3-Phenyl-2-(piperidin-1-yl)-3,5,6,8-tetrahydro-4H-thiopyrano[3′,4′:2,3]thieno[5,4-d]pyrimidin-4-one

In the title compound, C20H21N3OS2, the piperidinyl ring has a distorted chair conformation. Weak intermolecular C—H⋯O hydrogen bonds link the molecules into centrosymmetric dimers. The crystal packing exhibits short intermolecular S⋯S distances of 3.590 (2) Å.

In the title compound, C 20 H 21 N 3 OS 2 , the piperidinyl ring has a distorted chair conformation. Weak intermolecular C-HÁ Á ÁO hydrogen bonds link the molecules into centrosymmetric dimers. The crystal packing exhibits short intermolecular SÁ Á ÁS distances of 3.590 (2) Å .

Comment
The derivatives of heterocycles containing the thienopyrimidine system have proved to show significant antifungal, antibacterical, anticonvulsant and angiotensin antagonistic activities (Muller et al.,2002;Chambhare et al.2003). Recently, we have focused on the synthesis of fused heterocyclic systems containing thienopyrimidine via aza-wittig reaction at room temperature. Some X-ray crystal structures of fused pyrimidinone derivatives have been reported (Xie et al., 2007;Hu et al., 2007).
The title compound (I) can be used as a new precursor for obtaining of bioactive molecules with fluorescence properties.
In (I) (Fig. 1), the piperidinyl ring has a distored chair conformation. The weak intermolecular C-H···O hydrogen bonds (Table 2) link the molecules into centrosymmetric dimers (Fig. 2). The crystal packing exhibits relatively short intermolecular S···S distances of 3.590 (2) Å (Table 1), which is shorter than the sum of the van der Waals radii of the relevent atoms.

Experimental
To a solution of iminophosphorane(2mmol) in anhyd.CH 2 Cl 2 (10ml)aromatic isocyanate(2mmol)was added under nitrogen atmosphere at room temperature.After the reaction mixture was left unstirred for 6-12h at 0-5°C,the iminophosphorane had disappeared (TLC monitored).The solvent was removed off under redunced pressure and Et 2 O/petroleum ether (1:2,20ml) was added to precipitate triphenylphosphine oxide. Removal of the solvent gave carbodiimides,which were used directly without further purification. To a solution of carbodiimides in CH 2 Cl 2 (10ml)dialkylamine(2mmol). After the reaction mixture was left unstirred for 4-6h. The solvent was removed and anhyd.EtOH(10ml)with several drops of EtONa in EtOH was added. The mixture was stirred for 6-12h at room temperature. The solution was condensed and residue was recrystallized from EtOH to give the expected title compound in a good yield.

Refinement
All H atoms were positioned geometrically [C-H=0.93, 0.97 Å] and allowed to ride on their parent atoms , with U iso (H)=1.2Ueq(C). Fig. 1. The molecular structure of (I) with displacement ellipsoids drawn at the 30% probability level.

Special details
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 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.