Synthesis of Selenol Esters from Acid Chlorides and Organic Diselenides in the Presence of the Zn/AlCl3 System

Article abstract of DOI:10.1007/s00706-002-0545-0

Treatment of diphenyl and dibenzyl diselenides with aliphatic and aromatic acid chlorides in the presence of Zn/AlCl₃ affords selenol esters. Availability, low costs, and lack of toxicity of the catalysts, simple reaction work-up, and high yiel

Full text of DOI:10.1007/s00706-002-0545-0

Monatshefte f€ur Chemie 134, 831–835 (2003)
DOI 10.1007/s00706-002-0545-0
Synthesis of Selenol Esters from Acid
Chlorides and Organic Diselenides
in the Presence of the Zn=AlCl3 System
ꢀ
Barahman Movassagh and Fatemeh Mirshojaei
Department of Chemistry, K. N. Toosi University of Technology, P. O. Box 15875-4416,
Tehran, Iran
Received August 26, 2002; accepted September 3, 2002
Published online April 3, 2003 # Springer-Verlag 2003
Summary. Treatment of diphenyl and dibenzyl diselenides with aliphatic and aromatic acid chlorides
in the presence of Zn=AlCl3 affords selenol esters. Availability, low costs, and lack of toxicity of the
catalysts, simple reaction work-up, and high yields under relatively mild condition are distinct advan-
tages of this method.
Keywords. Selenol esters; Zn=AlCl3; Zinc selenoate; Reductive cleavage of diselenides.
Introduction
Selenol esters have been successfully used as liquid crystals [1] and in the synthe-
ses of steroids and sex hormones [2]. These compounds exhibit also a higher and
more selective reactivity toward nucleophiles than their O-analogs. These proper-
ties make selenol esters a valuable acyl transfer agent and permit selective trans-
formations in complex molecules. They are usually synthesized by one of the five
main methods: (i) reaction of carboxylic acids with diaryl diselenides [3] or aryl
selenocyanates [4], (ii) acylation of selenols [5] and their metal salts [6], (iii) reac-
tion of aroylhydrazine with benzeneseleninic acid [7], (iv) alkylation of seleno-
carboxylates [8], and (v) reaction of aldehydes with diisobutylaluminum selenoate
[9]. These methods suffer from laborious removal of by-products such as diaryl
diselenide, or in some cases, unavailability of reagents. Kato et al. [10] reported a
simple method for preparation of Se-aryl selenol esters via Se-aryl acylmethane-
sulfenoselenoates, which, in turn, are prepared both from reactions of acylsulfenyl
bromides with diaryl diselenides and from reactions of metal thiocarboxylates with
areneselenylbromides.
ꢀ
Corresponding author. E-mail: movassagh@hotmail.com

832
B. Movassagh and F. Mirshojaei
Scheme 1
We now describe a new method for preparation of Se-aryl and Se-alkyl selenol
esters 3 which involves treatment of diselenides 1 and different acid chlorides 2
with the Zn=AlCl3 system in dry dimethylformamide (DMF) at 65ꢁC (Scheme 1).
Results and Discussion
As seen in Table 1, both diaryl and dialkyl diselenides, diphenyl and dibenzyl
diselenides, were treated with various acid chlorides to afford the corresponding
selenol esters in high yields. Selenole esters prepared from aryl diselenides gen-
erally give higher yields than those produced from alkyl diselenides. In the case of
the aromatic acid chlorides a longer reaction time is generally required (3d, e, and
j, Table 1) which is due to their lower reactivity towards nucleophiles compared to
aliphatic acid chlorides. It is observed that during the course of reaction the zinc
dust is gradually consumed. This means that reductive cleavage of the Se–Se bond
may lead to the zinc selenoate intermediate I, which further undergoes nucleophilic
displacement with acid chloride in the presence of aluminum chloride to afford the
selenol esters (Scheme 2).
In conclusion, the selenol ester synthesis described above is a valuable alter-
native for all processes where direct transformation of a carboxylic acid to the
Table 1. Selenol esters 3 from diselenides 1 and acid chlorides 2
Product
R
R0
Reaction time=h
Isolated yield=%
3a
3b
3c
3d
3e
3f
Ph
CH3
0.75
2
89
86
87
85
80
81
82
80
74
76
Ph
CH3CH2
CH3CH2CH2
Ph
Ph
2
Ph
3
Ph
4-ClC6H4
CH3
4.5
1.5
2
PhCH2
PhCH2
PhCH2
PhCH2
PhCH2
3g
3h
3i
CH3CH2
CH3CH2CH2
Ph
3
2
3j
4-ClC6H4
3
Scheme 2

Synthesis of Selenol Esters
833
corresponding selenol ester is not required. This methodology complements other
methods, offering several advantages such as the greater availability of the starting
materials, simple reaction work-up, and higher yields.
Experimental
1
Melting points are uncorrected. H and 13C NMR spectra were recorded on a Jeol JNM-EX90A in
CDCl3 solutions. IR spectra were obtained using a Shimadzu IR-408. Mass spectra were recorded with
a Shimadzu GC-MS QP 1100EX instrument.
General Procedure for Synthesis of Selenol Esters from Acid Chlorides
A mixture of the 1 mmol diselenide, 4.6 mmol zinc powder, 2.0 mmol anhydrous AlCl3, and 15 cm3 dry
DMF were stirred at room temperature for 10–15 min. 4.0 mmol Acid chloride was then added at once
and stirring was continued for the specified time (Table 1) at 65ꢁC. Progress of the reaction was
monitored by TLC. After addition of ethyl ether (20 cm3) the mixture was washed with water
(2Â 25cm3), dried over anhydrous Na2SO4, and the ether evaporated. The resulting crude product
was purified by preparative thin layer chromatography (silica gel, eluent n-hexane: ethyl ether ¼ 6 : 1)
to afford the desired ester.
Se-Phenyl Ethaneselenoate (3a, C8H8OSe)
1
Oil ([4a]: bp 80ꢁC at 0.5 Torr); IR (neat): ꢀꢀ ¼ 1730 (C¼O), 940cmÀ 1; H NMR (CDCl3): ꢁ ¼ 2.4
(s, 3H, CH3), 7.3–7.7 (m, 5H, Ph) ppm.
Se-Phenyl Propaneselenoate (3b, C9H10OSe)
1
Oil; IR (neat): ꢀꢀ ¼ 1725, 930 cmÀ 1; H NMR (CDCl3): ꢁ ¼ 1.2 (t, 3H, CH3, J ¼ 8 Hz), 2.7 (q, 2H,
CH2, J ¼ 8 Hz), 7.2–7.7 (m, 5H, Ph) ppm; 13C NMR (CDCl3): ꢁ ¼ 9.3, 40.9, 126.3, 128.7, 129.2,
135.7, 200.9 ppm; MS: m=z (%) ¼ 213 (Mþ , 0.6), 156 (4), 57 (29), 44 (100).
Se-Phenyl Butaneselenoate (3c, C10H12OSe)
Oil; IR (neat): ꢀꢀ ¼ 1723, 940 cmÀ 1; 1H NMR (CDCl3): ꢁ ¼ 1.0 (t, 3H, CH3, J ¼ 8 Hz), 1.8 (sext, 2H,
CH3CH2, J ¼ 8 Hz), 2.7 (t, 2H, CH2CO, J ¼ 8 Hz), 7.2–7.7 (m, 5H, Ph) ppm; 13C NMR (CDCl3):
ꢁ ¼ 13.1, 18.6, 48.9, 126.4, 128.4, 128.9, 135.4, 199.4 ppm; MS: m=z (%) ¼ 227 (Mþ , 2), 156 (71), 77
(100), 71 (46), 51 (68).
Se-Phenyl Selenobenzoate (3d, C13H10OSe)
1
Oil ([4a]: mp 37–38ꢁC); IR (neat): ꢀꢀ ¼ 1690 cmÀ1; H NMR (CDCl3): ꢁ ¼ 7.3–7.7 (m, 8H, Ph),
7.8–8.1 (m, 2H, Ph) ppm.
Se-Phenyl 4-Chlorobenzeneselenoate (3e, C13H9ClOSe)
Mp 83ꢁC ([4a]: mp 83.5–84.5ꢁC); IR (KBr): ꢀꢀ ¼ 1690 cmÀ1; 1H NMR (CDCl3): ꢁ ¼ 7.4–7.8 (m, 7H,
Ph), 7.8–8.1 (m, 2H, Ph) ppm.

834
B. Movassagh and F. Mirshojaei
Se-Benzyl Ethaneselenoate (3f, C9H10OSe)
1
Oil; IR (neat): ꢀꢀ ¼ 1715 cmÀ1; H NMR (CDCl3): ꢁ ¼ 2.4 (s, 3H, CH3), 4.2 (s, 2H, PhCH2), 7.3 (s,
5H, Ph) ppm; 13C NMR (CDCl3): ꢁ ¼ 29.2, 34.3, 126.8, 128.5, 128.8, 139.1, 197.2 ppm; MS:
m=z (%) ¼ 213 (Mþ , 2), 170 (5), 91 (100), 65 (55), 43 (100).
Se-Benzyl Propaneselenoate (3g, C10H12OSe)
1
Oil; IR (neat): ꢀꢀ ¼ 1710, 930 cmÀ 1; H NMR (CDCl3): ꢁ ¼ 1.2 (t, 3H, CH3, J ¼ 8 Hz), 2.6 (q, 2H,
CH3CH2, J ¼ 8 Hz), 4.2 (s, 2H, PhCH2), 7.2 (s, 5H, Ph) ppm; 13C NMR (CDCl3): ꢁ ¼ 9.4, 28.6, 41.2,
126.8, 128.5, 128.8, 139.2, 202.0 ppm; MS: m=z (%) ¼ 227 (Mþ , 0.3), 91 (100), 57 (10).
Se-Benzyl Butaneselenoate (3h, C11H14OSe)
Oil; IR (neat): ꢀꢀ ¼ 1708, 950 cmÀ 1; 1H NMR (CDCl3): ꢁ ¼ 1.0 (t, 3H, CH3, J ¼ 8 Hz), 1.7 (sext, 2H,
CH3CH2, J ¼ 8 Hz), 2.6 (t, 2H, CH2CO, J ¼ 8 Hz), 4.2 (s, 2H, PhCH2), 7.3 (s, 5H, Ph) ppm; 13C NMR
(CDCl3): ꢁ ¼ 13.2, 18.8, 28.6, 49.5, 126.7, 128.4, 128.7, 139.2, 200.9 ppm; MS: m=z (%) ¼ 242 (Mþ ,
25), 91 (100), 71 (97), 43 (92).
Se-Benzyl Selenobenzoate (3i, C14H12OSe)
1
Oil; IR (neat): ꢀꢀ ¼ 1670 cmÀ1; H NMR (CDCl3): ꢁ ¼ 4.4 (s, 2H, PhCH2), 7.2–7.7 (m, 8H, Ph),
7.8–8.1 (m, 2H, Ph) ppm; 13C NMR (CDCl3): ꢁ ¼ 29.0, 126.9, 127.1, 128.5, 128.7, 128.9, 133.6,
138.9, 194.2 ppm; MS: m=z (%) ¼ 275 (Mþ , 3), 105 (91), 91 (100), 77 (96), 51 (78).
Se-Benzyl 4-Chlorobenzeneselenoate (3j, C14H11ClOSe)
1
Mp 70–71ꢁC; IR (KBr): ꢀꢀ ¼ 1675, 950 cmÀ 1; H NMR (CDCl3): ꢁ ¼ 4.4 (s, 2H, PhCH2), 7.2–7.6
(m, 7H, Ph), 7.7–8.0 (m, 2H, Ph) ppm; 13C NMR (CDCl3): ꢁ ¼ 29.3, 127.1, 128.5, 128.6, 129.1, 137.1,
138.6, 140.0, 193.2ppm; MS: m=z (%) ¼ 310 (Mþ , 3.8), 139 (100), 91 (79).
Acknowledgement
The financial support by K. N. Toosi University of Technology Research Council is gratefully
acknowledged.
References
[1] a) Heppke G, Martence J, Praefcke K, Simon H (1977) Angew Chem 89: 328; b) Heppke G,
Martence J, Praefcke K, Simon H (1977) Angew Chem Int Ed Engl 16: 318
[2] Pheninger J, Heuberger C, Graf W (1980) Helv Chim Acta 63: 2308
[3] Masamune S, Hayase Y, Schilling W, Chan WK, Bates GS (1977) J Am Chem Soc 99: 6756
[4] a) Grieco PA, Yokoyama Y, Williams E (1978) J Org Chem 43: 1283; b) Grieco PA, Jaw JY,
Claremon DA, Nicolaou KC (1981) J Org Chem 46: 1215
[5] a) Scheithauer S, Mayer R (1966) Z Chem 6: 375; b) Gais D (1977) Angew Chem 89: 251;
c) Gais D (1977) Angew Chem Int Ed Engl 16: 244; d) Gunther WHH, Mautner HG (1964) J Med
Chem 2: 229
[6] a) Taboury F (1908) Bull Soc Chim Fr 35: 672; b) Keimatsu S, Yokota K (1931) J Pharm Soc Jpn
51: 89; c) Reinboldt H, Giesbrecht D (1955) Chem Ber 88: 674; d) Gunther WHH (1967) J Org
Chem 32: 3931

Synthesis of Selenol Esters
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[7] Back TG, Collins S, Kerr RG (1981) J Org Chem 46: 1564
[8] a) Ishihara H, Sato S, Hirabayashi Y (1977) Bull Chem Soc Jpn 50: 3007; b) Ishihara H,
Hirabayashi Y (1976) Chem Lett 203
[9] Inoue T, Takeda T, Kambe N, Ogawa A, Ryu I, Sonoda N (1994) J Org Chem 59: 5824
[10] Kato S, Kabuto H, Ishihara H, Murai T (1985) Synthesis 520