Spontaneous chiral crystallization

SPONTANEOUS CHIRAL CRYSTALLIZATION OF ACHIRAL MATERIALS AND ABSOLUTE ASYMMETRIC TRANSFORMATION IN THE CHIRAL CRYSTALLINE ENVIRONMENT... 

Absolute Asymmetric Photochemistry Using Spontaneous Chiral Crystallization... 

Solid-state chiral photochemistry has been developed based on spontaneous chiral crystallization and supramolecular approaches. Since the report of solid-state [2 4- 2] photocycloaddition by Cohen and Schmidt in 1964 [11], the Weiz-mann Institute Group has been also a pioneer of solid-state chiral photochemistry. The research group first succeeded in absolute asymmetric [2 + 2] photocycloaddition by using chiral crystals spontaneously formed from achiral dienes in 1973 [12]. Thereafter, more than twenty successful examples of absolute asymmetric photoreactions have been reported by several research groups [9,10,13,14]. The... 

Solid-state asymmetric photoreactions have been already reviewed from various aspects [7-20]. However, the reviews do not seem to have given us a complete understanding of solid-state chiral photochemistry. In this chapter, solid-state asymmetric photoreactions are systematically reviewed by classification into supramolecular approaches and spontaneous chiral crystallization approaches since the beginning in the 1970s to the present. 

Even if a molecule is achiral, chiral crystals can form by spontaneous chiral crystallization [26]. The big advantage in utilizing a crystal as a reactant is that absolute asymmetric synthesis can be achieved by solid-state photoreaction of such a chiral crystal. The initial chiral environment in the crystal lattice is retained during the reaction process, owing to the low mobility of molecules in the crystalline state, and leads to an optically active product. The process represents transformation from crystal chirality to molecular chirality. This kind of absolute asymmetric synthesis does not need any external asymmetric source in the entire synthetic procedure [9-14]. 

VI. ABSOLUTE ASYMMETRIC PHOTOREACTIONS BY THE SPONTANEOUS CHIRAL CRYSTALLIZATION APPROACH... 

Fig. 19. Energy diagram for racemization of axially chiral and achiral materials available for asymmetric synthesis via spontaneous chiral crystallization...

Sakamoto, M. (2006). Spontaneous chiral crystallization of achiral materials and... 

Spontaneous Chiral Crystallization of Achiral Materials and Absolute Asymmetric Transformation in the Chiral Crystalline Environment by Sakamoto, M. (2007) in Enantiomer Separation Fundamentals and Practical Methods (ed. Toda, R), Kluwer Academic, Dordrecht/Boston, pp. 103-133. 

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