A photochemical two-step one-pot synthesis of novel biscyclopropyl-box-shaped compounds via the reaction of 2,5-dimethoxy-para-benzoquinone and monosubstituted alkynes is reported. The reaction mechanism for a process in which six new C–C bonds are formed is explored by means of experimental and computational techniques. The whole process occurs with complete selectivity, and only one densely decorated diastereomer is obtained; such a degree of control and substitution makes for a rather powerful and complexity-building process.