1,3-Cyclohexanediones. formation

Oxidation of triazine herbicides with chlorine and chlorine dioxide has been widely studied [105-108]. In the case of sulfur-containing triazines, oxidation occurs mainly via cleavage of the weakened R-S-CH3 bond rather than by addition of chlorine. Reactions of S-triazines with chlorine are faster than with chlorine dioxide, and form sulfoxide, sulfone, and a sulfone hydrolysis product. Chlorination with chlorine dioxide only produced sulfoxide [108]. Lopez et al. identified the formation of sulfonate esters during the chlorination of ametryn and terbutryn [106, 107]. Triazine DBFs identified by Brix et al. exhibited higher toxicities than the parent compounds [105]. Similar to triazines, clethodim, a cyclohexanedione herbicide, is oxidized by hypochlorite and chloramines to clethodim sulfoxide and then to sulfone [109]. 

Structures have been determined for [Fe(gmi)3](BF4)2 (gmi = MeN=CHCF[=NMe), the iron(II) tris-diazabutadiene-cage complex of (79) generated from cyclohexanedione rather than from biacetyl, and [Fe(apmi)3][Fe(CN)5(N0)] 4F[20, where apmi is the Schiff base from 2-acetylpyridine and methylamine. Rate constants for mer fac isomerization of [Fe(apmi)3] " were estimated indirectly from base hydrolysis kinetics, studied for this and other Schiff base complexes in methanol-water mixtures. The attenuation by the —CH2— spacer of substituent effects on rate constants for base hydrolysis of complexes [Fe(sb)3] has been assessed for pairs of Schiff base complexes derived from substituted benzylamines and their aniline analogues. It is generally believed that iron(II) Schiff base complexes are formed by a template mechanism on the Fe " ", but isolation of a precursor in which two molecules of Schiff base and one molecule of 2-acetylpyridine are coordinated to Fe + suggests that Schiff base formation in the presence of this ion probably occurs by attack of the amine at coordinated, and thereby activated, ketone rather than by a true template reaction. ... 

The only known example of 2-monoalkylaminopyran 123 in the series of tetrahydrochromenes was obtained by the less common three-component reaction of alkylisonitriles 124, acetylenedicarbonic esters 125, and dimedone or 1,3-cyclohexanedione 103 (03M1585) (Scheme 42). This example illustrates how the isonitrile —N =C group can be involved in the formation of a 2-aminopyran ring, similar to the other groups with triple bonds - nitrile C=N and alkynyl C=C. 

This is encouragingly small, especially considering the experimental uncertainty for the dioxime enthalpy of formation, althongh we have no real idea how mnch repnlsion or stabilization we might expect from vicinal dioxime gronps. (We likewise lack snch information for vicinally substituted alicycUc diones—there are literature enthalpy of formation data for 1,3- and 1,4- but not 1,2-cyclohexanedione there are also data for 2,3-pentanedione but not 1,2-cyclopentanedione.) Consider now the reaction 33. 

Accordingly, we derive an enthalpy of formation of —49 kJ mol for the acyclic dioxime and so an endothermicity of 40 kJmol for the cyclohexane dioxime forming reaction 33—only 25 kJmol would have been expected from the above cyclohexanedione reaction if we assume that the cyclohexane dioxime is destabilized by 15 kJmol . ... 

It is a colorless liquid with an oily-fruity odor with floral, petal-like notes. For synthesis, 1,3-cyclohexanedione is reacted with crotyl bromide in the presence of potassium hydroxyde to give the 2-alkenyl-substituted 1,3-diketone. Ring cleavage with sodium hydroxyde leads to the unsaturated keto acid which is reduced with NaBH4 under formation of the title compound [201]. 

Thus, a-sulfinyl lithium carbanion of 1-chloroethyl p-tolyl sulfoxide was reacted with 1,4-cyclohexanedione mono ethylene ketal (195) to afford the adduct (196) in quantitative yield. The adduct was treated with ferf-butylmagnesium chloride (magnesium alkoxide was initially formed) followed by isopropylmagnesium chloride to result in the formation of magnesium /3-oxido carbenoid 197. The /3-oxido carbenoid rearrangement then takes place to give one-carbon expanded magnesium enolate 198. Finally, an electrophile was... 

Cyclohexanedione, reaction with guanidinium groups, 126 Cyclophilin 488 human 488s D-Cycloserine 739s Cyclosporin 488, 488s p Cylinders 65, 66, 686 Cystathionine, 746s formation 746 Cystathionine p lyase 742 Cystathionine p-synthase 744 Cystathionine y-synthase 743, 746 Cystatins 622, 629... 

To achieve synthesis of (-)-arisugacin A [1], (7 J-89 was obtained readily from 2-methyl-l,3-cyclohexanedione 88 in 4 steps with an overall yield of 46%, featuring vinylogous ester formation, Stork-Danheiser double alpha methylation,52,68,69 vinyl Grignard addition followed by acidic work-up,68 and an asymmetric CBS reduction [Scheme 21].70,71... 

Do you remember Figure 12.13 2-Methyl-l,3-cyclopentanedione and 2-methyl-1,3-cyclohexanedione in acetic acid undergo Michael additions to methyl vinyl ketone to form 1,5-diketones. Their structure reappears in Figure 12.19 as the substrate A. In the discussion of the formation mechanism of these 1,5-diketones you were probably not at all surprised to... 

A second pathway which also contributes significantly to the adipic acid production, involves formation of 1,2-cyclohexanedione, perhaps by hydrolysis of the ketoxime tautomer of 2-nitrosocyclohexanone. Conversion of the ketoxime and of the diketone to adipic acid requires a vanadium(V) catalyst (Figure 10). The resulting vanadium(III) species, VO, is eventually reoxidized by nitric acid. The copper(II) apparently helps to reduce multiple nitrosation of cyclohexanone, as that eventually affords glutaric acid. 

High chemo- and regioselectivity were observed for the metal complex-catalyzed cycloisomerization of readily available 4-propargyl-cyclohexanediones, leading to the formation of fused oxabicycles. As can be seen in the reactions below, a proper choice of metal catalyst can provide the 2-alkylidenetetrahydrofuran almost exclusively . 

The addition of ethyl sodiomalonate to olefinic ketones followed by ring closure and /3-keto ester cleavage leads to 1,3-cyclohexanediones. The reaction has been applied to the formation of 2-alkyl-5-phenyl-1,3-cyclohexanediones and is typified by the preparation of 5,5-dimethyl-1,3-cyclohexanedione (85%). Other cyclizations for formation of four-and five-membered rings have been described. ... 

When a metal ion such as nickel (II) is absent, thiazoles and mercaptals are formed. Such reactions have been carried out in which the diketone was biacetyl, 2,3-pentanedione, 2,3-octanedione, l-phenyl-l,2-propane-dione, and 1,2-cyclohexanedione (51). In like manner, the tris complexes of W,W -dimethyl-2,3-butane diimine with iron(II), cobalt(II), and nickel(II) may be prepared from methylamine and biacetyl when the appropriate metal ion (27j 28j 41) is present. Replacing methylamine with hydroxylamine causes the formation of a-dioximes (13). 

In the case of cyclohexanedione-1.2-dihydrazone, the macrobicyclic dihydrazonate formation proceeded on the template Fe-+ ion more... 

---