Photoelectron spectroscopy of N-aryl cyclic amines. Variable conformations and relationships to gas- and solution-phase basicities

Photolabile coumarins with improved efficiency through azetidinyl substitution

“…The smaller dipole moments of 1 relative to 2 point to weaker electron-donating strength of the azetidinyl substituent. This observation is in agreement with the higher ionization potential of phenylazetidine (7.61 eV) 28 compared to that of N , N -diethylaniline (6.95 eV). 29 …”

Ring Strain and Other Factors Governing the Basicity of Nitrogen Heterocycles – An Interpretation by Triadic Analysis

“…At the end, it is useful to emphasize that triadic analysis clearly reveals not only that the correct trend in basicity of systems 2-5 cannot be explained by considering only the features of initial bases, but also that, in all four cases, both properties of different states and their diverse relative significance are factors governing their basicities. We note in passing that, despite the fact that throughout this work, cyclic amines NR(CH 2 ) n , with n = 3-5 and R = H, Me and Ph, exhibit an increase in the basicity with the ring size n, and that, within family of molecules, the corresponding amplifications in PA values cover ranges between 3.2 and as much as 7.4 kcal mol -1 , in water solution a distinct levelling behaviour was found in aqueous pK a values, 64 such that systems 3-5, 8-10 and 13-15 possess pK a values in a very narrow range between 11.22-11.29, 10.08-10.46 and 3.57-5.22 pK a units, respectively. This provides convincing evidence to why it is important to investigate and understand intrinsic solvent-free acidbase properties of target molecules.…”

“…Calculated proton affinities (PAs), dissected according to triadic analysis, proposed in Equation (3), are given in Table 1, together with the gas-phase basicities (GBs). As a final notice, we would like to emphasize that protonation-induced changes in both the geometry and the electron distribution in these cyclic systems have already been discussed in the literature 42,64 and are not subject matter of the present study. Before we start analyzing the results presented in Table 1, let us take a look at some general features emerging from these numbers.…”

N‐arylhexahydropyrimidines. Part 1. Synthesis and 1H NMR characterization of 1,3‐Di and 1,2,3‐trisubstituted derivatives

“…In N,N'-dialkylhexahydropyrimidines the absence of a 2-substituent lowers the energy barrier for ring reversal and N-inversion [9h]. Although N-arylhexahydropyrimidines have not been studied, literature indicates that in acyclic [20] and six membered cyclic [21,22] tertiary arylamines, the nitrogen atom has substantial sp 3 character. Thus, in N-arylhexa- hydropyrimidines 1 the aryl substituent could in principle be axial or equatorial, as depicted in Scheme III.…”