Powdered host compounds, inclusion complexation using

A powdered 1 1 inclusion complex of (-)-l and 4-methoxy-l-methylpyridone 2c was irradiated by 100-W high-pressure Hg-lamp at room temperature in the solid state. The crude reaction product was chromatographed on silica gel using CHCI3 as a solvent to give a mixture of host compound and 3, from which 3 was isolated by distillation as an oil ([a]D-123° (c 0.026, CHC13), 100% ee). 

The photocyclization of acrylanilide (122) to 3,4-dihydroquinolinone (123), which was first reported in 1971 [74], can also be carried out enantioselectively by using a chiral host compound. Irradiation of the finely powdered 1 1 inclusion complex of 122 with 26 in a water suspension gave (-)-123 of 98% ee in 46% yield [75]. By the same procedure, optically active 125, 127 and 129 were prepared from 124, 126 and 128, respectively (Table 15-23) [75]. 

It was found that efficient inclusion crystallization can be accomplished simply by mixing powdered crystalline host and a hydrophobic guest compound in hexane or water. By using the inclusion crystallization in suspension media, very efficient optical resolution method was established. Furthermore, when inclusion complexation between chiral host and rac-guest in the solid state is combined with a distillation procedure, optical resolution can easily be accomplished by the fractional distillation procedure. 

The formation of such materials may be monitored by several techniques. One of the most useful methods is and C-nmr spectroscopy where stable complexes in solution may give rise to characteristic shifts of signals relative to the uncomplexed species (43). Solution nmr spectroscopy has also been used to detect the presence of soHd inclusion compound (after dissolution) and to determine composition (host guest ratio) of the material. Infrared spectroscopy (126) and combustion analysis are further methods to study inclusion formation. For general screening purposes of soHd inclusion stmctures, the x-ray powder diffraction method is suitable (123). However, if detailed stmctures are requited, the single crystal x-ray diffraction method (127) has to be used. 

Successful complexation of the exchanged transition metals by the tetradentate ligand salen was indicated by the typical yellow/brownish colour of the prepared inclusion compounds. X-ray powder diffraction and scanning electron microscopy reveal that the crystallinity of the zeolite host is virtually retained during the modification steps. Furthermore, no crystals of the salen ligand or of metal-salen complexes are visible on the external surface of the zeolite crystallites after careful piuification via soxhlet extraction with acetone. Analysis of the used solvent by UVATS-spectroscopy revealed that only salen but no metal-salen complexes were removed from the zeolite during extraction. This indicates that the complexes are truly entrapped in the intracrystalline voids of the zeolite. It has been demonstrated [7] that the presence of salen and PdSalen in zeolite Y can be probed by IR-spectroscopy in... 

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