Collect. Czech. Chem. Commun. 1983, 48, 3144-3153

Site-selectivity of 1,3-dipolar cycloadditions to 2,3-dimethoxycarbonyl-7-oxabicyclo[2,2,1]heptadiene

Lubor Fišera, František Považanec, Peter Zálupský, Jaroslav Kováč and Dušan Pavlovič

Department of Organic Chemistry, Slovak Institute of Technology, 812 37 Bratislava


Site-selectivity of dipolar cycloaddition to the title compound was studied. Azomethine X afforded a 1 : 1 cycloadduct XI at the deactivated double bond at room temperature; upon thermolysis at 110 °C it afforded the acetylated enamine XIII which was formed via a direct cycloaddition at the mentioned temperature. The cycloaddition course was investigated in various solvents; the enamine XIV formed by solvolysis of XIII was the final product in methanol. Cycloaddition of the title compound to azides, benzoylnitrile N-oxide and C-acetyl-N-phenylnitrilimine furnished the product of cycloreversion instead of the not isolable 1 : 1 cycloadducts. 5-Azido-2-furancarbaldehyde and 4-nitrophenylazide yielded cycloaddition products to both multiple bonds in an approximately 1 : 1 ratio; NH3, tosylazide, benzoylnitrile N-oxide and C-acetyl-N-phenylnitrilimine gave the addition products to the deactivated double bond. The solvent-effect of site-selectivity of 1,3-dipolar cycloaddition was investigated and the title compound was found to be an excellent synthetic equivalent for acetylene and dimethyl butinedioate.