Generation of N–H Imines from α-Azidocarboxylic Acids through Ru-Catalyzed Decarboxylation

Abstract

A new method for the synthesis of N−H imines from αazidocarboxylic acids was developed, which proceeds through decarboxylative C−C bond cleavage catalyzed by a commercial diruthenium complex ([CpRu(CO) 2 ] 2 ) under visible light irradiation at room temperature within several minutes. The reactive products undergo condensation, which forms cyclic trimers (2,4,6-trialkylhexahydro-1,3,5-triazines) or linear N,N′-bis-(arylmethylidene)arylmethanediamines in quantitative yields. Alternatively, the N−H imines can be trapped with benzylamine and 2-(aminomethyl)aniline, providing stable N-benylimines and tetrahydroquinazolines, respectively. Subsequent oxidation of tetrahydroquinazolines produced quinazolines.

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“…Confirmation of the Schiff base formation in the BNP/CMCS hydrogel could not be obtained via solid state nuclear magnetic resonance (NMR) or Fourier transform infrared spectroscopy (FTIR). For 1 H NMR, the predicted chemical shift of the Schiff base at ∼7.5 ppm is masked due to the reduced resolution of solid-state NMR (Figure S1A), as reported previously . Regarding 13 C NMR, the chemical shift of the Schiff base at ∼160–170 ppm is masked by the carboxyl shift in CMCS and the ester shift in PLA (Figure S1B), which is in accordance with a previous literature reporting the Schiff base shift was masked by that of the carboxyl group .…”

“…For 1 H NMR, the predicted chemical shift of the Schiff base at ∼7.5 ppm is masked due to the reduced resolution of solid-state NMR (Figure S1A), as reported previously. 34 Regarding 13 C NMR, the chemical shift of the Schiff base at ∼160−170 ppm is masked by the carboxyl shift in CMCS and the ester shift in PLA (Figure S1B), which is in accordance with a previous literature reporting the Schiff base shift was masked by that of the carboxyl group. 35 In FTIR analysis, the aldehyde peaks at ∼1750 cm −1 , recorded for BNPs (red spectra, Figure S1C).…”