| In this dissertation, electrophilic reactions of Nitrosonium (NO~+) with imines, aza-Diels-Alder reactions of N-arylimines with a variety of electron rich olefinic compounds induced by NO~+, and photoreactions of N-nitrosodiphenylamine with aromatic amines were studied. The principal results are listed as follows.(1) The reaction of NO~+ with carbon-nitrogen double bonds of Schiff bases produced diazonium salts and aldehydes in good yields. The reaction was assumed to be an electronphilic attack of nitrosonium on imines, resulting a four-member ring intermediate.(2) An efficient aza-Diels-Alder reaction of N-vinylpyrrolidinone with N-arylimines was achieved using nitrosonium tetrafluoroborate as a cation radical initiator, giving tetrahydroquinoline derivatives. The reaction occurred highly regiospecifically, and gave only cis isomers. The diastereoselectivity rooted in the endo transition state favorably stabilized by secondary orbital interactions between the carbonyl double bond and the aza diene. It may be one of the few examples in which NO~+ participates in reactions in a catalyzed amount (5% mol).(3) Aza-Diels-Alder reactions took place between N-arylimines and 2,3-dihydrofuran and/or 3,4-dihydro-2H-pyran, giving a cis and trans mixture of furo[3,2-c]- and/or pyrano[3,2-c]-quinoline derivatives. When 2,3-dihydrofuran was used as a dienophile, the reaction proceeded better than 3,4-dihydro-2H-pyran did. The single electron oxidation of 3,4-dihydro-2H-pyran with NO~+ was more difficult. The cation radical mediated aza-Diels-Alder reaction could not be initiated efficiently.(4) Amino aromatics reacted photochemically with N-nitrosodiphenylamine to give benzeneazo compounds. Benzotriazoles were detected when the aromatic amines beared two amino groups at the ortho positions. The two kinds of product are characteristic of special chromophores. Benzeneazo compounds are often used as dyes, and benzotriazoles as fluorescent probes in detecting NO in biological systems.
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