Base-catalyzed cascade synthesis of 2,3-dihydrofuro[2,3-b]pyridines and 2,3-dihydro-1H-pyrrolo[2,3-b]pyridines from N-propargylic ß-enaminones.

A novel protocol to prepare multi-substituted dihydrofuropyridine and dihydropyrrolopyridine derivatives from KOH-catalyzed reactions between readily available N-propargylic ß-enaminones and arylaldehydes or N-sulfonyl imines has been developed in moderate to good yields.

A convenient base-mediated synthesis of 3-aryol-4-methyl (or benzyl)-2-methylthio furans from α-oxo ketene dithioacetals and propargyl alcohols via domino coupling/annulations.

A convenient base-mediated strategy to synthesize 3-aryol-4-methyl (or benzyl)-2-methylthio furans 2 (trisubstituted furans) has been developed through the domino coupling/annulations between available α-oxo ketene dithioacetals 1 and propargyl alcohols. In this strategy, these types of bases play an important role in driving the domino coupling reaction of propargyl alcohols and further intramolecular annulations to realize the target compounds. The possible mechanism for the formation of the various products is believed to involve the generation of allenes 7, followed by intramolecular annulations.

Synthesis and insecticidal activities of novel pyrazole oxime ether derivatives with different substituted pyridyl rings.

BACKGROUND: Pyrazole oxime ether derivatives with different substituted pyridyl rings represent new types of compounds that possess good insecticidal and acarcidal activity against Aphis laburni Kaltenbach and Tetranychus cinnabarinus. RESULTS: In total, 82 novel pyrazole oxime ether derivatives were synthesized and identified by (1) H NMR, elemental analysis or high-resolution mass spectrometry, and their insecticidal and acarcidal activities were tested against A. laburni Kaltenbach and T. cinnabarinus. Bioassays showed that at a 200 mg L(-1) dosage, one-third of the compounds displayed high insecticidal activity against A. laburni Kaltenbach (> 90%), whereas most of of the compound II series exhibited excellent acarcidal activity against T. cinnabarinus (> 92%). Most compound II series exhibited good activity in both insecticidal and acarcidal tests. In addition, at a low concentration of 10 mg L(-1) , the insecticidal activity of compounds IB9 and IE4 exceeded 90%, and the acarcidal activity of compounds IIB1 and IIB2 was ≥ 95%. CONCLUSION: Structure-activity relationships were also examined. Results suggested that the tert-butoxycarbonyl group, as well as the position between tert-butoxycarbonyl and the atom N of the pyridyl ring, were essential to obtaining the acarcidal activity of the title compounds.

Synthesis and herbicidal activities of novel 3-(substituted benzyloxy or phenoxy)-6-methyl-4-(3-trifluoromethylphenyl)pyridazine derivatives.

BACKGROUND: 4-(3-Trifluoromethylphenyl)pyridazine represents a new series of compounds with bleaching and herbicidal activities. RESULTS: A total of 43 novel 3-(substituted benzyloxy or phenoxy)-6-methyl-4-(3-trifluoromethylphenyl)pyridazine derivatives were synthesised, and their bleaching and herbicidal activities were evaluated through Spirodela polyrrhiza and greenhouse tests. Some compounds exhibited excellent herbicidal activities, even at a dose of 7.5 g ha(-1). CONCLUSION: The results showed that a substituted phenoxy group at the 3-position of the pyridazine ring and the electron-withdrawing group at the para-position on the benzene ring were essential for high herbicidal activity.

Novel protoporphyrinogen oxidase inhibitors: 3H-pyrazolo[3,4-d][1,2,3]triazin-4-one derivatives.

A series of 3 H-pyrazolo[3,4-d][1,2,3]triazin-4-one derivatives were synthesized as candidate herbicides by diazotization of different 5(3)-amino- N-phenyl-1 H-pyrazole-4-carboxamide derivatives prepared by the reaction of substituted 5(3)-amino-pyrazole-4-carbonyl chloride with a substituted aniline. Their structures were identified by (1)H NMR and elemental analyses. The isomers D and E were isolated, and their structures were identified by two-dimensional NMR analyses (heteronuclear single quantum coherence and heteronuclear multiple-bond correlation) and single-crystal X-ray diffraction analysis. The bioassay results showed that some of the title compounds exhibited both excellent herbicidal activity at a dose of 93.75 g/ha and strong inhibition against protoporphyrinogen oxidase activity in vitro. The structure-activity relationship showed that D16 possessed the highest activities both in vivo and in vitro when the N-substituted group of the pyrazole ring was allyl and the N-substituted group of benzooxazinone was propargyl.

Synthesis and herbicidal activities of novel 3-N-substituted amino-6-methyl-4-(3-trifluoromethylphenyl)pyridazine derivatives.

4-(3-Trifluoromethylphenyl)pyridazine is a new series of compounds with bleaching and herbicidal activities. Starting from ethyl 2-(3-trifluoromethylphenyl)acetate, an important intermediate 7 was synthesized in five steps with a moderate total yield of 51.5% in a safe and practical way. Twenty-six novel 3-N-substituted amino-6-methyl-4-(3-trifluoromethylphenyl)pyridazine derivatives were synthesized and evaluated through a Spirodela polyrrhiza test and greenhouse test. Some compounds can completely inhibit Chl at 1 microg/mL and exhibit equal or higher herbicidal activities with the commercial bleaching herbicide diflufenican against dicotyledonous plants at a rate of 75 g/ha.

4-[3-(Trifluoro-meth-yl)phen-yl]-5,6,7,8-tetra-hydro-cinnolin-3(2H)-one.

The title compound, C(15)H(13)F(3)N(2)O, contains one benzene ring, one cyclo-hexane ring and a pyridazine ring. The dihedral angle formed by the pyridazine ring with the benzene ring is 61.5 (2)°. The crystal structure is stabilized by two inter-molecular hydrogen bonds (N-H⋯O and C-H⋯F). The cyclohexane ring adopts a screw-boat conformation. The CF(3) group is disordered over two positions; the site occupancy factors are ca 0.6 and 0.4.

Methyl 3-(4-{6-methyl-4-[3-(trifluoro-meth-yl)phen-yl]pyridazin-3-yl-oxy}phen-yl)propanoate.

In the title compound, C(22)H(19)F(3)N(2)O(3), the benzene rings of the trifluoro-methyl-phenyl and benzoyl-phenyl groups form dihedral angles of 41.89 (10) and 67.44 (10)°, respectively, with the pyridazine ring. The methyl-propanoate group is nearly coplanar with the attached benzene ring [dihedral angle = 3.9 (2)°]. The trifluoro-methyl group is disordered over two positions; the site-occupancy factors are ca 0.64 and 0.36. In the crystal structure, inversion-related mol-ecules are linked through C-H⋯O hydrogen bonds and C-H⋯π inter-actions.

Design, synthesis, and quantitative structure-activity relationship study of herbicidal analogues of pyrazolo[5,1-d][1,2,3,5]tetrazin-4(3H)ones.

A series of pyrazolo[5,1-d][1,2,3,5]tetrazin-4(3H)one derivatives were designed, synthesized, and evaluated for their herbicidal activities where some of these compounds provided >80% control of Brassica campestris at 10 microg/mL. Quantitative structure-activity relationship studies were performed on these compounds using physicochemical parameters (electronic, Verloop, or hydrophobic) as independent parameters and herbicidal activity as a dependent parameter, where herbicidal activity correlated best (r > 0.8) with physicochemical parameters in this set of molecules. The herbicidal activity against B. campestris was mainly affected by the molar refractivity (MR) for R1, Taft (Eso) for R2 or R6, Verloop (Lm) for R3 or R5, and electronic parameters (Hammett's constants) for R4. The optimal MR for herbicidal activity is 0.95. The herbicidal activity against Echinochloa crus-galli was mainly related with the substituents' hydrophobic parameter. The optimal pi parameters for R1 and R4 for herbicidal activity are 0.72 and 0.68, respectively. In general, these compounds showed greater herbicidal activity toward B. campestris than E. crus-galli.

tert-Butyl 4-({[(E)-1,3-dimethyl-5-phen-oxy-pyrazol-4-yl]meth-yl}amino-oxymeth-yl)benzoate.

The title compound, C(24)H(27)N(3)O(4), also known as fenpyroximate, is a commercial acaricide. The benzene ring of the phen-oxy group is approximately perpendicular to the pyrazole ring with a dihedral angle of 84.37 (11)°. The dihedral angle between the phen-oxy and the benzoate benzene rings is 48.83 (8)°.

A quantitative structure-activity relationship study of herbicidal analogues of alpha-hydroxy-substituted 3-benzylidenepyrrolidene-2,4-diones.

A series of pyrrolidine-2,4-dione and piperidine-2,4-dione derivatives were prepared and evaluated for their herbicidal activities where some of these compounds exhibited good bioactivity against Echinochloa crus-galli in comparison with sulcotrione. Quantitative structure-activity relationship studies were performed on these compounds using physicochemical parameters (hydrophobic, electronic, and Taft) as independent parameters and herbicidal activity as a dependent parameter, where herbicidal activity correlated best (r > 0.8) with hydrophobic (pi(o) + pi(p)), steric (Es), STERIMOL (B4), indicator (H(M)), van der Waals volume (V), and electronic parameter (sigma(m) + sigma(p)) in this set of molecules; the optimum van der Waals volume for R(2) is about 41.8 A3; when B4 is equal to 3, the target molecule possessed the lowest herbicidal activity.

Synthesis and herbicidal activity of novel alpha,alpha,alpha-trifluoro-m-tolyl pyridazinone derivatives.

A series of novel alpha,alpha,alpha-trifluoro-m-tolyl pyridazinone derivatives was synthesised. Herbicidal activities of the two intermediate compounds and 15 pyridazinone derivatives were evaluated through barnyardgrass and rape cup tests and Spirodela polyrrhiza (L.) Schleiden tests. Selected compounds were also evaluated under greenhouse conditions. Bleaching activities were observed at 10 microg ml(-1) and some compounds exhibited herbicidal activities at a rate of 300 g ha(-1). The relationship between crystal structures and herbicidal activities is discussed through a comparison of two compounds (5a and 5f).

Synthesis and herbicidal evaluation of novel 3-[(alpha-hydroxy-substituted)benzylidene]pyrrolidine-2,4-diones.

A series of 3-[(alpha-hydroxy-substituted) benzylidene]pyrrolidine-2,4-dione derivatives were synthesized as candidate herbicides by reacting different aroyl acetates with N-substituted glycine esters. The new compounds were identified by 1H NMR spectroscopy and elemental analyses. Their herbicidal activities were evaluated. Some compounds exhibited excellent herbicidal activities at a dose of 187.5 g/ha. A suitable electron-donating substituent at the 2- and/or 4-position of the phenyl ring was essential for high herbicidal activity, a result that has not been reported before. It was also found that the title compound's structure-activity relationships were different from those of other similar kinds of earlier compounds, a result that may depend on the enol structure difference.

The synthesis and herbicidal activity of 1-alkyl-3-(alpha-hydroxy-substituted benzylidene)pyrrolidine-2,4-diones.

In the search for better herbicides a series of 1-alkyl-3-(alpha-hydroxy-(un)substituted benzylidene)pyrrolidine-2,4-diones were prepared and their structure-activity relationships studied. All their structures have been confirmed by (1)H-NMR and elemental analysis. The preliminary bioassay results indicated that some of them have high herbicidal activity against annual dicotyledonous and monocotyledonous plants.