Photocycloaddition of Imines to Olefins

As mentioned in chapter 4.2.3, aliphatic imines are photochemically rather unreactive. When the C—N double bond is conjugated to an electron withdrawing group (e.g. carbonyl group), as in O-alkyl derivatives of succinimide and phthalimide, the reactivity increases and azetidines are obtained in cycloadditions to olefins486). A somehow similar example is the photoaddition of a 6-azauracil derivative to 2,3-dimethyl-2-butene 

An interesting modification of such a reaction, wherein the reactivity of the excited chromophore is increased by protonation is outlined in the following example whereby a pyrrolenine derivative is photocyclized to a pyrrolidine derivative (4.75) 488). 

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