(7RS,8SR)-Ethyl 6-(1,3-benzodioxol-5-yl)-3-(3-bromo-2-thien­yl)-2-oxocyclo­hex-3-ene-1-carboxyl­ate

The title compound, C₂₀H₁₇BrO₅S, crystallizes as a racemate. The dihedral angle between the thio­phene and benzene rings is 66.91 (13)°.

Key indicators

• Single-crystal X-ray study
• T = 299 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.052
• wR factor = 0.117
• Data-to-parameter ratio = 14.4

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT222_ALERT_3_B Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       4.14 Ratio
PLAT230_ALERT_2_B Hirshfeld Test Diff for    O2     -   C19     ..      10.68 su

Alert level C
PLAT220_ALERT_2_C Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       3.33 Ratio
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for         O4
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for        C13
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for        C19
PLAT360_ALERT_2_C Short  C(sp3)-C(sp3) Bond  C19    -   C20    ...       1.39 Ang.

Alert level G
PLAT793_ALERT_1_G Check the Absolute Configuration of C7     = ...          R
PLAT793_ALERT_1_G Check the Absolute Configuration of C8     = ...          S

   0 ALERT level A = In general: serious problem
   2 ALERT level B = Potentially serious problem
   5 ALERT level C = Check and explain
   2 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   6 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Chalcones and the corresponding heterocyclic analogues are valuable intermediates in organic synthesis (Dhar, 1981) and exhibit a multitude of biological activities (Dimmock et al., 1999). An important feature of chalcones and their heteroanalogues is their ability to act as activated unsaturated systems in conjugated addition reactions of carbanions in the presence of basic catalysts (House, 1972). This type of reaction may be exploited for obtaining highly functionalized cyclohexene derivatives (Tabba et al., 1995), but is more commonly used for the preparation of 3,5-diaryl-6-carbethoxycyclohexanones via Michael addition of ethyl acetoacetate. The mentioned cyclohexenones are efficient synthons in building spiro compounds (Padmavathi, Sharmila, Somashekara Reddy et al., 2001) or as intermediates in the synthesis of benzisoxazoles or carbazole derivatives (Padmavathi et al., 1999; 2000, Padmavathi, Sharmila, Balaiah et al., 2001). In view of the importance of these derivatives, the title compound was synthesized and crystallized and the structure was determined.

The compound is prepared by the cyclocondensation of ethyl acetoacetate with (2E)-3-(1,3-benzodioxol-5-yl)-1-(3-bromo-2-thienyl)prop-2-en-1-one, which leads to the generation of two chiral centers at C7 and C8. As the reaction is not stereoselective, both configurations of the chiral carbon atoms are expected to be obtained, which would result in a mixture of diastereomers. No attempts to separate the diastereomers were undertaken and the crystals were grown from the mixture after recrystallization.

The geometry of the molecule is unexceptional. The dihedral angle between the phenyl ring and the thiophene group is 66.91 (13)°.

Related literature

For related literature, see: Dhar (1981); Dimmock et al. (1999); House (1972); Padmavathi et al. (1999, 2000); Padmavathi, Sharmila, Balaiah et al. (2001); Padmavathi, Sharmila, Somashekara Reddy & Bhaskar Reddy (2001); Tabba et al. (1995).

S2. Experimental

(2E)-3-(1,3-Benzodioxol-5-yl)-1-(3-bromo-2-thienyl)prop-2-en-1-one(1.69 g, 5 mmol) and ethyl acetoacetate (0.65 g, 5 mmol) were refluxed for 4hrs in 20 ml e thanol in presence of 0.8 ml 10% NaOH. The reaction mixture was cooled to room temperature and the reaction mass was filtered and recrystallized using methanol. Crystals were grown from acetone. (Yield: 61%; m.p.: 391–393 K). Analysis for C₂₀H₁₇O₅SBr: Found (Calculated): C: 53.34 (53.46%); H: 3.71 (3.81%); S: 7.09 (7.14%).

S3. Refinement

Attempts to refine the structure using a disordered model for the ethoxy group did not yield satisfactory results. H atoms were placed at calculated positions and refined riding on the respective carrier atom (U_iso(H)=1.2 U_eq of the respective carrier atom (1.5 for the methyl group), d(C—H) 0.93 Å(aromatic/olefinic C), 0.96 Å (CH₃), 0.97 Å (CH₂), 0.98 Å (tertiary CH).

Computing details

Data collection: Collect (Nonius, 1999); cell refinement: DIRAX/LSQ (Duisenberg, 1992); data reduction: EVALCCD (Duisenberg et al., 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2007).

Figures

Fig. 1. : The molecular structure of the title compound. Displacement ellipsoids are drawn at the 40% probability level.

(7RS,8SR)-Ethyl 6-(1,3-benzodioxol-5-yl)-3-(3-bromo-2-thienyl)-2-oxocyclohex-3-ene-1-carboxylate

Crystal data

C20H17BrO5S	F(000) = 912
Mr = 449.32	Dx = 1.572 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 123 reflections
a = 17.3207 (12) Å	θ = 4.7–21.4°
b = 11.8106 (9) Å	µ = 2.30 mm^−1
c = 9.3661 (8) Å	T = 299 K
β = 97.736 (7)°	Plate, colourless
V = 1898.6 (3) Å^3	0.35 × 0.30 × 0.20 mm
Z = 4

Data collection

Bruker–Nonius KappaCCD diffractometer	2325 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.062
φ & ω scans	θmax = 25.5°, θmin = 4.6°
Absorption correction: numerical (Herrendorf & Bärnighausen, 1997)	h = −20→20
Tmin = 0.593, Tmax = 0.851	k = −14→14
17735 measured reflections	l = −11→11
3518 independent reflections

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)] = 0.052	H-atom parameters constrained
wR(F^2) = 0.118	w = 1/[σ^2(Fo^2) + (0.0317P)^2 + 2.7171P] where P = (Fo^2 + 2Fc^2)/3
S = 1.11	(Δ/σ)max = 0.001
3518 reflections	Δρmax = 0.43 e Å^−3
244 parameters	Δρmin = −0.47 e Å^−3
0 restraints

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > 2σ(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	0.41565 (3)	0.73085 (4)	0.98853 (6)	0.0749 (2)
S1	0.45442 (7)	0.47034 (12)	0.67283 (13)	0.0646 (4)
C1	0.3593 (3)	0.4947 (5)	0.6816 (5)	0.0695 (14)
H1	0.3189	0.4573	0.6251	0.083*
C2	0.3484 (3)	0.5738 (4)	0.7787 (5)	0.0617 (12)
H2	0.2996	0.5973	0.7981	0.074*
C3	0.4187 (2)	0.6175 (4)	0.8480 (4)	0.0499 (10)
C4	0.4839 (2)	0.5705 (3)	0.8045 (4)	0.0461 (10)
C5	0.5671 (2)	0.5879 (3)	0.8476 (4)	0.0433 (9)
C6	0.6226 (2)	0.5372 (4)	0.7523 (4)	0.0464 (10)
H6A	0.6277	0.5890	0.6738	0.056*
H6B	0.6006	0.4671	0.7109	0.056*
C7	0.7037 (2)	0.5131 (3)	0.8346 (4)	0.0432 (9)
H7	0.6972	0.4560	0.9081	0.052*
C8	0.7358 (2)	0.6195 (3)	0.9132 (4)	0.0455 (10)
H8	0.7445	0.6770	0.8416	0.055*
C9	0.6785 (3)	0.6662 (4)	1.0076 (4)	0.0536 (11)
C10	0.5963 (3)	0.6454 (4)	0.9659 (4)	0.0533 (11)
H10	0.5616	0.6736	1.0247	0.064*
C11	0.7569 (2)	0.4631 (3)	0.7358 (4)	0.0429 (9)
C12	0.7683 (3)	0.3478 (4)	0.7329 (5)	0.0636 (13)
H12	0.7440	0.3024	0.7948	0.076*
C13	0.8144 (3)	0.2966 (4)	0.6417 (6)	0.0769 (15)
H13	0.8203	0.2184	0.6394	0.092*
C14	0.8505 (3)	0.3653 (4)	0.5561 (5)	0.0589 (12)
C15	0.8405 (2)	0.4800 (4)	0.5584 (5)	0.0524 (11)
C16	0.7948 (2)	0.5316 (4)	0.6461 (5)	0.0518 (11)
H16	0.7891	0.6098	0.6462	0.062*
C17	0.9153 (4)	0.4379 (5)	0.3900 (6)	0.0843 (16)
H17A	0.8902	0.4358	0.2910	0.101*
H17B	0.9709	0.4474	0.3894	0.101*
C18	0.8121 (3)	0.5959 (4)	1.0062 (5)	0.0572 (12)
C19	0.9454 (5)	0.6571 (8)	1.0697 (8)	0.140 (3)
H19A	0.9557	0.5770	1.0852	0.169*
H19B	0.9842	0.6890	1.0157	0.169*
C20	0.9437 (5)	0.7139 (8)	1.1993 (10)	0.143 (3)
H20A	0.9317	0.7923	1.1803	0.215*
H20B	0.9936	0.7078	1.2572	0.215*
H20C	0.9046	0.6809	1.2499	0.215*
O1	0.7014 (2)	0.7217 (3)	1.1149 (4)	0.0782 (10)
O2	0.86292 (19)	0.6774 (3)	0.9936 (4)	0.0848 (11)
O3	0.8237 (2)	0.5135 (3)	1.0799 (4)	0.0757 (10)
O4	0.8855 (2)	0.5292 (3)	0.4645 (4)	0.0907 (12)
O5	0.9007 (2)	0.3362 (3)	0.4610 (4)	0.0807 (11)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0724 (4)	0.0617 (3)	0.0943 (4)	0.0033 (3)	0.0245 (3)	−0.0144 (3)
S1	0.0488 (7)	0.0880 (9)	0.0555 (7)	−0.0104 (6)	0.0022 (5)	−0.0191 (7)
C1	0.047 (3)	0.092 (4)	0.066 (3)	−0.013 (3)	−0.003 (2)	−0.004 (3)
C2	0.048 (3)	0.072 (3)	0.066 (3)	0.002 (2)	0.010 (2)	0.014 (3)
C3	0.050 (3)	0.048 (3)	0.052 (2)	−0.001 (2)	0.010 (2)	0.010 (2)
C4	0.043 (2)	0.050 (2)	0.045 (2)	−0.005 (2)	0.0039 (18)	0.008 (2)
C5	0.049 (2)	0.044 (2)	0.038 (2)	−0.0057 (19)	0.0074 (18)	0.0036 (19)
C6	0.043 (2)	0.050 (3)	0.045 (2)	−0.0074 (19)	0.0019 (18)	−0.007 (2)
C7	0.044 (2)	0.043 (2)	0.042 (2)	−0.0074 (18)	0.0034 (17)	0.0012 (18)
C8	0.046 (2)	0.044 (2)	0.044 (2)	−0.0114 (19)	−0.0023 (18)	0.0003 (19)
C9	0.065 (3)	0.047 (3)	0.047 (2)	−0.014 (2)	0.001 (2)	−0.006 (2)
C10	0.057 (3)	0.057 (3)	0.048 (2)	−0.006 (2)	0.013 (2)	−0.007 (2)
C11	0.036 (2)	0.048 (2)	0.043 (2)	−0.0083 (18)	−0.0022 (17)	−0.0015 (19)
C12	0.073 (3)	0.046 (3)	0.074 (3)	−0.004 (2)	0.016 (3)	0.004 (2)
C13	0.087 (4)	0.053 (3)	0.094 (4)	0.008 (3)	0.022 (3)	−0.001 (3)
C14	0.051 (3)	0.063 (3)	0.062 (3)	0.014 (2)	0.004 (2)	−0.004 (2)
C15	0.045 (2)	0.058 (3)	0.055 (3)	0.001 (2)	0.007 (2)	0.009 (2)
C16	0.053 (3)	0.041 (2)	0.060 (3)	0.004 (2)	0.008 (2)	0.000 (2)
C17	0.083 (4)	0.096 (5)	0.077 (4)	0.018 (3)	0.022 (3)	−0.007 (3)
C18	0.054 (3)	0.058 (3)	0.056 (3)	−0.015 (2)	−0.002 (2)	−0.004 (2)
C19	0.128 (6)	0.183 (8)	0.100 (5)	−0.103 (6)	−0.023 (5)	0.004 (6)
C20	0.102 (6)	0.174 (9)	0.152 (8)	0.012 (6)	0.013 (5)	0.040 (7)
O1	0.077 (2)	0.089 (3)	0.069 (2)	−0.028 (2)	0.0101 (18)	−0.037 (2)
O2	0.060 (2)	0.086 (3)	0.100 (3)	−0.036 (2)	−0.0207 (19)	0.017 (2)
O3	0.077 (2)	0.064 (2)	0.077 (2)	−0.0126 (18)	−0.0220 (18)	0.0174 (19)
O4	0.107 (3)	0.074 (3)	0.103 (3)	0.013 (2)	0.057 (2)	0.006 (2)
O5	0.083 (3)	0.078 (3)	0.087 (2)	0.026 (2)	0.030 (2)	−0.004 (2)

Geometric parameters (Å, º)

Br1—C3	1.883 (4)	C11—C16	1.393 (5)
S1—C1	1.686 (5)	C12—C13	1.385 (7)
S1—C4	1.736 (4)	C12—H12	0.9300
C1—C2	1.335 (7)	C13—C14	1.352 (7)
C1—H1	0.9300	C13—H13	0.9300
C2—C3	1.398 (6)	C14—C15	1.365 (6)
C2—H2	0.9300	C14—O5	1.370 (5)
C3—C4	1.369 (6)	C15—C16	1.359 (6)
C4—C5	1.458 (5)	C15—O4	1.379 (5)
C5—C10	1.339 (5)	C16—H16	0.9300
C5—C6	1.519 (5)	C17—O5	1.413 (7)
C6—C7	1.535 (5)	C17—O4	1.420 (6)
C6—H6A	0.9700	C17—H17A	0.9700
C6—H6B	0.9700	C17—H17B	0.9700
C7—C11	1.512 (5)	C18—O3	1.194 (5)
C7—C8	1.523 (5)	C18—O2	1.321 (5)
C7—H7	0.9800	C19—C20	1.391 (10)
C8—C18	1.508 (6)	C19—O2	1.527 (8)
C8—C9	1.518 (6)	C19—H19A	0.9700
C8—H8	0.9800	C19—H19B	0.9700
C9—O1	1.221 (5)	C20—H20A	0.9600
C9—C10	1.445 (6)	C20—H20B	0.9600
C10—H10	0.9300	C20—H20C	0.9600
C11—C12	1.377 (6)
C1—S1—C4	92.6 (2)	C12—C11—C7	119.9 (4)
C2—C1—S1	112.4 (4)	C16—C11—C7	121.3 (4)
C2—C1—H1	123.8	C11—C12—C13	122.7 (5)
S1—C1—H1	123.8	C11—C12—H12	118.7
C1—C2—C3	112.4 (4)	C13—C12—H12	118.7
C1—C2—H2	123.8	C14—C13—C12	117.1 (5)
C3—C2—H2	123.8	C14—C13—H13	121.5
C4—C3—C2	114.5 (4)	C12—C13—H13	121.5
C4—C3—Br1	126.7 (3)	C13—C14—C15	121.1 (5)
C2—C3—Br1	118.8 (3)	C13—C14—O5	128.3 (5)
C3—C4—C5	133.3 (4)	C15—C14—O5	110.6 (4)
C3—C4—S1	108.2 (3)	C16—C15—C14	122.6 (4)
C5—C4—S1	118.6 (3)	C16—C15—O4	128.4 (4)
C10—C5—C4	123.3 (4)	C14—C15—O4	108.9 (4)
C10—C5—C6	119.2 (4)	C15—C16—C11	117.7 (4)
C4—C5—C6	117.5 (3)	C15—C16—H16	121.2
C5—C6—C7	112.7 (3)	C11—C16—H16	121.2
C5—C6—H6A	109.0	O5—C17—O4	108.3 (4)
C7—C6—H6A	109.0	O5—C17—H17A	110.0
C5—C6—H6B	109.0	O4—C17—H17A	110.0
C7—C6—H6B	109.0	O5—C17—H17B	110.0
H6A—C6—H6B	107.8	O4—C17—H17B	110.0
C11—C7—C8	113.9 (3)	H17A—C17—H17B	108.4
C11—C7—C6	110.9 (3)	O3—C18—O2	125.7 (4)
C8—C7—C6	109.9 (3)	O3—C18—C8	123.4 (4)
C11—C7—H7	107.3	O2—C18—C8	110.9 (4)
C8—C7—H7	107.3	C20—C19—O2	101.7 (8)
C6—C7—H7	107.3	C20—C19—H19A	111.4
C18—C8—C9	108.8 (3)	O2—C19—H19A	111.4
C18—C8—C7	111.1 (3)	C20—C19—H19B	111.4
C9—C8—C7	110.8 (3)	O2—C19—H19B	111.4
C18—C8—H8	108.7	H19A—C19—H19B	109.3
C9—C8—H8	108.7	C19—C20—H20A	109.5
C7—C8—H8	108.7	C19—C20—H20B	109.5
O1—C9—C10	120.9 (4)	H20A—C20—H20B	109.5
O1—C9—C8	120.5 (4)	C19—C20—H20C	109.5
C10—C9—C8	118.6 (4)	H20A—C20—H20C	109.5
C5—C10—C9	123.9 (4)	H20B—C20—H20C	109.5
C5—C10—H10	118.0	C18—O2—C19	115.9 (5)
C9—C10—H10	118.0	C15—O4—C17	105.5 (4)
C12—C11—C16	118.8 (4)	C14—O5—C17	105.2 (4)