Aminomethyl Transfer (Mannich) Reactions Between an O-Triethylsilylated Hemiaminal and Anilines, Rn C6 H5-n NH2 Leading to New Diamines, Triamines, Imines, or 1,3,5-Triazines Dependent upon Substituent R.
Anwar JacintomorenoHemant K SharmaAlejandro Metta-MagañaKeith H PannellPublished in: Chemistry (Weinheim an der Bergstrasse, Germany) (2019)
The reactions of the Mannich reagent Et3 SiOCH2 NMe2 (1) with a variety of anilines (mono-substituted RC6 H4 NH2 , R=H, 4-CN, 4-NO2 , 4-Ph, 4-Me, 4-MeO, 4-Me2 N; di-substituted R2 C6 H3 NH2 , R2 =3,5-(CH3 )2 , 3,5-(CF3 )2 ; tri-substituted R3 C6 H2 NH2 , R3 =3,5-Me2 -4-Br and a "super bulky" aniline (Ar*NH2 ) [Ar*=2,6-bis(diphenylmethyl)-4-tert-butylphenyl]) led to the formation of a range of products dependent upon the substituent. With electron-withdrawing substituents, previously unknown diamines, RC6 H4 NH(CH2 NMe2 ) [R=CN (2 a), NO2 (2 b)] and R2 C6 H3 NH(CH2 NMe2 ) [R2 =3,5-(CF3 )2 (2 c)] were formed. Further reaction of 2 a, b, c with 1 yielded the corresponding triamines RC6 H4 N(CH2 NMe2 )2 (R=CN (3 a), NO2 (3 b) and R2 C6 H3 N(CH2 NMe2 )2 , R2 =3,5-(CF3 )2 (3 c). The new polyamines were characterized by NMR spectroscopy, and for 2 a, 2 c, and 3 c, by single crystal XRD. In the case of electron-donating groups, R=4-OMe, 4-NMe2 , 4-Me, 3,5-Me2 , 3,5-Me2 -4-Br, and for R=4-Ph, the reactions with 1 immediately led to the formation of the related 1,3,5-triazines, R=4-MeO (5 a), 4-Me2 N (5 b), 4-Me (5 c), 3,5-Me2 (5 d), 3,5-Me2 -4-Br (5 e), 4-Ph (5 f), 4-Cl (5 g). The "super bulky" aniline rapidly produced a single product, namely the corresponding imine Ar*N=CH2 (4) which was also characterized by single crystal XRD. Imine 4 is both thermally and oxidatively stable. All reactions are very fast, thus based upon the presence of Si we are tempted to denote the reactions of 1 as examples of "Silick" chemistry.