Synthesis, Crystal Structure and Herbicide Activity of Three Phenyl-naphthyl Methanone Derivatives

Three phenyl-naphthyl methanone derivatives have been designed and synthesized through alkylation and Friedel-Crafts acylation reactions. All the compounds were characterized by IR, H-1 NMR, C-13 NMR and H RMS. The single crystal structure of the compounds has been further determined by X-ray diffraction. (4-Ethoxynaphthalen-l-yl)(2-methylphenyl)methanone (3a) crystallizes in monoclinic system, P2(1)/c space group with a = 13.144(3), b = 11.041(2), c = 11.320(2) angstrom, beta = 106.65(3)degrees, V = 1573.7(5) angstrom(3), D-c = 1.225 Mg/m(3), Z = 4, F(000) = 616, mu(MoK alpha) = 0.078 mm(-1), R = 0.0928 and wR = 0.1556. (4-Ethoxynaphthalen-l-yl)(2-hydroxyphenyl)methanone (3b) belongs to the monoclinic system, P2(1)/c space group with a = 9.985(2), b = 10.814(2), c = 14.353(3) angstrom, beta = 105.49(3)degrees, V = 1493.6(5) angstrom(3), D-c = 1.300 Mg/m(3), Z = 4, F(000) = 616, mu(MoK alpha) = 0.087 mm(-1), R = 0.0568 and wR = 0.1262. (4-Methoxynaphthalen-1-yl)(4-methylphenyl)methanone (3c) crystallizes in monoclinic system, P2(1)/c space group with a = 7.6130(15), b = 15.068(3), c = 12.880(3) angstrom, beta = 100.63(3)degrees, V = 1452.1(5) angstrom(3), D-c = 1.264 Mg/m(3), Z = 4, F(000) = 584, mu(MoK alpha) = 0.081 mm(-1), R = 0.0804 and wR = 0.1349. The presence of van der Waals forces leads to the stability of the compounds. Especially, compounds 3a similar to c showed herbicidal activity against the monocotyledon plant barnyard grass (Echinochloa crus-galli). At the concentration of 0.75 mmol/m(2), compound 3b (C-t = 0.436 +/- 0.116 mg/g) exhibited better activity than pyrazoxyfen (C-t = 0.537 +/- 0.073 mg/g).