Taco complex-templated highly regio- and stereo-selective photodimerization of a coumarin-containing crown ether

We design a coumarin-containing bis( m -phenylene)-32-crown-10 derivative which efficiently controls the regio- and stereo-selectivity of the photodimerization of its two terminal coumarin groups templated by taco-type host–guest complex formation to selectively produce the syn -head-to-tail cryptand isomer in quantitative yield.