Manganese(III) acetate promoted acetoxylation of various α,β-unsaturated cyclopentanones

Article abstract of DOI:10.1016/S0040-4020(02)01634-4

We describe the results of manganese(III) acetate based regioselective oxidation of various α,β-unsaturated cyclopentanones leading to α′-acetoxy α,β-unsaturated cyclopentanones in good yields. Products due to monophenyl and diphenyl substituted dimerizat

Full text of DOI:10.1016/S0040-4020(02)01634-4

Tetrahedron 59 (2003) 1055–1058
Manganese(III) acetate promoted acetoxylation
of various a,b-unsaturated cyclopentanones
*
Cihangir Tanyeli, Ays¸egu¨l Tosun, Engin Turkut and Bengu¨ Sezen
Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey
Received 15 July 2002; revised 21 November 2002; accepted 12 December 2002
Abstract—We describe the results of manganese(III) acetate based regioselective oxidation of various a,b-unsaturated cyclopentanones
leading to a0-acetoxy a,b-unsaturated cyclopentanones in good yields. Products due to monophenyl and diphenyl substituted dimerization
have been identified as byproducts of the reaction. q 2003 Elsevier Science Ltd. All rights reserved.
1. Introduction
method for the a0-position of a,b-unsaturated cyclopenta-
nones prompted us to develop the method. We describe
herein the results obtained from the Mn(OAc)3 oxidation of
various a,b-unsaturated cyclopentanones and our optimi-
zation of the reaction conditions.
Synthetic methods for the selective oxidation of common
functional groups occupy a central position in organic
synthesis. In particular, regioselective oxidation of enones
to a0-acetoxy enones using lead(IV) acetate,1,2 MoOPh,3–5
triphenylphosphite ozonide (TPPO),6,7 MCPBA8,9 and
manganese(III) acetate10,11 has wide applicability. In the
literature, there are numerous examples of regioselective
oxidation of a,b-unsaturated cyclohexanone derivatives
using lead(IV)12–14 and manganese(III) acetate.15–17 How-
ever, only a few examples of lead(IV) acetate mediated
selective oxidation of a,b-unsaturated cyclopentanone
derivatives18 are to be found. Sasaki and Eguchi reported
that this procedure was not always effective.19 So far,
no general procedure for the synthesis of a0-acetoxy
a,b-unsaturated cyclopentanones has been reported with
manganese(III) acetate. The lack of a selective oxidation
2. Results and discussion
In the screening reactions, cyclopentenones 1 were
examined first with Mn(OAc)3 by varying the molar ratio
of substrate/oxidizing agent from 1:1 to 1:3 in benzene as
the solvent. A 1:2 molar ratio proved to be suitable for the
regioselective acetoxylation of cyclopentenones 1 to afford
products 2. Characterization of the major product revealed
that an acetoxy group had been introduced at the a0 position
2. The dimers 3 and 4 were also observed as minor
components (Scheme 1, Table 1).
Scheme 1.
Keywords: enones; manganese and compounds; oxidation.
*
Corresponding author. Tel.: þ90-312-210-32-22; fax: þ90-312-210-12-80; e-mail: tanyeli@metu.edu.tr
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)01634-4

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C. Tanyeli et al. / Tetrahedron 59 (2003) 1055–1058
Table 1. Selective oxidation of a,b-unsaturated cyclopentanones with Mn(OAc)3 in benzene
Entry
1
Reactant Product
2
Yield (%)
65
3
Yield (%)
4
Yield (%)
6
Time (h)
8
2a
–
4a
2a
2b
2c
79
81
–
4b
4c
7
8
10
11
3
3c
7
4b
2d
2e
77
63
–
–
4d
6
12
12
5c
–
a
2-Methyl-5-phenyl-2-cyclopentenone 8b was also isolated in 4% yield.
2,3-Dimethyl-5-phenyl-2-cyclopentenone 8d was also isolated in 7% yield.
No byproducts were isolated.
b
c
The reaction presumably proceeds via the formation of the
Mn(III) enolate 5c, w0hich loses Mn(II) upon one-electron
oxidation to give a -keto radical 6c20,21 (Scheme 2).
Oxidation of intermediate 6c by another equivalent of
Mn(OAc)3 provides a0-acetoxy cyclopentenones 2c.
3. Experimental
1H NMR spectra were recorded in CDCl3 on Bruker
Spectrospin Avance DPX 400 spectrometers. Chemical
shifts are given in ppm from tetramethylsilane. IR spectra
were obtained from a Perkin–Elmer Model 1600 series
FT-IR spectrometer and are reported in cm21. Mass spectra
were recorded on a Varian MAT 212. Thin layer
chromatography (TLC) was performed on Merck plastic-
backed silica gel plates. Compounds were visualized under
an UV lamp. Column chromatography was performed using
silica gel (Flash Silica 60, 32–63 mm). Cyclopentenones
were purchased from Aldrich.
In the screening reaction of entry 3, we found that the
product distribution depends mainly on the substrate/oxi-
dizing agent molar ratio. Using a 1:1 molar ratio,
compounds 2c, 3c and 4c were formed as a 5:3:2 mixture.
When the substrate/oxidizing agent molar ratio was 1:2, the
distribution of compounds 2c, 3c and 4c was found to be
8:1:1. A similar product distribution was obtained using a
1:3 molar ratio.
3.1. General procedure for the Mn(OAc)3 oxidation of
a,b-unsaturated ketones 2
In conclusion, Mn(OAc)3 oxidation of cyclopentenones can
be used to introduce an a0-acetoxy group. The applicability
of a one-pot oxidation method is attractive for further use in
synthesis.
A mixture of Mn(OAc)3 (3.25 g, 14.0 mmol) in benzene (or
corresponding solvent) (150 mL) was refluxed for 45 min
Scheme 2.

C. Tanyeli et al. / Tetrahedron 59 (2003) 1055–1058
1057
under a Dean-Stark trap, then cooled to room temperature.
3.2. Byproducts of the reaction
The cyclopentenone (7.0 mmol) was gradually added and
the mixture was allowed to reflux until the dark brown color
disappeared (TLC monitoring). The reaction mixture was
diluted with ethyl acetate (150 mL) and the organic phase
was washed with 1 M HCl (150 mL), saturated NaHCO3
(150 mL) and brine (150 mL). The organic phase was dried
over MgSO4 and evaporated in vacuo. The crude product
mixture was separated by flash column chromatography
using ethyl acetate/hexane as eluent to afford the products
noted in Table 1.
3.2.1. 4,40-Dimethyl-1-phenyl-bicyclopentyl-3,30-diene-
2,20-dione 3c. (0.13 g, 7%) as a colorless oil; Rf (EtOAc/
hexane 1:3) 0.33; nmax (neat) 1717, 1623, 755 cm21; dH
(400 MHz, CDCl3) (7:3 diastereomeric mixture) (major
isomer) 7.03–7.27 (5H, m, Ph), 5.97 (1H, s, CHv), 5.94
(1H, s, CHv), 3.49–3.53 (1H, m, CHCO), 3.20–3.25 (1H,
m, CHaHbCPh), 3.00 (2H, m, CH2CHCO), 2.61 (1H, m,
CHaHbCPh), 2.17 (3H, s, MeCv), 2.16 (3H, s, MeCv);
(minor isomer) 7.03–7.27 (5H, m, Ph), 5.93 (1H, s, CHv),
5.90 (1H, s, CHv), 3.49–3.53 (1H, m, CHCO), 3.20–3.25
(1H, m, CHaHbCPh), 3.00 (2H, m, CH2CHCO), 2.61 (1H,
m, CHaHbCPh), 2.15 (3H, s, MeCv), 2.13 (3H, s, MeCv);
dC (100.6 MHz, CDCl3) (major isomer) 209.0, 207.2, 177.8,
169.8, 156.0, 137.8, 129.5, 128.9, 128.7, 128.5, 127.6,
124.5, 84.6, 52.7, 42.8, 35.5, 21.7, 19.6; (minor isomer)
202.0, 200.6, 173.9, 159.5, 139.8, 130.7, 129.8, 128.8,
128.6, 128.4, 125.6, 126.9, 124.6, 85.4, 46.9, 38.8, 21.1,
19.4; m/z (EI) 266 (6), 232 (9), 172 (100), 171 (74), 141
(10), 128 (39), 105 (42), 77 (26%); HRMS (EI):
(M2C6H8O), found 172.0885. C12H10O requires 172.0888.
3.1.1. 5-Acetoxy-2-cyclopentenone 2a. (0.64 g, 65%) as a
colorless oil; Rf (EtOAc/hexane 1:3) 0.38; nmax (neat) 1743,
1635 cm21; dH (400 MHz, CDCl3) 7.76–7.78 (1H, m,
CHvCHCO), 6.34–6.36 (1H, m, CHvCHCO), 5.20 (1H,
dd, J¼3, 7 Hz, CHOAc), 3.21–3.29 (1H, m, CHaHbCHOAc),
2.66–2.73 (1H, ddd, J¼3, 5, 19 Hz, CHaHbCHOAc), 2.22
(3H, s, MeCO2); dC (100.6 MHz, CDCl3) 202.5, 174.2,
169.1, 129.3, 75.2, 40.4, 21.2; HRMS (EI): Mþ, found
140.0468. C7H8O3 requires 140.0473.
3.1.2. 5-Acetoxy-2-methyl-2-cyclopentenone 2b. (0.85 g,
79%) as a colorless oil; Rf (EtOAc/hexane 1:2) 0.35; nmax
(neat) 3018, 2926, 1730, 1716, 1216 cm21; dH (400 MHz,
CDCl3) 7.05 (1H, d, J¼7 Hz, CHCvCMe), 4.90 (1H, d, J¼
7 Hz, CHOAc), 2.80–2.85 (1H, ddd, J¼7, 7, 18 Hz,
CHaHbCHOAc), 2.24 (1H, d, J¼18 Hz, CHaHbCHOAc),
1.91 (3H, s, MeCO2), 1.58 (3H, s, MeCv); dC (100.6 MHz,
CDCl3) 204.2, 170.9, 155.2, 140.9, 72.2, 34.1, 21.1, 10.8;
m/z (EI) 154 (100), 112 (6%); HRMS (EI): Mþ, found
154.0625. C8H10O3 requires 154.0630.
3.2.2. 1,10-Diphenyl-bicyclopentyl-3,30-diene-2,20-dione
4a. (0.13 g, 6%) as a colorless oil; Rf (EtOAc/hexane 1:3)
0.36; nmax (neat) 1673, 1632, 785 cm21; dH (400 MHz,
CDCl3) (8:2 diastereomeric mixture) (major isomer) 7.44–
7.52 (2£1H, m, CHvCHCO), 7.07–7.35 (2£5H, m, Ph),
6.06–6.12 (2£1H, m, CHvCHCO), 2.65–3.25 (2£2H, m,
CH2); (minor isomer) 7.38–7.41 (2£1H, m, CHvCHCO),
7.07–7.35 (2£5H, m, Ph), 6.01–6.04 (2£1H, m,
CHvCHCO), 2.65–3.25 (2£2H, m, CH2); dC
(100.6 MHz, CDCl3) (major isomer) 204.3, 200.3, 177.3,
176.5, 144.7, 135.3, 130.2, 128.6, 128.4, 128.1, 127.8,
127.6, 127.3, 71.5, 71.3, 45.4, 43.2; (minor isomer) 200.1,
175.8, 142.3, 129.5, 128.5, 128.2, 127.5, 71.0, 44.1; m/z (EI)
314 (100), 252 (7), 158 (23%). HRMS (EI): Mþ, found
314.1313. C22H18O2 requires 314.1306.
3.1.3. 5-Acetoxy-3-methyl-2-cyclopentenone 2c. (0.87 g,
81%) as a colorless oil; Rf (EtOAc/hexane 1:3) 0.36; nmax
(neat) 1740, 1629 cm21; dH (400 MHz, CDCl3) 5.91 (1H, s,
CHv), 5.05 (1H, dd, J¼3, 7 Hz, CHOAc), 2.96 (1H, dd,
J¼7, 18 Hz, CHaHbCHOAc), 2.43 (1H, dd, J¼3, 18 Hz,
CHaHbCHOAc), 2.09 (3H, s, MeCO2), 2.05 (3H, s, MeCv);
dC (100.6 MHz, CDCl3) 203.6, 176.2, 170.8, 129.1, 73.1,
40.0, 21.1, 20.1; HRMS (EI): Mþ, found 154.0628.
C8H10O3 requires 154.0630.
3.2.3. 3,30-Dimethyl-1,10-diphenyl-bicyclopentyl-3,30-
diene-2,20-dione 4b. (0.17 g, 7%) as a colorless oil; Rf
(EtOAc/hexane 1:2) 0.33; nmax (neat) 1680, 1644,
787 cm21; dH (400 MHz, CDCl3) (7:3 diastereomeric
mixture) (major isomer) 7.05–7.53 (2£5H, m, Ph), 6.91–
7.01 (2£1H, m, CHv), 2.91–3.94 (2£2H, m, CH2), 1.47
(3H, s, MeCv), 1.42 (3H, s, MeCv); (minor isomer) 7.05–
7.53 (2£5H, m, Ph), 6.81 (2£1H, d, J¼7 Hz, CHv), 2.91–
3.94 (2£2H, m, CH2), 1.47 (2£3H, s, MeCv); dC
(100.6 MHz, CDCl3) (major isomer) 204.0, 202.5, 177.6,
177.2, 143.4, 140.5, 131.5, 129.2, 129.4, 128.6, 128.5,
127.9, 127.8, 127.5, 127.4, 127.1, 74.5, 70.6, 46.2, 45.3,
20.8, 19.3; (minor isomer) 200.6, 176.2, 143.1, 129.0, 128.9,
128.3, 127.6, 74.1, 45.0, 20.5; m/z (EI) 342 (100), 278 (26),
172 (33%). HRMS (EI): Mþ, found 342.1636. C24H22O2
requires 342.1620.
3.1.4. 5-Acetoxy-2,3-dimethyl-2-cyclopentenone 2d.
(0.90 g, 77%) as a colorless oil; Rf (EtOAc/hexane 1:4)
0.36; nmax (neat) 3018, 2923, 1742, 1708, 1219 cm21
;
dH (400 MHz, CDCl3) 5.05 (1H, d, J¼6 Hz, CHOAc),
2.89–2.95 (1H, dd, J¼6, 18 Hz, CHaHbCHOAc), 2.37 (1H,
d, J¼18 Hz, CHaHbCHOAc), 2.06 (3H, s, MeCO2), 2.00
(3H, s, MeCvCMeCO), 1.66 (3H, s, MeCOCv); dC
(100.6 MHz, CDCl3) 203.6, 170.9, 167.7, 135.4, 72.0, 39.1,
21.1, 17.5, 8.3; m/z (EI) 168 (100), 126 (23), 108 (8%);
HRMS (EI): Mþ, found 168.0779. C9H12O3 requires 168.0786.
3.1.5. 5-Acetoxy-4,4-dimethyl-2-cyclopentenone 2e.
(0.74 g, 63%) as a colorless oil; Rf (EtOAc/hexane 1:3)
0.34; nmax (neat) 2968, 2929, 2871, 1738, 1721, 1236 cm21
;
3.2.4. 4,40-Dimethyl-1,10-diphenyl-bicyclopentyl-3,30-
diene-2,20-dione 4c. (0.19 g, 8%) as a colorless oil;
Rf (EtOAc/hexane 1:3) 0.32; nmax (neat) 1687, 1631,
780 cm21; dH (400 MHz, CDCl3) (7:3 diastereomeric
mixture) (major isomer) 6.99–7.20 (2£5H, m, Ph), 5.64–
5.68 (2£1H, m, CHv), 3.85–3.90 (2£1H, m, CHaHb),
2.48–2.54 (2£1H, m, CHaHb), 1.99 (3H, s, MeCv), 1.97
dH (400 MHz, CDCl3) 7.30 (1H, d, J¼6 Hz, CHvCHCO),
5.88 (1H, d, J¼6 Hz, CHvCHCO), 4.85 (1H, s, CHOAc),
1.98 (3H, s, MeCO2), 1.13 (3H, s, MeMeC), 0.86 (3H, s,
MeMeC); dC (100.6 MHz, CDCl3) 203.3, 171.7, 170.5,
129.3, 80.0, 44.4, 26.2, 23.5, 20.7; HRMS (EI): Mþ, found
168.0782. C9H12O3 requires 168.0786.

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C. Tanyeli et al. / Tetrahedron 59 (2003) 1055–1058
(3H, s, MeCv); (minor isomer) 6.99–7.20 (2£5H, m, Ph),
5.74 (2£1H, s, CHv), 3.85–3.90 (2£1H, m, CHaHb), 2.48–
2.54 (2£1H, m, CHaHb), 1.99 (2£3H, s, MeCv); dC
(100.6 MHz, CDCl3) (major isomer) 208.9, 206.5, 177.8,
176.7, 140.4, 139.7, 130.4, 129.9, 129.7, 128.7, 128.6,
128.5, 128.3, 128.2, 128.1, 127.6, 127.5, 127.4, 127.0, 74.1,
60.1, 53.2, 45.9, 20.1, 19.7; (minor isomer) 206.1, 177.1,
140.2, 129.5, 127.7, 128.9, 127.3, 74.4, 53.1, 20.4; m/z (EI)
342 (13), 172 (100), 141 (3), 128 (12), 115 (4), 77 (3%).
HRMS (EI): (M2C12H10O), found 172.0888. C12H12O
requires 172.0888.
grants (no. AFP-2001-01-03-04 and AFP-2001-07-02-00-
22), the Turkish Scientific and Technical Research Council
for a grant [no. TBAG-1883 (100T026)], Turkish State
Planning Organization for a grant (no. BAP-07-02-DPT-
2002 K120540-04).
References
1. Rawlinson, D. J.; Sosnovsky, G. Synthesis 1973, 567–603.
2. (a) Criegee, R. Angew. Chem. 1958, 70, 173. (b) Criegee, R.
In Oxidation in Organic Chemistry, Part A, Wiberg, K. B.,
Ed.; Academic: New York, 1965; Chapter 5. (c) Criegee, R.
Newer Methods of Preparative Organic Chemistry, Foerst,
W., Ed.; Academic: New York, 1963; Vol. 2.
3. Murai, A.; Ono, M.; Abiko, A.; Masamune, T. J. Am. Chem.
Soc. 1978, 100, 7751–7753.
3.2.5. 3,30,4,40-Tetramethyl-1,10-diphenyl-bicyclopentyl-
3,30-diene-2,20-dione 4d. (0.16 g, 6%) as a colorless oil;
Rf (EtOAc/hexane 1:4) 0.33; nmax (neat) 3835, 3742, 3615,
1691, 1651 cm21; dH (400 MHz, CDCl3) (6:4 diastereo-
meric mixture) (major isomer) 7.06–7.18 (2£5H, m, Ph),
3.79–3.84 (2£1H, m, CHaHb), 2.39–2.48 (2£1H, m,
CHaHb), 1.88 (3H, s, MeCvCMe), 1.86 (3H, s,
MeCvCMe), 1.53 (3H, s, MeCvCMe), 1.52 (3H, s,
MeCvCMe); (minor isomer) 7.06–7.18 (2£5H, m, Ph),
3.79–3.84 (2£1H, m, CHaHb), 2.39–2.48 (2£1H, m,
CHaHb), 1.88 (2£3H, s, MeCvCMe), 1.53 (2£3H, s,
MeCvCMe); dC (100.6 MHz, CDCl3) (major isomer)
206.4, 202.4, 177.1, 175.2, 145.4, 142.1, 130.2, 129.7,
129.3, 128.8, 128.4, 128.2, 127.8, 127.5, 127.2, 127.1, 76.1,
75.3, 44.6, 44.2, 20.2, 19.8, 19.2, 9.8; (minor isomer) 204.5,
175.8, 143.6, 129.9, 128.7, 128.6, 127.9, 127.4, 75.8, 46.7,
17.3, 10.9; m/z (EI) 370 (2), 186 (100), 142 (11%); HRMS
(EI): Mþ, found 370.1932. C26H26O2 requires 370.1934.
4. Vedejs, E.; Engler, D. A.; Telschow, J. E. J. Org. Chem. 1978,
43, 188–196.
5. Mimoun, H.; Seree de Roche, L.; Sajus, L. Bull. Soc. Chim. Fr.
1969, 1481–1492.
6. Iwata, C.; Takemoto, Y.; Nakamura, Y.; Imanishi, T.
Tetrahedron Lett. 1985, 26, 3227–3230.
7. Iwata, C.; Takemoto, Y.; Kubota, H.; Kuroda, T.; Imanishi, T.
Tetrahedron Lett. 1985, 26, 3231–3234.
8. Rubottom, G.; Gruber, J. M. J. Org. Chem. 1978, 43,
1599–1602.
9. Musser, A. K.; Fuchs, P. L. J. Org. Chem. 1982, 47,
3121–3131.
10. Arndt, D. Manganese Compounds as Oxidizing Agents in
Organic Chemistry, Open Court: La Salle IL, 1981; Chapter 1.
11. de Klein, W. J. In Organic Syntheses by Oxidation with
Metal Compounds, Mijs, W. J., de Jonge, C. R. H., Eds.;
Plenum: New York, 1986; Chapter 4.
3.2.6. 2-Methyl-5-phenyl-2-cyclopentenone 8b. (0.05 g,
4%) as a colorless oil; Rf (EtOAc/hexane 1:2) 0.38; nmax
(neat) 3010, 2913, 1692, 1643, 782 cm21; dH (400 MHz,
CDCl3) 7.16–7.37 (5H, m, Ph), 7.07 (1H, d, J¼7 Hz,
CHv), 3.49 (1H, dd, J¼2, 7 Hz, CHPh), 3.01–3.07 (1H, m,
CHaHb), 2.60 (1H, dd, J¼2, 19 Hz, CHaHb), 1.77 (3H, s,
MeCv); dC (100.6 MHz, CDCl3) 206.3, 177.2, 140.5,
130.5, 129.2, 128.7, 127.9, 127.1, 126.9, 61.2, 44.1, 17.3;
HRMS (EI): Mþ, found 172.0886. C12H12O requires
172.0888.
12. Ellis, J. W. J. Org. Chem. 1969, 34, 1154.
13. Oppolzer, W.; Sarkar, T.; Mahalanabis, K. K. Helv. Chim.
Acta 1976, 59, 2012–2020.
14. Wenkert, E.; Golob, N. F.; Smith, R. A. J. J. Org. Chem. 1973,
38, 4068–4070.
15. Williams, G. J.; Hunter, N. R. Can. J. Chem. 1976, 54,
3830–3832.
3.2.7.
2,3-Dimethyl-5-phenyl-2-cyclopentenone
8d.
16. Dunlap, N. K.; Sabol, M. R.; Watt, D. S. Tetrahedron Lett.
1984, 25, 5839–5842.
(0.09 g, 7%) as a colorless oil; Rf (EtOAc/hexane 1:4)
0.39; nmax (neat) 3025, 2933, 1668, 1632 cm21; dH
(400 MHz, CDCl3) 7.02–7.52 (5H, m, Ph), 3.47 (d, 1H,
J¼7 Hz),1.67 (s, 3H), 2.03 (s, 3H), 2.50 (d, 1H, J¼18 Hz),
2.91–2.98 (dd, 1H, J¼7, 18 Hz). 13C NMR: d 10.1, 17.8,
45.2, 75.3, 127.2, 127.4, 127.8, 128.4, 129.1, 130.2, 143.4,
176.1, 204.5; m/z (EI) 186 (100), 171 (46), 143 (46), 128
(23), 104 (15%); HRMS (EI): Mþ, found 186.1040.
C13H14O requires 186.1045.
17. Demir, A. S.; Gross, R. S.; Dunlap, N. K.; Hashemi, A. B.;
Watt, D. S. Tetrahedron Lett. 1986, 27, 5567–5570.
18. Russel, G. A.; Blankespoor, R. L.; Trahanowsky, K. D.;
Chung, C. S. C.; Whittle, P. R.; Mattox, J.; Myers, C. L.;
Penny, R.; Ku, T.; Kosugi, Y.; Givens, R. S. J. Am. Chem. Soc.
1975, 97, 1906–1911.
19. Sasaki, T.; Eguchi, S. Bull. Chem. Soc. Jpn 1968, 41,
2453–2457.
20. Snider, B. B.; Kiselgof, E. Y. Tetrahedron 1996, 52,
6073–6084.
Acknowledgements
21. Vinogradov, M. G.; Verenchikov, S. P.; Fedora, T. M.;
Nikishin, G. I. Zh. Org. Khim. 1975, 11, 947–952.
We thank the Middle East Technical University for the