ИСТИНА

Borylated derivatives of tetrapyrrole compounds are versatile building blocks for the creation of new dyes and photosensitizers through cross-coupling reactions [J. Org. Chem. 2019, 84, 10, 6158–6173; J. Am. Chem. Soc. 2005, 127, 23, 8264–8265]. A large number of publications reported various methods of synthesis of borylated tetrapyrroles, but all the methods possessed two key drawbacks - the multi-stage synthesis and the high cost of the catalysts used. In this work, the method of direct insertion of the pinacolboranyl group at the terminal position of the vinyl group of the Ni(II) complexes of the methyl ester of pyropheophorbide a (1), the dimethyl ester of protoporphyrin IX (2), the meso-vinyl-β-octaethylporphyrin (7) and meso-vinyl-β-octaethylchlorin (8) was elaborated. For this purpose, the synthesis of alkenylboronates from alkenes and bis(pinacolato)diboron via copper catalyst by using TEMPO (2,2,6,6-tetramethylpiperidin-1-yl)oxyl) as a mild oxidant reported by Wenkui Lu and Zengming Shen [Org. Lett. 2019, 21, 1, 142–146] was exploited. Ni(II) complexes were obtained from the corresponding Ni(II) complexes of β-octaethylporphyrin (5) and β-octaethylchlorin (6) via sequential Vilsmeier-Haack and Wittig reactions. Borylated derivatives of Ni(II) complexes of the pyropheophorbide a methyl ester (3), the protoporphyrin IX dimethyl ester (4), the meso-vinyl-β-octaethylporphyrin (7) and meso -vinyl-β-octaethylchlorin (8) were synthesized by direct insertion of pinacolborane at the vinyl groups of the compounds.