One-pot three-component synthesis of 2-(alkylimino)-7-oxo-1-oxa-6- azaspiro[4.4]nona-3,8-diene-3,4-dicarboxylates

Article abstract of DOI:10.1002/hlca.200800324

The reactive zwitterionic 1:1 intermediate 6 generated in situ from the reaction between an isocyanide 2 and a dialkyl acetylenedicarboxylate (=dialkyl but-2-ynedioate) 3 was trapped by an N-arylmaleimide or -phthalimide 4 to produce a highly functionaliz

Full text of DOI:10.1002/hlca.200800324

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Helvetica Chimica Acta – Vol. 92 (2009)
One-Pot Three-Component Synthesis of 2-(Alkylimino)-7-oxo-1-oxa-6-
azaspiro[4.4]nona-3,8-diene-3,4-dicarboxylates
by Mehdi Adib*a), Setareh Moghimia), Mohammad Hosein Sayahia), and Hamid Reza Bijanzadehb)
a) School of Chemistry, University College of Science, University of Tehran, P. O. Box 14155-6455,
Tehran, Iran (phone/fax: þ 98-21-66495291; e-mail: madib@khayam.ut.ac.ir)
b) Department of Chemistry, Tarbiat Modarres University, P. O. Box 14115-175, Tehran, Iran
The reactive zwitterionic 1:1 intermediate 6 generated in situ from the reaction between an
isocyanide 2 and a dialkyl acetylenedicarboxylate (¼dialkyl but-2-ynedioate) 3 was trapped by an N-
arylmaleimide or -phthalimide 4 to produce a highly functionalized 1-oxa-6-azaspiro[4.4]nona-3,8-diene-
3,4-dicarboxylate 5 in excellent yield (Scheme and Table).
Introduction. – Multicomponent reactions (MCRs) have emerged as an efficient
and powerful tool in modern synthetic organic chemistry due to their valued features
such as atom economy, straightforward reaction design, and the opportunity to
construct target compounds by the introduction of several diverse functions in a single
chemical event. Typically, purification of products resulting from MCRs is also simple
since all the organic reagents employed are consumed and are incorporated into the
target compound [1]. MCRs leading to interesting heterocyclic scaffolds are
particularly useful for the construction of diverse chemical libraries of ꢀdrug-likeꢁ
molecules. The isocyanide-based MCRs are especially important in this area [1g][1h].
Spiro compounds having cyclic structures connected at a C-atom are of interest due
to their interesting conformational features and their structural implications on
biological systems. The asymmetric character of a molecule due to the stereogenic spiro
C-atom is one of the important criteria of the biological activities [2][3]. Spiroaminals
represent an important class of naturally occurring spiro compounds characterized by
their highly pronounced biological properties [4 – 7]. For example, azaspiracids 1 are
the causative agents of a recently defined class of human poisoning resulting from
consumption of tainted shellfish [8].
In the arena of photochromism, spiroaminals, due to their steric constraints,
equilibrate with the corresponding non-spiro analogue and exhibit various photo-
chemical phenomena [9]. Some more related applications based on this equilibrium are
self-development photography, actinometry, displays, and filters and lenses of variable
optical density [10].
The development of new methods for the synthesis of spiroaminals has thus
attracted much attention in recent years [11].
Results and Discussion. – As part of current studies of our group and others on the
development of multicomponent reactions of isocyanides and electron-deficient
ꢂ 2009 Verlag Helvetica Chimica Acta AG, Zꢃrich

Helvetica Chimica Acta – Vol. 92 (2009)
945
acetylenic compounds for the preparation of biologically active heterocyclic com-
pounds [12][13], we report herein a simple one-pot three-component synthesis of
highly functionalized 1-oxa-6-azaspiro[4.4]nona-3,8-dienes using simple starting mate-
rials. Thus, a mixture of an isocyanide 2 and a dialkyl acetylenedicarboxylate (¼dialkyl
but-2-ynedioate) 3 in the presence of a cyclic conjugated imide 4 underwent a smooth
1:1:1 addition reaction in anhydrous CH2Cl2 at room temperature to produce. within
24 h, a 2-(alkylimino)-7-oxo-1-oxa-6-azaspiro[4.4]nona-3,8-diene-3,4-dicarboxylate 5
in 85 – 97% yield (Scheme and Table).
Schemea)
a) See Table for 4, R and R’.
The structures of the isolated products 5a – 5j were deduced from their elemental
1
analyses and their IR, H- and 13C-NMR, and MS data. The MS of 5a displayed the
molecular-ion (Mþ) peak at m/z 424, which was consistent with the 1:1:1 adduct of
cyclohexyl isocyanide, dimethyl acetylenedicarboxylate, and N-phenylmaleimide. The
1H-NMR spectrum of 5a exhibited two sharp s for the two MeO groups (d(H) 3.73 and
3.80), two d (d(H) 6.47 and 6.91 (J ¼ 5.8)) for the two H-atoms of the five-membered
aza ring, and characteristic signals with appropriate chemical shifts and coupling
constants for eleven cyclohexyl H-atoms and five aromatic H-atoms. The 1H-decoupled
13C-NMR spectrum of 5a showed 21 distinct signals, in agreement with the proposed
structure (see Exper. Part). The 1H- and 13C-NMR spectra of the products 5b – 5j were
similar to those of 5a, except for the 2-(alkylimino) function, the ester groups, and the
aza-ring moiety; they all exhibited characteristic signals with appropriate chemical
shifts and coupling constants (see Exper. Part).

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Helvetica Chimica Acta – Vol. 92 (2009)
Table. Reaction of Isocyanides 2 with Acetylenedicarboxylates 3 and Cyclic Conjugated Imides 41)
Product
R
R’
4
Yield
[%]
Product
R
R’
4
Yield
[%]
5a
Me
93
85
94
91
90
5f
Et
90
92
92
87
97
5b
5c
5d
5e
Et
5g
5h
5i
Me
Et
Me
Et
Me
Et
Me
5j
a) Reaction conditions: In anh. CH2Cl2 at r.t. for 24 h.
On the basis of the well-established chemistry of isocyanides [1g][1h][14 – 17], it is
reasonable to assume that the 1-oxa-6-azaspiro[4.4]nona-3,8-diene-3,4-dicarboxylates 5
apparently result from the initial addition of the isocyanides to the acetylenedicarbox-
ylates esters and subsequent nucleophilic attack of the zwitterionic 1:1 intermediates 6
on the C¼O group of 4 and formation of the 1:1:1 adducts 7. The intramolecular
addition of the alkoxide to the nitrilium moiety within 7 yields the iminofuran
derivatives 5 (Scheme).
In summary, we have demonstrated that the one-pot three-component reaction
between isocyanides, dialkyl acetylenedicarboxylates, and cyclic conjugated imides
provides a simple method for the preparation of 2-(alkylimino)-7-oxo-1-oxa-6-
azaspiro[4.4]nona-3,8-diene-3,4-dicarboxylates of potential synthetic and pharmaco-
logical interest. Excellent yields of the products, the ready availability of the starting
materials, as well as mild reaction conditions and simplicity of the reaction are the main
advantages of this method. The present transformation has the additional advantage of
being performed under neutral conditions and requiring no activation or modification
of the starting materials.

Helvetica Chimica Acta – Vol. 92 (2009)
947
This research was supported by the Research Council of the University of Tehran as a research project
(6102036/1/03).
Experimental Part
General. Dimethyl and diethyl acetylenedicarboxylates, cyclohexyl and 1,1,3,3-tetramethylbutyl
isocyanides, as well as imides 4 were obtained from Merck (Germany), and were used without further
purification. Column chromatography (CC): silica gel 60 (SiO2; Merck). Melting points (M.p.):
1
Electrothermal-9100 apparatus; uncorrected. IR Spectra: Shimadzu-IR-460 spectrometer; in cmꢀ1. H-
and 13C-NMR Spectra: Bruker-DRX-500-Avance (at 500.1 and 125.8 MHz, resp.) and Bruker-DPX-250
(at 250.1 and 62.9 MHz, resp.) instruments; in CDCl3; d in ppm rel. to Me4Si (¼0 ppm), J in Hz. EI-MS
(20 eV): Agilent-Technologies-(HP)-5973 mass spectrometer; in m/z (rel. %). Elemental analyses:
Heraeus-CHN-O-Rapid analyzer.
Preparation of Compounds 5: General Procedure. To a magnetically stirred soln. of 3 (1 mmol) and 4
(1 mmol) in anh. CH2Cl2 (6 ml), was added dropwise a soln. of 2 (1 mmol) in anh. CH2Cl2 (2 ml) at 258
over 10 min. The mixture was stirred for 24 h. The solvent was evaporated and the residue purified by CC
(SiO2, hexane/AcOEt 3 :1) and recrystallization (hexane/AcOEt 1:1).
Dimethyl 2-(Cyclohexylimino)-7-oxo-6-phenyl-1-oxa-6-azaspiro[4.4]nona-3,8-diene-3,4-dicarboxyl-
ate (5a). Yield 93%. Colorless crystals. M.p. 187 – 1888. IR (KBr): 1788, 1753, 1732, 1701, 1659 (C¼O),
1
1466, 1420, 1373, 1344, 1317, 1275, 1215, 1090, 1011, 945, 918, 878, 752. H-NMR (500.1 MHz, CDCl3):
1.20 – 1.74 (m, 10 H); 3.65 – 3.71 (m, 1 H); 3.73 (s, 3 H); 3.80 (s, 3 H); 6.47 (d, J ¼ 5.8, 1 H); 6.91 (d, J ¼
5.8, 1 H); 7.15 (d, J ¼ 8.0, 2 H); 7.30 (t, J ¼ 7.0, 1 H); 7.33 – 7.37 (m, 2 H). 13C-NMR (125.8 MHz, CDCl3):
24.5; 24.6; 25.6; 33.3; 33.4; 52.8; 53.1; 57.1; 101.2; 126.8; 128.1; 129.3; 129.7; 133.8; 137.0; 140.6; 142.7;
151.0; 159.7; 161.2; 168.7. EI-MS: 424 (5, Mþ), 373 (100), 289 (45), 169 (75), 92 (24), 77 (20). Anal. calc.
for C23H24N2O6 (424.45): C 65.08, H 5.70, N 6.60; found: C 64.89, H 5.79, N 6.51.
Diethyl 2-(Cyclohexylimino)-7-oxo-6-phenyl-1-oxa-6-azaspiro[4.4]nona-3,8-diene-3,4-dicarboxylate
(5b). Yield 85%. Colorless crystals. M.p. 96 – 978. IR (KBr): 1747, 1718, 1688 (C¼O), 1495, 1448, 1377,
1361, 1339, 1271, 1246, 1097, 1026, 951, 829, 762, 716. 1H-NMR (250.1 MHz, CDCl3): 1.20 – 1.75 (m, 10 H);
1.23, 1.27 (2t, J ¼ 7.3, 6 H); 3.65 – 3.76 (m, 1 H); 4.19 (q, J ¼ 7.3, 2 H); 4.28 (q, J ¼ 7.3, 2 H); 6.47 (d, J ¼ 6.0,
1 H); 6.93 (d, J ¼ 6.0, 1 H); 7.15 – 7.19 (m, 2 H); 7.25 – 7.39 (m, 3 H). 13C-NMR (62.9 MHz, CDCl3): 13.8;
13.9; 24.5; 24.6; 25.7; 33.3; 33.4; 56.9; 62.1; 62.4; 101.3; 126.8; 128.1; 129.3; 129.6; 133.8; 136.9; 140.6;
142.9; 151.2; 159.3; 160.8; 168.8. EI-MS: 452 (7, Mþ), 401 (100), 317 (60), 254 (27), 197 (81), 120 (19), 77
(17). Anal. calc. for C25H28N2O6 (452.51): C 66.36, H 6.24, N 6.19; found: C 66.22, H 6.30, N 6.03.
Dimethyl 5-(Cyclohexylimino)-2’,3’-dihydro-3’-oxo-2’-phenylspiro[furan-2(5H),1’-[1H]isoindole]-
3,4-dicarboxylate (5c). Yield. 94%. Colorless crystals. M.p. 155 – 1568. IR (KBr): 1755, 1728, 1690,
1655 (C¼O), 1492, 1436, 1350, 1284, 1261, 1174, 1039, 970, 883, 746, 702. 1H-NMR (250.1 MHz, CDCl3):
1.24 – 1.75 (m, 10 H); 3.60 (s, 3 H); 3.61 – 3.65 (m, 1 H); 3.84 (s, 3 H); 7.25 (dd, J ¼ 7.9, 1.4, 2 H); 7.35 – 7.44
(m, 4 H); 7.62 – 7.67 (m, 2 H); 7.96 – 8.02 (m, 1 H). 13C-NMR (62.9 MHz, CDCl3): 24.5; 24.6; 25.6; 33.2;
33.4; 52.8; 53.2; 57.1; 100.1; 122.0; 124.4; 127.4; 128.5; 129.4; 131.0; 131.2; 133.3; 134.0; 137.7; 140.0; 140.5;
151.5; 159.7; 161.3; 166.9. EI-MS: 474 (29, Mþ), 442 (38), 392 (67), 377 (65), 317 (81), 301 (100), 290
(54), 231 (83), 202 (70), 163 (48), 69 (48), 55 (74). Anal. calc. for C27H26N2O6 (474.51): C 68.34, H 5.52, N
5.90; found: C 68.19, H 5.61, N 5.82.
Diethyl 5-(Cyclohexylimino)-2’,3’-dihydro-3’-oxo-2’-phenylspiro[furan-2(5H),1’-[1H]isoindole]-3,4-
dicarboxylate (5d). Yield 91%. Colorless crystals. M.p. 1248. IR (KBr): 1794, 1736, 1728, 1688, 1663
(C¼O), 1495, 1466, 1356, 1277, 1215, 1178, 1115, 1039, 999, 758, 702. 1H-NMR (250.1 MHz, CDCl3): 1.02
2
(t, J ¼ 7.0, 3 H); 1.22 – 1.75 (t, J ¼ 7.0, 3 H, and m, 10 H); 3.67 – 3.69 (m, 1 H); 3.95 – 4.15 (2dq, J ¼ 11.0,
3J ¼ 7.0, 2 H); 4.30 (q, J ¼ 7.0, 2 H); 7.25 (dd, J ¼ 7.9, 1.5, 2 H); 7.34 – 7.45 (m, 4 H); 7.55 – 7.77 (m, 2 H);
7.96 – 8.00 (m, 1 H). 13C-NMR (62.9 MHz, CDCl3): 13.6; 13.9; 24.5; 24.5; 25.6; 33.2; 33.4; 57.0; 61.8; 62.4;
100.0; 122.0; 124.3; 127.4; 128.4; 129.4; 130.9; 131.3; 133.2; 134.1; 137.8; 140.5; 141.1; 151.6; 159.2; 160.9;
166.9. EI-MS: 502 (15, Mþ), 456 (22), 421 (30), 405 (34), 376 (15), 331 (35), 302 (100), 276 (18), 231
(35), 202 (49), 149 (24), 55 (18). Anal. calc. for C29H30N2O6 (502.57): C 69.31, H 6.02, N 5.57; found: C
69.17, H 6.16, N 5.44.

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Helvetica Chimica Acta – Vol. 92 (2009)
Dimethyl 2’,3’-Dihydro-3’-oxo-2’-phenyl-5-[(1,1,3,3-tetramethylbutyl)imino]spiro[furan-2(5H),1’-
[1H]isoindole]-3,4-dicarboxylate (5e). Yield 90%. Colorless crystals. M.p. 146 – 1478. IR (KBr): 1749,
1730, 1724, 1684 (C¼O), 1497, 1437, 1354, 1279, 1257, 1173, 1034, 974, 914, 773, 690. 1H-NMR
(250.1 MHz, CDCl3): 0.96 (s, 9 H); 1.30 (s, 3 H); 1.35 (s, 3 H); 1.52 (d, 2J ¼ 14.5, 1 H); 1.63 (d, 2J ¼ 14.5,
1 H); 3.60 (s, 3 H); 3.81 (s, 3 H); 7.28 (dd, J ¼ 7.9, 1.5, 2 H); 7.35 – 7.45 (m, 4 H); 7.59 – 7.68 (m, 2 H); 7.96 –
8.02 (m, 1 H). 13C-NMR (62.9 MHz, CDCl3): 29.6; 29.8; 31.6; 31.9; 52.7; 52.9; 55.5; 58.9; 100.6; 121.7;
124.4; 127.5; 128.4; 129.4; 130.9; 131.1; 133.2; 134.1; 135.9; 141.2; 142.2; 148.1; 159.7; 161.6; 167.0. EI-MS:
504 (7, Mþ), 433 (21), 401 (32), 377 (61), 342 (42), 317 (37), 281 (36), 149 (35), 97 (37), 57 (100). Anal.
calc. for C29H32N2O6 (504.58): C 69.03, H 6.39, N 5.55; found: C 68.83, H 6.47, N 5.40.
Diethyl 2’,3’-Dihydro-3’-oxo-2’-phenyl-5-[(1,1,3,3-tetramethylbutyl)imino]spiro[furan-2(5H),1’-
[1H]isoindole]-3,4-dicarboxylate (5f). Yield 90%. Colorless crystals. M.p. 116 – 1178. IR (KBr): 1743,
1736, 1685 (C¼O), 1497, 1466, 1355, 1335, 1273, 1213, 1174, 1036, 928, 903, 773, 702. 1H-NMR
(250.1 MHz, CDCl3): 0.96 (s, 9 H); 1.02 (t, J ¼ 7.3, 3 H); 1.28 (t, J ¼ 7.3, 3 H); 1.31 (s, 3 H); 1.35 (s, 3 H);
1.53 (d, 2J ¼ 14.5, 1 H); 1.64 (d, 2J ¼ 14.5, 1 H); 4.03 (q, J ¼ 7.3, 2 H); 4.28 (q, J ¼ 7.3, 2 H); 7.28 (dd, J ¼ 8.0,
1.5, 2 H); 7.33 – 7.42 (m, 4 H); 7.56 – 7.69 (m, 2 H); 7.96 – 8.00 (m, 1 H). 13C-NMR (62.9 MHz, CDCl3):
12.6; 12.9; 28.7; 28.8; 30.5; 30.9; 54.5; 57.8; 60.7; 61.1; 99.5; 120.8; 123.2; 126.5; 127.3; 128.3; 129.8; 130.2;
132.1; 133.1; 135.0; 140.4; 141.3; 147.2; 158.2; 160.2; 165.9. EI-MS: 532 (9, Mþ), 517 (9), 461 (32), 405
(100), 342 (89), 304 (58), 276 (51), 231 (46), 202 (70), 149 (33), 57 (58). Anal. calc. for C31H36N2O6
(532.64): C 69.91, H 6.81, N 5.26; found: C 69.73, H 6.85, N 5.11.
Dimethyl
2’-(4-Chlorophenyl)-5-(cyclohexylimino)-2’,3’-dihydro-3’-oxospiro[furan-2(5H),1’-
[1H]isoindole]-3,4-dicarboxylate (5g). Yield 92%. Colorless crystals. M.p. 209 – 2108. IR (KBr): 1753,
1730, 1683, 1655 (C¼O), 1497, 1437, 1362, 1280, 1039, 972, 746. 1H-NMR (250.1 MHz, CDCl3): 1.22 – 1.74
(m, 10 H); 3.60 (s, 3 H); 3.62 – 3.69 (m, 1 H); 3.86 (s, 3 H); 7.21 (d, J ¼ 8.8, 2 H); 7.39 (d, J ¼ 8.8, 2 H);
7.35 – 7.43 (m, 1 H); 7.60 – 7.70 (m, 2 H); 7.95 – 8.01 (m, 1 H). 13C-NMR (62.9 MHz, CDCl3): 24.5; 24.6;
25.6; 33.2; 33.5; 52.9; 53.2; 57.2; 100.0; 122.0; 124.5; 128.5; 129.7; 130.8; 131.1; 132.7; 133.5; 134.2; 137.4;
140.5; 140.8; 151.2; 159.6; 161.2; 166.8. EI-MS: 510 (13, Mþ (37Cl)), 508 (39, Mþ (35Cl)), 476 (20), 426
(62), 411 (82), 351 (65), 335 (100), 324 (40), 302 (68), 265 (43), 236 (54), 163 (80), 55 (40). Anal. calc. for
C27H25ClN2O6 (508.96): C 63.72, H 4.95, N 5.50; found: C 63.66, H 5.03, N 5.37.
Diethyl 2’-(4-Chlorophenyl)-5-(cyclohexylimino)-2’,3’-dihydro-3’-oxospiro[furan-2(5H),1’-[1H]iso-
indole]-3,4-dicarboxylate (5h). Yield 92%. Colorless crystals. M.p. 1708. IR (KBr): 1747, 1736, 1724, 1688
(C¼O), 1493, 1466, 1356, 1296, 1273, 1178, 1078, 1039, 968, 904, 854, 721. 1H-NMR (250.1 MHz, CDCl3):
2
1.03 (t, J ¼ 7.3, 3 H); 1.18 – 1.76 (t, J ¼ 7.3, 3 H, and m, 10 H); 3.60 – 3.74 (m, 1 H); 3.94 – 4.10 (2dq, J ¼
11.0, 3J ¼ 7.3, 2 H); 4.32 (q, J ¼ 7.3, 2 H); 7.22 (d, J ¼ 8.8, 2 H); 7.38 (d, J ¼ 8.8, 2 H); 7.41 – 7.45 (m,
1 H); 7.59 – 7.71 (m, 2 H); 7.93 – 7.99 (m, 1 H). 13C-NMR (62.9 MHz, CDCl3): 13.6; 14.0; 24.4; 24.5; 25.6;
33.2; 33.5; 57.0; 62.0; 62.5; 100.0; 122.1; 124.3; 128.6; 129.6; 131.0; 131.0; 132.8; 133.4; 134.1; 137.5; 140.6;
140.9; 151.3; 159.1; 160.7; 166.8. EI-MS: 539 (3, Mþ (37Cl)), 537 (9, Mþ (35Cl)), 454 (44), 439 (78), 365
(46), 335 (100), 236 (47), 202 (32), 149 (32). Anal. calc. for C29H29ClN2O6 (537.01): C 64.86, H 5.44, N
5.22; found: C 64.78, H 5.36, N 5.19.
Dimethyl 2’-(4-Chlorophenyl)-2’,3’-dihydro-3’-oxo-5-[(1,1,3,3-tetramethylbutyl)imino]spiro[furan-
2(5H),1’-[1H]isoindole]-3,4-dicarboxylate (5i). Yield 87%. Colorless crystals. M.p. 1648. IR (KBr):
1
1732, 1691 (C¼O), 1495, 1468, 1439, 1354, 1259, 1215, 1092, 1036, 974, 816, 791. H-NMR (250.1 MHz,
CDCl3): 0.97 (s, 9 H); 1.31 (s, 3 H); 1.36 (s, 3 H); 1.52 (d, 2J ¼ 14.5, 1 H); 1.64 (d, 2J ¼ 14.5, 1 H); 3.60 (s,
3 H); 3.84 (s, 3 H); 7.23 (d, J ¼ 8.8, 2 H); 7.38 (d, J ¼ 8.8, 2 H); 7.38 – 7.41 (m, 1 H); 7.60 – 7.68 (m, 2 H);
7.95 – 7.99 (m, 1 H). 13C-NMR (62.9 MHz, CDCl3): 29.6; 29.8; 31.6; 31.9; 52.8; 53.0; 55.5; 59.0; 100.5;
121.8; 124.5; 128.6; 129.6; 130.8; 131.0; 132.8; 133.4; 134.1; 135.5; 141.1; 142.3; 147.8; 159.6; 161.2; 167.0.
EI-MS: 541 (<1, Mþ (37Cl)), 539 (4, Mþ (35Cl)), 435 (11), 411 (16), 281 (49), 84 (37), 57 (100), 43 (53).
Anal. calc. for C29H31ClN2O6 (539.03): C 64.62, H 5.80, N 5.20; found: C 64.57, H 5.76, N 5.09.
Diethyl 2’-(4-Chlorophenyl)-2’,3’-dihydro-3’-oxo-5-[(1,1,3,3-tetramethylbutyl)imino]spiro[furan-
2(5H),1’-[1H]isoindole]-3,4-dicarboxylate (5j). Yield 97%. Colorless crystals. M.p. 118 – 1198. IR
(KBr): 1733, 1682, 1657 (C¼O), 1607, 1493, 1466, 1396, 1362, 1336, 1257, 1213, 1178, 1086, 1036, 903, 854,
820, 746, 688. 1H-NMR (250.1 MHz, CDCl3): 0.96 (s, 9 H); 1.03 (t, J ¼ 7.3, 3 H); 1.30 (t, J ¼ 7.3, 3 H); 1.31
(s, 3 H); 1.35 (s, 3 H); 1.52 (d, 2J ¼ 14.5, 1 H); 1.65 (d, 2J ¼ 14.5, 1 H); 3.94 – 4.13 (2 dq, 2J ¼ 11.0, 3J ¼ 7.3,
2 H); 4.30 (q, J ¼ 7.3, 2 H); 7.24 (d, J ¼ 8.8, 2 H); 7.38 (d, J ¼ 8.8, 2 H); 7.38 – 7.42 (m, 1 H); 7.58 – 7.70 (m,

Helvetica Chimica Acta – Vol. 92 (2009)
949
2 H); 7.95 – 7.99 (m, 1 H). 13C-NMR (62.9 MHz, CDCl3): 13.6; 14.0; 29.8; 29.9; 31.7; 31.9; 55.5; 58.9; 61.9;
62.3; 100.5; 121.8; 124.3; 128.7; 129.6; 130.9; 130.9; 132.9; 133.4; 134.0; 135.8; 141.4; 142.4; 148.0; 159.2;
161.1; 166.9. EI-MS: 569 (<1, Mþ (37Cl)), 567 (2, Mþ (35Cl)), 495 (32), 439 (72), 376 (57), 338 (36), 296
(38), 194 (53), 57 (100). Anal. calc. for C31H35ClN2O6 (567.08): C 65.66, H 6.22, N 4.94; found: C 65.48, H
6.36, N 4.88.
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Received August 19, 2008