13C-NMR Based Evaluation of the Electronic and Steric Interactions in Aromatic Amines

Abstract

Chemical shifts of the para carbon atoms, δ( 13 C-4), in a series of aromatic amines were used to calculate the σ p , σ R and O R σ substituent constants for different amino groups. N, and N,N-diethylamino groups were found to be the most strong electron-donors. ortho-Substitution decreases the donor properties of the amino group. The amino groups in 2,6-di-i-propylaniline and N,N-2,6-tetramethylaniline have very weak electron-donor properties. The nitrogen atom in benzoquinuclidine and N,N-dimethyl-2,6-di-i-propylaniline have an electron-acceptor character. The calculated substituent constants of the amino groups studied are consistent with the spectral and reactivity data available in literature. Values of δ( 15 N) cannot be used as a direct measure of electronic effects of the N atom in anilines.

Stereospecific alkylation of substituted adenines by the Mitsunobu coupling reaction under microwave-assisted conditions

“…Reactions between (RS)-12, (R)-12 and (S)-12 and 6-(N-methyl)adenine produce the regioisomers (RS)-23 (N-3: 45%) and (RS)-24 (N-9: 45%), (S)-23 (N-3: 48%) and (S)-24 (N-9: 42%), (R)-23 (N-3: 47%) and (R)-24 (N-9: 42%), respectively. This is consistent with the electron-releasing nature of the methylamino group: s p ¼ À0.76 19. In the case of the NHMe group compared to the NMe 2 one, the lesser electron-releasing power of the former in relation to the latter explains the approximately equal amount of both N-3(23) and N-9 (24) regioisomers in the reaction between 12 and N-methyladenine, whilst in the case of N,N-dimethyladenine the major product is the N-3 regioisomer (RS)-, (R)-, and (S)-17, being the ratio N-9/N-3 z 7/1.…”

“…This is consistent with the electron-releasing nature of the dimethylamino group: s p ¼ À0.83, 18 or À0.82. 19 Although the electronic inuence of the NMe 2 group on N-1 and N-3 of the purine nucleus is basically the same (its mesomeric electron-releasing effect is much more important than its inductive electronwithdrawing one), the lack of alkylation of N,N-dimethyladenine at its N-1 site could be attributed to the steric hindrance The structure of (RS)-17 has been determined by 1 H, 13 C NMR, HMBC (Fig. 2), HSQC and moreover by X-ray crystallography.…”

“…The methylamino moiety is an electron-releasing group with a s p similar to that of the dimethylamino moiety {s p (MeHN) ¼ À0.76; 21 s p (Me 2 N) ¼ À0.83, 18 or 0.82 (ref. 19)} and then favours the nucleophilicity of the N-3 atom of purine. However the presence of an electron-withdrawing atom such as chlorine {s I (Cl) ¼ 0.47 (ref.…”

Fluorescence lifetime predicts performance of voltage sensitive fluorophores in cardiomyocytes and neurons

“…S2, ESI †), matching literature values for reported dialkylanilines. 40,[43][44][45][46][47][48][49] Similarily, the calculated HOMO energy level for molecular wire precursors increases as aniline conjugation increases across the VF dye series (Fig. S3, ESI †).…”

Aromatic Amines in Organic Synthesis. Part II. p-Aminocinnamaldehydes

“…Organic compounds containing different amino groups (or their derivatives) have attracted remarkable attention by virtue of their giant potential as dyes [ 1 ], solar cells [ 2 , 3 ], spectroscopic probes [ 4 , 5 , 6 ], one- [ 7 , 8 ] and multi-photon [ 9 ] polymerization initiators and drugs [ 10 ]. They have been studied for applications in various areas of photochemistry due to their structure versatility and facile modifications for electron-donating abilities [ 11 , 12 , 13 ]. In general, organic compounds bearing an alkylamino group may be synthesized through a related synthetic strategy using one of the following: Heck reaction [ 14 ], Knoevenagel condensation [ 13 , 15 ], Wittig reaction [ 16 ], Suzuki-Miyaura cross-coupling reaction [ 17 ] and several different reagents, such as aryl bromides with amino substituents [ 14 ], p -aminobenzaldehydes [ 13 , 15 ] and p -aminobenzoic acid derivatives [ 18 , 19 ].…”