New Studies on [2 + 3] Cycloadditions of Thermally Generated N-Isopropyl- and N-(4-Methoxyphenyl)-Substituted Azomethine Ylides

Article abstract of DOI:10.1002/hlca.200490047

The thermal reaction of 1-substituted 2,3-diphenylaziridines 2 with thiobenzophenone (6a) and 9H-fluorene-9-thione (6b) led to the corresponding 1,3-thiazolidines (Scheme 2). Whereas the cis-disubstituted aziridines and 6a yielded only trans-2,4,5,5-tetraphenyl-1,3-thiazolidines of type 7, the analogous reaction with 6b gave a mixture of trans- and cis-2,4-diphenyl-1,3-thiazolidines 7 and 8. During chromatography on SiO ₂, the trans-configured spiro[9H-fluorene-9,5′ -[1,3]thiazolidines] 7c and 7d isomerized to the cis-isomers. The substituent at N(1) of the aziridine influences the reaction rate significantly, i.e., the more sterically demanding the substituent the slower the reaction. The reaction of cis-2,3-diphenylaziridines 2 with dimethyl azodicarboxylate (9) and dimethyl acetylenedicarboxylate (11) gave the trans-cycloadducts 10 and 12, respectively (Schemes 3 and 4). In the latter case, a partial dehydrogenation led to the corresponding pyrroles. Two stereoisomeric cycloadducts, 15 and 16, with a trans-relationship of the Ph groups were obtained from the reaction with dimethyl fumarate (14; Scheme 5); with dimethyl maleate (17), the expected cycloadduct 18 together with the 2,3-dihydropyrrole 19 was obtained (Scheme 6). The structures of the cycloadducts 7b, 8a, 15b, and 16b were established by X-ray crystallography.

Full text of DOI:10.1002/hlca.200490047

496
Helvetica Chimica Acta Vol. 87 (2004)
New Studies on [2 ‡ 3] Cycloadditions of Thermally Generated N-Isopropyl-
and N-(4-Methoxyphenyl)-Substituted Azomethine Ylides
by Katarzyna Urbaniak1), Rados¯aw Szyman¬ski2), Jaros¯aw Roman¬ski, and Grzegorz Mloston¬*
¬
¬
¬
¬
Section of Heteroorganic Compounds, University of Ëodz, Narutowicza 68, PL-90-136 Ëodz
and Ma¯gorzata Domaga¯a
¬
¬
¬
¬
Department of Crystallography and Crystal Chemistry, University of Ëodz, Pomorska 149/153, PL-90-236Ëo dz
and Anthony Linden and Heinz Heimgartner*
Organisch-chemisches Institut der Universit‰t Z¸rich, Winterthurerstrasse 190, CH-8057 Z¸rich
The thermal reaction of 1-substituted 2,3-diphenylaziridines 2 with thiobenzophenone (6a) and 9H-
fluorene-9-thione (6b) led to the corresponding 1,3-thiazolidines (Scheme 2). Whereas the cis-disubstituted
aziridines and 6a yielded only trans-2,4,5,5-tetraphenyl-1,3-thiazolidines of type 7, the analogous reaction with
6b gave a mixture of trans- and cis-2,4-diphenyl-1,3-thiazolidines 7 and 8. During chromatography on SiO2, the
trans-configured spiro[9H-fluorene-9,5'-[1,3]thiazolidines] 7c and 7d isomerized to the cis-isomers. The
substituent at N(1) of the aziridine influences the reaction rate significantly, i.e., the more sterically demanding
the substituent the slower the reaction. The reaction of cis-2,3-diphenylaziridines
2 with dimethyl
azodicarboxylate (9) and dimethyl acetylenedicarboxylate (11) gave the trans-cycloadducts 10 and 12,
respectively (Schemes 3 and 4). In the latter case, a partial dehydrogenation led to the corresponding pyrroles.
Two stereoisomeric cycloadducts, 15 and 16, with a trans-relationship of the Ph groups were obtained from the
reaction with dimethyl fumarate (14; Scheme 5); with dimethyl maleate (17), the expected cycloadduct 18
together with the 2,3-dihydropyrrole 19 was obtained (Scheme 6). The structures of the cycloadducts 7b, 8a, 15b,
and 16b were established by X-ray crystallography.
Introduction. Recently, we focused our attention on 1,3-dipolar cycloadditions of
thiocarbonyl dipolarophiles with azomethine ylides by different procedures for their
generation (cf. [1] and refs. cit. therein). One of the most frequently used procedures is
the thermal, stereoselective ring opening of N-substituted aziridines [2][3]. This
method was explored to synthesize 1,3-thiazole derivatives in a regio- and stereo-
selective manner [4 6]. In some cases, drastic reaction conditions were necessary,
which led to the formation of unexpected products. For example, the reaction of
2,2,4,4-tetramethyl-3-thioxocyclobutanone (1) with dimethyl 1,3-diphenylaziridine-2,2-
dicarboxylate (2a) gave, among other products, dimethyl 1,3-thiazolidine-2,2-dicarbox-
ylate 4, which is formally a cycloadduct of the azomethine ylide with dimethyl-
thioketene (Scheme 1) [7]. Furthermore, reactions of 1 with 1-methyl- and 1-isopropyl-
2,3-diphenylaziridine 2b and 2c, respectively, led to the expected 1,3-thiazolidines 5a
and 5b, respectively, but the reaction with 2c was considerably slower and accompanied
by significant decomposition (Scheme 1). This different reactivity can be explained by
1
¬
¬
Part of the planned Ph.D. thesis of K. U., University of Ëodz.
)
)
2
¬
¬
Part of the diploma thesis of R. S., University of Ëodz.

Helvetica Chimica Acta Vol. 87 (2004)
497
Scheme 1
the assumption of a severe steric interaction between the i-Pr substituent and a Ph
group in the intermediate azomethine ylide.
To gain more insight into the influence of the N-substituent of 2,3-diphenylazir-
idines on the reactivity of the azomethine ylides generated therefrom, we compared the
reactions of 2b and 2c as well as those of trans-1-benzyl-2,3-diphenylaziridine (2d) and
cis-1-(4-methoxyphenyl)-2,3-diphenylaziridine (2e). For these studies, aromatic thio-
ketones, dimethyl acetylenedicarboxylates, dimethyl fumarate and maleate, as well as
dimethyl azodicarboxylate were selected as dipolarophiles.
Results and Discussion. The thermal reaction of 2b with thiobenzophenone (6a)
was reported to occur smoothly (4 h) and gave the expected 1,3-thiazolidine 7a in high
yield [8]. Under analogous conditions, 2c and 6a yielded, after 24 h, 7b as the sole
product (49%). The predicted trans-relationship of the Ph substituents at C(2) and
C(4) was confirmed by X-ray crystallography (Fig. 1). Under the same conditions, 2d
and 6a gave, after 7-h heating, the cis-configured cycloadduct 8c in 44% yield.
To compare the reactivities of the aziridines with a Me and i-Pr group, respectively,
at the N-atom, a mixture of equimolar amounts of 2b, 2c, and 6a in toluene was heated
1
under reflux for 3 h3). The ratio 7a/7b was established by H-NMR spectroscopy: the
singlets from HÀC(2) and HÀC(4) of the two adducts (7a: 5.40 and 5.13 ppm; 7b: 5.78
and 5.68 ppm) showed intensities with a ratio of ca. 3 :1. Based on kinetic evidence,
Huisgen et al. concluded that, in the case of N-benzyl aziridine 2d and dimethyl
fumarate, the rate of the formation of the cycloadduct depends exclusively on the rate
of the ring opening [10a]. In our system, the interception of the azomethine ylides by
the −superdipolarophile× 6a is assumed to occur very fast, and, therefore, the higher
yield of 7a indicates that 2b undergoes the electrocyclic ring opening faster than 2c. The
bulkier i-Pr substituent apparently reduces the rate of the conrotatory ring opening.
3
)
After this time, the blue color of 6a had disappeared completely.

498
Helvetica Chimica Acta Vol. 87 (2004)
Fig. 1. ORTEPPlot [9] of the molecular structure of one of the two symmetry-independent molecules of 7b (40%
probability ellipsoids, arbitrary numbering of atoms)
Analogously, the reaction of 2b with 9H-fluorene-9-thione (6b) gave 7c and traces
of 8a (1H-NMR; Scheme 2). After chromatography (SiO2), only 8a was obtained in
35% yield, i.e., an isomerization 7c ! 8a took place during chromatographic workup.
The cis-configuration of 8a has been unambigously confirmed by X-ray crystallography
(Fig. 2). In the case of 2c and 6b, again a mixture of two cycloadducts was formed. The
product isolated in 42% yield after chromatographic separation4) corresponded to the
minor component of the reaction mixture. Based on their spectroscopic data, both
products are 3-isopropyl-1,3-thiazolidines, which differ in the relative configuration of
the Ph ring at C(2) and C(4). By analogy to the reaction with 2b, we assign the trans-
configuration to the major product 7d, and the cis-configuration to 8b. Thus, the
primarily formed trans-configured products 7c and 7d, i.e., the spirofluorenyl
compounds, undergo a smooth isomerization to give the cis-isomers 8a and 8b,
respectively, during chromatographic workup5). Attempted separations by fractional
crystallization always led to mixtures of the isomers. When a sample of recrystallized
material containing 7d and 8b (9 :1 mixture) was dissolved in CDCl3 in the presence of
catalytic amounts of CF3COOH, the isomerization to 8b was complete after 3 d at
4
)
)
The ratio 7d/8b of the isolated material depended on how long the mixture was exposed to SiO2. After
12 h, the isomerization was complete.
It is worth mentioning that an analogous isomerization was not observed in the case of 7b.
5

Helvetica Chimica Acta Vol. 87 (2004)
499
Scheme 2
Fig. 2. ORTEPPlot [9] of the molecular structure of one of the two symmetry-independent molecules of 8a (50%
probability ellipsoids, arbitrary numbering of atoms)

500
Helvetica Chimica Acta Vol. 87 (2004)
room temperature6). This isomerization can be rationalized by a ring-opening/ring-
closure process in which a thiocarbonylium ion (via cleavage of the C(2)ÀN(3) bond)
or an azomethinium ion (via cleavage of the S(1)ÀC(2) bond) is the intermediate.
The isomerizations of 7c and 7d to 8a and 8b, respectively, indicate that the cis-
configured 2,4-diphenyl-1,3-thiazolidines are the thermodynamically more stable
stereoisomers. This observation was confirmed in an additional experiment in which
trans-aziridine 2d was reacted with 6b. In this case, only one cycloadduct, 8d
(Scheme 2), which was stable during chromatography (SiO2), was found in the mixture.
The similarity of its NMR spectra with those of 8a and 8b indicated the expected cis-
configuration.
When a 1:1 mixture of 2c and dimethyl azodicarboxylate (9) was heated in toluene
for 15 h7), the cycloadduct 10a (Scheme 3) was obtained, which was purified by
8
chromatography on Al2O3 ). As an additional precursor of an azomethine ylide, the 1-
aryl-substituted aziridine 2e was reacted with 9 in boiling toluene to give 10b (cf. [12]).
In this case, the reaction was complete after only 2 h9).
Scheme 3
Dimethyl acetylenedicarboxylate (11) is frequently used as an electron-deficient
dipolarophile (cf. [13]). The reaction with 2c in refluxing toluene was complete after
8 h. By 1H-NMR analysis, the products 12a and 13a were detected in a ratio of 85 :15
(Scheme 4). The main differences were the presence of a singlet at 5.61 ppm (2 H) and
two doublets for the i-Pr group in the case of the major product 12a, whereas 13a
showed only one doublet for the i-Pr substituent. Crystallization from MeOH gave 13a,
and subsequent chromatographic separation of the mother liquor led to an additional
amount of 13a and to 12a. In a second experiment, the mixture was heated for 24 h to
yield 13a exclusively.
The higher reactivity of 2e was confirmed in the reaction with 11: here, 2e was
completely consumed after just 1 h. Again, two products were obtained, which were
identified as 12b and 13b. The smooth conversion of 2,5-dihydro-1H-pyrroles into 1H-
6
)
A similar isomerization of N-methyl- and N-benzyl-2,4,5-triaryl-1,3-oxazolidines was reported to occur
thermally or during chromatography on SiO2 [11b,c].
7
8
9
)
)
)
No 2c could be detected after this time.
First attempts with SiO2 as the adsorbent led to decomposition of 10a.
In 1966, Heine et al. reported the reaction of 1,2,3-triphenylaziridine with 9 in refluxing toluene (4 h) [3b].
No reaction mechanism was proposed, as, at that time, the electrocyclic ring opening of aziridines to
azomethine ylides was not known. Neither the configuration of the starting material nor of the product
were given.

Helvetica Chimica Acta Vol. 87 (2004)
501
Scheme 4
pyrroles by spontaneous dehydrogenation in the presence of air-O2 (autoxidation) or
after addition of an oxidizing agent is well-established [14][15].
Thermal as well as photochemical reactions of 2,3-diarylaziridines with 11 have
been reported. Under conditions similar to those described above, trans-1-methyl-2,3-
diphenylaziridine gave dimethyl cis-2,5-dihydro-1-methyl-2,5-diphenyl-1H-pyrrole-3,4-
dicarboxylate as the sole product [16]. On the other hand, UV irradiation of trans-1,2,3-
triphenylaziridine in the presence of 11 led to a mixture of the trans-disubstituted 2,5-
dihydro-1H-pyrrole 12 (R ˆ Ph) and the corresponding 1H-pyrrole derivative 13 (R ˆ
Ph) [15]. In some cases, the formation of 2,3-dihydro-1H-pyrroles has been observed.
For example, thermolysis of 1-methyl-2-(4-methylphenyl)-3-(2-pyridyl)aziridine and
11 was reported to yield a compound of this type [17]. Furthermore, photolysis of trans-
1-butyl-2,3-diphenylaziridine and 11 afforded a mixture of all three types of 1H-pyrrole
derivatives [18]. Apparently, the formation of 2,3-dihydro-1H-pyrroles is the result of
an isomerization of the initially formed 2,5-dihydro-1H-pyrrole10).
Both aziridines, 2c and 2e, were reacted with dimethyl fumarate (ˆdimethyl (E)-
but-2-enedioate; 14) to yield mixtures of the two diastereoisomeric pyrrolidine-3,4-
dicarboxylates 15 and 16 (Scheme 5). Whereas the ratio 15a/16a was almost 1:1, it was
1
established as 4 :1 in the case of 15b/16b. On the basis of the H-NMR spectra, we
proposed that compounds 15 are the (r-2, t-3, c-4, t-5) isomers: HÀC(3), HÀC(4)
absorb as dd at ca. 4.1 and 3.5 ppm in the cases of 16 and 15, respectively. The high-field
shift in 15a and 15b is a result of the shielding effect of the Ph group at C(2) and C(5).
The pure isomers of type 15 and 16 were obtained after chromatographic separation,
and, in the case of 15b and 16b, the predicted structures were established by X-ray
Scheme 5
10
)
In analogous reactions with 2-benzoyl- and 2-(methoxycarbonyl)-substituted aziridines, the formation of
2,5-dihydro- and/or 2,3-dihydro-1H-pyrroles as well as 1H-pyrroles was observed [14][19 22].

502
Helvetica Chimica Acta Vol. 87 (2004)
crystallography (Fig. 3). These results are similar to the ratios reported earlier for the
diastereoisomeric pyrrolidinedicarboxylates obtained from the reactions of the
corresponding N-benzyl- and N-Ph-substituted aziridines, respectively, and 14 [10][23].
Dimethyl maleate (17) is known to be less reactive than the above dipolarophiles
[13]. In a previous study, however, it has been shown that the respective pyrrolidine was
formed via interception of the azomethine ylide generated either by thermal ring
opening of 2b or by addition of methyl(phenyl)carbene to N-benzylidenemethylamine
[24]. Unexpectedly, thermolysis of 2c in the presence of 17 gave none of the expected
interception products. After heating for 100 h, analysis of the crude mixture showed the
presence of small amounts of 15a and 16a, i.e., the products of the reaction with 14
(Scheme 5). This result shows that 17 is not reactive enough to trap the intermediate
azomethine ylide. Instead, slow isomerization of 17 to 14 takes place.
On the other hand, the reaction of 2e and 17 in boiling toluene for 24 h led to a
mixture of the expected [2 ‡ 3] cycloadduct 18 and the 2,3-dihydro-1H-pyrrole 19,
which is a partially dehydrogenated product of 18, in a ratio of 5 :2 (Scheme 6)11). The
partial dehydrogenation of 18 could, in principle, lead to three different products, one
of them being the already described 12b. The elucidation of the structure of 19 was
based on the disappearence of the high-field-shifted dd for HÀC(4) (d 3.40 ppm) and
the signal of one of the H-atoms ascribed to HÀC(2) and HÀC(5) (d 5.60/5.84 ppm) in
18.
Scheme 6
In summary, the present study shows that the N-substituent of cis-2,3-diphenylazir-
idines 2 significantly influences their reactivity as precursors of the corresponding
azomethine ylides. In all cases, the N-isopropyl derivative showed the lowest reactivity,
but, in spite of this, [2 ‡ 3] cycloaddition products with CˆS, NˆN, and electron
deficient CꢀC dipolarophiles were obtained. The formation of a cycloadduct was also
observed in the case of dimethyl fumarate, whereas no reaction occurred with dimethyl
maleate. The influence of the i-Pr substituent compared with that of a Me or 4-
MeOC6H4 group is remarkable. It seems likely that steric as well as electronic effects
are responsible for the reduced stability of the ylide and for its slower formation.
Furthermore, steric hindrance may be the reason for the more sluggish cycloaddition
reaction that generates five-membered heterocycles.
We thank the analytical sections of our institutes for spectra and elemental analyses. Financial support of
the Polish State Committee for Scientific Research (Grant No. 3 T09A 25), the Swiss National Science
Foundation, and F. Hoffmann-La Roche AG, Basel, is gratefully acknowledged.
11
)
In an earlier experiment with cis-1,2,3-triphenylaziridine and 17, Huisgen et al. described the cycloadduct
analogous to 18, but no secondary product of type 19 was mentioned [10b].

Fig. 3. ORTEPPlots [9] of the molecular structures of 15b and 16b (50% probability ellipsoids; arbitrary numbering of atoms)

504
Helvetica Chimica Acta Vol. 87 (2004)
Experimental Part
1. General. See [25].
2. Starting Materials. cis-1-Methyl-2,3-diphenylaziridine (2b) and cis-1-isopropyl-2,3-diphenylaziridine (2c)
were prepared by Gabriel×s method according to [11], trans-1-benzyl-2,3-diphenylaziridine (2d) and cis-1-(4-
methoxyphenyl)-2,3-diphenylaziridine (2e) were synthesized according to procedures described by Huisgen et
al. [10][23]. Thiobenzophenone (6a) was obtained from benzophenone by treatment with Lawesson×s reagent
[26], and 9H-fluorene-9-thione (6b) was prepared according to [27] by thionation of 9H-fluorenone with a H2S/
HCl mixture at 0 58 in EtOH. Other reagents used in the present study were commercially available. Reported
yields refer to isolated products.
3. Thermal Reactions of Aziridines 2b 2d with Dipolarophiles. 3.1. Reaction of 2c with 6a. A soln. of 2c
(261 mg, 1.1 mmol) and freshly purified, blue 6a (198 mg, 1.0 mmol) dissolved in toluene (4 ml) was heated
under reflux for 24 h. After this time, the blue color of 6a disappeared; the mixture was cooled to r.t., and the
solvent was removed in vacuo. The thick, oily residue was analyzed by 1H-NMR, and only one product with two
s for CH at 5.68 and 5.78 ppm was detected. Isolation of the product was achieved chromatographically (SiO2;
petroleum ether with increasing amounts of CH2Cl2). The 1H-NMR spectrum of the isolated material
corresponded to that recorded for the crude mixture.
trans-3-Isopropyl-2,4,5,5-tetraphenyl-1,3-thiazolidine (7b). Yield: 213 mg (49%). Colorless crystals. M.p.
99 1018 (dec.; blue color; MeOH). IR (KBr): 1601m, 1492s, 1454s, 1362m, 1239s, 1181s, 749s, 729s, 6 96vs.
1H-NMR: 0.58, 1.07 (2d, J ˆ 6.6, Me2CH); 2.99 (m, Me2CH); 5.68, 5.78 (2s, HÀC(4), HÀC(2)); 6.84 7.67
(m, 20 arom. H). 13C-NMR: 19.3, 21.7 (2q, Me2CH); 48.8 (d, Me2CH); 68.9 (s, C(5)); 69.9, 73.9 (2d, C(4), C(2));
125.7, 125.9, 126.8, 127.2, 127.4, 127.5, 127.7, 128.0, 128.1, 129.0, 130.1 (11d, 20 arom. CH); 140.3, 142.5, 143.4,
‡
150.7 (4s, 4 arom. C). CI-MS (NH3): 436(100, [ M ‡ 1] ), 230 (7), 208 (7). Anal. calc. for C30H29NS (435.63): C
82.72, H 6.71, N 3.22, S 7.36; found: C 82.74, H 6.65, N 3.26, S 7.46.
3.2. Reaction of 2d with 6a. A soln. of 2d (314 mg, 1.1 mmol) and 6a (198 mg, 1.0 mmol) in toluene was
heated under reflux for 7 h. The analysis of the crude mixture and isolation of the product were carried out as
described in 3.1.
cis-3-Benzyl-2,4,5,5-tetraphenyl-1,3-thiazolidine (8c). Yield: 213 mg (44%). Colorless crystals. M.p. 121
1238 (MeOH). IR (KBr): 1500s, 1460s, 1450s, 1220m, 1150m (br.), 1090m, 1050m, 780s, 770s, 710vs. 1H-NMR:
3.70, 3.76( AB, J ˆ 14.0, CH2); 5.17, 5.25 (2s, HÀC(4), HÀC(2)); 6.92 7.74 (m, 20 arom. H). 13C-NMR: 51.8
(t, CH2); 68.4 (s, C(5)); 69.5, 72.5 (2d, C(4), C(2)); 126.2, 126.3, 127.0, 127.2, 127.8, 127.9, 128.1, 128.3, 128.7, 130.0,
130.2, 130.7 (12d, 20 arom. CH); 134.9, 138.5, 139.9, 142.7, 147.1 (5s, 5 arom. C). EI-MS: 285 (76), 195 (21), 194
(100), 178 (6), 121 (8), 91 (20). Anal. calc. for C34H29NS (483.68): C 84.43, H 6.04, N 2.89, S 6.63; found: C 84.59,
H 6.04, N 2.90, S 6.39.
3.3. Reactions of 2b, 2c, and 2d with 6b. A soln. of 1.1 mmol of the corresponding aziridine 2 in 2 ml of
toluene was heated under reflux. To these mixtures, a soln. of 6b (196mg, 1 mmol) in toluene (2 ml) was added
in three portions in intervals of ca. 20 min.
Reaction with 2b. The reaction was complete after 2 h. After careful evaporation of the solvent, the thick
oily residue was analyzed by 1H-NMR (presence of two s for CH at 6.06 and 4.98 ppm, resp.). After
chromatographic workup (SiO2; petroleum ether with increasing amounts of CH2Cl2), a colorless, thick oil was
isolated, which subsequently solidified in the refrigerator. Crystallization from MeOH afforded an anal. pure
sample of 8a.
trans-3'-Methyl-2',4'-diphenylspiro[9H-fluorene-9,5'-[1,3]thiazolidine] (7c, unstable primary cycloadduct).
1H-NMR: 2.05 (s, MeN); 4.98, 6.06 (2s, HÀC(4'), HÀC(2')).
cis-3'-Methyl-2',4'-diphenylspiro[9H-fluorene-9,5'-[1,3]thiazolidine] (8a). Yield: 140 mg (35%). Colorless
needles. M.p. 154 1568 (MeOH/CH2Cl2). IR (KBr): 1493m, 1448s, 1244m, 1144m, 1024m, 959m, 745vs, 732vs,
701s. 1H-NMR: 2.20 (s, MeN); 4.25, 5.18 (2s, HÀC(4'), HÀC(2')); 6.74 8.21 (m, 18 arom. H). 13C-NMR: 39.2
(q, MeN); 66.2 (s, C(5')); 75.3, 84.2 (2d, C(4'), C(2')); 118.9, 119.6, 124.9, 126.8, 127.2, 127.5, 127.6, 127.9, 128.2,
128.3, 128.5, 128.8 (12d, 18 arom. CH); 134.9, 139.1, 139.6, 140.8, 146.9, 148.5 (6s, 6arom. C). CI-MS (NH 3): 422
‡
‡
(15, [M ‡ NH3] ), 406(97, [ M ‡ 1] ), 284 (41), 152 (100). Anal. calc. for C28H23NS (405.57): C 82.92, H 5.72, N
3.45, S 7.91; found: C 82.95, H 5.87, N 3.36, S 8.08.
Reaction with 2c. The reaction was complete after 13 h. After evaporation of the solvent, the thick oily
residue was analyzed by 1H-NMR (presence of two sets of s at 5.17 and 6.30, and at 4.73 and 5.77 ppm, attributed
to HÀC(4) and HÀC(2) of 7d and 8b, resp.; ratio of isomers ca. 7:3). After chromatographic separation (SiO2;
petroleum ether with increasing amounts of CH2Cl2), a crystalline fraction identified as a 2 :8 mixture of 7d and
8b was isolated. Attempted separation by fractional crystallization failed. In a second experiment, the crude

Helvetica Chimica Acta Vol. 87 (2004)
505
mixture of 7d and 8b was put on a SiO2 column, and the separation was carried out only after 12 h. In this case,
only isomerized cycloadduct 8b was isolated and purified by crystallization.
cis-3'-Isopropyl-2',4'-diphenylspiro[9H-fluorene-9,5'-[1,3]thiazolidine] (8b). Yield: 182 mg (42%). Color-
less crystals. M.p. 162 1648 (MeOH/CH2Cl2). IR (KBr): 1448s, 1384w, 1174m, 1155m, 748s, 731vs, 702vs.
1H-NMR: 0.77, 0.98 (2d, J ˆ 7.1, 6.7, Me2CH); 3.19 (m, Me2CH); 4.73, 5.77 (2s, HÀC(4'), HÀC(2')); 6.67 8.19
(m, 18 arom. H). 13C-NMR: 14.8, 21.8 (2q, Me2CH); 49.9 (d, Me2CH); 65.5 (s, C(5')); 68.2, 81.2 (2d, C(4'),
C(2')); 118.8, 119.4, 124.7, 126.5, 126.6, 127.0, 127.3, 127.4, 127.9, 128.0, 128.2, 128.3, 128.6 (13d, 18 arom. CH);
‡
136.1, 139.2, 140.7, 141.9, 147.7, 148.8 (6s, 6arom. C). CI-MS (NH 3): 434 (100, [M ‡ 1] ), 400 (17), 312 (23), 180
(7), 148 (15), 106(7). Anal. calc. for C 30H27NS (433.61): C 83.10, H 6.28, N 3.23, S 7.39; found: C 83.14, H 6.27, N
3.23, S 7.53.
Reaction with 2d. The reaction was complete after 1 h, and the crude mixture was purified by
chromatography according to the procedure described for 2b.
cis-3'-Benzyl-2',4'-diphenylspiro[9H-fluorene-9,5'-[1,3]thiazolidine] (8d). Yield: 212 mg (44%). Colorless
needles. M.p. 161 1628 (MeOH). IR (KBr): 1493m, 1448s, 1119m (br.), 1067m, 1029m, 748s, 700s. 1H-NMR:
3.89 (s, CH2); 4.40, 5.45 (2s, HÀC(4'), HÀC(2')); 6.58 8.20 (m, 23 arom. H). 13C-NMR: 52.0 (t, CH2); 65.9
(s, C(5')); 69.6, 79.7 (2d, C(4')), C(2')); 119.2, 119.8, 125.1, 127.0, 127.2, 127.5, 127.7, 127.9, 128.1, 128.2, 128.4,
128.7, 128.8, 129.2, 129.4, 130.9 (16d, 23 arom. CH); 133.7, 134.9, 139.5, 139.8, 141.1, 147.6, 149.1 (7s, 7 arom. C).
‡
CI-MS (NH3): 483 (43), 482 (100, [M ‡ 1] ), 478 (16), 392 (7), 360 (5), 212 (6), 196 (10). Anal. calc. for
C34H27NS (481.66): C 84.78, H 5.65, N 2.91, S 6.66; found: C 84.89, H 5.64, N 2.90, S 6.54.
3.4. Reactions of 2c and 2e with Dimethyl Azodicarboxylate (9). A soln. of 9 (175 mg, 1.2 mmol) and
1 mmol of the corresponding 2 in abs. toluene (2 ml) was heated under reflux.
Reaction with 2c. After 11 h, additional 9 (29 mg, 0.2 mmol) was added to the mixture, and heating was
continued for 4 h (15 h totally). After evaporation of the solvent, the oily residue was worked up by
chromatography (Al2O3; petroleum ether with increasing amounts of CH2Cl2). The main fraction was obtained
with 50% of CH2Cl2, and 10a was isolated as a thick, colorless oil. Attempts to obtain a crystalline product were
not successful.
Dimethyl trans-4-Isopropyl-3,5-diphenyl-1,2,4-triazolidine-1,2-dicarboxylate (10a). Yield: 276mg (72%).
Colorless, thick oil. IR (neat): 1716s (br., CˆO), 1444s, 1335vs (br.), 1209s (br.), 1124s, 1043m, 1028m, 972w,
827w, 760vs, 710s. 1H-NMR: 1.06, 1.29 (2d, J ˆ 6.3, 6.5, Me2CH); 3.17 (m, Me2CH); 3.96( s, 2 MeO); 6.33
(s, HÀC(3), HÀC(5)); 7.53 7.79 (m, 10 arom. H). 13C-NMR: 21.2, 22.9 (2q, Me2CH); 47.1 (d, Me2CH); 53.3,
53.4 (2q, 2 MeO); 78.3, 78.4 (2d, C(3), C(5)); 127.3, 128.3, 128.4 (3d, 10 arom. CH); 138.0 (s, 2 arom. C); 157.4
(s, 2 CˆO). Anal. calc. for C21H25N3O4 (383.45): C 65.78, H 6.57, N 10.96; found: C 65.25, H 6.29, N 10.88.
Reaction with 2e. After heating for 2 h, 2d was completely consumed. The solvent was evaporated, and the
solid residue was analyzed by 1H-NMR, which showed the presence of 10b as the sole product (s at 6.78 ppm).
The crude product was triturated with a small amount of EtOH, and, after filtration, the crystalline product was
purified by recrystallization.
Dimethyl trans-4-(Methoxyphenyl)-3,5-diphenyl-1,2,4-triazolidine-1,2-dicarboxylate (10b). Yield: 320 mg
(71%). Colorless crystals. M.p. 156 161 8 (EtOH/CH2Cl2) ([12]: 149 1518). IR (KBr): 1716vs (CˆO), 1515s,
1444s, 1352vs, 1295s, 1276s, 1252vs, 1125s, 1038s, 819m, 76 3m, 706s. 1H-NMR: 3.48 (br. s, 2 MeO); 3.63 (s, MeO);
6.35, 6.62 (AA'BB', J ˆ 8.5, 4 arom. H); 6.85 (s, HÀC(3), HÀC(5)); 7.28 7.37 (m, 10 arom. H). 13C-NMR: 53.5,
55.4 (2q, 2 MeO); 75.2 (d, C(3), C(5)); 114.7, 114.9, 126.7, 128.58, 128.62 (5d, 14 arom. CH); 135.7, 137.5, 151.9
‡
(3s, 4 arom. C); 157.5 (s, 2 CˆO). CI-MS (NH3): 449 (7), 448 (25, [M ‡ 1] ), 254 (10), 238 (13), 237 (100), 212
(23). Anal. calc. for C28H25N3O5 (447.49): C 67.10, H 5.63, N 9.39; found: C 67.03, H 5.73, N 9.35.
3.5. Reactions of 2c and 2e with Dimethyl Acetylenedicarboxylate (11). A soln. of 11 (171 mg, 1.2 mmol) and
1.0 mmol of the corresponding 2 in 2 ml of abs. toluene was heated under reflux.
Reaction with 2c. After 8-h heating, the solvent was evaporated, and the crude residue was analyzed by
1H-NMR, which revealed the presence of ca. 50% of unconverted 2c. The cycloadduct 12a and 1H-pyrrole 13a
were present in a ratio of ca. 85 :15 (based on the intensities of the Me2CH d between 0.70 and 1.15 ppm).
Chromatographic separation (prep. TLC; SiO2; hexane/CH2Cl2 1:1) led to 12a as the less polar fraction and 13a
as the more polar one. The products were purified by crystallization from MeOH.
In a similar experiment, the mixture was heated for 24 h. After typical workup, the 1H-NMR spectrum of
the crude residue revealed the presence of 13a as the sole product. The product was triturated with a small
amount of MeOH, filtered, and purified by recrystallization from MeOH.
Dimethyl trans-2,5-Dihydro-1-isopropyl-2,5-diphenyl-1H-pyrrole-3,4-dicarboxylate (12a). Yield (after 8 h):
133 mg (35%). Colorless crystals. M.p. 100 1028 (MeOH). IR (KBr): 1744vs (CˆO), 1721vs (CˆO), 1455m,
1433m, 1317s, 1287m, 1244s, 1198s, 1031s, 750m, 706s. 1H-NMR: 0.69, 0.82 (2d, Me2CH); 2.87 (m, Me2CH); 3.56

506
Helvetica Chimica Acta Vol. 87 (2004)
(s, 2 MeO); 5.61 (s, HÀC(2), HÀC(5)); 7.23 7.42 (m, 10 arom. H). 13C-NMR: 21.5, 21.7 (2q, Me2CH); 47.1
(d, Me2CH); 51.8 (q, 2 MeO); 71.7 (d, C(2), C(5)); 127.7, 128.1, 128.2 (3d, 10 arom. CH); 139.6( s, 2 arom. C);
‡
140.8 (s, CˆC); 163.7 (s, 2 CˆO). ESI-MS (MeOH): 380 (100, [M ‡ 1] ). Anal. calc. for C23H25NO4 (379.45): C
72.80, H 6.65, N 3.69; found: C 72.61, H 6.79, N 3.57.
Dimethyl 1-Isopropyl-2,5-diphenyl-1H-pyrrole-3,4-dicarboxylate (13a). Yield (after 24 h): 318 mg (84%).
Colorless crystals. M.p. 174 1768 (MeOH). IR (KBr): 1716vs (CˆO), 1482s, 1443s, 1341m, 1253s, 1199vs,
1169vs, 1061m, 76 6m, 703m. 1H-NMR: 1.11 (d, J ˆ 7.1, Me2CH); 3.59 (s, 2 MeO); 4.24 (m, Me2CH); 7.42 (br.
s, 10 arom. CH). 13C-NMR: 23.2 (q, Me2CH); 50.0 (d, Me2CH); 51.3 (q, 2 MeO); 127.8, 128.6
, 131.2
.
‡
(3d, 10 arom. CH); 114.7, 131.8, 136.2 (3s, 6arom. C); 165.3 ( s, 2 CˆO). EI-MS: 377 (100, M ), 346(17),
335 (67), 304 (72), 303 (49), 272 (19).
Reaction with 2e. The reaction was complete after 1 h. After evaporation of the solvent, the 1H-NMR
spectrum of the crude residue established the ratio 12b/13b as ca. 2 :1 (based on the intensities of the of MeO s at
3.62 and 3.71 ppm for 12b and 13b, resp.). The solvent was evaporated, and the semi-solid residue was dissolved
in hot acetone. After cooling to r.t., the material crystallized was filtered and identified as 12b. After one night in
the refrigerator, the mother liquor yielded colorless crystals of 13b. Anal. pure samples were obtained after
recrystallization.
Dimethyl trans-2,5-Dihydro-1-(4-methoxyphenyl)-2,5-diphenyl-1H-pyrrole-3,4-dicarboxylate (12b). Yield:
186mg (42%). Yellow crystals. M.p. 216 219 8 (acetone). IR (KBr): 1736s (CˆO), 1720s (CˆO), 1512s,
1454m, 1436m, 1343m (br.), 1253s (br.), 1102m, 1030m, 815s, 759m, 703m. 1H-NMR: 3.56( s, MeO); 3.62
(s, 2 MeO); 6.22 (s, HÀC(2), HÀC(5)); 6.37, 6.51 (AA'BB', J ˆ 8.8, 4 arom. CH); 7.20 7.34 (m, 10 arom. CH).
13C-NMR: 52.0 (q, 2 MeO); 55.2 (q, MeO); 71.1 (d, C(2), C(5)); 114.1, 115.3, 127.3, 128.0, 128.6(5 d, 14 arom.
CH); 136.7, 138.0, 138.9 (3s, 3 arom. C); 151.2 (s, CˆC, 1 arom. C); 163.1 (s, 2 CˆO). CI-MS (NH3): 444 (100,
‡
[M ‡ 1] ), 306(7), 225 (10). Anal. calc. for C 27H25NO5 (443.50): C 73.12, H 5.68, N 3.16; found: C 73.04, H 5.71,
N 3.14.
Dimethyl 1-(4-Methoxyphenyl)-2,5-diphenyl-1H-pyrrole-3,4-dicarboxylate (13b). Yield: 102 mg (23%).
Colorless crystals. M.p. 196 198 8 (acetone; [28]: 210 2118). IR (KBr): 1731vs (CˆO), 1712vs (CˆO), 1515s,
1
1483s, 1445s, 1254s, 1212s, 1182s, 1102m, 1061m, 76 3m, 701m. H-NMR: 3.66 (s, MeO); 3.71 (s, 2 MeO); 6.58,
6.74 (AA'BB', J ˆ 8.9, 4 arom. CH); 7.17 7.25 (m, 10 arom. CH). 13C-NMR: 51.6( q, 2 MeO); 55.1 (q, MeO);
113.6, 127.5, 127.9, 129.7, 130.7 (5d, 14 arom. CH); 114.6, 130.4, 136.8, 158.6 (4s, 8 arom. C); 165.5 (s, 2 CˆO).
‡
CI-MS: 442 (100, [M ‡ 1] ), 427 (7), 306(13). Anal. calc. for C 27H23NO5 (441.48): C 73.46, H 5.25, N 3.17;
found: C 73.53, H 5.25, N 3.14.
3.6. Reactions of 2c and 2e with Dimethyl Fumarate (14). A soln. of 14 (173 mg, 1.2 mmol) and 1.0 mmol of
the corresponding 2 in 2 ml of abs. toluene was heated under reflux. The progress of the reaction was followed by
TLC.
Reaction with 2c. After heating for 18 h, the solvent was evaporated, and the crude residue was analyzed by
1H-NMR. Based on the intensities of the Me2CH m at 2.70 and 3.02 ppm, the ratio 15a/16a was established as ca.
1:1. After evaporation of CDCl3, the residue was dissolved in hot MeOH, cooled to r.t., and kept overnight in
the refrigerator. Colorless crystals of 16a were filtered, and the mother liquor was evaporated. The semi-solid
residue was separated by prep. TLC (SiO2; hexane/CH2Cl2). The less polar main fraction was isolated and
identified as 15a, and some additional 16a was obtained as the more polar fraction.
Dimethyl trans,trans,trans-1-Isopropyl-2,5-diphenylpyrrolidine-3,4-dicarboxylate (15a). Yield: 88 mg
(23%). Colorless crystals. M.p. 42 458 (hexane). IR (KBr): 1732vs (CˆO), 1456m, 1436m, 1263m, 1206vs,
1174s, 1005w, 76 2m, 704s. 1H-NMR: 0.27, 0.83 (2d, J ˆ 6.7, 6.9, Me2CH); 2.70 (m, Me2CH); 3.42 (m, 2 H); 3.57
(s, 2 MeO); 4.72 (m, 2 H); 7.13 7.34 (m, 10 arom. CH). 13C-NMR: 18.8, 20.6(2 q, Me2CH); 46.6 (d, Me2CH);
52.0, 52.1 (2q, 2 MeO); 55.0, 67.1 (2d, C(2), C(3), C(4), C(5)); 127.4, 128.2, 128.3 (3d, 5 arom. CH); 143.8
‡
(s, 2 arom. C); 173.6( s, 2 CˆO). CI-MS (NH3): 382 (100, [M ‡ 1] ). Anal. calc. for C23H27NO4 (381.47): C
72.42, H 7.13, N 3.67; found: C 72.04, H 6.91, N 3.50.
Dimethyl cis,trans,cis-1-Isopropyl-2,5-diphenylpyrrolidine-3,4-dicarboxylate (16a). Yield: 88 mg (23%).
Colorless crystals. M.p. 111 1138 (MeOH). IR (KBr): 1744vs (CˆO), 1732vs (CˆO), 1454m, 1440m, 1209vs,
1172s, 1006m, 703s. 1H-NMR: 0.80, 0.82 (2d, J ˆ 6.7, 7.0, Me2CH); 3.02 (m, Me2CH); 3.26( s, 2 MeO); 4.10
(m, 2 H); 5.01 (m, 2 H); 7.20 7.30 (m, 10 arom H). 13C-NMR: 21.7, 22.8 (2q, Me2CH); 48.3 (d, Me2CH); 49.4
(d, C(3), C(4)); 51.2 (q, 2 MeO); 65.8 (d, C(2), C(5)); 127.3, 127.8, 127.9 (3d, 10 arom. CH); 141.8 (s, 2 arom.
.
‡
‡
C); 170.7 (s, 2 CˆO). EI-MS: 381 (<1, M ), 366 (100, [M À Me] ), 338 (44), 194 (41), 150 (24). Anal. calc. for
C23H27NO4 (381.47): C 72.42, H 7.13, N 3.67; found: C 72.34, H 7.20, N 3.54.
Reaction with 2e. The reaction was complete after 12 h. The solvent was evaporated, and the crude residue
was analyzed by 1H-NMR. Based on the intensities of signals at 5.66 (m, HÀC(2), HÀC(5) in 15b) and

Helvetica Chimica Acta Vol. 87 (2004)
507
5.44 ppm (m, HÀC(2), HÀC(5) in 16b), the ratio 15b/16b was established as ca. 1:2. Attempted separation of
the diastereoisomers by fractional crystallization failed. Chromatography (prep. TLC; SiO2; hexane/CH2Cl2
1:4) led to 15b as the less polar fraction and 16b as the more polar one. Recrystallization gave anal. pure
samples.
Dimethyl trans,trans,trans-1-(4-Methoxyphenyl)-2,5-diphenylpyrrolidine-3,4-dicarboxylate (15b). Yield:
334 mg (75%). M.p. 132 1348 (MeOH/CH2Cl2). IR (KBr): 1732s (CˆO), 1513s, 1455m, 1438m, 1244vs,
1038m, 816m, 76 3m, 703m. 1H-NMR: 3.54 (s, 2 MeO); 3.54 3.59 (m, HÀC(3), HÀC(4)); 3.59 (s, MeO); 5.65
5.67 (m, HÀC(2), HÀC(5)); 6.32, 6.52 (AA'BB', J ˆ 9.1, 4 arom. H); 7.15 7.27 (m, 10 arom. H). 13C-NMR:
52.2 (q, 2 MeO); 55.2 (q, MeO); 55.3 (d, C(3), C(4)); 66.0 (d, C(2), C(5)); 113.9, 117.0, 126.6, 127.1, 128.4
(5d, 14 arom. CH); 138.2, 141.7, 151.3 (3s, 4 arom. C); 172.0 (s, 2 CˆO). CI-MS (NH3): 447 (30), 446(100, [ M ‡
‡
1] ), 236(24), 222 (47). Anal. calc. for C 27H27NO5 (445.51): C 72.79, H 6.11, N 3.14; found: C 72.73, H 6.05, N
3.06.
Dimethyl cis,trans,cis-1-(4-Methoxyphenyl)-2,5-diphenylpyrrolidine-3,4-dicarboxylate (16b). Yield: 85 mg
(19%). Colorless crystals. M.p. 263 2658 (MeOH/CH2Cl2). IR (KBr): 1733vs (CˆO), 1511vs, 1454m, 1437m,
1
1297m, 1259s, 1239s, 1219s, 1177vs, 1041m, 814m, 755m, 704m. H-NMR: 3.34 (s, 2 MeO); 3.52 (s, MeO); 4.07
(m, HÀC(3), HÀC(4)); 5.44 (m, HÀC(2), HÀC(5)); 6.20, 6.48 (AA'BB', J ˆ 8.5, 4 arom. H); 7.11 7.25
(m, 10 arom. H). 13C-NMR: 48.7 (d, C(3), C(4)); 51.6( q, 2 MeO); 55.3 (q, MeO); 63.9 (d, C(2), C(5)); 114.4,
126.9, 127.8, 128.4 (4d, 14 arom. CH); 137.8, 138.9, 151.0 (3s, 4 arom. C); 169.7 (s, 2 CˆO). Anal. calc. for
C27H27NO5 (445.51): C 72.79, H 6.11, N 3.14; found: C 72.73, H 6.05, N 3.06.
3.7. Reaction of 2d with Dimethyl Maleate (17). A soln. of 17 (173 mg, 1.2 mmol) and 2d (285 mg, 1.0 mmol)
in abs. toluene (2 ml) was heated under reflux. After 24 h, no 2d was detected (TLC). The solvent was
1
evaporated, and the crude residue was analyzed by H-NMR showing the presence of 18/19 in a ratio of 2 :1.
After evaporation of CDCl3, the solid residue was dissolved in hot EtOH. After cooling to r.t., the colorless
precipitate was filtered and identified as 18. The mother liquor was kept in the refrigerator, and, the next day,
crystalline 19 was filtered. Recrystallization of the crude products led to anal. pure compounds.
Dimethyl cis,cis,trans-1-(4-Methoxyphenyl)-2,5-diphenylpyrrolidine-3,4-dicarboxylate (18). Yield: 192 mg
(43%). Colorless crystals. M.p. 197 1998 (EtOH/CH2Cl2). IR (KBr): 1744s (CˆO), 1514vs, 1454m, 1438m,
1243s (br.), 1217s (br.), 1178m, 1039m, 815w, 700m. 1H-NMR: 3.18, 3.54, 3.62 (3s, 3 MeO); 3.40, 3.87
(2dd, HÀC(3), HÀC(4)); 5.60, 5.84 (AB, J ˆ 7.2, HÀC(2), HÀC(5)); 6.27, 6.41 (AA'BB', J ˆ 9.0, 4 arom. H);
7.10 7.41 (m, 10 arom. H). 13C-NMR: 51.3, 51.9, 52.8 (3q, 3 MeO); 55.1 (d, C(3), C(4)); 65.8, 66.7 (2d, C(2),
C(5)); 113.3, 118.7, 126.9, 127.4, 127.5, 127.8, 127.9, 128.2 (8d, 14 arom. CH); 137.9, 138.2, 143.3, 151.2 (4s, 4 arom.
‡
C); 171.0 (s, 2 CˆO). CI-MS (NH3): 447 (28), 446(100, [ M ‡ 1] ), 444 (5). Anal. calc. for C27H27NO5 (445.51):
C 72.79, H 6.11, N 3.14; found: C 72.61, H 6.15, N 3.12.
Dimethyl trans-4,5-Dihydro-1-(4-methoxyphenyl)-2,5-diphenyl-1H-pyrrole-3,4-dicarboxylate (19). Yield:
75 mg (17%). Colorless crystals. M.p. 152 1548 (EtOH/CH2Cl2). IR (KBr): 2949m, 1736vs, 1674s, 1611s, 1593s,
1573s, 1509s, 1437s, 1363s (br.), 1210vs (br.), 1114s, 1055s, 1030s, 840s, 76 5s, 6 96s. 1H-NMR: 3.53, 3.62, 3.79
(3s, 3 MeO); 3.94, 4.96( AB, J ˆ 5.5, HÀC(4), HÀC(5)); 6.51, 6.62 (AA'BB', J ˆ 9.0, 4 arom. H); 7.22 7.48
(m, 10 arom. H). 13C-NMR: 50.5, 52.3, 55.1 (3q, 3 MeO); 56.5, 73.0 (2d, C(4), C(5)); 99.1 (s, C(3)); 113.8, 126.3,
126.7, 127.5, 128.0, 128.9, 129.2, 130.0 (8d, 14 arom. CH); 161.0 (s, C(2)); 131.0, 135.5, 142.0, 156.9 (4s, 4 arom.
‡
C); 165.5, 174.2 (2s, 2 CˆO). CI-MS (NH3): 444 (100, [M ‡ 1] ). Anal. calc. for C27H25NO5 (443.50): C 73.12, H
5.68, N 3.16; found: C 73.05, H 5.69, N 3.15.
4. Crystal-Structure Determination of 7b, 8a, 15b, and 16b12). All measurements for 7b were made on a KM-
4 Kuma diffractometer [29] with graphite monochromatized CuKa radiation (l 1.54178 ä). For the other
compounds, the measurements were conducted on a Nonius KappaCCD area-detector diffractometer [30] with
graphite-monochromated MoKa radiation (l 0.71073 ä) and an Oxford Cryosystems Cryostream 700 cooler.
The data collection and refinement parameters are given in the Table, views of the molecules are shown in
Figs. 1 3. Data reduction for 7b was performed with Dataproc [31], while HKL Denzo and Scalepack [32] was
used for 8a, 15b, and 16b. The intensities were corrected for Lorentz and polarization effects. Anal. [33] and
empirical (multi-scan method [34]) absorption corrections were applied for 7b and 8a, resp. Each structure was
solved by direct methods [35][36], which revealed the positions of all non-H-atoms. The non-H-atoms were
12
)
CCDC-198065 and 208506-208508 contain the supplementary crystallographic data for this paper. These
data can be obtained, free of charge, via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, U.K.; fax:
‡441223336033; e-mail: deposit@ccdc.cam.ac.uk).

508
Helvetica Chimica Acta Vol. 87 (2004)
Table. Crystallographic Data for Compounds 7b, 8a, 15b, and 16b
7b
8a
15b
16b
Crystallized from
Empirical formula
Formula weight
Crystal color, habit
Crystal dimensions [mm]
Temp. [K]
Crystal system
Space group
Z
EtOH
C30H29NS
435.60
MeOH
C28H23NS
405.56
MeOH/CH2Cl2 MeOH/CH2Cl2
C27H27NO5
445.51
C27H27NO5
445.51
colorless, prism colorless, plate
colorless, prism colorless, tablet
0.20 Â 0.30 Â 0.50 0.07 Â 0.30 Â 0.30 0.15 Â 0.20 Â 0.27 0.12 Â 0.15 Â 0.18
293(1)
160(1)
orthorhombic
Pbca
160(1)
monoclinic
Cc
4
160(1)
monoclinic
P21/c
triclinic
≈
P1
4
16
4
Reflections for cell determination
54
64406
3469
5290
2q Range for cell determination [8] 10 22
4
55
4
6 0
4 55
Unit cell parameters a [ä]
11.768(2)
12.9886(1)
22.8639(2)
28.9652(3)
90
90
90
8601.8(1)
1.253
0.165
12.4880(2)
14.7967(3)
13.8734(3)
90
116.6317(8)
90
2291.57(8)
1.291
0.0888
11.0645(2)
20.1040(4)
10.7831(2)
90
110.4783(8)
90
2247.02(7)
1.317
0.0906
b [ä]
c [ä]
a [8]
b [8]
15.276(3)
15.660(3)
73.90(2)
71.04(2)
71.87(2)
2481.1(8)
1.166
g [8]
V [ä3]
Dx [g cmÀ3
]
Linear absorption coefficient [mmÀ1] 1.27
Transmission factors [min; max]
Scan type
2q(max) [8]
0.592; 0.802
w
0.893; 0.992
f and w
55
f and w
60
w
135
55
Total reflections measured
Symmetry-independent reflections
Reflections with I > 2s(I)
Reflections used in refinement
Parameters refined; restraints
Final R(F) (I > 2s(I)
reflections)
8624
8293
5705
8293
589
89971
9845
6209
9844
544
27716
3359
2828
3358
302; 2
54079
5131
3831
5129
302
80.05460.046 0.0415
0.0438
wR(F2) (all data)
0.1887
0.1264; 0.1241
1.112
0.1249
0.0995
0.0053; 0.1625
0.1154
0.0574; 0.4651
Weighting parameters [a; b]a)
Goodness-of-fit
0.0625; 0.4740
1.0161.0361.045
0.0011(2)
0.001
0.27; À 0.43
Secondary extinction coefficient
Final Dmax/s
0.012(2)
0.001
0.24; À 0.19
0.012(2)
0.001
0.20; À 0.26
0.003
0.88; À 0.35
D1 (max; min) [e äÀ3
]
a) wÀ1 ˆ s2(F2o) ‡ (aP)2 ‡ bP, where P ˆ (Fo2 ‡ 2F2c )/3
refined anisotropically. All of the H-atoms were placed in geometrically calculated positions and refined with a
riding model where each H-atom was assigned a fixed isotropic displacement parameter with a value equal to
1.2Ueq of its parent C-atom (1.5Ueq for Me groups). In both 7b and 8a, there are two symmetry-independent
molecules in the asymmetric unit. The atomic coordinates of the two molecules were tested carefully for a
relationship from a higher symmetry space group with the program PLATON [37], but none could be found.
One Me C-atom in molecule B of 7b, C(33B), is disordered. Two positions were defined for this atom and the
site occupation factor of the major component refined to 0.535(14). Refinement of each structure was carried
À
Á2
P
out on F2 by full-matrix least-squares procedures, which minimized the function w Fo2 À F2c . For 8a, 15b, and
16b, corrections for secondary extinction were applied, and one, one, and two reflections, resp., whose intensities
were considered to be extreme outliers, were omitted from the final refinements.
Neutral-atom-scattering factors for the non-H-atoms were taken from [38a], and the scattering factors for
H-atoms were taken from [39]. Anomalous dispersion effects were included in Fc [40]; the values for f' and f''

Helvetica Chimica Acta Vol. 87 (2004)
509
were those of [38b]. The values of the mass-attenuation coefficients are those of [38c]. All calculations were
performed using SHELXL97 [41].
REFERENCES
[1] A. Gebert, A. Linden, G. Mloston, H. Heimgartner, Pol. J. Chem. 2003, 77, 157.
[2] a) R. Huisgen, W. Scheer, G. Szeimies, H. Huber, Tetrahedron Lett. 1966, 377; b) R. Huisgen, W. Scheer, H.
Huber, J. Am. Chem. Soc. 1967, 89, 1753; c) R. Huisgen, W. Scheer, H. M‰der, Angew. Chem., Int. Ed. 1969,
8, 602; d) H. Hermann, R. Huisgen, H. M‰der, J. Am. Chem. Soc. 1971, 93, 1779.
[3] a) J. W. Lown, in −1,3-Dipolar Cycloaddition Chemistry×, Ed. A. Padwa, Wiley-Interscience, New York,
1984, Vol. 1, p. 653; b) H. W. Heine, R. Peavy, A. J. Durbetaki, J. Org. Chem. 1966, 31, 3924; c) P. La Porta,
L. Capuzzi, F. Bettarini, Synthesis, 1994, 287; d) I. Coldham, A. J. Collis, R. J. Mould, D. E. Robinson,
Synthesis 1995, 1147; e) K. Matsumoto, R. Ohta, T. Uchida, H. Nishioka, M. Yoshida, A. Kakehi, J.
Heterocycl. Chem. 1995, 32, 367; f) G. Gonzales, M. V. Martin, M. C. Paredes, Heterocycles 2000, 52, 237.
[4] a) G. Mloston, A. Linden, H. Heimgartner, Pol. J. Chem. 1997, 71, 32; b) G. Mloston, A. Linden, H.
Heimgartner, Helv. Chim. Acta 1998, 81, 558.
[5] G. Mloston, K. Urbaniak, H. Heimgartner, Helv. Chim. Acta 2002, 85, 2056.
[6] A. Gebert, A. Linden, G. Mloston, H. Heimgartner, Heterocycles 2002, 56, 393.
[7] G. Mloston, K. Urbaniak, A. Linden, H. Heimgartner, Helv. Chim. Acta 2002, 85, 2644.
[8] G. Mloston, Z. Skrzypek, Bull. Soc. Chim. Belg. 1990, 99, 16 7.
[9] C. K. Johnson, −ORTEP II×. Report ORNL-5138, Oak Ridge National Laboratories, Oak Ridge,
Tennessee, 1976.
[10] a) R. Huisgen, C. H. Ross, K. Matsumoto, Heterocycles 1981, 15, 1131; b) J. H. Hall, R. Huisgen, J. Chem.
Soc., Chem. Commun. 1971, 1187.
[11] a) R. Bartnik, G. Mloston, S. Lesniak, Pol. J. Chem. 1979, 53, 537; b) R. Bartnik, G. Mloston, Tetrahedron
1984, 40, 2569; c) C. Wittland, M. Arend, N. Risch, Synthesis 1996, 36 7.
[12] E. Brunn, R. Huisgen, Tetrahedron Lett. 1971, 473.
[13] R. Huisgen, X. Li, H. Giera, E. Langhals, Helv. Chim. Acta 2001, 84, 981.
[14] D. Ramaiah, M. Muneer, K. R. Gopidas, P. K. Das, N. P. Rath, M. V. George, J. Org. Chem. 1996, 61, 4240.
[15] O. Tsuge, K. Oe, N. Kawaguchi, Chem. Lett. 1981, 1585.
[16] W. K. Anderson, A. S. Milowsky, J. Med. Chem. 1986, 29, 2241.
[17] O. Tsuge, K. Sone, S. Urano, K. Matsuda, J. Org. Chem. 1982, 47, 5171.
[18] C. Gaebert, J. Mattay, Tetrahedron 1997, 53, 14297.
[19] J. W. Lown, K. Matsumoto, Can. J. Chem. 1970, 48, 2215.
[20] A. Derdour, F. Texier, Can J. Chem. 1985, 63, 2245.
[21] E. Vedejs, J. W. Grissom, J. Org. Chem. 1988, 53, 1882.
[22] A. Boruah, B. Baruah, D. Prajapati, J. S. Sandhu, A. C. Ghosh, Tetrahedron Lett. 1996, 37, 4203.
[23] J. H. Hall, R. Huisgen, C. H. Ross, W. Scheer, J. Chem. Soc., Chem. Commun. 1971, 1188; see also: R.
Bartnik, G. Mloston, Synthesis 1983, 924.
[24] R. Bartnik, in −Nitrogen, Oxygen and Sulfur Ylide Chemistry×, Ed. J. S. Clark, Oxford University Press,
Oxford, 2002, pp. 188 190.
[25] G. Mloston, J. Romanski, H. Heimgartner, Pol. J. Chem. 2001, 75, 975.
[26] B. S. Pedersen, S. Scheibye, N. H. Nilsson, S.-O. Lawesson, Bull. Soc. Chim. Belg. 1978, 87, 223.
[27] E. Campaigne, W. B. Reid, J. Am. Chem. Soc. 1946, 68, 769.
[28] W. E. McEwen, A. S. Grossi, R. J. MacDonald, A. P. Stamegna, J. Org. Chem. 1980, 45, 1301.
[29] Kuma, Data Collection Program, Version v.10.2.1. Kuma Diffraction, Wroclaw, Poland, 1998.
[30] R. Hooft, KappaCCD Collect Software, Nonius BV, Delft, The Netherlands, 1999.
[31] Kuma, Dataproc Kuma Diffraction. Kuma Diffraction, Wroclaw, Poland, 1996.
[32] Z. Otwinowski, W. Minor, in −Methods in Enzymology×, Vol. 276, −Macromolecular Crystallography×, Part
A, Eds. C. W. Carter Jr., R. M. Sweet, Academic Press, New York, 1997, p. 307.
[33] J. de Meulenaer, H. Tompa, Acta Crystallogr. 1965, 19, 1014.
[34] R. H. Blessing, Acta Crystallogr., Sect. A 1995, 51, 33.
[35] G. M. Sheldrick, Acta Crystallogr., Sect. A 1990, 46, 46 7.
[36] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M. C. Burla, G. Polidori, M. Camalli, −SIR92×, J.
Appl. Crystallogr. 1994, 27, 435.

510
Helvetica Chimica Acta Vol. 87 (2004)
[37] A. L. Spek, −PLATON×, Program for the Analysis of Molecular Geometry, University of Utrecht, The
Netherlands, 2003.
[38] a) E. N. Maslen, A. G. Fox, M. A. O×Keefe, in −International Tables for Crystallography×, Ed. A. J. C.
Wilson, Kluwer Academic Publishers, Dordrecht, 1992, Vol. C, Table 6.1.1.1, p. 477; b) D. C. Creagh, W. J.
McAuley, in −International Tables for Crystallography×, Ed. A. J. C. Wilson, Kluwer Academic Publishers,
Dordrecht, 1992, Vol. C, Table 4.2.6.8, p. 219; c) D. C. Creagh, J. H. Hubbell, in −International Tables for
Crystallography×, Ed. A. J. C. Wilson, Kluwer Academic Publishers, Dordrecht, 1992, Vol. C, Table 4.2.4.3,
p. 200.
[39] R. F. Stewart, E. R. Davidson, W. T. Simpson, J. Chem. Phys. 1965, 42, 3175.
[40] J. A. Ibers, W. C. Hamilton, Acta Crystallogr. 1964, 17, 781.
[41] G. M. Sheldrick, −SHELXL97×, Program for the Refinement of Crystal Structures, University of Gˆttingen,
Germany, 1997.
Received August 12, 2003