Abstract
SummarySelective linkage of renewable alcohols and ammonia into functional products would not only eliminate the prepreparation steps to generate active amino agents but also help in the conservation of our finite fossil carbon resources and contribute to the reduction of CO2 emission. Herein the development of a novel 2-(4-methoxyphenyl)-1,8-naphthyridine-based iridium (III) complex is reported, which exhibits excellent catalytic performance toward a new hydrogen transfer-mediated annulation reaction of 2-nitrobenzylic alcohols with alcohols and ammonia. The catalytic transformation proceeds with the striking features of good substrate and functional group compatibility, high step and atom efficiency, no need for additional reductants, and liberation of H2O as the sole by-product, which endows a new platform for direct access to valuable quinazolines. Mechanistic investigations suggest that the non-coordinated N-atom in the ligand serves as a side arm to significantly promote the condensation process by hydrogen bonding.
Highlights
Mass mining and consumption of fossil resources have resulted in a call for the development of new catalytic transformations, enabling production of functional chemicals from renewable resources with high step and atom efficiency (Goldemberg, 2007; Michlik and Kempe, 2013a, 2013b; Kozlowski and Davis, 2013)
The catalytic transformation proceeds with the striking features of good substrate and functional group compatibility, high step and atom efficiency, no need for additional reductants, and liberation of H2O as the sole by-product, which endows a new platform for direct access to valuable quinazolines
We initiated our investigations by choosing the synthesis of quinazoline 3aa from o-nitrobenzene methanol 1a, alcohol 2a, and ammonia as a model reaction
Summary
Mass mining and consumption of fossil resources have resulted in a call for the development of new catalytic transformations, enabling production of functional chemicals from renewable resources with high step and atom efficiency (Goldemberg, 2007; Michlik and Kempe, 2013a, 2013b; Kozlowski and Davis, 2013). The strategy of acceptorless dehydrogenative coupling (ADC) proceeded to renew the construction of N-heteroarenes. In this strategy, dehydrogenation is involved in the activation of alcohols via in situ formation of carbonyl intermediates, and H2 and/or H2O are generally generated as the byproducts. It is important to note that these transformations mainly rely on the utilization of specific amines, whereas the synthesis of N-heteroarenes by combining alcohols with ammonia, an abundant and renewable nitrogen source, has been rarely explored, the related transformations would eliminate prepreparation steps to generate active amino agents, and result in high step and atom efficiency. Milstein and the co-workers have presented a synthesis of pyrroles and pyrazines from alcohols and ammonia (Scheme 1, Equation 2) (Daw et al, 2018)
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