and Type Cycloaddition Reactions of 1-Ethoxycarbonyl-1H-azepine and 1-Ethoxycarbonyl-1H-1,2-diazepine with 3,4,5,6-Tetrachloro-1,2-benzoquinone

Article abstract of DOI:10.1246/bcsj.59.2485

The reaction of 1-ethoxycarbonyl-1H-azepine with 3,4,5,6-tetrachloro-1,2-benzoquinone at room temperature gave a <6+4>-type cycloadduct as the major product and two kinds of <2+4>-type cycloadducts.In this reaction the diketone moiety of the benzoquinone derivative was used as the 4? component to form ether linkages.The <6+4>-type cycloadduct became rearranged to one of the <2+4>-type cycloadducts by heating at 90 deg C.The same reaction, but using 1-ethoxycarbonyl-1H-1,2-diazepine, afforded two kinds of <2+4>-type cycloadducts.An electronic attraction between the oxygen atoms of the benzoquinone derivative and the carbons in the 2 and 7-positions of the azepine derivative is considered to be one of the driving force of the <6+4>-type cycloaddition reaction.The <2+4>-type cycloadducts are regarded to be formed via inverse electron demand Diels-Alder reactions.