Solid-state kinetic resolution

Preparation of optically active P-ionone epoxide by a solid state kinetic resolution in the presence of the chiral host 10a is also possible. When a mixture of 10a, P-ionone (66) and m-chloroperbenzoic acid (MCPBA) is ground by mortar and pestle in the solid state, (+)-67 of 88% ee was obtained.29 Mechanism of the kinetic resolution is shown below. Of course, all processes proceed in the solid state. Firstly, oxidation of 66 with MCPBA gives rac-P-ionone epoxide (67). Secondly, enantioselective inclusion of (+)-67 with 10a occurs. Thirdly, uncomplexed (-)-67 is oxidized to give the Baeyer- Villiger oxidation product (-)-68 of 72% ee. This is the first example of the resolution by an enantioselective inclusion complexation in the solid state. 

Toda, F., Mori, K., Matsuura, Y., and Akai, H. (1990) Solid State Kinetic Resolution of b-Ionone Epoxide and Dialkyl Sulphoxides in the Presence of Optically Active Host Compounds. The First Enantioselective Host-Guest Inclusion Complexation in the Solid State,... 

These schemes have been frequently suggested [105-107] as possible mechanisms to achieve the chirally pure starting point for prebiotic molecular evolution toward our present homochiral biopolymers. Demonstrably successftd amplification mechanisms are the spontaneous resolution of enantiomeric mixtures under race-mizing conditions, [509 lattice-controlled solid-state asymmetric reactions, [108] and other autocatalytic processes. [103, 104] Other experimentally successful mechanisms that have been proposed for chirality amplification are those involving kinetic resolutions [109] enantioselective occlusions of enantiomers on opposite crystal faces, [110] and lyotropic liquid crystals. [Ill] These systems are interesting in themselves but are not of direct prebiotic relevance because of their limited scope and the specialized experimental conditions needed for their implementation. 

This work foreshadows one way in which mechanistic studies of conventional (heterogeneous) and biological catalysts may proceed in future. When one recognizes that parallel H and 2H CP/MAS NMR studies could also be carried out in situ, there are good prospects that kinetic isotope effects will prove directly accessible through the agency of high-resolution solid-state NMR. 

TG/DTA, TPR, and complementary techniques for characterizing catalysts in the working state (e.g., XRD Raman, IR, and UV-vis spectroscopies) can provide structural and metal valence information under reaction conditions. However, the capability of TR-XAFS spectroscopy to reveal quantitative phase composition and average metal valence together with the evolution of the local structure of a catalyst under varying (reaction) conditions, combined with a time resolution of 100 ms will continue to be a very powerful tool for kinetics investigations in solid-state chemistry and heterogeneous catalysis. 

The kinetic Monte Carlo (KMC) simulation method focuses on the state-to-state dynamic transitions and neglects the short-time system fluctuations. This approximation allows much longer timescales to be reached, without chemically relevant compromise in the resolution of the simulation, especially for solid-state systems. This is particularly important, since the diffusion of an oxygen ion on the surface of a YSZ electrolyte (among defect sites) requires approximately 1 ps, and the adsorption of one molecular oxygen onto the YSZ at 0.01 atm pressure requires approximately 0.5 ps [32]. Thus, deterministic simulation methods, like MD, are not easily able to capture this behavior, so other methods must be employed. 

Enantioselective oxidation of 2 to the epoxide 3 in its inclusion complex 5 with 4 c in the presence of a small amount of water is described in Section 2.2.2.1. However, the same reaction in the absence of water gave rac-3 [5]. For example, when 5 was treated with an equimolar amount of 1 for 2 days at room temperature in the solid state, rac-3 was obtained in 73% yield as an inclusion complex with 4 c. Nevertheless, the same reaction of 5 with two molar amounts of 1 gave (+)-3 of 66 % ee as an inclusion complex with 4 c together with the further oxidized product, (-)-65 of 72 % ee, in 43 and 33 % yields, respectively. The same reactions of 5 with three and four molar amounts of 1 gave (+)-3 (88% ee, 29% yield) and (—)-65 (36% ee, 55% yield) in the optical and chemical yields indicated. Finally, when 5 was reacted with four molar amounts of 1, rac-55 was obtained in 88% yield. These data can be interpreted by a kinetic resolution of the rac-3 initially formed by complexation... 

Section 4 is entirely devoted to ferroelectric and H-bonded systems. It also provides a nice illustration of results that always maintained the utility of proton NMR in solid state, even wideline, or how the old question of the order disorder or displacive nature of some ferroelectric phase transitions were reopened by progresses in NMR resolution. A number of structural phase transition is discontinuous, but the examples of coexistence in solid-state and kinetic studies are rather scarce this is the object of Section 5. Section 6 is devoted to single-crystal studies that allow very precise comprehension of subtle phase transition mechanisms. Section 7 introduces the salient features of NQR that represent an interesting alternative to NMR in some cases. The section ends with a table of miscellaneous phase transitions that complete the references given in the text. Section 8 concludes and presents some perspectives in NMR phase transition studies. 

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