SYNTHESIS AND SHG EFFICIENCY OF 2-(AMINOMETHYLENE)-BENZO[B]THIOPHEN-3(2H)-ONES DERIVED BY RING CONTRACTION OF 1-BENZOTHIOPYRAN DERIVATIVES

2-(Aminomethylene)-benzo[ b ]thiophen-3(2 H)-ones[2] and their sulfoxides were prepared by ring contraction of 3-bromo-4 H-1-benzothiopyran-4-one and 3-bromothiochroman-4-one, respectively, with amines. The crystal structures of typical second harmonic generation (SHG) active conpounds in this series were determined by X-ray analysis. Relationship between the structures and the SHG activities of these compounds was investigated. The structure factors of compound C 2 ) required for SHG activities are trans-configuration between the amino group and the carbonyl group and the presence of an amino proton (NH) to form an intermolecular hydrogen bonding between the carbonyl group and the NH. On the other hand, 2-(anilinomethylene)-benzo[ b ]thiophen-3(2 H)-one 1-oxides and 1, 1-dioxides have cis-configuration and an intramolecular hydrogen bond between the carbonyl group and NH. Comparison with [ 2 ] and its sulf oxides or sulfones shows that transformation of sulfide moiety in [ 2 ] into sulfoxide or sulfone moiety leads to low SHG efficiency, but brings about blue shift of absorption maxima for blue-region transparency (below 400 nm).