Regioselective syntheses and structural characterizations of 2,3-dibromo- and 2,3,7,8,12,13-hexabromo-5,10,15,20- tetraphenylporphyrins
The title dibromoporphyrins 4/5 and hexabromoporphyrins 11/12 are prepared from H2(2NO2TPP) 1 and Cu(2-NO2TPP) 8, respectively. The β-nitro group confines the 18-π-annulene system of a tetraphenylporphyrin to its N22H-N24H aromatic delocalization pathway which induces the localization of an antipodal double bond on the porphyrin periphery and enhances its susceptibility to electrophilic attack. Dibromination of H2(2- NO2TPP) 1 occurs regioselectively affording the 12,13-dibromo-2- nitroporphyrin 2 which, upon Michael addition of NaBH4 and re- aromatization of the resulting nitrochlorin 3, provides an entry to 2,3-dibromoTPP 4/5 as well as an improved route to 2,3- dicyanoporphyrins 6/7. Perbromination of Cu(2-NO2TPP) 8 and denitration of 9 gave, after demetalation, 2,3,7,8,12,13- hexabromoTPP 12. Both 4 and 12 are structurally characterized by X-ray crystallography.
Publication Source (Journal or Book title)
Jaquinod, L., Khoury, R., Shea, K., & Smith, K. (1999). Regioselective syntheses and structural characterizations of 2,3-dibromo- and 2,3,7,8,12,13-hexabromo-5,10,15,20- tetraphenylporphyrins. Tetrahedron, 55 (46), 13151-13158. https://doi.org/10.1016/S0040-4020(99)00811-X