Stereoselective synthesis of tetrahydronaphthocyclobuta[1,2-d]pyrimidinediones from 5-fluoro-1,3-dimethyluracil and naphthalenes.

Upon UV-irradiation in the presence of piperylene, 5-fluoro-1,3-dimethyluracil (5-FDMU) couples with naphthalenes having either an electron-withdrawing group or an electron-donating group by way of 1,2-cycloaddition via mode selectivity to give the corresponding naphthocyclobutapyrimidines regio- and stereo-selectively.