Formation And Cleavage Of Acetals Catalysed By Montmorillonite K 10 And Some Properties Of Some Stable Ozonides And The Spectrometric Identification Of The Related Compounds

This thesis consists of three parts. In the first part, an efficient and convenient procedures for the formation and cleavage of acetals catalysed by montmorillonite K-1O has been presented. The present methods have the additional advantages of non-corrosivity, mild reaction conditions, high yield and selectivity, and ease of set-up and work-up over the class methods. In the second part, Oxidation of cholesterol (la) or pregnenolone (lb) with pyridinium dichromate (PDC) in dimethylformamide (DMF) or in dichloromethane (DCM) and pyridinium chlorochromate (PCC) in DCM provided cholest-4-en-3,6-dione (2a) or pregn-4-en-3,6,20-trione (2b). TLC monitoration of the reactions implied that cholest-5- en-3-one (3a) or pregn-5-en-3,20-dione (3b) and cholest-4-en-3-one (4a) or pregn-4-en- 3,20-dione (4b) might be intermediates. Individual oxidation of 3a or 3b with PDC and PCC could give 2a or 2b, but 4a or 4b remained unchanged. Further investigation indicated that 4a or 4b was an isomerization product of 3a or 3b on silica gel TLC plate rather than really existence in the reaction mixture. These results shown steroidal 5-en-3- ones were intermediates of the transformation of steroidal 5-en-3 P-ols to steroidal 4-en- 3,6-diones oxidized by PDC and PCC. In the third part: some Properties of Some Stable Ozonides. First, the thermal rearrangement reaction of some stable ozonides was investigated. It was shown that: (1). More substituted alkyl group has a strong tendency to migrate; (2). The configuration of migrated group reserved in the rearrangement reaction. Second, the results demonstrate that the less stable ozonides can be converted into the more stable ozonides.