Organized media such as micelles have shown great promise in achieving regio-and stereoselectivity in photochemical cycloaddition reactions as has been shown by recent reports. 7-Alkoxy-and 4-methyl-7-alkoxycoumarins dimerize in organic solvents to give the syn head-tail dimer. However, dimerization of these coumarins in SDS and CTAB micelles did not show any reversal in this trend. The results probably indicate that the micellar ...