82498-08-6Relevant academic research and scientific papers
Nearly chromatography-free synthesis of the A3B-porphyrin 5-(4-hydroxymethylphenyl)-10,15,20-tri-p-tolylporphinatozinc(II)
Zaidi, Syeda Huma H.,Loewe, Robert S.,Clark, Brad A.,Jacob, Marc J.,Lindsey, Jonathan S.
, p. 304 - 314 (2006)
Rational routes to synthetic porphyrins bearing distinct meso-substituents have typically been implemented at modest scale (3B-porphyrin 5-(4-hydroxymethylphenyl)-10,15,20-tri-p- tolylporphinatozinc(II) (Zn-1) is required in multigram quantities for possible commercial use in information storage applications. The synthesis of Zn-1 has been carried out by reaction of 5-(4-hydroxymethylphenyl)dipyrromethane and the dicarbinol derived from 1,9-di-p-toluoyl-5-p-tolyldipyrromethane. Four improvements have been made to the steps leading to the dipyrromethane and dipyrromethane-dicarbinol: (i) use of 50 equiv of pyrrole in the condensation of an aldehyde to give the dipyrromethane (versus 100 equiv previously), (ii) 1,9-diacylation of a dipyrromethane using the hindered Grignard reagent 2,6-dimethylphenylmagnesium bromide and p-toluoyl chloride to give the 1,9-diacyl versus 1-acyl products in > 10:1 ratio (versus 4:1 using EtMgBr), (iii) isolation of the dibutyltin complex of the 1,9-diacyldipyrromethane from the crude reaction mixture by direct crystallization using methanol/methyl tert-butyl ether (MTBE) (versus silica chromatography), and (iv) reduction of the dibutyltin complex of the 1,9-diacyldipyrromethane (250 mM) with ～10-15 mol equiv of NaBH4 (versus 25 mM and 40 mol equiv). The procedures have been carried out with no chromatography at large scale, affording the dipyrromethane (31, 59, or 79 g), the dibutyltin complex of a 1,9-diacyldipyrromethane (361 g), and reduction of the latter (45 g). The porphyrin-forming reaction has been performed (25 mM reactants at 50-mmol scale, or 10 mM at 64-mmol scale) in a two-step process of condensation and oxidation to give the free base porphyrin 1 in 3.7- or 5.8-g quantities. Metalation with zinc acetate afforded Zn-1, which was isolated by direct crystallization. Taken together, the various improvements facilitate synthesis of the target porphyrin Zn-1 and may have broad applicability.
