Crystal structure of (S)-5,7-diphenyl-4,7-dihydrotetrazolo[1,5-a]pyrimidine

Acknowledgements The authors thank Christopher Daley, A. Rheingold and C. Moore (UCSD) for the data collection. Funding for this work was provided by the University of California, Merced and the National Science Foundation (CHE-1300686)Peer reviewedPublisher PD

Use of Programmed Damped Temperature Cycles for the Deracemization of a Racemic Suspension of a Conglomerate Forming System

The current research has developed a potential route toward process optimization for the deracemization of a racemizable conglomerate forming system. The use of damped temperature cycleswhere the magnitude of the temperature cycles is reduced as the enantiomeric excess (ee) in the solid phase increasesis a promising methodology for optimizing the temperature cycle induced deracemization process. This process requires significantly less time and energy to reach an enantiopure state compared with the use of constant amplitude temperature cycles. There was evidence of some crystal breakage occurring in the system; however, the limited amount of breakage did not produce any change in the enantiomeric excess in the solid phase in the absence of temperature cycles in the system. Hence, the primary mechanism in this process is neither Viedma ripening nor Ostwald ripening. Scanning electron micrographs of the crystals taken during the series of temperature cycles show that the amplification of the ee in the solid phase is caused by dissolution and growth phenomena induced by the temperature cycles. The promotion of the larger or faster growing crystals at the expense of the smaller or slower growing crystals during the cycles and entrainment from a mother liquor having ee = 0 are both responsible for this deracemization

Racemic compound versus conglomerate: Concerning the crystal chemistry of the triazoylketone, 1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl) pentan-3-one

The triazoylketone discussed in this paper crystallises from racemic solutions as a conglomerate. Here, we report the ternary phase diagram confirming the conglomerate behaviour of this molecule. Through computation we also explore the underlying reasons for the absence of a racemic compound in this system and the evident epitaxial crystallisation leading to crystals of almost racemic compositions but which retain the crystal structure of the pure enantiomer. This journal is © the Partner Organisations 2014

CCDC 969515: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures