2-Propyl 3,3-di­bromo-2-hy­droxy­pyrrolidine-1-carboxyl­ate

The title compound, C₈H₁₃Br₂NO₃, crystallizes as a non-merohedral twin with twin law −0.6 0 0.4/0 − 1 0 /1.6 0 0.6, and the structure has a refined twin domain ratio of 0.546 (5). The structure shows a compact conformation, with the ester unit roughly coplanar with a mean plane fitted through the non-H atoms of the pyrrolidine ring [dihedral angle = 8.23 (9)°]. In the crystal, inversion dimers linked by pairs of O—H⋯O hydrogen bonds generate an R²₂(12) motif.

Related literature

For details of the synthesis, see: Magnus et al. (1994); Salamant & Hulme (2006). For puckering parameters, see: Cremer & Pople (1975). For hydrogen-bonding motifs, see: Bernstein et al. (1995).

Experimental

Crystal data

• C₈H₁₃Br₂NO₃

• M_r = 331.01

• Monoclinic, P 2₁ /n

• a = 10.1061 (5) Å

• b = 5.9914 (3) Å

• c = 18.5496 (9) Å

• β = 95.880 (2)°

• V = 1117.26 (10) ų

• Z = 4

• Mo Kα radiation

• μ = 7.24 mm⁻¹

• T = 100 K

• 0.44 × 0.16 × 0.11 mm

Data collection

• Bruker Kappa APEXII DUO CCD diffractometer

• Absorption correction: multi-scan (TWINABS; Sheldrick, 1996) T_min = 0.144, T_max = 0.514

• 34994 measured reflections

• 9572 independent reflections

• 7956 reflections with I > 2σ(I)

• R_int = 0.042

Refinement

• R[F² > 2σ(F²)] = 0.032

• wR(F²) = 0.082

• S = 1.03

• 9572 reflections

• 138 parameters

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 1.41 e Å⁻³

• Δρ_min = −0.77 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1O⋯O2^i	0.83 (3)	1.92 (3)	2.7479 (16)	176 (3)
Symmetry code: (i) -x+1, -y, -z.

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT and CELL_NOW (Sheldrick, 2004); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXTL and local programs.

Supporting information

S1. Comment

We are working to develop new synthetic methodology by application of hypervalent iodine reagents (oxidation state III) in conjunction with bromotrimethylsilane (TMSBr). Specifically, iodosobenzene (Magnus et al., 1994) or iodobenzenediacetate in the presence of TMSBr promotes controlled formation of an oxidized product in one pot, derived from cyclic amides. The transformation represents an α, β, β oxidative process, and the yield of the product, (I), was optimized by varying reaction parameters (Salamant & Hulme, 2006). The structure of this molecule generated from one simple microwave-assisted protocol was confirmed by X-ray crystallography.

The molecular structure of (I) is shown in Fig. 1. Molecular dimensions are unexceptional and the compound has a compact conformation; as evidenced by the torsion angle C2—N—C5—O2 = 0.1 (2)° the ester moiety is essentially co-planar with the pyrrolidine ring. Furthermore the angle between a least-squares plane fitted through all non-hydrogen atoms of the pyrrolidine ring (r.m.s. deviation = 0.1666 Å) and the ester moiety (r.m.s. deviation = 0.0226 Å) is 8.23 (9)°. The pyrrolidine ring adopts an envelope conformation with a Cremer–Pople puckering parameter Q of 0.4053 (15) Å (Cremer & Pople, 1975). The compound forms a hydrogen-bonded dimer by means of an R²₂(12) motif (Fig. 2; Bernstein et al., 1995) although there is no further hydrogen bonding in the crystal structure.

Related literature

For details of the synthesis, see: Magnus et al. (1994); Salamant & Hulme (2006). For puckering parameters, see Cremer & Pople (1975). For hydrogen-bonding motifs, see: Bernstein et al. (1995).

S2. Experimental

To a solution of isopropyloxypyrrolidine (0.050 g, 0.318 mmol) in anhydrous dichloromethane (1 ml) was added iodobenzene diacetate (0.410 g, 1.272 mmol). Bromotrimethylsilane (0.330 ml, 2.540 mmol) was added dropwise and the mixture irradiated with a Biotage Initiator^TM for 20 min at 120°C. The red-brown solution was then dissolved in EtOAc (25 ml) and quenched with 1M Na₂S₂O₃ (2 × 10 ml). The organic layer was washed with 1M NaHCO₃ (2 × 20 ml), saturated Na₂CO₃ (20 ml), brine solution (20 ml), and dried (MgSO₄). The solvent was evaporated in vacuo and purified by column chromatography (CHCl₃) to afford the α,β,β product (0.068 g, 0.207 mmol, 65%) as a white solid. MS (+ESI) m/z 354 [M+Na]⁺

S3. Refinement

The crystal used was a two-component non-merohedral twin. The two components of the diffraction pattern were easily separated using CELL_NOW (Sheldrick, 2004) with twin law -0.6 0 0.4/0 -1 0 /1.6 0 0.6 and the structure has a refined twin scale factor of 0.546 (5). H atoms were identified from a difference Fourier map. The O—H H atom was freely refined with O—H = 0.83 (3) Å. C—H atoms were refined with U_iso(H) = 1.5U_eq(C) (methyl) U_iso(H) = 1.5U_eq(C) (all others) with constrained C—H distances in the range 0.98–1 Å.

Computing details

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007) and CELL_NOW (Sheldrick, 2004); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and local programs.

Figures

	Fig. 1. The molecular structure of (I) with anisotropic displacement ellipsoids at the 50% probability level.
	Fig. 2. An a-axis packing plot of (I). Blue dotted lines indicate hydrogen bonds; red dotted lines indicate hydrogen bond continuation.

2-Propyl 3,3-dibromo-2-hydroxypyrrolidine-1-carboxylate

Crystal data

C8H13Br2NO3	F(000) = 648
Mr = 331.01	Dx = 1.968 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 4995 reflections
a = 10.1061 (5) Å	θ = 2.2–36.3°
b = 5.9914 (3) Å	µ = 7.24 mm^−1
c = 18.5496 (9) Å	T = 100 K
β = 95.880 (2)°	Rod, colourless
V = 1117.26 (10) Å^3	0.44 × 0.16 × 0.11 mm
Z = 4

Data collection

Bruker Kappa APEXII DUO CCD diffractometer	9572 independent reflections
Radiation source: fine-focus sealed tube with Miracol optics	7956 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.042
ϕ and ω scans	θmax = 36.4°, θmin = 2.2°
Absorption correction: multi-scan (TWINABS; Sheldrick, 1996)	h = −16→16
Tmin = 0.144, Tmax = 0.514	k = 0→9
34994 measured reflections	l = 0→30

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.032	Hydrogen site location: difference Fourier map
wR(F^2) = 0.082	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ^2(Fo^2) + (0.041P)^2 + 0.6397P] where P = (Fo^2 + 2Fc^2)/3
9572 reflections	(Δ/σ)max < 0.001
138 parameters	Δρmax = 1.41 e Å^−3
0 restraints	Δρmin = −0.77 e Å^−3

Special details

Experimental. 1H- NMR (300 MHz, CDCl3) δ ppm 1.26 (d, J = 6.0 Hz, 6H), 2.78 (m, 1H), 3.00 (m, 1H), 3.55 (m, 2H), 4.65 (s, 1H), 5.00 (m, 1H), 5.66 (d, J = 18.6 Hz, 1H)

13 C-NMR (75 MHz, CDCl3) δ ppm 22.6, 43.4, 44.6, 64.9, 70.2, 77.9, 155.3

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

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 (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.276925 (16)	0.10387 (3)	0.190848 (8)	0.01807 (4)
Br2	0.113078 (15)	0.17803 (3)	0.039208 (9)	0.01933 (4)
O1	0.39288 (12)	0.2381 (2)	−0.01016 (6)	0.01668 (19)
H1O	0.371 (3)	0.120 (5)	−0.0310 (15)	0.029 (7)*
O2	0.68184 (12)	0.16332 (19)	0.07343 (7)	0.0190 (2)
O3	0.69480 (10)	0.47225 (18)	0.14461 (6)	0.01432 (18)
N	0.49624 (12)	0.3442 (2)	0.10291 (7)	0.0134 (2)
C1	0.27415 (14)	0.2599 (2)	0.09769 (7)	0.0137 (2)
C2	0.40238 (14)	0.1940 (2)	0.06403 (7)	0.0125 (2)
H2	0.4265	0.0345	0.0745	0.015*
C3	0.43486 (14)	0.5339 (2)	0.13709 (8)	0.0153 (2)
H3A	0.4716	0.6776	0.1219	0.018*
H3B	0.4479	0.5230	0.1906	0.018*
C4	0.28818 (15)	0.5100 (2)	0.10886 (8)	0.0156 (2)
H4A	0.2297	0.5644	0.1448	0.019*
H4B	0.2673	0.5919	0.0628	0.019*
C5	0.62874 (14)	0.3155 (2)	0.10427 (8)	0.0137 (2)
C6	0.84008 (14)	0.4710 (2)	0.14715 (8)	0.0146 (2)
H6	0.862 (2)	0.423 (4)	0.1000 (12)	0.014 (5)*
C7	0.88361 (16)	0.7097 (2)	0.16218 (9)	0.0185 (3)
H7A	0.8399	0.8076	0.1247	0.028*
H7B	0.9803	0.7206	0.1619	0.028*
H7C	0.8588	0.7553	0.2097	0.028*
C8	0.89639 (17)	0.3118 (3)	0.20548 (10)	0.0223 (3)
H8A	0.9936	0.3090	0.2069	0.033*
H8B	0.8610	0.1617	0.1949	0.033*
H8C	0.8711	0.3613	0.2525	0.033*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.02072 (7)	0.02068 (7)	0.01338 (6)	−0.00119 (5)	0.00450 (5)	0.00190 (5)
Br2	0.01232 (6)	0.02662 (8)	0.01853 (7)	−0.00274 (5)	−0.00098 (5)	−0.00543 (5)
O1	0.0195 (5)	0.0195 (5)	0.0112 (4)	−0.0029 (4)	0.0021 (4)	−0.0022 (4)
O2	0.0149 (5)	0.0183 (5)	0.0239 (5)	0.0008 (4)	0.0017 (4)	−0.0089 (4)
O3	0.0113 (4)	0.0153 (4)	0.0160 (4)	−0.0003 (3)	−0.0004 (3)	−0.0044 (4)
N	0.0116 (5)	0.0136 (5)	0.0150 (5)	−0.0012 (4)	0.0007 (4)	−0.0046 (4)
C1	0.0126 (5)	0.0162 (5)	0.0119 (5)	−0.0013 (4)	−0.0003 (4)	−0.0009 (4)
C2	0.0120 (5)	0.0142 (5)	0.0113 (5)	−0.0017 (4)	0.0016 (4)	−0.0021 (4)
C3	0.0142 (6)	0.0137 (5)	0.0179 (6)	0.0002 (4)	0.0018 (5)	−0.0047 (5)
C4	0.0148 (6)	0.0145 (6)	0.0173 (6)	0.0018 (4)	0.0010 (5)	−0.0021 (5)
C5	0.0127 (5)	0.0149 (5)	0.0132 (5)	0.0000 (4)	0.0004 (4)	−0.0014 (4)
C6	0.0106 (5)	0.0160 (5)	0.0170 (6)	−0.0002 (4)	0.0009 (4)	−0.0011 (5)
C7	0.0160 (6)	0.0165 (6)	0.0226 (7)	−0.0032 (5)	−0.0006 (5)	0.0003 (5)
C8	0.0187 (7)	0.0180 (6)	0.0286 (8)	0.0002 (5)	−0.0052 (6)	0.0022 (6)

Geometric parameters (Å, º)

Br1—C1	1.9624 (14)	C3—H3B	0.990
Br2—C1	1.9250 (14)	C3—C4	1.527 (2)
O1—H1O	0.83 (3)	C4—H4A	0.990
O1—C2	1.3949 (17)	C4—H4B	0.990
O2—C5	1.2286 (18)	C6—H6	0.97 (2)
O3—C5	1.3360 (17)	C6—C7	1.513 (2)
O3—C6	1.4641 (18)	C6—C8	1.510 (2)
N—C2	1.4457 (18)	C7—H7A	0.980
N—C3	1.4695 (19)	C7—H7B	0.980
N—C5	1.3478 (19)	C7—H7C	0.980
C1—C2	1.546 (2)	C8—H8A	0.980
C1—C4	1.517 (2)	C8—H8B	0.980
C2—H2	1.000	C8—H8C	0.980
C3—H3A	0.990
H1O—O1—C2	106.6 (19)	C1—C4—H4B	111.3
C5—O3—C6	117.15 (11)	C3—C4—H4A	111.3
C2—N—C3	114.36 (12)	C3—C4—H4B	111.3
C2—N—C5	121.99 (12)	H4A—C4—H4B	109.2
C3—N—C5	123.58 (12)	O2—C5—O3	124.43 (13)
Br1—C1—Br2	108.05 (7)	O2—C5—N	124.50 (13)
Br1—C1—C2	107.27 (9)	O3—C5—N	111.06 (12)
Br1—C1—C4	110.95 (9)	O3—C6—H6	107.0 (13)
Br2—C1—C2	113.74 (9)	O3—C6—C7	105.83 (12)
Br2—C1—C4	112.98 (10)	O3—C6—C8	109.23 (12)
C2—C1—C4	103.71 (12)	H6—C6—C7	111.1 (13)
O1—C2—N	110.45 (12)	H6—C6—C8	110.8 (13)
O1—C2—C1	111.97 (11)	C7—C6—C8	112.58 (13)
O1—C2—H2	111.3	C6—C7—H7A	109.5
N—C2—C1	99.99 (11)	C6—C7—H7B	109.5
N—C2—H2	111.3	C6—C7—H7C	109.5
C1—C2—H2	111.3	H7A—C7—H7B	109.5
N—C3—H3A	111.3	H7A—C7—H7C	109.5
N—C3—H3B	111.3	H7B—C7—H7C	109.5
N—C3—C4	102.54 (11)	C6—C8—H8A	109.5
H3A—C3—H3B	109.2	C6—C8—H8B	109.5
H3A—C3—C4	111.3	C6—C8—H8C	109.5
H3B—C3—C4	111.3	H8A—C8—H8B	109.5
C1—C4—C3	102.32 (11)	H8A—C8—H8C	109.5
C1—C4—H4A	111.3	H8B—C8—H8C	109.5
C3—N—C2—O1	99.81 (14)	Br1—C1—C4—C3	73.49 (12)
C3—N—C2—C1	−18.30 (15)	Br2—C1—C4—C3	−165.00 (10)
C5—N—C2—O1	−77.31 (17)	C2—C1—C4—C3	−41.39 (13)
C5—N—C2—C1	164.59 (13)	N—C3—C4—C1	29.33 (14)
Br1—C1—C2—O1	161.81 (9)	C6—O3—C5—O2	5.0 (2)
Br1—C1—C2—N	−81.21 (11)	C6—O3—C5—N	−176.05 (12)
Br2—C1—C2—O1	42.39 (14)	C2—N—C5—O2	0.1 (2)
Br2—C1—C2—N	159.37 (9)	C2—N—C5—O3	−178.85 (12)
C4—C1—C2—O1	−80.72 (13)	C3—N—C5—O2	−176.76 (14)
C4—C1—C2—N	36.26 (13)	C3—N—C5—O3	4.3 (2)
C2—N—C3—C4	−6.68 (16)	C5—O3—C6—C7	152.87 (13)
C5—N—C3—C4	170.38 (13)	C5—O3—C6—C8	−85.69 (15)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1O···O2^i	0.83 (3)	1.92 (3)	2.7479 (16)	176 (3)

Symmetry code: (i) −x+1, −y, −z.