Studies On The Stereoselective Nitration And Oxidative Aromatization With NO

In this dissertation, I will represent my study on the stereoselective nitration of enantiopure epoxides and asymmetric hydrazones with nitric oxide. the oxidative aromatization of 1,3,5-trisubstituted pyrazolines and 3,5- disubstituted 2-isoxazolines with nitric oxide will be reported. In addition, I will represent a catalytically efficient deprotection of tert-butyldimethylsilyl (TBS) and tetrahydropyranyl (THP) ethers by NOBF4 in methanol. The results are shown as follows:1. Highly stereoselective syn-ring opening of enantiopure epoxides with nitric oxideReaction of enantiopure epoxides with NO occurred highly stereoselectively, affording syn-ring opened products, nitrates. The configuration of nitrates was confirmed to be retained by determining the configuration of reduced products 1,2-glycols from nitrates. A possible mechanism is suggested to trace out the syn-ring opening pathway.2. Stereoselective nitration of asymmetric hydrazones with nitric oxideNitration of asymmetric hydrazones with nitric oxide occurred stereoselectively at C1-atom, giving mono-nitrated trans isomer as a major outcome. The ratio of trans to cis was up to >99. Higher isolated yields of nitrated products and higher trans/cis ratios of isomers suggest that this procedure offers advantages for synthesizing asymmetry nitro compounds.3. Oxidative aromatization of 1, 3, 5-trisubstituted pyrazolines and 3, 5-disubstituted 2-isoxazolines with nitric oxideA series of 1, 3, 5-trisubstituted pyrazolines and 3, 5-disubstituted 2-isoxazolines were highly efficiently oxidized to corresponding pyrazoles and isoxazoles with nitric oxide at room temperature in CH₂Cl₂. The structure of products was characterized by various spectroscopic data. This entry offers several advantages like simply handlings, mild reaction conditions and high yields of products.4. Catalytical removal of protective tert-butyldimethylsilyl (TBS) and tetrahydropyranyl (THP) groups by NOBF₄ in methanolA catalytical effective method to remove protective TBS and THP groups has been developed. Its highlight is the selectivity to TBS and THP ethers. TBDPS ethers, phenolic TBS ethers, and NHTS group will be unchanged under the present conditions.