Sedaxane, Isopyrazam and Solatenol™: Novel Broad-spectrum Fungicides Inhibiting Succinate Dehydrogenase (SDH) - Synthesis Challenges and Biological Aspects.

Sedaxane (SDX) 1, isopyrazam (IZM) 2 and Solatenol™ (STL) 3 are broad-spectrum pyrazole carboxamides, which originate from novel chemical classes of fungicides. Their mode of action (MoA) is inhibition of succinate dehydrogenase (SDH), which was recognized for a long time to deliver only compounds with a narrow biological spectrum. This view changed with the market introduction of BASF's boscalid in 2003. All major agro-companies subsequently worked in parallel on this MoA successfully and recently introduced new compounds to the market. Syngenta entered the SDHI area in 1998 and was able to introduce three complementary compounds to the market between 2010 and 2012. In this short review some synthesis challenges and biological effects of SDX 1, IZM 2 and STL 3 will be covered. New cost-efficient synthesis strategies for the preparation of o-biscyclopropyl-aniline, new benzonorbornene intermediates and the key pyrazole carboxylic acid intermediate which is essential for all three Syngenta SDHIs, will be in the focus of this review.

Sedaxane, Isopyrazam and Solatenol™: Novel Broad-spectrum Fungicides Inhibiting Succinate Dehydrogenase (SDH) - Synthesis Challenges and Biological Aspects.

Sedaxane (SDX) 1, isopyrazam (IZM) 2 and Solatenol™ (STL) 3 are broad-spectrum pyrazole carboxamides, which originate from novel chemical classes of fungicides. Their mode of action (MoA) is inhibition of succinate dehydrogenase (SDH), which was recognized for a long time to deliver only compounds with a narrow biological spectrum. This view changed with the market introduction of BASF's boscalid in 2003. All major agro-companies subsequently worked in parallel on this MoA successfully and recently introduced new compounds to the market. Syngenta entered the SDHI area in 1998 and was able to introduce three complementary compounds to the market between 2010 and 2012. In this short review some synthesis challenges and biological effects of SDX 1, IZM 2 and STL 3 will be covered. New cost-efficient synthesis strategies for the preparation of o-biscyclopropyl-aniline, new benzonorbornene intermediates and the key pyrazole carboxylic acid intermediate which is essential for all three Syngenta SDHIs, will be in the focus of this review.

Transition-state stabilization by a secondary substrate-ligand interaction: a new design principle for highly efficient transition-metal catalysis.

A library of monodentate phosphane ligands, each bearing a guanidine receptor unit for carboxylates, was designed. Screening of the library gave some excellent catalysts for regioselective hydroformylation of beta,gamma-unsaturated carboxylic acids. A terminal alkene, but-3-enoic acid, was hydroformylated with a linear/branched (l/b) regioselectivity up to 41. An internal alkene, pent-3-enoic acid was hydroformylated with regioselectivity up to 18:1. Further substrate selectivity (e.g., acid vs. methyl ester) and reaction site selectivity (monofunctionalization of 2-vinylhept-2-enoic acid) were also achieved. Exploration of the structure-activity relationship and a practical and theoretical mechanistic study gave us an insight into the nature of the supramolecular guanidinium-carboxylate interaction within the catalytic system. This allowed us to identify a selective transition-state stabilization by a secondary substrate-ligand interaction as the basis for catalyst activity and selectivity.

Ruthenium catalyzed decarbonylative arylation at sp3 carbon centers in pyrrolidine and piperidine heterocycles.

This paper describes the development of a new catalytic transformation, the ruthenium-catalyzed decarbonylative arylation of cyclic 2-amino esters, which replaces the ester group with an aryl ring at the sp3 carbon center. For example, proline ester amidine 1 is converted to 2-arylpyrrolidine 3 in the presence of arylboronic acids or esters as arene donors and Ru(3)(CO)(12) as the catalyst. This process provides a rapid access to a variety of 2-arylpyrrolidines and piperidines from commercially available proline, hydroxyproline, and pipecolinate esters. The examination of the substrate scope also showed that many arene boronic acids and boronate esters serve as coupling partners. The high chemoselectivity of this process was demonstrated and ascribed to the significant rate difference between the decarbonylative arylation and the C-H arylation. The decarbonylative arylation complements the C-H arylation, since the latter process lacks control over the extent of functionalization, affording a mixture of mono- and bis-arylpyrrolidines. When applied in tandem, these two processes provide 2,5-diarylpyrrolidines in two steps from the corresponding proline esters. It was also demonstrated that the required amidine or iminocarbamate directing group fulfills two major functions: first, it is essential for the ester activation step, which occurs via the coordination-assisted metal insertion into the acyl C-O bond; second, it facilitates the decarbonylation, via the stabilization of a metallacycle intermediate, assuring the formation of the 2-arylated products instead of the corresponding ketones observed before by others.

Phosphine-free palladium-catalyzed C-H bond arylation of free (N-H)-indoles and pyrroles.

This paper describes a phosphine-free palladium-catalyzed method for direct C-arylation of free (N-H)-indoles and pyrroles with iodo- and bromoarene donors. Employing commercially available materials, this new and operationally simple procedure provides a rapid entry to a wide range of C-arylated (N-H)-indoles including derivatives of tryptamine. In the course of this study, a profound halide effect was uncovered, affecting both the efficiency and regioselectivity of indole arylation.

sp3 C-H bond arylation directed by amidine protecting group: alpha-arylation of pyrrolidines and piperidines.

A new ruthenium-catalyzed direct sp3 C-H to C-C bond transformation is disclosed. Specifically, a method for the alpha-arylation of cyclic amines, containing either permanent (pyridine, pyrimidine) or removable (amidine) directing groups, is described. This cross-coupling reaction involves heating amine substrates with arylboronate ester at 150 degrees C in a ketone solvent with a catalytic amount of ruthenium carbonyl [Ru3(CO)12]. Arylboronate esters containing either electron-withdrawing or electron-donating substituents could be efficiently coupled. Heteroarene boronates were also effective donors.

3,3'-Bis(trisarylsilyl)-substituted binaphtholate rare earth metal catalysts for asymmetric hydroamination.

Chiral 3,3'-bis(trisarylsilyl)-substituted binaphtholate rare earth metal complexes (R)-[Ln{Binol-SiAr3}(o-C6H4CH2NMe2)(Me2NCH2Ph)] (Ln = Sc, Lu, Y; Binol-SiAr3 = 3,3'-bis(trisarylsilyl)-2,2'-dihydroxy-1,1'-binaphthyl; Ar = Ph (2-Ln), 3,5-xylyl (3-Ln)) and (R)-[La{Binol-Si(3,5-xylyl)3}{E(SiMe3)2}(THF)2] (E = CH (4a), N (4b)) are accessible via facile arene, alkane, and amine elimination. They are efficient catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, giving TOF of up to 840 h(-1) at 25 degrees C for 2,2-diphenyl-pent-4-enylamine (5c) using (R)-2-Y. Enantioselectivities of up to 95% ee were achieved in the cyclization of 5c with (R)-2-Sc. The reactions show apparently zero-order rate dependence on substrate concentration and first-order rate dependence on catalyst concentration, but rates depend on total amine concentrations. Activation parameters for the cyclization of pent-4-enylamine using (R)-2-Y (deltaH(S)(double dagger) = 57.4(0.8) kJ mol(-1) and deltaS(S)(double dagger) = -102(3) J K(-1) mol(-1); deltaH(R)(double dagger) = 61.5(0.7) kJ mol(-1) and deltaS(R)(double dagger) = -103(3) J K(-1) mol(-1)) indicate a highly organized transition state. The binaphtholate catalysts were also applied to the kinetic resolution of chiral alpha-substituted aminoalkenes with resolution factors f of up to 19. The 2,5-disubstituted aminopentenes were formed in 7:1 to > or = 50:1 trans diastereoselectivity, depending on the size of the alpha-substituent of the aminoalkene. Rate studies with (S)-1-phenyl-pent-4-enylamine ((S)-15e) gave the activation parameters for the matching (deltaH(double dagger) = 52.2(2.8) kJ mol(-1), deltaS(double dagger) = -127(8) J K(-1) mol(-1) using (S)-2-Y) and mismatching (deltaH(double dagger) = 57.7(1.3) kJ mol(-1), deltaS(double dagger) = -126(4) J K(-1) mol(-1) using (R)-2-Y) substrate/catalyst combination. The absolute configuration of the Mosher amide of (2S)-2-methyl-4,4-diphenyl-pyrrolidine and (2R)-methyl-(5S)-phenyl-pyrrolidinium chloride, prepared from (S)-15e, were determined by crystallographic analysis. Catalyst (R)-4a showed activity in the anti-Markovnikov addition of n-propylamine to styrene.

Kinetic resolution of chiral aminoalkenes via asymmetric hydroamination/cyclisation using binaphtholate yttrium complexes.

Chiral binaphtholate yttrium aryl complexes are highly active and enantioselective catalysts for the asymmetric hydroamination of aminoalkenes, as well as the kinetic resolution of alpha-substituted 1-aminopent-4-enes to give trans-2,5-disubstituted pyrrolidines with good enantiomeric excess and high k(rel).

Synthesis and characterization of new biphenolate and binaphtholate rare-Earth-metal amido complexes: catalysts for asymmetric olefin hydroamination/cyclization.

Monomeric diolate amido yttrium complexes [Y[diolate][N(SiHMe(2))(2)](thf)(2)] can be prepared in good yield by treating [Y[N(SiHMe(2))(2)](3)(thf)(2)] with either 3,3'-di-tert-butyl-5,5',6,6'-tetramethyl-1,1'-biphenyl-2,2'-diol (H(2)(Biphen)), 3,3'-bis(2,4,6-triisopropylphenyl)-2,2'-dihydroxy-1,1'-dinaphthyl (H(2)(Trip(2)BINO)) or 3,3'-bis(2,6-diisopropylphenyl)-2,2'-dihydroxy-1,1'-dinaphthyl (H(2)(Dip(2)BINO)) in racemic and enantiopure form. The racemic complex [Y(biphen)[N(SiHMe(2))(2)](thf)(2)] dimerizes upon heating to give the heterochiral complex (R,S)-[Y(biphen)[N(SiHMe(2))(2)](thf)](2). The corresponding dimeric heterochiral lanthanum complex was the sole product in the reaction of H(2)(Biphen) with [La[N(SiHMe(2))(2)](3)(thf)(2)]. Single-crystal X-ray diffraction of both dimeric complexes revealed that the two Ln(biphen)[N(SiHMe(2))(2)](thf) fragments are connected through bridging phenolate groups of the biphenolate ligands. The two different phenolate groups undergo an intramolecular exchange process in solution leading to their equivalence on the NMR timescale. All complexes were active catalysts for the hydroamination/cyclization of aminoalkynes and aminoalkenes at elevated temperature, with [Y((R)-dip(2)bino)[N(SiHMe(2))(2)](thf)(2)] being the most active one giving enantioselectivities of up to 57 % ee. Kinetic resolution of 2-aminohex-5-ene proceeded with this catalyst with 6.4:1 trans selectivity to give 2,5-dimethylpyrrolidine with a k(rel) of 2.6.