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A Facile and Regioselective Synthesis of Trans-Heterofunctionalized Porphyrazine Derivatives

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journal contribution
posted on 03.01.1998, 00:00 by Timothy P. Forsyth, D. Bradley G. Williams, Antonio Garrido Montalban, Charlotte L. Stern, Anthony G. M. Barrett, Brian M. Hoffman
New methodology was developed for the selective synthesis of regiochemically defined porphyrazines of the form M[pz(A2;B2)] (shown in Chart ) where A and B represent peripheral functionalization attached to the β-positions of the pyrroles. Specifically, phthalonitriles or derivatives thereof with sterically bulky groups in positions 3 and 6, in particular 4,7-bis(isopropyloxy)-1,3-diiminoisoindoline (3) act as a “trans director” when macrocyclized with heteroatom-appended maleonitriles under Linstead conditions, the result being preferential formation of the trans-M[pz(A2;B2)] pigment where A = SR, NMe2, OR, as well as R (shown in Chart ). Linstead crossover macrocyclization of 3 with 4, 11, 15, and 18 gave pigments 10, 14, 17, and 19, respectively. These pigments were characterized by 1H NMR, 13C NMR, UV−visible spectroscopy, mass spectrometry, microanalysis, and 17 was characterized by single-crystal X-ray analysis.