Star-shaped compounds, having a benzene (9a,b) or a 1,3,5-triazine (11a,b) core and stilbenoid arms were prepared. Hexyloxy chains, attached in the middle of the arms, provide nematic discotic phases N D , which are unusual for such systems. The position of the sidechains prevents the micro-segregation, which is valid for star-shaped discs of columnar phases. The stilbenoid character of 9a,b and 11a,b guarantees a high light sensitivity. Apart from the statistical CC bond formation by irradiation in solution or in the LC phases, a topochemically controlled chemo-, regio- and stereoselective photocyclodimerization 11a->12 was found in the crystalline state. The structure determination of 12 is based on different two-dimensional NMR techniques (COSY, NOESY, HMQC, HMBC).