| Abstract
| - 5-Methoxy-8,8,18,18-tetramethyl-2,12-di-p-tolylbacteriochlorin (MeO-BC) undergoes regioselective electrophilic bromination with NBS to give the 15-bromo analogue (MeO-BC-Br15) in 85% yield. By contrast,the bacteriochlorin lacking the 5-methoxy group (8,8,18,18-tetramethyl-2,12-di-p-tolylbacteriochlorin,H-BC) gives a mixture of two monobromo- and two dibromobacteriochlorins. Deuterium exchange ofboth bacteriochlorins (H-BC and MeO-BC) in acidic media (TFA-d) occurs preferentially at the β-pyrrolepositions (3, 13) > unhindered meso-positions (5, 15 for H-BC; 15 for MeO-BC)> hindered meso-positions (10, 20). The 15-bromo-5-methoxybacteriochlorin MeO-BC-Br15 was subjected to three typesof Pd-mediated coupling reactions (Suzuki, Sonogashira, Hartwig−Buchwald) to give six bacteriochlorinsbearing functional groups at the 15-position (49% to 85% yield). The groups include 4-(tert-butoxycarbonylmethoxy)phenyl, 4-pyridyl, 3,5-diformylphenyl, phenylethynyl, TIPS-ethynyl, and N-benzamido. The presence of the 15-ethynyl moiety shifts the position of the long-wavelength Qy bandfrom 732 nm to ∼753 nm. The ability to introduce a range of groups at a specific site enables syntheticbacteriochlorins to be tailored for a variety of applications.
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