2 : 5-Hexadion

Specific aliphatic and aromatic hydrocarbons found in petroleum products are known to be metabolized via cytochrome P-450 pathways to reactive metabolic intermediates that are thought to cause non-cancer and cancer effects from chronic exposure (e.g., peripheral neuropathy from 2,5-hexadione, a metabolite of hexane, and cancer effects from various intermediary metabolites of benzene and carcinogenic PAHs). There are no known clinical methods to interfere with these mechanisms of action. However, current research programs are studying the basis of how the consumption of cruciferous vegetables may protect... 

Later it was shown that promotion is unspecific. Other toxic axonopatie (e.g. 2,5 -hexadione) [106] were promoted by PMSF. Promotion is less effective in chicks where the compensation-repair mechanisms are thought to be more efficient [23], The mechanism involved in promotion is not activated by the lesion/ insult to the nerve, but appears to be present and perhaps active in the healthy axon. Thus promotion was also found when promoter phosphorothioic acid-0-(2-chloro-2,3,3-trifluorocyclobutyl)-0-ethyl S-propyl ester (KBR-282) was given... 

Nonaqueous two-phase systems employ two largely immiscible liquids. Examples include dissolving the Lewis base in acetonitrile, nitrobenzene, or 2,5-hexadione and the organometallic acid chloride in a nonpolar organic liquid such as hexane, decane, or carbon tetrachloride. 

Figure 16. Photocleavage of (/V-methylanilinojacetone 19 in acetonitrile- . The plot shows the temperature dependence of the CIDNP signals of the CH2-protons (underlined in the formulas given) in the geminate reaction product 19 (bottom) and in the escape product 2,5-hexadione (top). [Adapted from ref. [104c] with permission. Copyright 1992 Elsevier Sequoia.]...

TSA (2) can act as a safe and recyclable catalyst for the reaction of aromatic primary amines and 2,5-hexadione under thermal and solvent-free conditions to afford some known pyrrole derivatives in good to excellent yields (Scheme 3.9). This also afforded some novel pyrrole derivatives (Scheme 3.10) (Karami et al 2013a). 

Those bis(trimethylsiloxy)alkenes resulting in the first step are reactive intermediates which can be converted into a variety of compounds — they give an easy access to many products in a one pot synthesis. For instance via bromination of 3,4-bis(trimethylsiloxy)-3-hexene (303) 2,5-dibromo-3,4-hexadione (307) can be achieved199 whereas l,2-bis(trimethylsiloxy)stilbene (304) yieldsbenzil (308)i99 Simmons-Smith conditions were applied, too, and 2,3-bis(trimethylsiloxy)-2-butene (290) gives l,2-dimethyl-l,2-bis(trimethylsiloxy)cyclopropane (306)2OO ... 

We next turn our attention to the intramolecular aldol reaction, typified by the Hajos-Parrish-Wiechert-Eder-Sauer reaction (Scheme 6.7). Houk ° first examined the intramolecular proline-catalyzed aldol reaction of 4-methyl-2,6-hexadione... 

Isomerisierung nnd Ringoffnung tritt bei der Belichtung von 6- Amino-2,4- dimet hyl-pyrimidin (II) in wafirigem Phosphat-Puffer (pn = 8,5-8,7) auf1. tFber 5-Amino-l,3-dimethyl-2,6-diaza-bicyclo [2.2.0]hexadion-(2,5) (III) und das isomere 4-Amino-2,4-di-methyl-3-cyan-l-azetin (IV) wird 2-Amino-4-imino-3-cyan- penten-(2) (V) gebildet, das weiter zu 2-Hydroxy-4-oxo-3-cyan-pmtm- 2) hydrolysiert ... 

Dialkylation in intermolecular substitutions with dimethyl malonate and 2-methyl-l,3-cyclo-hexadione as soft carbanions is minimized by the chiral ligand19. As expected, enantioselectiv-ity is not dependent on the choice of nucleophile. 

Bui and Barbas in the year 2000 introduced a single-step enantioselective synthesis of the Wieland-Miescher ketone (44). The keto-enone 44 is formed by the reaction MVK, 2-methyl-1,3-hexadione, in the presence of (5)-proline in 49% and 76% ee. By screening the different catalysts, 46-48 show synthesis of the (5)-(+)-44 in 60-75%... 

The derivative 39 has also been reported to catalyze the aldol reaction between underivatized hydroxyacetone and activated benzaldehydes, affording the products with low diastereoselectivity and in moderate to high ee [109]. The best results were obtained with (R,R)-tartaric acid as co-catalyst and the absence of a solvent. In addition, a scalable procedure for the reaction with 4-nitrobenzaldehyde was developed involving a single crystallization step in order to obtain the enantiopure branched product of the aldol reaction. j n example of an intramolecular aldol reaction is provided by work of List and coworkers, who found that the formation of enantioenriched 5-substituted-3-methyl-2-cyclohexene-l-ones could be obtained from 4-substituted-2,6-hexadiones with 36 as the catalyst (Scheme 6.51) [llOj. 

Rueping et al. developed a sequential [3+2] cascade reaction between 1,2-cyclo-hexadione 147 and enals through a Michael-aldol sequence to furnish the bicyclic... 

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