Synthesis, Reactivity and Electronic Properties of Quinazolin-2-one-Based N-Heterocyclic Carbenes

Abstract

The electronic properties of a new member F of the family of cyclic (aryl)(amido)carbenes (CArAmC) have been determined. Suitable precursors can easily be obtained by a straightforward synthesis starting from 2-nitrobenzaldehyde (5). Metal complexes (14, 15) and chalcogen adducts (12, 13) were prepared and their spectroscopic data were evaluated and compared with those reported for CArAmCs (C, D) and the mixed (amino)(amido)carbene E which is a constitutional isomer of the newly reported carbene F. The IR spectroscopic determination indicates an unexceptional TEP value of 2055 cm−1, whereas the strong π-accepting character is reflected by a chemical shift of δ(77Se) 936 ppm for the Se-adduct 12 a. However, a significant degree of electrophilic reactivity of the in situ-generated carbene F was not observed, as, for example, no cyclopropanation reactions with olefins could be detected. DFT calculations provide a rationale for these experimental observations.