1-Dichloroacetyl-8a-methyl-1,2,3,4,6,7,8,8a-octahydropyrrolo[1,2-a]pyrimidin-6-one

In the title compound, C10H14Cl2N2O2, the five-membered ring adopts an envelope conformation (with the methylene C atom closest to the C—N bridge as the flap), while the conformation of the six-membered ring is close to a twist-boat. In the crystal, molecules are linked by weak C—H⋯O hydrogen bonds, forming chains along the c-axis direction.

In the title compound, C 10 H 14 Cl 2 N 2 O 2 , the five-membered ring adopts an envelope conformation (with the methylene C atom closest to the C-N bridge as the flap), while the conformation of the six-membered ring is close to a twist-boat. In the crystal, molecules are linked by weak C-HÁ Á ÁO hydrogen bonds, forming chains along the c-axis direction.
The molecular structure of the title compound is shown in Fig. 1. In the crystal, molecules are linked by weak intermolecular C-H···O hydrogen bonds, forming chains along the c direction (Fig. 2).

Experimental
The title compound was prepared according to the literature procedure (Sun & Ye, 2010). The single crystal suitable for X-ray structural analysis was obtained by slow evaporation of a solution in the mixture of petroleum ether and ethyl acetate at room temperature.

Refinement
All H atoms were initially located in a difference Fourier map. The C-H atoms were then constrained to an ideal geometry, with C-H distances of 0.96/0.98 Å, and with U iso (H) = 1.2/1.5 U eq (C).

Computing details
Data collection: RAPID-AUTO (Rigaku, 1999); cell refinement: RAPID-AUTO (Rigaku, 1999); data reduction: CrystalClear (Rigaku/MSC, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to   Special details Geometry. All s.u.'s (except the s.u.'s in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 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 (Å 2 )
x y z U iso */U eq C1 0.44507 (