organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

(S)-2-(Iodo­meth­yl)-1-tosyl­pyrrolidine

aDepartment of Chemistry, State Key Laboratory of Applied Organic Chemstry, College of Chemical Engineering, Lanzhou University, Lanzhou 730000, People's Republic of China
*Correspondence e-mail: pengyu@lzu.edu.cn

(Received 7 November 2007; accepted 14 November 2007; online 6 December 2007)

In the title mol­ecule, C12H16INO2S, the pyrrolidine ring is in an envelope conformation. The dihedral angle between the four essentially coplanar atoms of the pyrrolidine ring and the benzene ring is 75.5 (4)°.

Related literature

For leading reviews, see: Allemann et al. (2004[Allemann, C., Gordillo, R., Clemente, F. R., Cheong, P. H. & Houk, K. N. (2004). Acc. Chem. Res. 37, 558-569.]); List (2004[List, B. (2004). Acc. Chem. Res. 37, 548-557.]); Notz et al. (2004[Notz, W., Tanaka, F. & Barbas, C. F. III (2004). Acc. Chem. Res. 37, 580-591.]); For related literature, see: Bahmanyar et al. (2003[Bahmanyar, S., Houk, K. N., Martin, H. J. & List, B. (2003). J. Am. Chem. Soc. 125, 2475-2479.]); List et al. (2000[List, B., Lerner, R. A. & Barbas, C. F. III (2000). J. Am. Chem. Soc. 122, 2395-2396.]); Northrup & MacMillan, (2002[Northrup, A. B. & MacMillan, D. W. C. (2002). J. Am. Chem. Soc. 124, 6798-6799.]); Sakthivel et al. (2001[Sakthivel, K., Notz, W., Bui, T. & Barbas, C. F. III (2001). J. Am. Chem. Soc. 123, 5260-5267.]); Barbas et al. (1997[Barbas, C. F. III, Heine, A., Zhong, G., Hoffmann, T., Gramatikova, S., Björnestedt, R., List, B., Anderson, J., Stura, E. A., Wilson, I. A. & Lerner, R. A. (1997). Science, 278, 2085-2092.]); Dalko & Moisan (2004[Dalko, P. L. & Moisan, L. (2004). Angew. Chem. Int. Ed. 43, 5138-5175.]); Eder et al. (1971[Eder, U., Sauer, G. & Wiechert, R. (1971). Angew. Chem. Int. Ed. Engl. 10, 496-497.]); Hajos & Parrish (1974[Hajos, Z. G. & Parrish, D. R. (1974). J. Org. Chem. 39, 1615-1621.]); Machajewski & Wong (2000[Machajewski, T. D. & Wong, C.-H. (2000). Angew. Chem. Int. Ed. 39, 1352-1374.]); Seayed & List (2005[Seayed, J. & List, B. (2005). Org. Biomol. Chem. 3, 719-724.]); Wagner et al. (1995[Wagner, J., Lerner, R. A. & Barbas, C. F. III (1995). Science, 270, 1797-1800.]).

[Scheme 1]

Experimental

Crystal data
  • C12H16INO2S

  • Mr = 365.22

  • Monoclinic, P 21

  • a = 7.6345 (16) Å

  • b = 7.7084 (16) Å

  • c = 12.071 (3) Å

  • β = 93.17 (1)°

  • V = 709.3 (3) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 2.40 mm−1

  • T = 294 (2) K

  • 0.25 × 0.16 × 0.16 mm

Data collection
  • Bruker APEX CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.586, Tmax = 0.701

  • 4398 measured reflections

  • 2424 independent reflections

  • 1787 reflections with I > 2σ(I)

  • Rint = 0.033

Refinement
  • R[F2 > 2σ(F2)] = 0.037

  • wR(F2) = 0.092

  • S = 1.02

  • 2424 reflections

  • 156 parameters

  • 1 restraint

  • H-atom parameters constrained

  • Δρmax = 0.43 e Å−3

  • Δρmin = −0.48 e Å−3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), with 664 Friedel pairs

  • Flack parameter: 0.02 (5)

Data collection: SMART (Bruker, 2000[Bruker (2000). SMART, SAINT, SADABS and SHELXTL. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2000[Bruker (2000). SMART, SAINT, SADABS and SHELXTL. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); molecular graphics: SHELXTL (Bruker, 2000[Bruker (2000). SMART, SAINT, SADABS and SHELXTL. Bruker AXS Inc., Madison, Wisconsin, USA.]); software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

During the past few years, the field of asymmetric catalysis, previously dominated by biocatalysis, has been complemented by organocatalysis (List, 2004; Notz et al., 2004; Allemann et al., 2004) using small organic molecules as a third powerful tool. Organocatalysis reagents are usually non-toxic, highly efficient and selective, readily available, metal-free and robust, explaining the growing interest in their use for organic synthesis (Dalko & Moisan, 2004; Seayed & List, 2005). Considering the above features, low cost and availability in both enantiomeric forms, proline is attractive especially to synthetic chemists. Developed by two industrial laboratories in the early 1970 s (Hajos & Parrish, 1974; Eder et al., 1971), a proline-catalyzed aldol reaction was reinvestigated recently and many novel results were obtained. For example, direct intermolecular asymmetric aldol reactions between aldehydes and the ketones (List et al., 2000; Sakthivel et al., 2001) or aldehydes (Northrup & MacMillan, 2002) afforded good to excellent enantioselectivity. The origin of stereoselectivity in this type of aldol reaction was examined in detail (Bahmanyar et al., 2003) and it was generally accepted this involved enamine intermediates. Similar mechanisms are found in type-1 aldolases (Machajewski & Wong, 2000) and catalytic antibodies that are type-1 aldolase mimics (Wagner et al., 1995; Barbas et al., 1997).

The molecular structure of the title compound (Fig.1) contains a pyrrolidine ring, which exists in an envelope conformation. The dihedral angle between the plane of atoms N1–C1–C3–C5 and the benzene ring is 75.5 (4) °, which potentially provides enough space as a binding-site for substrates during asymmetric catalysis process.

Related literature top

For leading reviews, see: Allemann et al. (2004); List (2004); Notz et al. (2004); For related literature, see: Bahmanyar et al. (2003); List et al. (2000); Northrup & MacMillan, (2002); Sakthivel et al. (2001); Barbas et al. (1997); Dalko & Moisan (2004); Eder et al. (1971); Hajos & Parrish (1974); Machajewski & Wong (2000); Seayed & List (2005); Wagner et al. (1995).

Experimental top

The title compound was prepared by the cascade reaction of p-toluenesulfonyl chloride with (S)-prolinol (commercial available) and iodine. 1H NMR (400 MHz, CDCl3): 7.73 (d, J = 6.8 Hz, 2H), 7.34 (d, J = 6.8 Hz, 2H), 3.77–3.71 (m, 1H), 3.63–3.60 (m, 1H), 3.51–3.46 (m, 1H), 3.23 (t, J = 9.6 Hz, 2H), 2.44 (s, 3H), 1.90–1.77 (m, 3H), 1.56–1.50 (m, 1H) p.p.m.; 13C NMR (100 MHz, CDCl3): 143.7, 134.2, 129.8 (2 C), 127.5 (2 C), 60.7, 50.0, 31.9, 23.8, 21.5, 11.5 p.p.m.. Single crystals suitable for X-ray determination were obtained by slow evaporation of a EtOAc solution over a period of several days.

Refinement top

All H atoms were placed geometrically (C—H distances were set to 0.98, 0.97, 0.96 and 0.93 A° for atoms CH, CH2, CH3, and CH (phenyl), respectively) and refined with a riding model, with Uiso(H) = 1.2 or 1.5 times Ueq(C).

Structure description top

During the past few years, the field of asymmetric catalysis, previously dominated by biocatalysis, has been complemented by organocatalysis (List, 2004; Notz et al., 2004; Allemann et al., 2004) using small organic molecules as a third powerful tool. Organocatalysis reagents are usually non-toxic, highly efficient and selective, readily available, metal-free and robust, explaining the growing interest in their use for organic synthesis (Dalko & Moisan, 2004; Seayed & List, 2005). Considering the above features, low cost and availability in both enantiomeric forms, proline is attractive especially to synthetic chemists. Developed by two industrial laboratories in the early 1970 s (Hajos & Parrish, 1974; Eder et al., 1971), a proline-catalyzed aldol reaction was reinvestigated recently and many novel results were obtained. For example, direct intermolecular asymmetric aldol reactions between aldehydes and the ketones (List et al., 2000; Sakthivel et al., 2001) or aldehydes (Northrup & MacMillan, 2002) afforded good to excellent enantioselectivity. The origin of stereoselectivity in this type of aldol reaction was examined in detail (Bahmanyar et al., 2003) and it was generally accepted this involved enamine intermediates. Similar mechanisms are found in type-1 aldolases (Machajewski & Wong, 2000) and catalytic antibodies that are type-1 aldolase mimics (Wagner et al., 1995; Barbas et al., 1997).

The molecular structure of the title compound (Fig.1) contains a pyrrolidine ring, which exists in an envelope conformation. The dihedral angle between the plane of atoms N1–C1–C3–C5 and the benzene ring is 75.5 (4) °, which potentially provides enough space as a binding-site for substrates during asymmetric catalysis process.

For leading reviews, see: Allemann et al. (2004); List (2004); Notz et al. (2004); For related literature, see: Bahmanyar et al. (2003); List et al. (2000); Northrup & MacMillan, (2002); Sakthivel et al. (2001); Barbas et al. (1997); Dalko & Moisan (2004); Eder et al. (1971); Hajos & Parrish (1974); Machajewski & Wong (2000); Seayed & List (2005); Wagner et al. (1995).

Computing details top

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXL97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2000); software used to prepare material for publication: SHELXTL (Bruker, 2000).

Figures top
[Figure 1] Fig. 1. The molecular structure showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.
(S)-2-(Iodomethyl)-1-tosylpyrrolidine top
Crystal data top
C12H16INO2SF(000) = 360
Mr = 365.22Dx = 1.710 Mg m3
Monoclinic, P21Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ybCell parameters from 1240 reflections
a = 7.6345 (16) Åθ = 3.1–21.5°
b = 7.7084 (16) ŵ = 2.40 mm1
c = 12.071 (3) ÅT = 294 K
β = 93.17 (1)°Block, colorless
V = 709.3 (3) Å30.25 × 0.16 × 0.16 mm
Z = 2
Data collection top
Bruker APEX CCD area-detector
diffractometer
2424 independent reflections
Radiation source: fine-focus sealed tube1787 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.033
φ and ω scansθmax = 27.9°, θmin = 1.7°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 99
Tmin = 0.586, Tmax = 0.701k = 69
4398 measured reflectionsl = 1515
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.037 w = 1/[σ2(Fo2) + (0.0387P)2 + 0.1584P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.092(Δ/σ)max = 0.001
S = 1.02Δρmax = 0.43 e Å3
2424 reflectionsΔρmin = 0.48 e Å3
156 parametersExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
1 restraintExtinction coefficient: 0.0027 (10)
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack (1983), 664 Friedel pairs
Secondary atom site location: difference Fourier mapAbsolute structure parameter: 0.02 (5)
Crystal data top
C12H16INO2SV = 709.3 (3) Å3
Mr = 365.22Z = 2
Monoclinic, P21Mo Kα radiation
a = 7.6345 (16) ŵ = 2.40 mm1
b = 7.7084 (16) ÅT = 294 K
c = 12.071 (3) Å0.25 × 0.16 × 0.16 mm
β = 93.17 (1)°
Data collection top
Bruker APEX CCD area-detector
diffractometer
2424 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1787 reflections with I > 2σ(I)
Tmin = 0.586, Tmax = 0.701Rint = 0.033
4398 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.037H-atom parameters constrained
wR(F2) = 0.092Δρmax = 0.43 e Å3
S = 1.02Δρmin = 0.48 e Å3
2424 reflectionsAbsolute structure: Flack (1983), 664 Friedel pairs
156 parametersAbsolute structure parameter: 0.02 (5)
1 restraint
Special details top

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
I10.74117 (5)1.0996 (2)0.25200 (3)0.0737 (2)
S10.26704 (16)0.6075 (3)0.31530 (11)0.0533 (3)
O20.4219 (6)0.5601 (6)0.2627 (4)0.0703 (15)
C20.3980 (7)0.9338 (7)0.3147 (5)0.0492 (14)
H20.37900.91880.23430.059*
C10.5919 (8)0.9208 (9)0.3477 (5)0.0572 (16)
H1A0.63200.80330.33550.069*
H1B0.61080.94700.42600.069*
C30.3090 (8)1.0976 (12)0.3511 (5)0.0749 (17)
H3A0.21551.13110.29770.090*
H3B0.39251.19220.35940.090*
C50.1722 (9)0.8691 (9)0.4444 (5)0.0579 (16)
H5A0.16850.80740.51430.069*
H5B0.05660.86680.40680.069*
C40.2361 (10)1.0518 (9)0.4619 (6)0.074 (2)
H4A0.32651.05780.52140.089*
H4B0.14061.12870.47880.089*
N10.3058 (6)0.7944 (6)0.3740 (4)0.0484 (11)
O10.1979 (6)0.4989 (6)0.3981 (4)0.0676 (12)
C60.0698 (7)0.5882 (12)0.2289 (4)0.0566 (15)
H60.09570.53810.29620.068*
C70.1002 (8)0.6359 (9)0.2101 (4)0.0491 (18)
C90.0007 (11)0.7369 (10)0.0301 (5)0.073 (2)
H90.02350.78880.03690.088*
C110.2011 (7)0.6151 (13)0.1476 (5)0.0652 (16)
H110.31470.57990.16050.078*
C100.1693 (9)0.6917 (9)0.0491 (5)0.0614 (17)
C80.1366 (10)0.7067 (9)0.1096 (5)0.0651 (19)
H80.25140.73430.09440.078*
C120.3186 (12)0.7276 (15)0.0368 (7)0.107 (3)
H12A0.35450.84650.03150.160*
H12B0.41600.65320.02330.160*
H12C0.27950.70570.10970.160*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
I10.0663 (3)0.0651 (3)0.0898 (3)0.0125 (3)0.00491 (18)0.0064 (3)
S10.0550 (7)0.0350 (7)0.0701 (8)0.0009 (11)0.0039 (6)0.0016 (12)
O20.062 (2)0.042 (4)0.107 (3)0.006 (2)0.007 (2)0.016 (2)
C20.060 (4)0.032 (3)0.056 (3)0.001 (3)0.000 (3)0.003 (3)
C10.062 (4)0.047 (4)0.062 (4)0.006 (3)0.002 (3)0.002 (3)
C30.079 (4)0.036 (3)0.111 (5)0.002 (5)0.020 (3)0.004 (6)
C50.067 (4)0.050 (4)0.058 (4)0.002 (3)0.009 (3)0.005 (3)
C40.082 (5)0.050 (5)0.094 (5)0.000 (3)0.022 (4)0.025 (4)
N10.052 (3)0.035 (3)0.058 (3)0.000 (2)0.003 (2)0.002 (2)
O10.084 (3)0.042 (3)0.076 (3)0.006 (2)0.004 (2)0.016 (2)
C60.064 (3)0.055 (4)0.052 (3)0.013 (4)0.014 (2)0.010 (4)
C70.062 (3)0.036 (5)0.050 (3)0.006 (3)0.013 (2)0.004 (3)
C90.109 (6)0.070 (5)0.042 (4)0.012 (4)0.007 (4)0.002 (3)
C110.059 (3)0.067 (5)0.070 (4)0.004 (5)0.011 (3)0.012 (5)
C100.075 (4)0.056 (4)0.053 (4)0.002 (3)0.002 (3)0.012 (3)
C80.074 (4)0.063 (5)0.061 (4)0.024 (4)0.021 (3)0.005 (3)
C120.110 (7)0.118 (8)0.089 (6)0.007 (6)0.028 (5)0.001 (5)
Geometric parameters (Å, º) top
I1—C12.163 (6)C5—H5B0.9700
S1—O21.420 (4)C4—H4A0.9700
S1—O11.427 (4)C4—H4B0.9700
S1—N11.625 (5)C6—C111.379 (8)
S1—C71.762 (6)C6—C71.380 (8)
C2—N11.490 (7)C6—H60.9300
C2—C31.511 (10)C7—C81.372 (8)
C2—C11.515 (8)C9—C101.366 (10)
C2—H20.9800C9—C81.401 (10)
C1—H1A0.9700C9—H90.9300
C1—H1B0.9700C11—C101.361 (9)
C3—C41.518 (9)C11—H110.9300
C3—H3A0.9700C10—C121.523 (10)
C3—H3B0.9700C8—H80.9300
C5—N11.480 (7)C12—H12A0.9600
C5—C41.502 (9)C12—H12B0.9600
C5—H5A0.9700C12—H12C0.9600
O2—S1—O1120.8 (3)C3—C4—H4A111.1
O2—S1—N1106.7 (3)C5—C4—H4B111.1
O1—S1—N1106.3 (3)C3—C4—H4B111.1
O2—S1—C7107.2 (3)H4A—C4—H4B109.1
O1—S1—C7107.3 (3)C5—N1—C2110.8 (4)
N1—S1—C7108.1 (3)C5—N1—S1118.7 (4)
N1—C2—C3103.3 (5)C2—N1—S1120.6 (4)
N1—C2—C1107.9 (5)C11—C6—C7119.7 (6)
C3—C2—C1115.3 (5)C11—C6—H6120.1
N1—C2—H2110.0C7—C6—H6120.1
C3—C2—H2110.0C8—C7—C6119.3 (6)
C1—C2—H2110.0C8—C7—S1120.8 (5)
C2—C1—I1110.7 (4)C6—C7—S1119.8 (4)
C2—C1—H1A109.5C10—C9—C8121.2 (6)
I1—C1—H1A109.5C10—C9—H9119.4
C2—C1—H1B109.5C8—C9—H9119.4
I1—C1—H1B109.5C10—C11—C6122.0 (6)
H1A—C1—H1B108.1C10—C11—H11119.0
C2—C3—C4104.8 (6)C6—C11—H11119.0
C2—C3—H3A110.8C11—C10—C9118.2 (6)
C4—C3—H3A110.8C11—C10—C12120.7 (7)
C2—C3—H3B110.8C9—C10—C12121.1 (7)
C4—C3—H3B110.8C7—C8—C9119.4 (6)
H3A—C3—H3B108.9C7—C8—H8120.3
N1—C5—C4102.5 (5)C9—C8—H8120.3
N1—C5—H5A111.3C10—C12—H12A109.5
C4—C5—H5A111.3C10—C12—H12B109.5
N1—C5—H5B111.3H12A—C12—H12B109.5
C4—C5—H5B111.3C10—C12—H12C109.5
H5A—C5—H5B109.2H12A—C12—H12C109.5
C5—C4—C3103.1 (6)H12B—C12—H12C109.5
C5—C4—H4A111.1
N1—C2—C1—I1173.7 (4)C7—S1—N1—C272.0 (5)
C3—C2—C1—I171.5 (6)C11—C6—C7—C81.2 (12)
N1—C2—C3—C424.5 (7)C11—C6—C7—S1178.1 (7)
C1—C2—C3—C492.9 (7)O2—S1—C7—C836.5 (7)
N1—C5—C4—C336.7 (7)O1—S1—C7—C8167.6 (6)
C2—C3—C4—C538.7 (7)N1—S1—C7—C878.2 (6)
C4—C5—N1—C222.3 (7)O2—S1—C7—C6144.1 (6)
C4—C5—N1—S1168.3 (5)O1—S1—C7—C613.0 (7)
C3—C2—N1—C51.4 (6)N1—S1—C7—C6101.2 (7)
C1—C2—N1—C5121.1 (5)C7—C6—C11—C101.5 (14)
C3—C2—N1—S1143.9 (4)C6—C11—C10—C92.3 (13)
C1—C2—N1—S193.6 (5)C6—C11—C10—C12177.0 (8)
O2—S1—N1—C5174.4 (4)C8—C9—C10—C110.3 (11)
O1—S1—N1—C544.3 (5)C8—C9—C10—C12179.0 (7)
C7—S1—N1—C570.6 (5)C6—C7—C8—C93.1 (11)
O2—S1—N1—C243.0 (5)S1—C7—C8—C9176.3 (5)
O1—S1—N1—C2173.1 (4)C10—C9—C8—C72.4 (11)

Experimental details

Crystal data
Chemical formulaC12H16INO2S
Mr365.22
Crystal system, space groupMonoclinic, P21
Temperature (K)294
a, b, c (Å)7.6345 (16), 7.7084 (16), 12.071 (3)
β (°) 93.17 (1)
V3)709.3 (3)
Z2
Radiation typeMo Kα
µ (mm1)2.40
Crystal size (mm)0.25 × 0.16 × 0.16
Data collection
DiffractometerBruker APEX CCD area-detector
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.586, 0.701
No. of measured, independent and
observed [I > 2σ(I)] reflections
4398, 2424, 1787
Rint0.033
(sin θ/λ)max1)0.658
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.037, 0.092, 1.02
No. of reflections2424
No. of parameters156
No. of restraints1
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.43, 0.48
Absolute structureFlack (1983), 664 Friedel pairs
Absolute structure parameter0.02 (5)

Computer programs: SMART (Bruker, 2000), SAINT (Bruker, 2000), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 2000).

 

Acknowledgements

We acknowledge financial support from the Research Fund for the new faculty at the State Key Laboratory of Applied Organic Chemistry.

References

First citationAllemann, C., Gordillo, R., Clemente, F. R., Cheong, P. H. & Houk, K. N. (2004). Acc. Chem. Res. 37, 558–569.  Web of Science CrossRef PubMed CAS Google Scholar
First citationBahmanyar, S., Houk, K. N., Martin, H. J. & List, B. (2003). J. Am. Chem. Soc. 125, 2475–2479.  Web of Science CrossRef PubMed CAS Google Scholar
First citationBarbas, C. F. III, Heine, A., Zhong, G., Hoffmann, T., Gramatikova, S., Björnestedt, R., List, B., Anderson, J., Stura, E. A., Wilson, I. A. & Lerner, R. A. (1997). Science, 278, 2085–2092.  CrossRef CAS PubMed Web of Science Google Scholar
First citationBruker (2000). SMART, SAINT, SADABS and SHELXTL. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationDalko, P. L. & Moisan, L. (2004). Angew. Chem. Int. Ed. 43, 5138–5175.  Web of Science CrossRef CAS Google Scholar
First citationEder, U., Sauer, G. & Wiechert, R. (1971). Angew. Chem. Int. Ed. Engl. 10, 496–497.  CrossRef CAS Web of Science Google Scholar
First citationFlack, H. D. (1983). Acta Cryst. A39, 876–881.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationHajos, Z. G. & Parrish, D. R. (1974). J. Org. Chem. 39, 1615–1621.  CrossRef CAS Web of Science Google Scholar
First citationList, B. (2004). Acc. Chem. Res. 37, 548–557.  Web of Science CrossRef PubMed CAS Google Scholar
First citationList, B., Lerner, R. A. & Barbas, C. F. III (2000). J. Am. Chem. Soc. 122, 2395–2396.  Web of Science CrossRef CAS Google Scholar
First citationMachajewski, T. D. & Wong, C.-H. (2000). Angew. Chem. Int. Ed. 39, 1352–1374.  CrossRef CAS Google Scholar
First citationNorthrup, A. B. & MacMillan, D. W. C. (2002). J. Am. Chem. Soc. 124, 6798–6799.  Web of Science CrossRef PubMed CAS Google Scholar
First citationNotz, W., Tanaka, F. & Barbas, C. F. III (2004). Acc. Chem. Res. 37, 580–591.  Web of Science CrossRef PubMed CAS Google Scholar
First citationSakthivel, K., Notz, W., Bui, T. & Barbas, C. F. III (2001). J. Am. Chem. Soc. 123, 5260–5267.  Web of Science CrossRef PubMed CAS Google Scholar
First citationSeayed, J. & List, B. (2005). Org. Biomol. Chem. 3, 719–724.  Web of Science PubMed Google Scholar
First citationSheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.  Google Scholar
First citationSheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.  Google Scholar
First citationWagner, J., Lerner, R. A. & Barbas, C. F. III (1995). Science, 270, 1797–1800.  CrossRef CAS PubMed Web of Science Google Scholar

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