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, C13H15NO2 (1), 3-[(tert-butyl-amino)-methyl-idene]pentan-2,4-dione, C10H17NO2 (2) and 3-{[(S)-benz-yl(meth-yl)amino]-methyl-idene}pentane-2,4-dione, C14H17NO2 (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.

Synthesis and crystal structures of three Schiff bases derived from 3-formyl-acetyl-acetone and o-, m- and p-amino-benzoic acid.

Treatment of 3-formyl-acetyl-acetone with the isomeric o-, m- and p-amino-benzoic acids led to the formation of the corresponding Schiff bases, namely, 3-[(2-carb-oxy-phenyl-amino)-methyl-idene]pentane-2,4-dione, 1, 3-[(3-carb-oxy-phenyl-amino)-methyl-idene]pentane-2,4-dione, 2, and 3-[(4-carb-oxy-phenyl-amino)-methyl-idene]pentane-2,4-dione, 3, all C13H13NO4, that contain a planar amino-methyl-ene-pentane-2,4-dione core with a strong intra-molecular N-H⋯O hydrogen bridge. The carb-oxy-phenyl groups attached to the nitro-gen atom are almost coplanar to the central mol-ecular fragment. Depending on the position of the carboxyl unit, different supra-molecular structures with hydrogen-bonding networks are formed in the three title structures.