Intramolecular rhodium-catalyzed activation of α-amino C-H bonds: decisive influence of conformational factors in the synthesis of bicyclic aminals from N-sulfamoyloxyacetyl azacycloalkanes

Article abstract of DOI:10.1016/j.tetlet.2007.09.148

The activation of α-amino C-H bonds in azacycloalkanes by way of intramolecular rhodium-catalyzed amination is reported. In this study, the 'activating' sulfamoyloxy group is attached to the endocyclic nitrogen atom with an appropriate linker. The influence of various structural parameters was studied. Results obtained demonstrate the remarkable conformational control that is possible with such azacycloalkane systems. This work leads to the first example of a successful intramolecular catalyzed amination of a tertiary sulfamic ester, a substrate known to be highly prone to elimination and/or nucleophilic displacement.

Full text of DOI:10.1016/j.tetlet.2007.09.148

Available online at www.sciencedirect.com
Tetrahedron Letters 48 (2007) 8531–8535
Intramolecular rhodium-catalyzed activation of a-amino C–H
bonds: decisive influence of conformational factors in the
synthesis of bicyclic aminals from N-sulfamoyloxyacetyl
azacycloalkanes
Marie S. T. Morin,a Sylvestre Toumieux,a Philippe Compain,a,* Sandrine Peyrata
and Justyna Kalinowska-Tluscikb
aInstitut de Chimie Organique et Analytique, UMR CNRS 6005, Universite´ d’Orle´ans, BP 6759, 45067 Orle´ans Cedex 2, France
bFaculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland
Received 27 July 2007; accepted 24 September 2007
Available online 22 October 2007
Abstract—The activation of a-amino C–H bonds in azacycloalkanes by way of intramolecular rhodium-catalyzed amination is
reported. In this study, the ‘activating’ sulfamoyloxy group is attached to the endocyclic nitrogen atom with an appropriate linker.
The influence of various structural parameters was studied. Results obtained demonstrate the remarkable conformational control
that is possible with such azacycloalkane systems. This work leads to the first example of a successful intramolecular catalyzed
amination of a tertiary sulfamic ester, a substrate known to be highly prone to elimination and/or nucleophilic displacement.
ꢀ 2007 Elsevier Ltd. All rights reserved.
The direct and selective transformation of unactivated
C–H bonds is expected to have a profound impact on
many areas of chemistry, from reaction design to the
synthesis of pharmaceuticals and complex organic mole-
cules.1 The high prevalence of nitrogen-based functional
groups in natural and synthetic products has stimulated
the development of efficient catalytic methods for the
amination of unactivated C–H bonds.2,3 One of the
major advances in this field has recently involved
Rh-catalyzed intramolecular C–H insertion reactions
using sulfamic ester substrates.3–5 This highly diastereo-
and regioselective process leads generally to the forma-
tion of the corresponding six-membered ring insertion
product (Fig. 1).3
Electronic effects were found to have a dramatic influ-
ence on the regioselectivity of the intramolecular amina-
tion reaction. Benzylic, allylic and tertiary C–H bonds as
well as sites adjacent to electron-donating groups are
generally favoured.3 In a study performed in the piperi-
dine series, we recently reported the first examples of
7-membered and 8-membered ring obtained by way of
intramolecular catalyzed amination of C–H bonds
(Scheme 1).6,7
Based on results obtained with various test substrates, it
was shown that the unusual regioselectivity observed in
nitrogen-containing systems could be rationalized by
subtle conformational factors.6 The major synthetic
interest of this process is to functionalize a C–H bond
in 1,7- or 1,8-relationship with respect to the activating
O
O
O
O
O
O
MgO
S
S
NH
PhI(OAc)2
NH2
R3
Ts
Ts
Ts
allylTMS
BF3.OEt2
R1
R3
R1
Rh2(OAc)4
cat.
Rh2(OAc)4 cat.
N
N
O
N
R2
R2
H
[O]
H
H
N
78%
Figure 1. Rh-catalyzed oxidative cyclization of sulfamic esters.
H2NSO2O
67%
H2NSO2O
3 de > 98%
S
O
2
1
O
*
Corresponding author. Tel.: +33 2 38 49 48 55; fax: +33 2 38 41 72
81; e-mail: philippe.compain@univ-orleans.fr
Scheme 1.
0040-4039/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2007.09.148

8532
M. S. T. Morin et al. / Tetrahedron Letters 48 (2007) 8531–8535
group to afford a reactive aminal function. Addition of
various nucleophiles to the N-tosyliminium ion pre-
cursor 2 leads to the stereoselective formation of a
new C–C bond and regenerates the sulfamic ester that
may be used again for further C–H amination of the
piperidine ring (Scheme 1).6,8 These results open the
way to unique strategies for the iterative multifunction-
alization of unactivated C–H bonds in nitrogen-contain-
ing heterocycles. To study the feasibility of this new
concept and increase its synthetic flexibility, we decided
to explore azacycloalkane systems in which the
sulfamoyloxymethyl group would be attached to the
endocyclic nitrogen with an appropriate linker (Scheme 2).
ClSO2NH2
( 3 equiv.)
N
N
N
N
DMA, 16h, r.t.
16
OSO2NH2
( )n
O
O
OH
O
O
O
R1
R1
R2
R2
( )n
N
N
N
OR
OR
OR
O
OR
O
15 (50%)
n = 2: 10 (77%)
n = 1: 11 (32%)
12 (79%)
n = 2: 13 (92%)
n = 1: 14 (84%)
In connection with our ongoing interest in the synthesis
of alkaloids related to iminosugars,9 we focused on
pyrrolidine- and piperidine-containing test substrates.
The sulfamoyloxymethyl group was linked to the endo-
cyclic nitrogen by way of a carbonyl group to prevent
unproductive coordination of the nitrogen lone-pair to
the catalyst. In pursuing the design of the ‘activating
arm’, various groups (R1 and R2) were introduced
to modulate or facilitate the amination reaction, for
example, by way of Thorpe–Ingold effect (R1,
R2 = H, methyl, cyclopropyl).10 The structure of the test
substrates was chosen to study the influence of confor-
mational factors (ring size, gem-dialkyl effect) as well
as electronic factors (allylic activation) on the amination
reaction. The two-step synthesis began with the coupling
of cyclic amines to unprotected b-hydroxy carboxylic
acids using HOBt and EDCI to produce the expected
amides 4–9 in 67–87% yield (Scheme 3).11,12
R = SO2NH2
Scheme 4.
It is noteworthy that direct coupling of piperidine to
glycolic acid in refluxing xylene was found to be much
less effective as only 25% of the expected product 4 could
be isolated.13 The second step turned out to be more
challenging (Scheme 4). Under typical sulfamoylation
conditions,3 reaction of primary alcohol
4 with
sulfamoyl chloride and pyridine in CH2Cl2 afforded
the expected sulfamic ester 10 in only 36% yield.
Sulfamoylation of tertiary gem-dimethyl alcohol 9 led
to the highly favoured formation of the elimination
product 16. It is indeed well-known that tertiary
sulfamic esters are intrinsically unstable because of the
activating nature of the sulfamoyl group for elimination
and/or nucleophilic displacement.3
Rh2(OAc)4
cat.
( )n
( )n
( )n
NuTMS
SO2
H
N
Decisive improvement was obtained by using N,N-di-
methylacetamide (DMA) as solvent, without pyridine,
according to the method described by Okada et al.14
for primary and secondary alcohols. The process was
applied successfully to tertiary alcohols 7–9 to provide
sulfamates 13–15 (Scheme 4).15,16
Nu
N
N
N
[O]
OSO2NH2
O
OSO2NH2
O
O
O
R1
R1
R1
R2
R2
R2
R1, R2 = H, cyclopropyl, methyl
Scheme 2.
Having test substrates 10–15 in hand, we first investi-
gated the influence of ring size on the amination reaction
outcome (Table 1). Quite surprisingly, following a stan-
dard protocol using PhI(OAc)2 (1.1 equiv), MgO
(2.3 equiv) and 5 mol % of Rh2(OAc)4,6 piperidine 10
was converted into the expected aminal 17 in 20% yield
only (entry 1). The amination reaction was then per-
formed with tetrahydropyridine 12, a close analog of
10, which was designed to strongly favoured the inser-
tion into the allylic a-amino C–H bond (entries 4 and
5). Even in this case, no improvement was observed
and the amination product 19 was obtained in low
yields. In contrast, ring size was found to play a key role
since pyrrolidine 11 provided the expected aminal 18 in
a much better yield of 47% (entry 2). The yield of the
reaction was not improved by using Rh2(esp)2, an effi-
cient C–H amination catalyst (entry 3).4b The influence
of the gem-dialkyl effect (Thorpe–Ingold effect)10 on
the formation of the cyclized amination product was
then studied. It is noteworthy that no intramolecular
EDCI (1.5 equiv.)
HOBt (1.1 equiv.)
NMM (2.2 equiv.)
OH
+
OH
R2
N
H
O
N
CH2Cl2, 16h, r.t.
R1
OH
R2
O
R1
( )n
( )n
N
N
N
N
OH
OH
OH
O
O
OH
O
O
(83%)
9 (75%)
n = 2: 4
6 (75%)
n = 2: 7 (67%)
n = 1: 8 (87%)
n = 1: 5 (72%)
Scheme 3.

M. S. T. Morin et al. / Tetrahedron Letters 48 (2007) 8531–8535
8533
Table 1. Study of the influence of various structural parameters in C–
H insertion of sulfamic estersa
[Rh] catalyst
PhI(OAc)2, MgO
H
N
N
O
O
N
S
O
CH2Cl2, Δ, 16h
O
OSO2NH2
O
R1
R1
R2
R2
Entry
Catalyst
Product
Yieldc (%)
( )n
1 (10)b
2 (11)b
3 (11)b
Rh2(OAc)4
Rh2(OAc)4
Rh2(esp)2
17 (n = 2) 20
18 (n = 1) 47
18 (n = 1) 40
H
N
N
O
O
S
O
Figure 2. One of the two molecules in the crystal structure of 10. The
asymmetric unit contains two molecules with slightly different confor-
mations. Visualization made with ORTEP-3.0,23 ellipsoids drawn at
30% probability level.
O
4 (12)b
5 (12)b
Rh2(OAc)4
Rh2(esp)2
19
19
12
25
H
N
N
N
O
O
S
O
O
O
As supported by X-ray crystallographic analysis of 10
(Fig. 2),20,21 the piperidine ring of compounds 10, 13
and 15 is expected to be in a well-defined chair confor-
mation. Additional conformational constraints are
introduced by the amide conjugation, which induce a
planar arrangement of the NC@O group. This stabilized
conformation is likely to place the nitrene centre in an
unfavourable position with respect to the more reactive
axial C–H bond at C-2 (Fig. 3b).18 By analogy with the
study performed on cyclic ethers by Ingold et al.,18 we
assume that stereoelectronic weakening of the C–H
bond adjacent to the amide nitrogen is at a maximum
when the dihedral angle, h, between the C–H bond
and the p-type lone pair orbital on the nitrogen is 0ꢁ
and at a minimum when this angle is 90ꢁ (Fig. 3).
H
N
6 (15)b
7 (15)b
Rh2(OAc)4
Rh2(oct)4
20
20
12d
8d
O
O
S
O
( )n
H
N
8 (13)b
9 (14)b
10 (14)b Rh2(esp)2
Rh2(OAc)4
Rh2(OAc)4
21 (n = 2) 24
22 (n = 1) 86
22 (n = 1) 83
N
O
O
S
O
O
a All reactions have been carried out in the presence of 2.3 equiv of
MgO, 1.1 equiv of PhI(OAc)2 and a catalytic amount of Rh2(OAc)4
(5 mol %), Rh2(esp)2 (4 mol %) or Rh2(oct)4 (4 mol %).
b Amination substrate.
c Isolated yield.
d Elimination product 16 was also isolated (7–10%).
The more flexible pyrrolidine five-membered ring may
adopt an averaged planar conformation as suggested
by X-ray crystallographic and 1H NMR analysis of
1416,20,22 (Fig. 4). In this conformation the two geminal
a-amino C–H bonds are both activated with an average
h value of ca. 30ꢁ (Fig. 3a). The dramatic influence of the
replacement of a methylene group by a cyclopropyl
group in pyrrolidine systems can be rationalized by the
‘reactive rotamer’ concept.10
catalyzed amination has been described from tertiary
sulfamic ester so far. Not surprisingly, gem-dimethyl-
containing compound 15 was found to be a poor
substrate and the expected aminal 20 was obtained in
8–12% yield, along with an equal amount of the elimina-
tion product 16 (entries 6 and 7).
The influence of ring-size and gem-dialkyl effect on
a-amino C–H insertion could be nicely demonstrated
from substrates 13 and 14. Conversion of cyclopropyl-
containing pyrrolidine 14 afforded the desired cyclized
product 2217 in an excellent yield of 86% whereas no
decisive improvement was observed for the correspond-
ing piperidine analog 13 (entries 8–10). To our knowl-
As shown by X-ray crystallographic analysis of 14 and
10,20 the conformation of both molecules is different.
Conformation of compound 14 is much more rigid
due to the presence of a strained cyclopropane ring.
The aliphatic part of the molecule in compound 10,
which has almost linear conformation, changes strongly
in the structure of 14 in which the distance between the
sulfamate nitrogen atom and the a-amino C–H bond is
remarkably shorter. The dihedral angles N–CO–C–O(–S)
are equal to 55.6(3)ꢁ in 14 and 21.2(3)ꢁ in the cyclized
edge, this is the first example of
a successful
intramolecular catalyzed C–H amination from a tertiary
sulfamic ester.3 Results presented in Table 1 remarkably
highlight the decisive influence of conformational
effects, which may dominate electronic effects; the intro-
duction of an electronically favoured allylic site was
indeed less effective to improve the insertion process
(Table 1, entries 4 and 5). The better yields observed
for pyrrolidine systems compared to piperidine systems
may be explained by the fact that the pyrrolidine five-
membered ring is more conformationally flexible and
thus better accommodates the transition state for C–H
insertion.18,19
θ
O
H
Heq
H
H
H
R1
R2
OSO2NH2
O
R1
R2
H
H
Hax
OSO2NH2
(a)
(b)
Figure 3.

8534
M. S. T. Morin et al. / Tetrahedron Letters 48 (2007) 8531–8535
example of a successful intramolecular catalyzed amina-
tion of a tertiary sulfamic ester and to the first example
of a-C–H substitution in azacycloalkane by a group
linked to the endocyclic nitrogen. Further studies to
explore the potential of this chemistry are currently
underway in our laboratory.
Acknowledgments
Financial support of this work by the CNRS and the
´
University of Orleans is gratefully acknowledged. S.T.
Figure 4. The projection of the asymmetric unit of compound 14.
Visualization made with ORTEP-3.0,23 ellipsoids drawn at 30%
probability level.
thanks the French department of research for a fellow-
ship. The authors express their gratitude to O. R.
Martin for his interest in this work and for helpful
discussions.
product 22 (Figs. 4 and 6).20,24 In 10, the values of these
angles, which correspond to the above-mentioned linear
conformation, are 175.6(2)ꢁ and 176.6(2)ꢁ for the first
and second molecule of the asymmetric unit, respec-
tively. These results suggest that the cyclopropyl group
favours a reactive conformation, which places the
nitrene precursor in close proximity to the reacting
C–H bond. The amination reaction is thus facilitated
by a higher population of the reactive rotamer due to
the presence of the cyclopropyl group (Fig. 5).
References and notes
1. (a) Bergman, R. G. Nature 2007, 446, 391; (b) Godula, K.;
Sames, D. Science 2006, 312, 67; (c) Kakiuchi, F.; Chatani,
N. Adv. Synth. Catal. 2003, 345, 1077; (d) Davies, H. M.
L.; Beckwith, E. J. Chem. Rev. 2003, 103, 2861; (e) Dick,
A. R.; Sanford, M. S. Tetrahedron 2006, 62, 2439; (f)
Doyle, M. P.; Forbes, D. C. Chem. Rev. 1998, 98, 911; (g)
Murai, S. In Activation of Unreactive Bonds and Organic
Synthesis; Springer: Berlin, 1999.
In conclusion, rhodium-catalyzed C–H amination of
cyclic amines leading to bicyclic aminals is reported. In
this original system, the ‘activating’ sulfamoyloxy group
is attached to the endocyclic nitrogen with an appropri-
ate linker. The results obtained further demonstrate the
remarkable conformational control that is possible in
azacycloalkane derivatives. This work leads to the first
2. (a) Davies, H. M. L.; Long, M. S. Angew. Chem., Int. Ed.
2005, 44, 3518; (b) Muller, P.; Fruit, C. Chem. Rev. 2003,
¨
103, 2905; (c) Dauban, P.; Dodd, R. H. Synlett 2003, 1571.
3. (a) Espino, C. G.; Du Bois, J. In Modern Rhodium-
Catalyzed Organic Reaction; Evans, P. A., Ed.; Wiley-
VCH: Weinheim, 2005; pp 379–416; (b) Du Bois, J.
Chemtracts 2005, 18, 1.
4. See for example: (a) Espino, C. G.; Wehn, P. M.; Chow, J.;
Du Bois, J. J. Am. Chem. Soc. 2001, 123, 6935; (b) Espino,
C. G.; Fiori, K. W.; Kim, M.; Du Bois, J. J. Am. Chem.
O
O
OSO2NH2
Soc. 2004, 126, 15378; (c) Fruit, C.; Muller, P. Helv. Chim.
¨
Acta. 2004, 87, 1607; (d) Liang, J.-L.; Yuan, S.-X.; Huang,
J.-S.; Yu, W.-Y.; Che, C.-M. Angew. Chem., Int. Ed. 2002,
41, 3465; (e) Liang, J.-L.; Yuan, S.-X.; Huang, J.-S.; Che,
C.-M. J. Org. Chem. 2004, 69, 3610; (f) Cui, Y.; He, C.
Angew. Chem., Int. Ed. 2004, 43, 4210.
O
O
S
Steric strain
N
N
O
H
H
H
H
5. For pioneering work on intramolecular nitrene C–H
insertion see: Breslow, R.; Gellman, S. H. J. Am. Chem.
Soc. 1983, 105, 6728.
H
2 N
6. Toumieux, S.; Compain, P.; Martin, O. R.; Selkti, M. Org.
Lett. 2006, 8, 4493.
Figure 5.
7. For the first example of a metal-catalyzed amination of a
pseudo-anomeric C–H bond see: Toumieux, S.; Compain,
P.; Martin, O. R. Tetrahedron Lett. 2005, 46, 4731.
8. Toumieux, S.; Compain, P.; Martin, O. R. unpublished
results.
9. For selected references see: (a) Godin, G.; Compain, P.;
Masson, G.; Martin, O. R. J. Org. Chem. 2002, 67, 6960;
(b) Godin, G.; Compain, P.; Martin, O. R. Org. Lett.
2003, 5, 3269; (c) Compain, P.; Martin, O. R.; Boucheron,
C.; Godin, G.; Yu, L.; Ikeda, K.; Asano, N. ChemBio-
Chem 2006, 7, 1356; (d) Iminosugars: From Synthesis to
Therapeutic Applications; Compain, P., Martin, O. R.,
Eds.; Wiley-VCH: Weinheim, 2007.
10. Jung, M. E.; Piizzi, G. Chem. Rev. 2005, 105, 1735.
´
´
11. Bozso, Z.; Toth, G.; Murphy, F.; Lovas, S. Lett. Pept. Sci.
Figure 6. The projection of the asymmetric unit of compound 22.
Visualization made with ORTEP-3.0,23 ellipsoids drawn at 30%
probability level.
2000, 7, 157.
12. Typical amidation procedure: To a 0.3 M solution of b-
hydroxy carboxylic acid (1.5 equiv) in anhydrous CH2Cl2,

M. S. T. Morin et al. / Tetrahedron Letters 48 (2007) 8531–8535
8535
˚
were added successively the cyclic amine (1 equiv), HOBt
(1.1 equiv), N-methylmorpholine (NMM, 2.2 equiv) and
EDCI (1.5 equiv) at room temperature under argon. The
solution was stirred overnight. The reaction mixture was
quenched with a solution of NH4Cl and diluted with water
and CH2Cl2. The mixture was extracted with CH2Cl2
(three times). The combined organic layer was dried
(MgSO4) and concentrated under reduced pressure. Puri-
fication on silica gel (CH2Cl2/acetone 95/5) afforded the
expected amide.
diffractometer using MoKa radiation (k = 0.7107 A) at
293(2) K. The phase problem was solved with direct
methods with SIR9225 for 10 and 14, and with SHELXS-9726
for 22. All structures were refined by full-matrix least-
squares on F2 (SHELXL-97).26 All non-hydrogen atoms
were refined anisotropically. The positions of all hydrogen
atoms were found in the difference Fourier map. The
hydrogen atoms were refined with isotropic displacement
parameter equal 1.2 times that of the parent atom with the
use of the riding model. Crystallographic data (excluding
structure factors) for structures 10, 14 and 22 in this Letter
have been deposited with the Cambridge Crystallographic
Data Centre as supplementary Publication Nos. CCDC
653256, CCDC 653257 and CCDC 655724, respectively.
Copies of the data can be obtained, free of charge, on
application to CCDC, 12 Union Road, Cambridge CB2
13. Li, M.; Scott, J.; O’Doherty, G. A. Tetrahedron Lett. 2004,
45, 1005.
14. Okada, M.; Iwashita, S.; Koizumi, N. Tetrahedron Lett.
2000, 41, 7047.
15. Typical sulfamoylation procedure: To a 0.6 M solution of
the alcohol substrate in N,N-dimethylacetamide (DMA)
was added ClSO2NH2 (3 equiv) at 0ꢁ C under argon. The
solution was stirred overnight at room temperature. Water
and EtOAc were added and the mixture was extracted
with EtOAc (three times). The combined organic layer was
dried (MgSO4) and concentrated under reduced pressure.
After the removal of DMA by coevaporation with toluene
in vacuo, purification of the residual product on silica gel
(CH2Cl2/acetone 99/1 to 90/10) afforded the expected
sulfamic ester.
1EZ, UK, (fax: +44
deposit@ccdc.cam.ac.uk).
0 1223 336033 or e-mail:
21. Crystal data for compound 10: Moiety formula
C7H14N2O4S, crystal size: 0.28 · 0.20 · 0.13 mm3, M =
˚
222.26, monoclinic, space group P21/c, a = 9.6309(1) A,
˚
˚
b = 20.4516(3) A, c = 10.4859(1) A, b = 94.9689(6)ꢁ, V =
2057.62(4) A , Z = 8, Dc = 1.435 g/cm3, l(MoKa) =
3
˚
0.31 mmÀ1
, F(000) = 944; theta range: 1.00–27.48ꢁ,
66,982 collected reflections, 9446 independent (R(int) =
0.048). The refinement parameters are R1 = 0.039 for
reflections with F2 > 2r(F2), wR2 = 0.095, S = 1.04.
1
16. Selected data for sulfamic ester 14: H NMR (400 MHz,
acetone-d6): d 1.24 (m, 2H); 1.38 (m, 2H); 1.81 (m, 2H);
1.91 (m, 2H); 3.36 (t, 2H, J = 6.8 Hz); 3.72 (t, 2H,
J = 6.4 Hz); 6.93 (s, 2H); 13C NMR (75 MHz, acetone-d6):
d 11.7; 24.1; 26.7; 47.2; 47.3; 63.3; 166.4; IR (neat) 3406,
1633, 1462, 1373, 1136 cmÀ1; HRMS (ESI) m/z 257.0566
[M+Na]+ (C8H14N2O4NaS requires: 257.0572).
22. Crystal data for compound 14: Moiety formula
C8H14N2O4S, crystal size: 0.20 · 0.13 · 0.05 mm3,
ꢀ
˚
M = 234.27, triclinic, space group P1, a = 7.4825(1) A,
˚
˚
b = 8.1228(2) A, c = 9.4670(2) A, a = 79.1433(9)ꢁ, b =
3
˚
81.5618(9)ꢁ, c = 73.5428(9)ꢁ, V = 539.27(2) A , Z = 2,
17. Selected data for aminal 22: 1H NMR (400 MHz, acetone-
d6): d 1.27–1.37 (m, 2H); 1.47–1.60 (m, 2H); 1.85–2.02 (m,
3H); 2.39 (m, 1H); 3.46–3.55 (m, 2H), 5.47 (t, 1H,
J = 6.0 Hz); 8.06 (s, 1H); 13C NMR (75 MHz, acetone-
d6): d 14.8; 15.6; 21.7; 33.5; 48.0; 64.1; 68.5; 166.8. IR
(neat) 3442, 1628, 1466, 1373, 1192, 1148 cmÀ1; HRMS
(ESI) m/z 255.0408 [M+Na]+ (C8H12N2O4NaS requires:
255.0415).
Dc = 1.443 g/cm3, l(MoKa) = 0.30 mmÀ1, F(000) = 248;
theta range: 1.00–27.48ꢁ, 12,821 collected reflections, 2479
independent (R(int) = 0.051). The refinement parameters
are R1 = 0.048 for reflections with F2 > 2r(F2), wR2 =
0.121, S = 1.03.
23. Farrugia, L. J. J. Appl. Cryst. 1997, 30, 565.
24. Crystal data for compound 22: Moiety formula
C8H12N2O4S, crystal size: 0.30 · 0.22 · 0.05 mm3, M =
˚
3
18. Malatesta, V.; Ingold, K. U. J. Am. Chem. Soc. 1981, 103,
609.
19. Davies, H. M. L.; Venkataramani, C.; Hansen, T.;
Hopper, D. W. J. Am. Chem. Soc. 2003, 125, 6462, and
references cited therein.
20. The crystals of compounds 10, 14 and 22 were transparent,
white colour and stable in the air. Suitable crystals were
obtained after crystallization from acetone/water (2/1) via
slow evaporation of the solvent at room temperature. The
intensity measurements for crystals of all presented
structures were carried out on a Nonius KappaCCD
232.26, orthorhombic, space group Pbca, a = 8.3408(1) A,
˚
˚
˚
b = 14.9800(2) A, c = 16.2865(3) A, V = 2034.92(5) A ,
Z = 8,
Dc = 1.516 g/cm3,
l(MoKa) = 0.31 mmÀ1
,
F(000) = 976; theta range: 1.00–27.48ꢁ, 62,691 collected
reflections, 9288 independent (R(int) = 0.038). The refine-
ment parameters are R1 = 0.042 for reflections with
F2 > 2r(F2), wR2 = 0.101, S = 1.08.
25. Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliarch,
A. J. Appl. Cryst. 1993, 26, 343.
26. Sheldrick, G. M. SHELX 97, 1997. Programs for Crystal
Structure Analysis. University of Go¨ttingen, Germany.