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Various valuable properties of azoarenes (“azo dyes”), including their vivid colors and their facile cis – trans photoisomerization, lead to their wide use in the chemical industry. As a result, ∼700 000 metric tons of azo dyes are produced each year. Most currently utilized synthetic methods towards azoarenes involve harsh reaction conditions and/or toxic reagents in stoichiometric amounts, which may affect selectivity and produce significant amounts of waste. An efficient alternative method towards this functional group includes transition metal catalyzed nitrene coupling. This method is generally more sustainable compared with most stoichiometric methods as it uses only catalytic amounts of co-reactants (metal catalysts), requires easily synthesizable organoazide precursors, and forms only dinitrogen as a by-product of catalysis. During the last decade, several catalytic systems were reported, and their reactivity was investigated. This perspective article will review these systems, focusing on various nitrene coupling mechanisms, and the substrate scope for each system. Particular attention will be devoted to the iron-alkoxide catalytic systems investigated in the PI's laboratory. The design and structural features of several generations of iron bis(alkoxide) complexes will be discussed, followed by the structure–activity studies of these catalysts in nitrene homo- and heterocoupling.
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Identification of key active residues and solution conditions that affect peptide-catalyzed ester hydrolysis
Peptides respresent intriguing materials to achieve sustainable catalytic reactivity that mimic the natural functions of enzymes, but without the limitations of temperature/solvent sensitivity. They could also be applicable to a wide variety of substrates, thus expanding their potential use at different reaction levels ranging from the benchtop to industrial. Unfortunately, signfiicant use of catalytic peptides remains limited due to the general lack of understanding of the fundamental basis of their inherent reactivity. In this contribution, we examine the reactviity of a peptide (termed CPN3) previously isolated with ester hydrolysis reactivity. It is demonstrated that the system is most reactive under slightly basic conditions. While the system is slower than comparable enzymes, it demonstrates signficiant reactivity across multiple substrates and different reaction conditions that coud likely lead to enzymatic denaturation. In addition, key active site residues were identified to begin to elucidate the fundamental basis of the reactivity. Such results could be used to design new sequences with enhanced reactivity under sustainable conditions.
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- Award ID(s):
- 2203862
- PAR ID:
- 10517924
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- New Journal of Chemistry
- Volume:
- 48
- Issue:
- 17
- ISSN:
- 1144-0546
- Page Range / eLocation ID:
- 7997 to 8003
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D4NJ00977K
