A method of forming a cyclopropane having enhanced chirality said method comprising reacting together:
a symmetrical 1,2-dioxine of the formula (1), wherein X and Y are the same and are groups in which a carbon atom is bonded to the dioxine backbone; and a phosphorus ylide or a phosphorus ylide precursor, in the presence of a cobalt catalyst containing a chiral ligand.
Sensitized photo-oxygenation of a wide variety of acyclic 1,3-dienes was investigated. The 1,4-cycloaddition of singlet oxygen to acyclic conjugated dienes was closely related to the thermal Diels-Alder reaction in stereospecificity, and steric and electronic effects of substituents. Reactivity order of singlet oxygen toward conjugated dienes and isolated C—C double bonds was exhibited as follows: