Physicochemical property guidelines for modern agrochemicals.

The relentless need for the discovery and development of new agrochemicals continues as a result of driving forces such as loss of existing products through the development of resistance, the necessity for products with more favorable environmental and toxicological profiles, shifting pest spectra, and the changing agricultural needs and practices of the farming community. These new challenges underscore the demand for novel, high-quality starting points to accelerate the discovery of new agrochemicals that address market challenges. This article discusses the efforts to identify the optimum ranges of physicochemical properties of agrochemicals through analysis of modern commercial products. Specifically, we reviewed literature studies examining physicochemical property effects and analyzed the properties typical of successful fungicides, herbicides, and insecticides (chewing and sap-feeding pests). From the analysis, a new set of physicochemical property guidelines for each discipline, as well as building block class, are proposed. These new guidelines should significantly aid in the discovery of next-generation agrochemicals. © 2018 Society of Chemical Industry.

Improved synthetic route to quinoxyfen photometabolite 2-chloro-10-fluorochromeno[2,3,4-de]quinoline.

BACKGROUND: Quinoxyfen is a fungicide developed by Dow AgroSciences for the control of powdery mildew. Re-registration studies required gram quantities of 2-chloro-10-fluorochromeno[2,3,4-de]quinoline, a photometabolite of quinoxyfen. The only previous method of preparation of this photometabolite was by photolysis of quinoxyfen in less than 1% yield. Therefore, a new method allowing for the preparation of this photometabolite in gram quantities was required. RESULTS: Several different metal catalyzed intramolecular cyclization approaches were investigated for the synthesis of 2-chloro-10-fluorochromeno[2,3,4-de]quinoline. While most methods failed to provide the desired product from a 2-bromophenyl derivative of quinoxyfen, a novel one-pot two-step synthesis led to the desired material in good yield from quinoxyfen. CONCLUSION: A short and efficient synthetic route was developed to access 2-chloro-10-fluorochromeno[2,3,4-de]quinoline from readily available (4-fluoro-2-hydroxyphenyl)boronic acid and quinoxyfen and was found to be scalable, which enabled the preparation of the desired photometabolite in gram quantities thus meeting material requirements to complete regulatory studies for the re-registration of quinoxyfen. © 2017 Society of Chemical Industry.

Enantio- and diastereoselective synthesis of syn-ß-hydroxy-α-vinyl carboxylic esters via reductive aldol reactions of ethyl allenecarboxylate with 10-TMS-9-Borabicyclo[3.3.2]decane and DFT analysis of the hydroboration pathway.

An enantio- and diastereoselective synthesis of syn-ß-hydroxy-α-vinyl carboxylate esters 3 via the reductive aldol reaction of ethyl allenecarboxylate (2) with 10-trimethylsilyl-9-borabicyclo[3.3.2]decane (1R) has been developed. Density functional theory calculations suggest that the allene hydroboration involves the 1,4-reduction of 2 with the 1R, leading directly to dienolborinate Z-(O)-8a.

Development of a Double Allylboration Reagent Targeting 1,5-syn-(E)-Diols: Application to the Synthesis of the C(23)-C(40) Fragment of Tetrafibricin.

Interest in the synthesis of the C(23)-C(40) fragment 2 of tetrafibricin prompted us to develop a new method for the synthesis of 1,5-syn-(E)-diols. Toward this end, the kinetically controlled hydroboration of allenes 6, 33, ent-39, 42 and 45 with the Soderquist borane 25R were studied. Tetrabutylammonium allenyltrifluoroborate 45 gave superior results and was utilized in a double allylboration sequence with two different aldehydes to provide the targeted 1,5-syn-(E)-diols in generally high yields (72-98%), and with high enantioselectivity (>95% e.e.), diastereoselectivity (d.r. >20:1), and (E)/(Z) selectivity (>20:1). This new method was applied to the synthesis of the C(23)-C(40) fragment 2 of tetrafibricin.

Enantio- and diastereoselective synthesis of (E)-1,5-syn-diols: application to the synthesis of the C(23)-C(40) fragment of tetrafibricin.

A highly stereoselective synthesis of (E)-1,5-syn-diols 6 is described. The kinetically controlled hydroboration of allenyltrifluoroborate 8 with Soderquist borane 2 provides the (Z)-allylic trifluoroborate 9, which undergoes sequential allylboration with two different aldehydes to provide (E)-1,5-syn-diols 6 in 72-98% yields with >95% ee and >20:1 dr. Application of this method to the synthesis of the tetrafibricin C(23)-C(40) fragment 19 is described.

A novel and specific NADPH oxidase-1 (Nox1) small-molecule inhibitor blocks the formation of functional invadopodia in human colon cancer cells.

The NADPH oxidase (Nox) proteins catalyze the regulated formation of reactive oxygen species (ROS), which play key roles as signaling molecules in several physiological and pathophysiological processes. ROS generation by the Nox1 member of the Nox family is necessary for the formation of extracellular matrix (ECM)-degrading, actin-rich cellular structures known as invadopodia. Selective inhibition of Nox isoforms can provide reversible, mechanistic insights into these cellular processes in contrast to scavenging or inhibition of ROS production. Currently no specific Nox inhibitors have been described. Here, by high-throughput screening, we identify a subset of phenothiazines, 2-acetylphenothiazine (here referred to as ML171) (and its related 2-(trifluoromethyl)-phenothiazine) as nanomolar, cell-active, and specific Nox1 inhibitors that potently block Nox1-dependent ROS generation, with only marginal activity on other cellular ROS-producing enzymes and receptors including the other Nox isoforms. ML171 also blocks the ROS-dependent formation of ECM-degrading invadopodia in colon cancer cells. Such effects can be reversed by overexpression of Nox1 protein, which is suggestive of a selective mechanism of inhibition of Nox1 by this compound. These results elucidate the relevance of Nox1-dependent ROS generation in mechanisms of cancer invasion and define ML171 as a useful Nox1 chemical probe and potential therapeutic agent for inhibition of cancer cell invasion.

Origin of thermodynamic versus kinetic control of allene hydroboration with 9-borabicyclo[3.3.1]nonane and 10(R)-trimethylsilyl-9-borabicyclo[3.3.2]decane.

Density functional theory was used to locate transition states for hydroboration reactions of allenes with 9-borabicyclo[3.3.1]nonane and 10-R-9-borabicyclo[3.3.2]decane, as well as transition states for [1,3]-boratropic shift and aldehyde addition reactions of the derived allylboranes. The origin of kinetic versus thermodynamic control in the allene hydroboration step is described.

Quantum-mechanical study of 10-R-9-borabicyclo[3.3.2]decane alkene hydroboration.

Density functional theory and correlated ab initio quantum mechanical methods were used to locate and analyze alkene hydroboration transition structures for 10-R-9-borabicyclo[3.3.2]decane reagents. Transition-state ensembles quantitatively modeled enantioselectivity for hydroboration of cis-, trans-, and gem-disubstituted alkenes in excellent agreement with experiment. The 10-R group and borabicyclo[3.3.2]decane ring conformation effects were analyzed to understand the origin of asymmetric selectivity.

Stereoselective synthesis of gamma-substituted (Z)-allylic boranes via kinetically controlled hydroboration of allenes with 10-TMS-9-borabicyclo[3.3.2]decane.

Kinetically controlled hydroboration of allenes 8 and 14a-d with the readily accessible Soderquist borane 7, which is generated in situ from borohydride 6, constitutes a convenient and preparatively useful method for synthesis of (Z)-gamma-(substituted)allylboranes 9 and 15a-d. These allylboranes undergo highly diastereo- (> or = 90: 10) and enantioselective (typically 89-96% e.e.) allylboration reactions with representative aldehydes to give syn-beta-functionalized homoallylic alcohols.

Trichloromethyltrimethylsilane, sodium formate, and dimethylformamide: a mild, efficient, and general method for the preparation of trimethylsilyl-protected 2,2,2-trichloromethylcarbinols from aldehydes and ketones.

New conditions for the preparation of trimethylsilyl-protected 2,2,2-trichloromethylcarbinols 2 from aldehydes and ketones are reported. Compounds 2, which are important intermediates in organic synthesis, were obtained in excellent yields by use of a combination of trichloromethyltrimethylsilane (TMSCCl3), and a catalytic amount of sodium formate (HCOONa) in dimethylformamide (DMF). Substrates bearing highly sensitive protecting groups have been successfully subjected to our conditions. We also describe a one-pot procedure that gives direct access to 2,2,2-trichloromethylcarbinols 3. This methodology avoids the use of strong bases usually required for the synthesis of 3 (Wyvratt et al. J. Org. Chem. 1987, 52, 944; Aggarwal and Mereu, J. Org. Chem. 2000, 65, 7211).