Synthesis and photochemistry of novel 3,5-diacetyl-1,4-dihydropyridines. II [1]

DOI: 10.1007/s00706-003-0139-5

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Monatshefte fur Chemie p. 833 - 838 (2004)

Update date:2022-08-11

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Authors:

Memarian, Hamid R.

Bagheri, Mohammad

Doepp, Dietrich

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Article abstract of DOI:10.1007/s00706-003-0139-5

In continuation of previous work some novel 3,5-diacetyl-1,4- dihydropyridine derivatives were synthesized and their photochemical behavior was studied under oxygen and argon atmosphere. Oxidation of the dihydropyridine ring and formation of pyridine derivatives was the result of the reaction. The presence of oxygen affects not only on the rate of oxidation, but also the formation of some unidentified by-products was observed on irradiation under this atmosphere. Springer-Verlag 2004.

Full text of DOI:10.1007/s00706-003-0139-5

Monatshefte f€ur Chemie 135, 833–838 (2004)

DOI 10.1007/s00706-003-0139-5

Synthesis and Photochemistry

of Novel 3,5-Diacetyl-1,4-

dihydropyridines. II [1]

Hamid R. Memarian^1;ꢀ, Mohammad Bagheri , and Dietrich Dopp

University of Isfahan, Faculty of Sciences, Department of Chemistry,

81746-73441 Isfahan, Iran

€

Institut f€ur Chemie, Gerhard Mercator-Universitat=GH Duisburg, D-47048

Duisburg, Germany

Received September 23, 2003; accepted September 29, 2003

Published online February 5, 2004 # Springer-Verlag 2004

Summary. In continuation of previous work some novel 3,5-diacetyl-1,4-dihydropyridine derivatives

were synthesized and their photochemical behavior was studied under oxygen and argon atmosphere.

Oxidation of the dihydropyridine ring and formation of pyridine derivatives was the result of the

reaction. The presence of oxygen affects not only on the rate of oxidation, but also the formation of

some unidentiﬁed by-products was observed on irradiation under this atmosphere.

Keywords. Aromatization; 1,4-Dihydropyridines; Heterocycles; Photochemistry; Photooxidation.

Introduction

Recently we have reported on the synthesis and photochemistry of novel 3,5-

diacetyl-1,4-dihydropyridines 1a–1e [1]. These results indicated that besides the

presence or absence of oxygen atmosphere, the type and nature of the 4-sub-

stituent has an effect on the rate or type of reaction. Two types of reactions

have been observed: oxidation with retention and with expulsion of the 4-

substituent.

Our experience with the photochemistry of 1,4-dihydropyridine-3,5-diesters,

known as Hantzsch esters [2], showed also such dependence of the reaction on

both factors [3, 4]. In continuation of our recent work, we synthesized some

other novel 3,5-diacetyl-1,4-dihydropyridines 1f–1l and investigated their photo-

chemical behavior under oxygen and argon atmosphere. The aim of this work

was to study the effect of various substituents in position 4 on the rate or type of

reaction.

ꢀ

Corresponding author. E-mail: memarian@sci.ui.ac.ir

834

H. R. Memarian et al.

Scheme 1

Results and Discussion

A 15 ꢁ 10^ꢂ3M solution of 1f–1l in chloroform was irradiated under oxygen and

argon atmosphere until total disappearance of starting material. The results are

summarized in Table 1.

As shown in Table 1, only the product with retention of the 4-substituent was

obtained under both atmospheres, except for 1f. In this case, reaction under oxygen

atmosphere resulted in the formation of an unidentiﬁed salt, may be the pyridinium

salt. This is supported by the fact, that the isolated yield of products is lower in the

reaction under oxygen atmosphere than under argon atmosphere. The presence of

oxygen could induce a radical reaction and formation of HCl in chloroform solu-

tion, which leads to the formation of the pyridinium salt. Therefore we should

obtain a higher yield of product in reaction under argon atmosphere. Another

interesting result is that the irradiation time under oxygen is shorter than under

argon atmosphere, except for 1h. This should be due to the involvement of the

triplet excited state of 1h and quenching of this excited state by the presence of

oxygen.

Scheme 2

Novel 3,5-Diacetyl-1,4-dihydropyridines

835

Table 1. Irradiation of dihydropyridines 1f–1l under oxygen and argon atmosphere

O₂

Product (yield=%)^a

Time=h^b

Product (yield=%)^a

Time=h^b

–

3f (60)

3g (92)

3h(94)

3i (85)

3j (90)

3k (90)

3l (81)

13.5

3g (85)

3h (86)

3i (82)

3j (85)

3k (61)

3l (50)

8.25

Isolated yield; The irradiation times are given after total disappearance of the starting material

IR, H NMR, and UV data allowed the structural assignments of the photo-

products 3f–3l. A comparison of the IR spectra of educts and products showed the

disappearance of the NH band and a shift of the CO vibration to higher frequency

due to oxidation and aromatization of the ring, which cause a decrease in the

conjugation of the CO group with the C¼C bonds. H NMR spectra showed the

loss of the NH and C₄–H signals and aromatization of ring. Due to the missing

conjugation of the CO group with the pyridine ring, the signals of the methyl

groups in positions 2 and 6 are shifted upﬁeld and the protons of the acetyl groups

are shifted downﬁeld in comparison with the starting materials. Also, a comparison

of the UV spectra did not show any strong absorption above 300 nm, which indi-

cates aromatization of the ring and formation of pyridine derivatives.

Experimental

All melting points were determined with a Stuart Scientiﬁc SMP 2. IR: Shimadzu IR-435; ¹H NMR:

Bruker AW 80 (80 MHz); UV: Shimadzu UV-160; Mass spectra: Micromass Platform II: EI mode

(70 eV). Elemental analyses: Euro EA CHNS Analysator; the results agreed favourably with the

calculated values. Preparative thin layer chromatography (PLC) was carried out on 20ꢃ20cm²plates

coated with a 1 mm layer of Merck silica gel PF₂₅₄. Column chromatography: Merck silica gel 60, 70–

230 mesh ASTM.

All irradiations were performed using a 400W high-pressure Hg-vapour lamp from NARVA with

cooling of samples in Duran glass (ꢀ ꢄ 280 nm) by running cold H₂O. Ar (99.99%) or O₂(99.99%)

was bubbled through the solutions during irradiation.

General Procedure for the Preparation of 3,5-Diacetyl-1,4-dihydropyridines

A mixture of 0.05 mol of freshly distilled acetyl acetone, 0.025mol of the corresponding aldehyde, and

30cm³of conc. NH₃(in the case of 1f NH₃gas was used) in 15cm³of C₂H₅OH was reﬂuxed for the

time given. The solvent was evaporated, the precipitate was washed with cold diethyl ether, and

recrystallized from ethanol.

3,5-Diacetyl-2,4,6-trimethyl-1,4-dihydropyridine (1f, C₁₂H₁₇NO₂)

Reﬂuxed for 4 h, yield 32%, yellow crystals, mp 150–152^ꢅC; IR (KBr): ꢁꢀ¼ 3280 (NH), 1665 (CO)

cm^ꢂ1; ¹H NMR (CDCl₃): ꢂ ¼ 0.9 (d, J ¼ 7.2 Hz, 4-CH₃), 2.3 (s, 2- and 6-CH₃, 3- and 5-COCH₃), 3.8

836

H. R. Memarian et al.

(q, 4-H), 6.3 (brd s, NH) ppm; EI-MS: m=z (%) ¼ 208 [M^þþ1] (11), 207 [M^þ] (52), 192 [M^þ–CH₃]

(100), 176 [M^þ–2CH₃–H] (20), 164 [M^þ–CH₃CO] (37), 150 [M^þ–CH₃–CH₂CO] (66), 149 [M^þ–

CH₃–CH₃CO] (65), 106 [M^þ–CH₃–2CH₃CO] (57), 43 [CH₃CO^þ] (64); UV (CHCl₃): ꢀ (log ") ¼ 368

(3.82), 250 (3.98) nm.

3,5-Diacetyl-2,6-dimethyl-4-phenyl-1,4-dihydropyridine (1g, C₁₇H₁₉NO₂)

Reﬂuxed for 3 h, yield 31%, yellow crystals, mp 169–170^ꢅC; IR (KBr): ꢁꢀ¼ 3280 (NH), 1665 (CO)

cm^ꢂ1; ¹H NMR (CDCl₃): ꢂ ¼ 2.2 (s, 2- and 6-CH₃), 2.25 (s, 3- and 5-COCH₃), 5.05 (s, 4-H), 6.7 (brd s,

NH), 7.1 (s, C₆H₅) ppm; EI-MS: m=z (%) ¼ 270 [M^þþ1] (7), 269 [M^þ] (39), 268 [M^þ–H] (43), 254

[M^þ–CH₃] (13), 226 [M^þ–CH₃CO) (39), 192 [M^þ–C₆H₅–CH₃CO–CH₃] (16), 106 [M^þ–C₆H₅–

2CH₃CO] (15), 43 [CH₃CO^þ] (56); UV (CHCl₃): ꢀ (log ") ¼ 367 (3.55), 254 (3.88) nm.

3,5-Diacetyl-4-(4-chlorophenyl)-2,6-dimethyl-1,4-dihydropyridine (1h, C₁₇H₁₈NO₂Cl)

Reﬂuxed for 3 h, yield 26%, yellow crystals, mp 140–141^ꢅC; IR (KBr): ꢁꢀ¼ 3300 (NH), 1670 (CO)

cm^ꢂ1; ¹H NMR (CDCl₃): ꢂ ¼ 2.2 (s, 2- and 6-CH₃), 2.3 (s, 3- and 5-COCH₃), 5.2 (s, 4-H), 5.9 (brd s,

NH), 7.3 (s, C₆H₄) ppm; EI-MS: m=z (%) ¼ 305 [M^þCl] (67), 303 [M^þCl] (89), 288 [M^þ–CH₃)

(75), 262 [M^þ(³⁷Cl)–CH₃CO] (73), 260 [M^þ(³⁵Cl)–CH₃CO] (89), 192 [M^þ–C₆H₄Cl] (100), 149

[M^þ–C₆H₄Cl–CH₃CO] (81), 134 [M^þ–C₆H₄Cl–CH₃CO–CH₃] (88), 106 [M^þ–C₆H₄Cl–2CH₃CO]

(72) 43 [CH₃CO^þ] (81); UV (CHCl₃): ꢀ (log ") ¼ 368 (3.79), 252 (4.14) nm.

3,5-Diacetyl-4-(2-methoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine (1i, C₁₈H₂₁NO₃)

Reﬂuxed for 3.25h, yield 30%, yellow crystals, mp 172–173^ꢅC; IR (KBr): ꢁꢀ¼ 3280 (NH), 1670 (CO)

cm^ꢂ1; H NMR (CDCl₃): ꢂ ¼ 2.2 (s, 2- and 6-CH₃, 3- and 5-COCH₃), 3.75 (s, OCH₃), 5.3 (s, 4-H),

6.1 (brd s, NH), 6.8–7.1 (m, C₆H₄) ppm; EI-MS: m=z (%) ¼ 300 [M^þþ1] (4), 299 [M^þ] (11), 297

[M^þ–2H] (16), 284 [M^þ–CH₃] (110), 268 [M^þ–OCH₃] (85), 192 [M^þ–C₆H₄OCH₃] (100), 150 [M^þ–

C₆H₄OCH₃–CH₂CO] (61), 134 [M^þ–C₆H₄OCH₃–CH₃CO–CH₃] (36), 107 [C₆H₄OCH₃^þ] (22), 43

[CH₃CO^þ] (73); UV (CHCl₃): ꢀ (log ") ¼ 348 (3.84), 252 (4.03) nm.

3,5-Diacetyl-4-(3-methoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine (1j, C₁₈H₂₁NO₃)

Reﬂuxed for 3 h, yield 29%, yellow crystals, mp 196–198^ꢅC; IR (KBr); ꢁꢀ¼ 3260 (NH), 1660 (CO)

cm^ꢂ1; ¹H NMR (CDCl₃): ꢂ ¼ 2.3 (s, 2- and 6-CH₃), 2.4 (s, 3- and 5-COCH₃), 3.8 (s, OCH₃), 5.2 (s, 4-

H), 6.1 (brd s, NH), 6.7–7.3 (m, C₆H₄) ppm; EI-MS: m=z (%) ¼ 300 [M^þþ1] (50), 299 [M^þ] (82), 284

[M^þ–CH₃] (64), 256 [M^þ–CH₃CO] (83), 241 [M^þ–CH₃CO–CH₃] (16), 192 [M^þ–C₆H₄OCH₃] (100),

149 [M^þ–C₆H₄OCH₃–COCH₃] (76), 134 [M^þ–C₆H₄OCH₃–COCH₃–CH₃] (85), 106 [M^þ–

C₆H₄OCH₃–2COCH₃] (69), 92 [C₆H₄O^þ] (42), 43 [CH₃CO^þ] (85); UV (CHCl₃): ꢀ (log ") ¼ 366

(3.81), 252 (4.10) nm.

3,5-Diacetyl-4-(4-methoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine (1k, C₁₈H₂₁NO₃)

Reﬂuxed for 7 h, yield 33%, yellow crystals, mp 175–176^ꢅC; IR (KBr): ꢁꢀ¼ 3300 (NH), 1660 (CO)

cm^ꢂ1; ¹H NMR (CDCl₃): ꢂ ¼ 2.2 (s, 2- and 6-CH₃), 2.25 (s, 3- and 5-COCH₃), 3.7 (s, OCH₃), 5.0 (s, 4-

H), 6.5 (brd s, NH), 6.7–7.15 (m, C₆H₄) ppm; EI-MS: m=z (%) ¼ 300 [M^þþ1] (9), 299 [M^þ] (45), 298

[M^þ–H] (56), 284 [M^þ–CH₃] (19), 256 [M^þ–CH₃CO] (63), 240 [M^þ–CH₃CO–CH₃–H] (23), 192

[M^þ–C₆H₄OCH₃] (100), 149 [M^þ–C₆H₅OCH₃–CH₃CO] (20), 106 [M^þ–C₆H₅–2CH₃CO] (15), 43

[CH₃CO^þ] (12); UV (CHCl₃): ꢀ (log "): 368 (3.66), 253 (4.13) nm.

Novel 3,5-Diacetyl-1,4-dihydropyridines

837

3,5-Diacetyl-4-(3-nitrophenyl)-2,6-dimethyl-1,4-dihydropyridine (1l, C₁₇H₁₈N₂O₄)

Reﬂuxed for 2.75 h, yield 45%, yellow crystals, mp 210–211^ꢅC; IR (KBr): ꢁꢀ¼ 3300 (NH), 1670

(CO) cm^ꢂ1; H NMR (CDCl₃): ꢂ ¼ 2.25 (s, 2- and 6-CH₃), 2.4 (s, 3- and 5-COCH₃), 5.25 (s, 4-H),

6.35 (brd s, NH) 7.2–8.0 (m, C₆H₄) ppm; EI-MS: m=z (%) ¼ 314 [M^þ] (4), 297 [M^þ–OH] (17), 271

[M^þ–CH₃CO] (17), 192 [M^þ–C₆H₄NO₂] (100), 149 [M^þ–C₆H₄NO₂–CH₃CO] (16), 134 [M^þ–

C₆H₄NO₂–CH₃CO–CH₃] (13), 43 [CH₃CO^þ] (65); UV (CHCI₃): ꢀ (log ") ¼ 348 (3.74), 254

(4.31) nm.

General Procedure for the Irradiation of Dihydropyridines

A 0.015 M solution of 1f–1l in chloroform was irradiated under Ar or O₂atmosphere until total

disappearance of dihydropyridines was observed (TLC; the corresponding irradiation times are given

in Table 1). When the reaction was complete, the product was puriﬁed by chromatography.

3,5-Diacetyl-2,4,6-trimethylpyridine (3f, C₁₂H₁₅NO₂)

Column chromatography, petroleum ether=ethyl acetate (3=2), yield 60%, white crystals, mp 58–59^ꢅC;

IR (KBr): ꢁꢀ¼ 1700 (CO) cm^ꢂ1; ¹H NMR (CDCl₃): ꢂ ¼ 2.05 (s, 4-CH₃), 2.35 (s, 2- and 6-CH₃), 2.4 (s,

3- and 5-COCH₃) ppm; EI-MS: m=z (%) ¼ 205 [M^þ] (10), 190 [M^þ–CH₃] (24), 162 [M^þ–CH₃CO]

(8), 147 [M^þ–CH₃–CH₃CO] (2), 120 [M^þ–CH₃CO–CH₂CO] (21), 105 [M^þ–CH₃CO–CH₂CO–CH₃]

(5), 44 [CH₃COH^þ] (100), 43 [CH₃CO^þ] (64); UV (CHCl₃): ꢀ (log "): 272 (3.51) nm.

3,5-Diacetyl-2,6-dimethyl-4-phenylpyridine (3g, C₁₇H₁₇NO₂)

PLC, petroleum ether=ethyl acetate (5=3), yield 85%, mp 185–186^ꢅC; IR (KBr): ꢁꢀ¼ 1690 (CO) cm^ꢂ1

;

¹H NMR (CDCl₃): ꢂ ¼ 1.8 (s, 2- and 6-CH₃), 2.5 (s, 3- and 5-COCH₃), 7.1–7.6 (m, C₆H₅) ppm; EI-

MS: m=z (%) ¼ 268 [M^þþ1] (8), 267 [M^þ] (39), 252 [M^þ–CH₃] (47), 224 [M^þ–CH₃CO] (9), 210

[M^þ–CH₂CO–CH₃] (63), 209 [M^þ–CH₃CO–CH₃] (4), 191 [M^þ–C₆H₅] (2), 181 [M^þ–2CH₃CO] (5),

167 [M^þ–CH₃CO–CH₂CO–CH₃] (12), 43 [CH₃CO^þ] (100); UV (CHCl₃): ꢀ (log "): 252 (3.96) nm.

3,5-Diacetyl-4-(4-chlorophenyl)-2,6-dimethylpyridine (3h, C₁₇H₁₆NO₂Cl)

The solvent was evaporated and the residue was washed with cold ethanol, yield 86%, mp 174–175^ꢅC;

IR (KBr): ꢁꢀ¼ 1695 (CO) cm^ꢂ1; H NMR (CDCl₃): ꢂ ¼ 1.95 (s, 2- and 6-CH₃), 2.6 (s, 3- and 5-

COCH₃), 7.1–7.5 (m, C₆H₄) ppm; EI-MS: m=z (%) ¼ 303 [M^þCl] (83), 301 [M^þ³⁵Cl] (97), 288

[M^þ(³⁷Cl)–CH₃] (88), 286 [M^þ(³⁵Cl)–CH₃] (98), 260 [M^þ(³⁷Cl)–CH₃CO] (16), 258 [M^þ(³⁵Cl)–

CH₃CO] (46), 246 [M^þ(³⁷Cl)–CH₂CO–CH₃] (79), 244 [M^þ(³⁵Cl)–CH₂CO–CH₃] (94), 163 [M^þ–

C₆H₄Cl–CH₃CO] (16), 139 (100), 113 [C₆H₄³⁷Cl] (36), 111 [C₆H₄Cl] (8), 43 [CH₃CO^þ] (86); UV

(CHCl₃): ꢀ (log ") ¼ 248 (4.24) nm.

3,5-Diacetyl-4-(2-methoxyphenyl)-2,6-dimethylpyridine (3i, C₁₈H₁₉NO₃)

Column chromatography, petroleum ether=ethyl acetate (3=2), yield 82%, white crystals, mp 142–

143^ꢅC; IR (KBr): ꢁꢀ¼ 1695 (CO) cm^ꢂ1; ¹H NMR (CDCl₃): ꢂ ¼ 1.9 (s, 2- and 6-CH₃), 2.5 (s, 3- and 5-

COCH₃), 3.7 (s, OCH₃), 6.8–7.4 (m, C₆H₄) ppm; EI-MS: m=z (%) ¼ 298 [M^þþ1] (15), 297 [M^þ] (45),

282 [M^þ–CH₃] (24), 267 [M^þ–2CH₃] (10), 266 [M^þ–CH₃O] (39), 264 [M^þ–CH₃OH–H] (30), 249

[M^þ–CH₃OH–H–CH₃] (24), 224 [M^þ–CH₃CO–2CH₃] (28), 196 [M^þ–2CH₃CO–CH₃] (16), 132

[M^þ–C₆H₅OCH₃–CH₃CO–CH₃] (15), 57 [CH₂COCH₃] (100), 44 [CH₃COH^þ] (67), 43 [CH₃CO^þ]

(88); UV (CHCl₃): ꢀ (log ") ¼ 250 (3.82) nm.

838

H. R. Memarian et al.: Novel 3,5-Diacetyl-1,4-dihydropyridines

3,5-Diacetyl-4-(3-methoxyphenyl)-2,6-dimethylpyridine (3j, C₁₈H₁₉NO₃)

Column chromatography, petroleum ether=ethyl acetate (3=1), yield 85%, white crystals, mp 111–

113^ꢅC; IR (KBr): ꢁꢀ¼ 1690 (CO) cm^ꢂ1; ¹H NMR (CDCl₃): ꢂ ¼ 1.9 (s, 2- and 6-CH₃), 2.6 (s, 3- and 5-

COCH₃), 3.8 (s, OCH₃), 6.7–7.6 (m, C₆H₄) ppm; EI-MS: m=z (%) ¼ 299 [M^þþ2] (13), 298 [M^þþ1]

(66), 297 [M^þ] (83), 282 [M^þ–CH₃] (76), 264 [M^þ–CH₃OH–H] (81), 254 [M^þ–CH₃CO] (63), 240

[M^þ–CH₂O–CH₃] (84), 211 [M^þ–2CH₃CO] (29), 197 [M^þ–CH₃CO–CH₂CO–CH₃] (61), 196 [M^þ–

2CH₃CO–CH₃] (37), 132 [M^þ–C₆H₅OCH₃–CH₃CO–CH₃] (100), 44 [CH₃COH^þ] (67), 43 [CH₃CO^þ)

(88); UV (CHCl₃): ꢀ (log ") ¼ 249 (3.71) nm.

3,5-Diacetyl-4-(4-methoxyphenyl)-2,6-dimethylpyridine (3k, C₁₈H₁₉NO₃)

PLC, petroleum ether=ethyl acetate (5=2), yield 61%, white crystals, mp 164–165^ꢅC; IR (KBr):

ꢁꢀ¼ 1700 (CO) cm^ꢂ1; H NMR (CDCl₃): ꢂ ¼ 1.85 (s, 2- and 6-CH₃), 2.45 (s, 3- and 5-COCH₃),

3.8 (s, OCH₃), 6.8–7.2 (m, C₆H₄) ppm; EI-MS: m=z (%) ¼ 298 [M^þþ1] (66), 297 [M^þ] (100), 282

[M^þ–CH₃] (96), 266 [M^þ–CH₃O] (8), 264 [M^þ–CH₃OH–H] (45), 254 [M^þ–CH₃O] (44), 240 [M^þ–

CH₂O–CH₃] (94), 211 [M^þ–2CH₃CO] (18), 196 [M^þ–2CH₃CO–CH₃] (23), 132 [M^þ–C₆H₅OCH₃–

CH₃CO–CH₃] (21), 57 ½CH₂COCH₃ꢆ (11), 44 [CH₃COH^þ] (13), 43 [CH₃CO^þ] (66); UV (CHCl₃):

ꢀ (log ") ¼ 274 (4.08) nm.

3,5-Diacetyl-4-(3-nitrophenyl)-2,6-dimethylpyridine (3l, C₁₇H₁₆N₂O₄)

PLC, petroleum ether=ethyl acetate (3=2), yield 50%, mp 126–127^ꢅC; IR (KBr): ꢁꢀ¼ 1700 (CO) cm^ꢂ1

;

¹H NMR (CDCl₃): ꢂ ¼ 1.9 (s, 2- and 6-CH₃), 2.5 (s, 3- and 5-COCH₃), 7.5–8.2 (m, C₆H₄) ppm; EI-

MS: m=z (%) ¼ 313 [M^þþ1] (7), 312 [M^þ] (30), 297 [M^þ–CH₃] (91), 295 [M^þ–OH] (90), 294 [M^þ–

H₂O] (5), 282 [M^þ–NO] (6), 269 [M^þ–CH₃O] (6), 266 [M^þ–NO₂] (9), 251 [M^þ–NO₂–CH₃] (8), 236

[M^þ–NO₂–2CH₃] (37), 223 [M^þ–NO₂–COCH₃] (19), 208 [M^þ–NO₂–COCH₃–CH₃] (17), 165 [M^þ–

NO₂–2COCH₃–CH₃] (11), 44 [CH₃COH^þ] (16), 43 [CH₃CO^þ] (83), 42 [CH₂CO^þ] (100); UV

(CHCl₃): ꢀ (log ") ¼ 253 (4.06) nm.

Acknowledgments

We are grateful to the Isfahan University Research Council for partial support to this work. H. R.

Memarian is indebted to the German Academic Exchange Service (DAAD) for a scholarship during

July–August 2002.

References

€

[1] Part I: Memarian HR, Sadeghi MM, Momeni AR, Dopp D (2002) Monatsh Chem 133: 661

[2] Hantzsch A (1882) Justus Liebigs Ann Chem 215: 1

[3] Memarian HR, Sadeghi MM, Aliyan H (1998) Indian J Chem 37B: 219

[4] Memarian HR, Sadeghi MM, Momeni AR (1999) Indian J Chem 38B: 800

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