Unlike ground state oxygen, singlet oxygen participates in Diels–Alder [4+2]- and [2+2]-cycloaddition reactions and formal concerted ene reactions.  It oxidizes thioethers to sulfoxides.  Organometallic complexes are often degraded by singlet oxygen. With some substrates 1,2-dioxetanes are formed; cyclic dienes such as 1,3-cyclohexadiene form [4+2] cycloaddition adducts.
The [4+2]-cycloaddition between singlet oxygen and furans is widely used in organic synthesis.
In singlet oxygen reactions with alkenic allyl groups, e.g., citronella, shown, by abstraction of the allylic proton, in an ene-like reaction, yielding the allyl hydroperoxide, R–O–OH (R = alkyl), which can then be reduced to the corresponding allylic alcohol.
In reactions with water trioxidane, an unusual molecule with three consecutive linked oxygen atoms, is formed.