Hydroamination of diphenylbutadiyne with secondary N-methyl-anilines using the dipotassium tetrakis(2,6-diisopropylanilino)calciate precatalyst

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 45; no. 14; pp. 6241 - 6250
• Main Authors: Younis, Fadi M, Krieck, Sven, Görls, Helmar, Westerhausen, Matthias
• Format: Journal Article
• Language: English
• Published: England 14.04.2016
• Subjects: Bonding; Butadiene; Nitrogen atoms; Olefins; Phenyls; Strain; Tetrahydrofuran; X-rays
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c5dt03818a

The approved precatalyst [K2Ca{N(H)Dipp}4] was employed to study the hydroamination of diphenylbutadiyne with N-methyl-anilines in tetrahydrofuran at room temperature. The hydroamination occurs regioselectively within a few hours yielding (N-methyl)-(N-aryl)-1,4-diphenylbut-1-ene-3-yne-1-ylamine with phenyl (1a), 4-tolyl (1b) and 4-fluorophenyl groups (1c). In all cases a mixture of E- and Z-isomers is obtained. The second hydroamination step requires drastically extended reaction times and is successful only for the reaction of diphenylbutadiyne with N-methyl-aniline and N-methyl-4-fluoroaniline giving 1,4-diphenyl-1,4-bis(N-methyl-anilino)buta-1,3-diene [R = H (2a) and F (2c)]; a mixture of E,E-, E,Z- and Z,Z-isomers is obtained. The X-ray structures of E-1a, E-1b and E-1c show a slightly shortened N-C bond to the alkene moieties. Due to enhanced steric strain the anilino units of Z,Z-2c and Z,Z-3 turn away from the butadiene unit and consequently, the lone pair at the planar nitrogen atoms slightly interacts with the adjacent aryl groups.