Synthesis and crystal structures of three Schiff bases derived from 3-formyl-acetyl-acetone and benzyl-, tert -butyl- and ( S )-methyl-benzyl-amine.

Treatment of 3-formyl-acetyl-acetone with the amines benzyl-amine, tert -butyl-amine and ( S )-methyl-benzyl-amine led to the formation of the corresponding Schiff bases 3-[(benzyl-amino)-methyl-idene]pentane-2,4-dione, C 13 H 15 NO 2 ( 1 ), 3-[( tert -butyl-amino)-methyl-idene]pentan-2,4-dione, C 10 H 17 NO 2 ( 2 ) and 3-{[( S )-benz-yl(meth-yl)amino]-methyl-idene}pentane-2,4-dione, C 14 H 17 NO 2 ( 3 ). The mol-ecules of all three compounds exist as enamine tautomers that contain a nearly planar amino-methyl-ene-pentane-2,4-dione core with a strong intra-molecular N-H⋯O hydrogen bridge. The R group attached to the enamine N atom has no significant influence on the bond lengths and angles of the amino-methyl-ene-pentane-2,4-dione core. The supra-molecular structures in 1 - 3 are mainly based on weak C-H⋯O hydrogen bonds.