Stereoselective synthesis of homochiral paracyclophanylindenofuranylimidazo[3.3.3]propellanes

The reaction between N-paracyclophanyl-substituted hydrazine-carbothioamides and dicyanomethylene-1,3-indanedione (CNIND) furnished planar and central chiral substituted (epiminomethanoimino)-indenofuranyl-1,4-(1,4-dibenzenocyclohexaphane)-1,2-carboxamides as a type of paracyclophanylfuroimidazo[3.3.3]propellanes in 35–81% yields as a major product as single diastereomers, and substituted spiro[indene-2,4′-indenopyran]-3′-carbonitrile (9–12% yields) as a minor product. To prepare the homochiral paracyclophanylpropellane, oxidation of scalemic formylparacyclophane afforded the corresponding acid. Afterward, the acid chloride formation of [2.2]paracyclophane was obtained by chlorination of the corresponding acid. By repeating the previous procedure and utilizing a final HPLC purification, we succeeded in obtaining the target homochiral propellane. Various spectroscopic techniques such as mass spectrometry, ¹H NMR, ¹³C NMR, and X-ray analysis have been used for structure determination and confirmation of the stereochemistry of the isolated products. Graphic abstract: [Figure not available: see fulltext.]