1,3-dipolar cycloaddition reactions of porphyrins with azomethine ylides.

[reaction: see text] The behavior of porphyrins as dipolarophiles in 1,3-dipolar cycloadditions with azomethine ylides was studied. Depending on the nature of the substituent groups on the porphyrin macrocycles, the reaction can give monoadducts (chlorins) or bisadducts (isobacteriochlorins and bacteriochlorins). When a large excess of azomethine ylide is used, trisadducts can also be obtained. Mixed isobacteriochlorin derivatives were prepared from the reaction of azomethine ylides with the chlorin monoadducts previously obtained via Diels-Alder reactions.