Formation of derivatives of 5,6-dihydro-1,3-thiazines in the reaction of acetothioacetic acid ethyl ester under the conditions of the Hantzsch synthesis

Abstract

Derivatives q/ 2H-5,6-dihydro-l,3-thiazine

Structure matching: measures of similarity and pseudosymmetry

“…If the MATCH algorithm detects large positional RMSDs for a structure containing either (or both) of these pseudo operators, there is a fair possibility that the symmetry needs raising, or that molecular similarity restraints will be needed (Watkin, 1994). Table 5 lists the bond lengths for QEQRUZ, which has a pseudo centre of The two independent molecules in QEQRUZ (Vigante et al, 2000) overlaid with the best match. Although the molecules are chiral in P2 1 , the best operator is a pseudo centre.…”

Structure refinement: some background theory and practical strategies

“…Fig. 7 (CSD refcode QEQRUZ; Vigante et al, 2000) is an example in which the space group must be acentric because the material is chiral, but which has a strong pseudo-centre of inversion relating two independent molecules in the asymmetric unit. The refinement does not proceed smoothly, as revealed by the published bond lengths and angles.…”

“…The two independent molecules in QEQRUZ (Vigante et al, 2000), overlaid with the best match using CRYSTALS. Although the molecules are chiral in P2 1 , the operator giving the best match between the molecules is a pseudo-centre of symmetry.…”