Microwave-accelerated, three-component, one-step synthesis of 2-acylimino-3-aryl-3H-thiazolines under solvent-free conditions

Article abstract of DOI:10.1080/00397910600616149

2-Acylimino-3-aryl-3H-thiazoline derivatives could be generated in excellent yields through three-component condensations of aroylisothiocyanates, primary amines, and ω-haloacetophenone under solvent-free microwave irradiation. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910600616149

This article was downloaded by: [Brown University]
On: 16 December 2012, At: 20:34
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
Microwave‐Accelerated,
Three‐Component, One‐Step Synthesis of
2‐Acylimino‐3‐aryl‐3H‐thiazolines under
Solvent‐Free Conditions
Min Xia a & Yue‐dong Lu a
a Department of Applied Chemistry, Zhejiang Science and Technology
University, Hangzhou, China
Version of record first published: 22 Aug 2006.
To cite this article: Min Xia & Yue‐dong Lu (2006): Microwave‐Accelerated, Three‐Component, One‐Step
Synthesis of 2‐Acylimino‐3‐aryl‐3H‐thiazolines under Solvent‐Free Conditions, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 36:12, 1637-1643
To link to this article: http://dx.doi.org/10.1080/00397910600616149
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions
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.
The publisher does not give any warranty express or implied or make any representation that the
contents will be complete or accurate or up to date. The accuracy of any instructions, formulae,
and drug doses should be independently verified with primary sources. The publisher shall not
be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or
howsoever caused arising directly or indirectly in connection with or arising out of the use of this
material.

Synthetic Communicationsw, 36: 1637–1643, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910600616149
Microwave-Accelerated, Three-Component,
One-Step Synthesis of 2-Acylimino-3-aryl-
3H-thiazolines under Solvent-Free
Conditions
Min Xia and Yue-dong Lu
Department of Applied Chemistry, Zhejiang Science and Technology
University, Hangzhou, China
Abstract: 2-Acylimino-3-aryl-3H-thiazoline derivatives could be generated in
excellent yields through three-component condensations of aroylisothiocyanates,
primary amines, and v-haloacetophenone under solvent-free microwave irradiation.
Keywords: Microwave, solvent-free, 3H-thiazolines, three-component
In recent years, microwave-assisted reactions have increasingly attracted
much attention in the field of organic synthesis because of their rapid access
to target compounds,[1] especially in those reactions carried out under
solvent-free conditions.[2] Compared with traditional solution-phase
reactions, solvent-free microwave-accelerated reactions have the advantages
of shortened reaction time, less environment pollution, easy operation, and
evidently improved yields, even completely different selectivities and reactiv-
ities in some cases. Moreover, the design of multicomponent reactions (MCR)
is an important research field in combinatorial chemistry;[3] therefore great
efforts have been and still are being made to develop new multicomponent
reations.[4] Because MCRs are one-component reactions, they generally
afford good yields and easy operation and are fundamentally different from
linear two-component reactions in several aspects.[5]
3H-iminothiazolines are important heterocyclic compounds with
remarkable bactericidal,[6] analgesicidal,[7] fungicidal,[8] and insecticidal[9]
Received in China December 10, 2005
Address correspondence to Min Xia, Department of Applied Chemistry,
Zhejiang Science and Technology University, Hangzhou 310018, China.
Tel: þ86(571)86843228; E-mail: xiamin@zist.edu.cn
1637

1638
M. Xia and Y.-D. Lu
bioactivities. Recently, it was reported[10] that 2-acylimino-3H-thiazolines
could be utilized as b-turn mimics with potent and selective GPIIb/IIIa inhibi-
tory activities. Classically, the synthesis of 3H-iminothiazolines involves the
Hantzsch condensation[11,12] of N-acylthioureas and a-halocarbonyl deriva-
tives in organic solvents. However, the lengthy procedure for the preparation
of starting materials, unsatisfactory yields, and prolonged time hindered the
convenient and rapid access to these significant compounds. Therefore, it
was necessary to develop a simple and effective approach to construct such
important scaffolds. Herein we describe our three-component, one-step con-
densation of aroylisothiocyanates, amines, and v-haloacetophenone under
solvent-free microwave irradiation. To the best of our knowledge, there has
been no such report in the literature on the microwave-promoted, one-pot
procedure for the preparation of 2-acylimino-3-aryl-3H-thiazolines.
The synthetic route to the three-component preparation of 2-acylimino-
3-aryl-3H-thiazolines 7 is outlined in Scheme l, and the results are indicated
in Table 1. In our one-pot operation, aroylisothiocyanates 1, generated from
the corresponding acyl chlorides and potassium thiocyanate,[13] were
reacted directly with amines 2 and v-haloacetophenone 3 to offer the target
products 7. The straightforward route, beginning from aroylisothiocyanates
instead of N-acylthioureas, facilitated the combinatorial construction of a
library with two variable positions and accelerated the access to compounds
7 without the troublesome preparation of N-acylthioureas as the starting sub-
strates. Moreover, the one-step procedure and solvent-free conditions made
the isolation and purification of the needed products quite simple; precipi-
tation and washing could afford the products with enough purity, avoiding
complicated workup such as water separation and chromatography.[14]
Besides, the microwave-promoted condensations could be smoothly accom-
plished in good to excellent yields within 30–45 s. In the same reaction
carried out in benzene, only low yields of 2-acylimino-3-aryl-3H-thiazolines
could be obtained and some complicated by-products were generated
(checked by TLC), even if the mixture was refluxed for 3 h (Table 1, yields
in brackets). To determine whether the microwave effect existed in our
Scheme 1.

2-Acylimino-3-aryl-3H-thiazolines Synthesis
1639
Table 1. One-step, three-component synthesis of 2-acylimino-3-aryl-3H-thiazolines
under solvent-free microwave irradiation
Entry
R1
R2
Product
Time (s)
Yields (%)a,b
1
2
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
7a
7b
7c
7d
7e
7f
30
30
30
45
30
45
30
45
30
30
45
90 (72)c
93 (77)c
98 (42)d
90 (62)c
87 (41)c
88 (49)d
84 (66)c
96 (71)c
91 (53)d
89 (40)d
83 (69)c
2-CH3C6H4
4-CH3C6H4
4-ClC6H4
3
4
5
4-CH3OC6H4
2-CH3C6H4
4-CH3C6H4
4-ClC6H4
6
4-ClC6H4
4-ClC6H4
4-CH3OC6H4
4-CH3OC6H4
4-O2NC6H4
C6H5
7
7g
7h
7i
8
9
4-CH3OC6H4
4-ClC6H4
3-ClC6H4
10
11
7j
7k
aYields referred to reactions under MW irradiation.
bv-Chloroacetophenone was utilized.
cyields in brackets refer to reactions at 808C for 1 h under neat conditions.
dYields in brackets refer to reactions at refluxing for 3 h in benzene.
one-pot and solvent-free operation, some solid-state, three-component
reactions were executed under traditional heating. When the three-
component mixtures were dispersed well and heated at 808C for 1 h, only
moderate yields of products 7 could be obtained (Table 1, yields in
brackets). It was obvious that remarkable microwave effect was displayed
in our one-pot and solvent-free condensations to formation of 2-acylimino-
3-aryl-3H-thiazolines.
It seemed there was no obvious substituent effect on acyl moieties, since 1
with an electron-withdrawing group like NO2 could carry out the three-
component condensations successfully to provide the products in excellent
yields (Table 1, entry 10). However, remarkable substituent effect took
place on anilines 2; only anilines with electron-donating groups could
smoothly fulfill the reactions. In our work, when 3-nitroaniline was applied
to react with 1 and 2, only N-aroyl-N0-(3-nitrophenyl) thioureas could be
afforded quantitatively without any formation of 7. A possible mechanism
of one-step condensations was proposed: in the three-component mixture,
the nucleophilic additions of 2 to aroylisothiocyanates 1 took place to
generate N-aroyl-N0-arythioureas 4 despite the presence of v-haloaceto-
phenone. This was supported by our two-step experiments, in which the inter-
mediates of a-aminoacetophenones, generated from the reactions of 2 and 3
under solvent-free microwave heating, were unable to undergo the further
transformations to the expected 7 in the presence of aroylisothiocyanates 1.
The intermediates 4 were coupled with v-haloacetophenone 3 to form the
intermediates 5 by dehydrohalogenation. The key step for the formation of

1640
M. Xia and Y.-D. Lu
2-acylimino-3-aryl-3H-thiazolines was the intramolecular nucleophilic
addition. Apparently, the addition could undergo successfully when there
were electron-donating groups on substituted aniline 2, but the process was
hindered if the substituents were electron-withdrawing groups. Through
dehydration, the target products of 2-acylimino-3-aryl-3H-thiazolines 7
were effectively obtained in high yields. For v-haloacetophenone, both
v-chloroacetophenone and v-bromoacetophenone were efficient reagents
for the one-step reactions, but v-chloroacetophenone appeared to be more
suitable for the generation of clear products.
In conclusion, we herein reported a novel and simple approach to
2-acylimino-3-aryl-3H-thiazolines under microwave-assisted, one-step
reactions. The advantages of excellent yields, convenient operation, a
concise route, and remarkably shortened time make our reaction one of the
most promising methods for synthesis of iminothiazoline derivatives.
EXPERIMENTAL
Melting points were determined on X4 mp apparatus, and the thermometer was
1
not corrected. H NMR spectra and 13C NMR spectra were obtained on a
Bruker Avance DMX 400-MHz instrument using TMS as internal standard
in DMSO-d6 or CDCl3. FT-IR spectra were recorded on Nicolet Avatar
spectrophotometer. MW reactions were carried out in
microwave oven (Galanz WG800DSL20II-K6, 0–800 W).
a domestic
General Procedure for the MW-Irradiated Preparation of
Compounds 7aj
At room temperature, aroylisothicyanate 1 (1 mmol), aniline 2 (1 mmol), and
v-chloroacetophenone 3 (2 mmol) were mixed well, and the resulted mixture
was irradiated at 580 W in a domestic microwave oven for the appropriate
time. After cooling to room temperature, ether was poured to precipitate
white solids by stirring. The solids with enough purity for spectral analysis
were obtained by washing with ether and ethanol several times.
7a: mp 2068C; IR (KBr): 3056, 1597, 1568, 1462, 1339, 1278, 898, 714 cm21
;
1H NMR (400 MHz, CDCl3) d ¼ 6.71 (s, 1H), 7.13 (m, 2H), 7.23–7.28
(m, 5H), 7.34 (m, 2H), 7.40 (m, 4H), 8.10 (d, 2H, J ¼ 8.0 Hz); 13C NMR
(100 MHz, CDCl3) d ¼ 107.4, 127.9, 128.3, 128.4, 128.5, 128.7, 128.9,
129.3, 130.5, 131.4, 136.6, 137.5, 139.0, 169.7, 174.4.
7b: mp 1728C; IR (KBr): 3101, 3064, 1593, 1550, 1466, 1343, 1274, 1029,
1
902, 714 cm21; H NMR (400 MHz, CDCl3) d ¼ 2.12 (s, 3H), 6.74 (s, 1H),
7.08–7.13 (m, 3H), 7.20–7.27 (m, 4H), 7.33 (m, 4H), 7.39 (m, 1H), 8.05
(d, 2H, J ¼ 7.3 Hz); 13C NMR (100 MHz, CDCl3) d ¼ 17.9, 107.2, 126.5,

2-Acylimino-3-aryl-3H-thiazolines Synthesis
1641
127.8, 128.3, 128.6, 128.7, 128.9, 129.1, 129.3, 130.3, 130.8, 131.3, 136.0,
136.7, 137.0, 139.1, 169.1, 174.5.
7c: mp 272–2748C; IR (KBr): 3109, 1597, 1564, 1458, 1339, 1274, 902, 722,
1
551 cm21; H NMR (400 MHz, CDCl3) d ¼ 2.40 (s, 3H), 6.70 (s, 1H), 7.14
(m, 4H), 7.19–7.29 (m, 5H), 7.35 (m, 2H), 7.41 (m, 1H), 8.12 (d, 2H,
J ¼ 7.6 Hz); 13C NMR (100 MHz, CDCl3) d ¼ 21.1, 107.2, 127.8, 128.0,
128.2, 128.6, 128.8, 129.2, 129.3, 130.61, 131.3, 134.9, 136.7, 136.3, 139.1,
169.7, 174.4.
7d: mp 210–2128C; IR (KBr): 3060, 1597, 1564, 1470, 1343, 1282, 902, 833,
710 cm21
;
1H NMR (400 MHz, CDCl3) d ¼ 6.72 (s, 1H), 7.13 (d, 2H,
J ¼ 7.2 Hz), 7.22–7.32 (m, 5H), 7.37 (m, 4H), 7.40–7.45 (m, 1H), 8.11
(d, 2H, J ¼ 7.8 Hz); 13C NMR (100 MHz, CDCl3) d ¼ 107.6, 128.0, 128.5,
128.8, 129.0, 129.3, 129.8, 130.2, 131.6, 134.3, 136.0, 136.4, 138.6, 169.7,
174.5.
7e: mp 2338C; IR (KBr): 3113, 1593, 1560, 1511, 1458, 1339, 1282, 1249,
1025, 906, 759, 722, 555 cm21
;
1H NMR (400 MHz, CDCl3) d ¼ 3.83
(s, 3H), 6.69 (s, 1H), 6.90 (d, 2H, J ¼ 8.4 Hz), 7.13–7.18 (m, 4H), 7.23–
7.28 (m, 3H), 7.33–7.36 (m, 2H), 7.41 (m, 1H), 8.12 (d, 2H, J ¼ 7.6 Hz);
13C NMR (100 MHz, CDCl3) d ¼ 55.4, 107.2, 13.9, 127.9, 128.3, 128.7,
128.9, 129.2, 129.4, 130.6, 131.4, 136.7, 139.2, 159.2, 169.9, 174.5.
7f: mp 155–1568C; IR (KBr): 3064, 1593, 1556, 1442, 1335, 1274, 1164,
1086, 1012, 902, 767, 735, 698 cm21
;
1H NMR (400 MHz, CDCl3)
d ¼ 2.11 (s, 3H), 6.76 (s, 1H), 7.08–7.13 (m, 3H), 7.22–7.33 (m, 8H), 7.96
(d, 2H, J ¼ 8.0 Hz); 13C NMR (100 MHz, CDCl3) d ¼17.9, 107.3, 126.6,
128.1, 128.3, 128.6, 128.6, 128.9, 129.2, 130.2, 130.6, 130.9, 135.29, 135.9,
136.9, 137.5, 139.2, 169.2, 173.4.
7g: mp 1838C; IR (KBr): 3072, 1601, 1458, 1343, 1278, 1086, 1012, 906, 771,
1
730 cm21; H NMR (400 MHz, CDCl3) d ¼ 2.40 (s, 3H), 6.73 (s, 1H), 7.13
(m, 4H), 7.20 (m, 2H), 7.24–7.27 (m, 3H), 7.31 (m, 2H), 8.03 (d, 2H,
J ¼ 8.0 Hz); 13C NMR (100 MHz, CDCl3) d ¼ 21.2, 107.5, 128.1 128.2,
128.3, 128.8, 128.9, 129.4, 130.7, 134.8, 135.3, 137.5, 138.5, 139.3, 169.9,
173.4.
7h: mp 2578C; IR (KBr): 3128, 3012, 2961, 2838, 1603, 1591, 1562, 1506,
1446, 1403, 1340, 1250, 1161, 1094, 1025, 905, 846, 777, 729, 700,
1
559 cm21; H NMR (400 MHz, DMSO-d6) d ¼ 3.78 (s, 3H), 6.95 (d, 2H,
J ¼ 8.4 Hz), 7.18 (s, 1H), 7.23 (m, 2H), 7.30 (m, 3H), 7.43 (d, 2H,
J ¼ 8.4 Hz), 7.53 (d, H, J ¼ 8.4 Hz), 7.88 (d, 2H, J ¼ 8.4 Hz); 13C NMR
(100 MHz, DMSO-d6) d ¼ 59.8, 112.2, 118.0, 125.0, 128.1, 129.3, 132.9,
133.3, 133.4, 133.6, 134.7, 135.1, 137.5, 140.9, 142.6, 172.1, 176.3.
7i: mp 2458C; IR (KBr): 3131, 3016, 2954, 2836, 1591, 1561, 1507, 1443,
1343, 1248, 1164, 1025, 904, 833, 777, 756, 699, 551 cm21 1H NMR
;
(400 MHz, DMSO-d6) d ¼ 3.77 (s, 6H), 6.93 (d, 2H, J ¼ 8.8 Hz), 6.98

1642
M. Xia and Y.-D. Lu
(d, 2H, J ¼ 8.8 Hz), 7.15 (s, 1H), 7.22 (m, 2H), 7.27–7.29 (m, 5H), 7.89
(d, 2H, J ¼ 8.4 Hz); 13C NMR (100 MHz, DMSO-d6) d ¼ 55.2, 55.4, 107.0,
113.1, 113.9, 128.3, 128.6, 128.9, 129.5, 129.6, 130.4, 130.7, 131.2, 139.0,
159.1, 162.3, 169.6, 174.1.
7j: mp 2058C; IR (KBr): 3091, 1577, 1548, 1465, 1409, 1336, 1285, 1089,
1
1013, 907, 855, 755, 720 cm21; H NMR (400 MHz, DMSO-d6) d ¼ 7.23
(m, 2H), 7.33 (m, 4H), 7.45 (d, 2H, J ¼ 8.4 Hz), 7.53 (d, 2H, J ¼ 8.4 Hz),
8.10 (d, 2H, J ¼ 8.4 Hz), 8.25 (d, 2H, J ¼ 8.4 Hz); 13C NMR (100 MHz,
DMSO-d6) d ¼ 113.2, 128.0, 132.8, 133.4, 133.5, 133.7, 134.2, 134.3
135.0, 137.8, 140.5, 143.2, 146.4, 153.6, 174.2, 175.5.
7k: mp 2188C; IR (KBr): 3062, 1595, 1565, 1473, 1431, 1342, 1284, 786, 770,
710 cm21; 1H NMR (400 MHz, CDCl3) d ¼ 6.70 (s, 1H), 7.14 (m, 3H), 7.25–
7.38 (m, 8H), 7.44 (t, 1H, J ¼ 7.2 Hz), 8.12 (d, 2H, J ¼ 7.2 Hz); 13C NMR
(100 MHz, CDCl3) d ¼ 107.6, 126.8, 128.0, 128.5, 128.7, 128.8, 128.9,
129.0, 129.3, 129.6, 130.1, 131.6, 134.3, 136.4, 138.5, 138.6, 169.7, 174.5.
REFERENCES
1. (a) Caddick, S. Microwave assisted organic reactions. Tetrahedron 1995, 51,
10403; (b) Larhed, M.; Moberg, C.; Hallberg, A. Microwave-accelerated homo-
geneous catalysis in organic chemistry. Acc. Chem. Res. 2002, 35, 717.
2. (a) Marwah, P.; Marwah, A.; Lardy, H. A. Microwave induced selective enoliza-
tion of steroidal ketones and efficient acetylation of sterols in semisolid state. Tet-
rahedron 2003, 59, 2273; (b) Rodriguez, H.; Suarez, M.; Parez, R.; Petit, A.;
Loupy, A. Solvent-free synthesis of 4-aryl substituted 5-alkoxycarbonyl-
6-methyl-3,4-dihydropyridones under microwave irradiation. Tetrahedron Lett.
2003, 44, 3709; (c) Kappe, C. O.; Kumar, D.; Verma, R. S. Microwave-assisted
high-speed parallel synthesis of 4-aryl-3,4-dihydropyrimidin-2(1H)-ones using a
solventless Biginelli condensation protocol. Synthesis 1999, 1799.
3. (a) Weber, L.; Illegen, K.; Almstetter, M. Discovery of new multicomponent
reactions with combinatorial methods. Synlett 1999, 366; (b) Astrong, R. W.;
Combs, A. P.; Tempest, P. A.; Brown, S. D.; Keating, T. A. Multiple-
component condensation strategies for combinatorial library synthesis. Acc.
Chem. Res. 1996, 29, 123.
4. (a) Domling, A.; Ugi, I. Multicomponent reactions with isocyanides. Angew.
Chem. Int. Ed. 2000, 39, 3168; (b) Cui, S. L.; Lin, X. F.; Wang, Y. G. Parallel
synthesis of strongly fluorescent polysubstituted 2,6-dicyanoanilines via
microwave-promoted multicomponent reaction. J. Org. Chem. 2005, 70, 2866;
(c) Zeng, R. S.; Zou, J. P.; Zhi, S. J. Novel synthesis of 1-aroyl-3-aryl-4-substituted
imidazole-2-thiones. Org. Lett. 2003, 5, 1657.
5. (a) Shestopalov, A. M.; Emeliyanova, Y. M.; Shestopalov, A. A.;
Rodinovskaya, L. A.; Niazimbetova, Z. I.; Evans, D. H. One-step synthesis
of substituted 6-amino-5-cyanospiro-4-(piperidine-40)-2H,4H-dihydropyrazolo
[3,4-b]pyrans. Org. Lett. 2002, 4, 423; (b) List, B.; Castello, C. A novel proline-
catalyzed three-component reaction of ketones, aldehydes, and Meldrum’s acid.
Synlett 2001, 1687; (c) Nair, V.; Vinod, A. U.; Rajesh, C. A novel synthesis of

2-Acylimino-3-aryl-3H-thiazolines Synthesis
1643
2-aminopyrroles using a three-component reaction. J. Org. Chem. 2001, 66,
4427; (d) Kappe, C. O. 100 years of the Biginelli dihydropyrimidine
synthesis. Tetrahedron 1993, 49, 6937.
6. Garmaise, D. L.; Chambers, C. H.; McCrae, R. C. Anthelmintic quaternary salts,
II: Thiazolium salts. J. Med. Chem. 1968, 11, 1205.
7. Misra, V. S.; Saxena, A. Potential antiviral and antituberculous compounds I:
N-1-Acyl-N-4-aryl or alkyl thiosemicarbazides, Schiff bases and condensation
products of hydrazines and isonitrosoketones. Indian J. Appl. Chem. 1969, 32, 373.
8. Tripathy, H.; Das, M. K.; Sahu, B.; Mahapatra, G. N. Synthesis of 2-thio-D4-
thiazolines as possible fungicides. J. Indian Chem. Soc. 1973, 50, 417.
9. Nagasaki, F.; Yamada, T.; Takahashi, E.; Kitagaya, Y.; Hatano, R. Preparation of
thiazoline derivatives as insecticides. Jpn. Kokai Tokkyo Koho JP 63,250,371
(Chem. Abstr. 1989, 110, 192810y).
10. Manaka, A.; Sato, M.; Aoki, M.; Tanaka, M.; Ikeda, T.; Toda, Y.; Yamane, Y.;
Nakaike, S. 2-Acylimino-3H-thiazoline derivatives: A novel template for
platelet GPIIb/IIIa receptor antagonists. Bioorg. Med. Chem. Lett. 2001, 11, 1031.
11. (a) De Kimpe, N.; Boelens, M.; Declercq, J. P. A. novel synthesis of 2-imino-4
-thiazolines via a-bromoketimines. Tetrahedron 1993, 49, 3411; (b) Qian, Q.;
So, S. S.; Goodnow, R. A. Stereochemical control factors in the Hantzsch
thiazole synthesis: A Hammett substitution correlation analysis. Org. Lett. 2001,
3, 3655.
12. Muraveva, K. M.; Shchukina, M. N. Synthesis and rearrangemnts in the thiazoli-
nimine series II: Condensation of v-bromoacetophenone with N-phenyl-
N0-acylthioureas. Zh. Obshch, Khim. 1960, 30, 2334.
13. Frank, R. L.; Smith, P. V. A-Phenylthiourea. Org. Synth. Coll. 3, 735; Vol. 28, 89,
1949.
14. Manaka, A.; Ishii, T.; Takahashi, K.; Sato, M. 2-Acylimino-3-alkyl-3H-thiazoline
derivatives: One-pot, three-component condensation synthesis of novel b-turn
mimics. Tetrahedron Lett. 2005, 46, 419.
15. Meyer, E.; Joussef, A. C.; Gallardo, H.; Bortoluzzi, A. J.; Longo, R. L. 1,5-Type
....
....
nonbonded O S and S S interactions in (acylimino) and (thioacylimino)
benzothiazoline systems: Crystal structures and theoretical calculations. Tetrahe-
dron 2003, 59, 10187.