Efficient syntheses of 2,4-dibromo- and 2,4-diiododeuteroporphyrin IX have been carried out by treating zinc(II) 2,4-bis(chloromercurio)deuteroporphyrin IX dimethyl ester (2) with bromine or iodine. Unavoidable meso-chlorination occurs when 2 is treated with chlorine and with other free-radical chlorinating agents. Regioselective meso-chlorination and peripheral (β) bromination are shown to occur from brief treatment of copper(II) deuteroporphyrin IX or β-unsubstituted a,c-biladienes with the corresponding copper(II) halide in refluxing dimethylformamide. Protoporphyrin IX has been synthesized by vinylation of 2 via ethylene/LiPdCl3(35% yield), with vinyl bromide and Wilkinson's catalyst (63%), or from 2,4-dibromodeuteroporphyrin IX with ethenyl-tributylstannane/(Ph3P)4Pd0(85%).
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Minnetian et al. (1989) studied this question.