
Toluene
Toluene
EtOH
9
10
Reflux
Reflux
aReaction conditions: 1a (1.5 mmol), I2 (1.6 mmol), 10 mL of 28% aq. NH3, and O,O-diethyl dithiopho-
sphoric acid (2) (1.5 mL).
bTemperature for step (ii).
cTime for step (ii).
dConversion (%) of benzaldehyde (1a) as determined by GC analysis.
eSelectivity (%) for thioamide 3a; the other side product was benzamide.
fYield of isolated and purifide product 3a.
Next, we examined the generality and substrate scope (Table 2). A wide range of
aldehydes, including aromatic, heterocyclic, and aliphatic, were converted into the
corresponding primary thioamides in good to excellent yields (76–93%). In the case
of aromatic aldehydes both electron-donating and electron-withdrawing groups were
tolerated. In general, the presence of an electron-withdrawing group in the substrates
required longer reaction time and afforded lower yields of the corresponding thioa-
mides 3 as compared to those bearing an electron-donating group (Table 2, entries
2 and 3 compared to entries 4–11 and 14). This might to be attributed to the difficulty
in protonation of the corresponding nitriles 5 with dithiophosphoric acid 2 (Scheme 2)
because aromatic aldehydes containing either electron-donating or electron-
withdrawing subtituents have already been reported to give nitriles 5 in comparable
yields under similar reaction conditions.[24]
On the basis of these experimental results and the literature prece-
dents,[12,21,22,24] a plausible mechanism for the conversion of aldehydes 1 to primary
thioamides 3 is depicted in Scheme 2. Aldehydes 1 on condensation with NH3 form
aldimines 4, which are oxidized with molecular iodine to nitriles 5. O,O-Diethyl
dihiophosphoric acid (2) protonates nitriles 5 to generate nitrilium ions 6, which com-
bine with the nucleophile 7 present in the reaction mixture to form dithiophosphoric
esters 8. The hydrolysis of 8 affords primary thioamides 3. Alternatively, nitrilium
ions 6 could combine with water to form primary amides 9 (Table 2, footnote d),
which react with 2 to give thioamides 3 via 10 (Scheme 2).

ALDEHYDES TO PRIMARY THIOAMIDES
411
Table 2. One-pot conversion of aldehydes to thioamides in aqueous mediaa
Time Conversion Select.
(%)d
Yield
(%)e
Entry
1
Aldehyde 1
Product 3b
(h)
(%)c
2
91
97
85
2
3
2
2
95
97
97
98
89
93
4
5
4
3
80
90
98
97
76
84
6
7
4
3
87
88
96
97
81
82
8
3
82
98
80
(Continued )

412
A. K. YADAV, V. P. SRIVASTAVA, AND L. D. S. YADAV
Table 2. Continued
Time Conversion Select.
(%)c
Yield
(%)e
Entry
Aldehyde 1
Product 3b
(h)
(%)d
9
2
90
96
83
78
10
3
89
92
11
12
3
2
83
93
98
95
79
86
13
14
2
4
92
84
93
94
83
76
15
16
3
4
87
88
96
92
80
78
17
18
4
3
84
89
98
96
80
83
aFor general procedure, see Experimental.
bAll the products are known compounds and were characterized by comparison of their mp and spectral
[12,19j,21,25]
data with those reported in the literature (Table 3).
cConversion (%) as determined by GC analysis.
dSelectivity (%) for thioamide 3; the other side product was the corresponding amide.
eYield of isolated and purified product 3..

ALDEHYDES TO PRIMARY THIOAMIDES
413
Scheme 2. Plausible mechanistic pathway for oxidative conversion of aldehydes to thioamides.
EXPERIMENTAL
Melting points were determined by open glass capillary method and are
1
uncorrected. H NMR spectra were recorded on a Bruker AVII 400 spectrometer
in CDCl3 using tetramethylsilane (TMS) as internal reference. Mass spectrometry
(MS) experiments were performed on a double-focusing MS spectrometer. All
chemicals used were reagent grade and were used as received without further
purification. Thin-layer chromatography (TLC) was performed using silica gel GF254
(Merck) plates.
General Procedure for the One-Pot Synthesis of Primary
Thioamides 3a–3r
A mixture of benzaldehyde 1 (l.5 mmol) and iodine (1.6 mmol) in ammonia
water (10 mL of 28% solution) was stirred at room temperature for 30 min. The dark
reaction mixture faded in color at the end of reaction. The excess of ammonia was
removed by stirring at 90 ꢁC, and the gas was trapped in water. Then, O,O-diethyl
dithiophosphoric acid (2) (1.5 mmol) was added and the reaction mixture was stirred
at 90 ꢁC for 2–4 h (Table 2, entry 1). After completion of the reaction (monitored by
TLC), the mixture was cooled to rt. The product thus precipitated was filtered,
washed with aqueous sodium thiosulfate solution followed by water, and dried under
reduced pressure to give pure primary thioamides 3 (Table 2, entry 1). All products
are known compounds and were characterized by comparison of mp and spectral
data with those reported in the literature.[12,19j,21,25]
Benzothioamide (3a)[25a]
Pale yellow solid; yield: mp 113–115 ꢁC [lit. mp 113–114 ꢁC]. 1H NMR
(400 MHz, CDCl3): d ¼ 7.91 (br s, 1H), 7.88 (d, J ¼ 8.0 Hz, 2H), 7.53 (t, J ¼ 8.0 Hz,
Hz, 1H), 7.42 (t, J ¼ 8.0 Hz, 2H), 7.29 (br s, 1H). HRMS (EI): calcd. for C7H7NS
137.0299; found 137.0298.

414
A. K. YADAV, V. P. SRIVASTAVA, AND L. D. S. YADAV
CONCLUSION
In summary, we have developed an efficient one-pot procedure for the conver-
sion of aldehydes to the corresponding primary thioamides in aqueous media. The
protocol involves tandem reactions of aldehydes with aqueous ammonia, molecular
iodine, and O,O-diethyl dithiophosphoric acid to afford primary thioamides in good
to excellent yields under environmentally benign conditions. The reagent O,O-
diethyl dithiophosphoric acid acts both as an acid and a source of sulfur. We believe
that the present operationally simple method would be a practical alternative to the
existing procedures for the synthesis of primary thioamides.
SUPPORTING INFORMATION
1
Full experimental detail and H NMR and HRMS data can be found via the
Supplementary Content section of this article’s Web page.
ACKNOWLEDGMENTS
We sincerely thank the SAIF, Punjab University, Chandigarh, for providing
spectra. V. P. S. is grateful to the Department of Science and Technology (DST),
Goverment of India, for the award of a Department of Science and Technology–
Inspire Faculty position (Ref. IFA-11CH-08) and financial support, and A. K. Y.
is grateful to the Council of Scientific and Industrial Research, New Delhi, for the
award of a junior research fellowship.
REFERENCES
1. (a) Wipf, P.; Venkatraman, S. A new thiazole synthesis by cyclocondensation of thioamides
and alkynyl(aryl)iodonium reagents. J. Org. Chem. 1996, 61, 8004–8005; (b) Attanasi, O.
A.; Berretta, S.; Crescentini, L. D.; Favi, G.; Filippone, P.; Giorgi, G.; Lillini, S.;
Mantellini, F. Unexpected regioselectivity in the reaction between cycloalkenyl-1-diazenes
and thioamides: Useful entry to fused cycloalkyl-thiazoline and cycloalkyl-thiazoline–
pyrazole systems. Tetrahedron Lett. 2007, 48, 2449–2451.
2. Padwa, A.; Beall, L. S.; Heidelbaugh, T. M.; Bing, L. S.; Sheehan, S. M. A one-pot
bicycloannulation method for the synthesis of tetrahydroisoquinoline systems. J. Org.
Chem. 2000, 65, 2684–2695.
3. McManus, S. P.; Lee, K. Y.; Pittman, C. U. Acid-catalyzed cyclization reactions, XI:
Competitive amide versus thioamide cyclization: Cyclization of N-allylrhodanine in strong
acid media. J. Org. Chem. 1974, 39, 3041–3042.
4. (a) Jagodzinski, T. S. Thioamides as useful synthons in the synthesis of heterocycles.
Chem. Rev. 2003, 103, 197–228; (b) Prokopcova, H.; Kappe, C. O. Palladium(0)-catalyzed,
copper(I)-mediated coupling of boronic acids with cyclic thioamides: Selective carbonꢀ
carbon bond formation for the functionalization of heterocycles. J. Org. Chem. 2007,
72, 4440–4448.
5. (a) Oare, D. A.; Sanner, M. A.; Heathcock, C. H. Acyclic stereoselection, 46: Stereochem-
istry of the michael addition of N, N-disubstituted amide and thioamide enolates to a,
b-unsaturated ketones. J. Org. Chem. 1990, 55, 132–157; (b) Heathcock, C. H.; Davidson,
S. K.; Mills, S. G.; Sanner, M. A. Daphniphyllum alkaloids, 10: Classical total synthesis of
methyl homodaphniphyllate. J. Org. Chem. 1992, 57, 2531–2544; (c) Magnus, P.;

ALDEHYDES TO PRIMARY THIOAMIDES
415
Mendoza, J. S.; Stamford, A.; Ladlow, M.; Willis, P. Nonoxidative coupling methodology
for the synthesis of the antitumor bisindole alkaloid vinblastine and a lower-half analog:
Solvent effect on the stereochemistry of the crucial C-15=C-180 bond. J. Am. Chem. Soc.
1992, 114, 10232–10245; (d) Kim, G.; Chu-Moyer, M. Y.; Danshefsky, S. J.; Schulte, G.
K. The total synthesis of indolizomycin. J. Am. Chem. Soc. 1993, 115, 30–39; (e) Hurd, R.
N.; Delmater, G. T. The preparation and chemical properties of thionamides. Chem. Rev.
1961, 61, 45–86.
6. Jeschke, P.; Harder, A.; Etzel, W.; Dau, W.; Thielking, G.; Bonse, G.; Linuma, K.
Synthesis and anthelmintic activity of thioamide analogues of cyclic octadepsipeptides
such as PF1022A. Pest Manag. Sci. 2001, 57, 1000–1004.
7. Cynamon, M. H.; Gimi, R.; Gyenes, F.; Sharpe, C. A.; Bergmann, K. E.; Han, H. J.;
Gregor, L. B.; Rapolu, R.; Luciano, G.; Welch, T. Pyrazinoic acid esters with broad
spectrum in vitro antimycobacterial activity. J. Med. Chem. 1995, 38, 3902–3907.
8. Albert, A.; Knecht, H.; Andersen, E.; Hungerford, V.; Schreier, M. H.; Papageorgiou, C.
Exploring structure–activity relationships around the phosphomannose isomarase inihibi-
tor AF14049 via combinotarial synthesis. Bioorg. Med. Chem. 1998, 8, 2203–2208.
9. Sherman, D. B.; Spatola, A. F.; Wire, W. S.; Burks, T. F.; Nguyen, T. M.-D.; Schiller, P.
W. Biological activities of cyclic enkephalin pseudopeptides containing thioamides as
amide bond replacements. Biochem. Biophys. Res. Commun. 1989, 162, 1126–1132.
10. Mehanna, A. S.; Belani, J. D.; Kelley, C. J.; Pallansc, L. A. Design, synthesis, and biologi-
cal evaluation of a series of thioamides as non-nucleoside reverse transcriptase inhibitors.
Med. Chem. 2007, 3, 513–519.
11. Petrov, K. A.; Andreev, L. N. Synthesis of thioamides. Usp. Khim. 1969, 38, 41–71.
12. Pathak, U.; Pandey, L. K.; Suryanarayana, M. V. A Thiophosphoryl chloride–assisted
transformation of arylaldoximes to thioamides. Synthesis 2012, 272–282.
13. Noei, J.; Khosropour, A. R. TiCl3OTf-[bmim]Br: A novel and efficient catalyst system for
chemoselective one-pot synthesis of thioamides from arylaldoximes. Tetrahedron Lett.
2008, 49, 6969–6971.
14. Yadav, A. K.; Srivastava, V. P.; Yadav, L. D. S. O,O-Diethyldithiophosphoric acid–
mediated synthesis of thioamides directly from aldehydes and ketones. Tetrahedron Lett.
2012, 53, 7113–7116.
15. (a) Ozturk, T.; Ertas, E.; Mert, O. Use of Lawesson’s reagent in organic syntheses. Chem.
Rev. 2007, 107, 5210–5278; (b) Varma, R. S.; Kumar, D. Microwave-accelerated solvent-
free synthesis of thioketones, thiolactones, thioamides, thionoesters, and thioflavonoids.
Org. Lett. 1999, 1, 697–700; (c) Curphey, T. J. Thionation with the reagent combination
of phosphorus pentasulfide and hexamethyldisiloxane. J. Org. Chem. 2002, 67, 6461–6473.
16. Charette, A. B.; Gernon, M. Mild method for the conversion of amides to thioamides.
J. Org. Chem. 2003, 68, 5792–5794.
17. Chao, D.; Ahn, J.; De Kastro, K. A.; Ahn, H.; Rhee, H. P4S10=dimethicone tandem:
Efficient reagent for thionation of various aromatic amides and esters. Tetrahedron.
2010, 66, 5583–5588.
18. Pathak, U.; Pandey, L. K.; Tank, R. Expeditious microwave-assisted thionation with the
system PSCl3=H2O=Et3N under solvent-free condition. J. Org. Chem. 2008, 73, 2890–2893.
19. (a) Kindler, K. Studien uber den mechanismus chemischer reaktionen. Erste abhandlung.
Reduktion of amiden und oxidation of aminen. Justus Liebigs Ann. Chem. 1923, 431, 187–
230; (b) Zbruyev, O. I.; Stiasni, N.; Kapper, C. Rapid preparation of thioamide building
blocks via microwave-promoted three-component Kindler reaction. J. Comb. Chem.
2002, 5, 145–148; (c) Taylor, E. C.; Zoltewicz, J. A. A new synthesis of aliphatic and
aromatic thioamides from nitriles. J. Am. Chem. Soc. 1960, 82, 2656–2657; (d) Liboska,
R.; Zyka, D.; Bobek, M. Synthesis of primary thioamides from nitriles and hydrogen
sulfide catalyzed by anion-exchange resin. Synthesis 2002, 1649–1651; (e) Benner, S. A.

416
A. K. YADAV, V. P. SRIVASTAVA, AND L. D. S. YADAV
Diphenylphosphinodithioic acid: A reagent for the conversion of nitriles to thioamides.
Tetrahedron Lett. 1981, 22, 1851–1854; (f) Benner, S. A. Mechanism of the reaction of
diphenylphosphinodithioic acid with nitriles. Tetrahedron Lett. 1981, 22, 1855–1858; (g)
Shiao, M. J.; Lai, L. L.; Ku, W. S.; Lin, P. Y.; Hwu, J. R. Chlorotrimethylsilane in combi-
nation with sodium sulfide as the equivalent of sodium trimethylsilanethiolate in organic
reactions. J. Org. Chem. 1993, 58, 4742–4744; (j) Brillon, D. A new thionation reagent:
Preparation of primary thioamides from nitriles. Synth. Commun. 1992, 22, 1397–1401.
20. Okamots, K.; Yamamoto, T.; Kanbara, T. Efficient synthesis of thiobenzanilides by
Willgerodt–Kindler Reaction with base catalysts. Synlett. 2007, 2687–2690.
21. Kaboudin, B.; Malekzadeh, L. Ammonium phosphorodithioate: A mild, easily handled,
efficient, and air-stable reagent for the conversion of amides into thioamides. Synlett.
2011, 2807–2810.
22. Talukdar, S.; Hsu, J.-L.; Cou, T.-K.; Fang, J.-M. Direct transformation of aldehydes to
nitriles using iodine in ammonia water. Tetrahedron Lett. 2001, 42, 1103–1105.
23. (a) Rai, A.; Yadav, L. D. S. A new application of Baylis–Hillman alcohols to a diastereo-
selective synthesis of 3-nitrothietanes. Tetrahedron. 2012, 68, 2459–2464; (b) Rai, A.;
Yadav, L. D. S. An efficient multicomponent stereoselective synthesis of 1,2,4-trisubsti-
tuted 1,3-thiazetidines. Tetrahedron Lett. 2011, 52, 3933–3936; (c) Yadav, L. D. S.;
Kapoor, R. Garima, Organocatalytic stereoselective aziridination of imines via ammonium
ylides. Synlett. 2009, 3123–3126; (d) Yadav, L. D. S.; Kapoor, R. An expeditious solvent
free synthesis of functionalised thietanes by nucleophile-induced cyclisation of O,O-diethyl
S-(1,3-diaryl-3-oxopropyl)phosphorodithioates. Synthesis 2002, 1502–1504; (e) Yadav, L.
D. S.; Kapoor, R. An expeditious one-pot synthesis of thiiranes from a-halo ketones in
solvent-free conditions using microwaves. Synthesis 2002, 2344–2346; (f) Ueno, Y.; Yadav,
L. D. S.; Okawara, M. A convenient synthesis of 2,4-diarylthietanes by reductive
cyclization of O,O-diethyl S-(1,3-diaryl-3-oxopropyl)phosphorodithioates. Synthesis
1981, 547–548.
24. Shie, J.-J.; Fang, J.-M. Direct conversion of aldehydes to amides, tetrazoles, and triazines
in aqueous media by one-pot tandem reactions. J. Org. Chem. 2003, 68, 1158–1160.
25. (a) Khosropour, A. R.; Noei, J.; Mirjafari, A. Efficient and green protocol for the synthesis
of thioamides in C6(mim)2Cl2 as a dicationic ionic liquid. J. Iran Chem. Soc. 2010, 7, 752–758;
(b) Cho, D.; Ahn, J.; De Castro, K. A.; Ahn, H.; Rhee, H. P4S10=dimethicone tandem:
Efficient reagent for thionation of various aromatic amides and esters. Tetrahedron. 2010,
66, 5583–5588.