unusual products are confirmed by X-ray crystal structure analysis. An efficient route for the synthesis of oxa-aza- and bis-oxathiaaza[3.3.3]propellanes via reactions of symmetrical and unsymmetrical N1,N2-disubstituted hydrazine-1,2-dicarbothioamides (2,5-dithiobiureas) with (1,3-dioxo-2,3-dihydro-1H-inden-2-ylidene)propanedinitrile in tetrahydrofuran is described. The rationale behind these conversions