A Study on Intermolecular and Intramolecular Cycloaddition Reactions of Heteroatom-Containing Unsaturated Compounds

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1. The alpha, beta : gamma, delta-thiocarbonyl compounds derived from 2-(phenylthio)tetralinethione reacted thermally or in the presence of a Lewis acid catalyst with a variety of dienophiles to afford the polycyclic hetero Diels-Alder Cycloadducts in good yields. 2. Thiochalcone underwent asymmetric hetero Diels-Alder reactions with some chiral dienophiles to give the cycloadducts with high level of stereoselectivities in excellent yields. The absolute structure was determined. 3. The hetero Diels-Alder reaction of heteroaromatic thioketones with 2-chloroacrylonitrile or 2-haloacrylic esters afforded, after treatment of the cycloadducts with an amine, heterocycle-fused 2H-thiopyran compounds having an ortho-quinodimethane structure. 4. The intermediary thiocarbonyl ylides derived from the reaction of heteroaromatic thioketones with disulfonylcarbene species underwent 1,5-dipolar cyclization with elimination of a sulfinic acid to afford heterocycle-fused [c] thiophenes. 5.1,2-Thiaphospholes, prepared from the reaction of bicyclic trithiophosphates with tributylphosphine, underwent double Diels-Alder reactions with a variety of dienophiles or tandem Diels-Alder reaction/Michael addition reaction to give phosphorus-containing heterocycles. 6. The conjugated carbodiimides preferentially afforded the electrocyclization products under thermal conditions, whereas in the presence of a Lewis acid catalyst they gave the intramolecular Diels-Alder products in a highly periselective manner. 7. Addition reaction of the conjugated carbodiimides with a nucleophile such as an alcohol, an amine and a thiol, followed by intramolecular Michael addition reaction, gave the dihydroquinazoline derivatives.