Reactivity with ketones

There are also dimethylaniline with dibenzoyl peroxide at room temperature (for normal/long gel times) dimethylparatoluidine (for very short gel times) cobalt octoate (mainly used with ketone peroxides for polyesters at room and elevated temperatures) cobalt/amine very high reactivity with ketone peroxides for very fast cure (for example polymer concrete) and vanadium special for ketone peroxide. 

Cobalt/amine very high reactivity with ketone peroxides for very fast cure (for example, polymer concrete) ... 

BetMIC is characterized by two key properties first, the good leaving ability of the benzotriazole (Bet) moiety and, second, the high acidity of the methylene protons. BetMIC is reactive with ketones to afford 4-ethoxy-2-oxazolines (94), which can be hydrolyzed to synthetically useful a-hydroxyaldehydes (95). It must be noted that unlike TosMIC, BetMIC forms 94/96 without the presence of highly toxic thallium alkoxides. The reaction works well in the absence of ethanol and provides better yields when using aliphatic ketones. With aromatic ketones, for example, ben-zophenone, partial conversion to oxazoline occurs probably due to steric effects. Reaction of BetMIC with aldehydes typically generates oxazoles 97 (Scheme 7.24) [43,44]. 

The preparation of 2 4-dimethyl-3 5-dicarbethoxypyrrole (II) is an example of the Knorr synthesis of pyrrole derivatives, involving the reaction of an -aminoketone (or a derivative thereof) with a reactive methylene ketone (or a derivative thereof). The stages In the present synthesis from ethyl acetoacetate (I) may be represented as follows ... 

The manufacture of crystal violet (1), however, is a special case which does not involve the isolation of the intermediate Michler s ketone (Fig. 3). Thus, phosgene is treated with excess dimethyl aniline in the presence of zinc chloride. Under these conditions, the highly reactive intermediate "ketone dichloride" is formed in good yield this intermediate further condenses with another mole of dimethyl aniline to give the dye. 

Isatin (190) is a compound with interesting chemistry. It can be iV-acetylated with acetic anhydride, iV-methylated via its sodium or potassium salt and O-methylated via its silver salt. Oxidation of isatins with hydrogen peroxide in methanolic sodium methoxide yields methyl anthranilates (81AG(E)882>. In moist air, O-methylisatin (191) forms methylisatoid (192). Isatin forms normal carbonyl derivatives (193) with ketonic reagents such as hydroxylamine and phenylhydrazine and the reactive 3-carbonyl group also undergoes aldol condensation with active methylene compounds. Isatin forms a complex derivative, isamic acid (194), with ammonia (76JCS(P1)2004). 

Another method for improving the reactivity of nitro compounds is provided by the double deprotonadon of nitroalkanes. In this case, the reacdon with ketones affords fi-nitro alcohols in 4Q-6Q% yield CEq.d.lQi ... 

Other compounds with reactive methylene and methyl groups are completely analogous to the nitroalkanes. Compounds with ketonic carbonyl groups are the most important. Their simplest representatives, formaldehyde and acetone, were considered for many decades to be unreactive with diazonium ions until Allan and Podstata (1960) demonstrated that acetone does react. Its reactivity is much lower, however, than that of 2-nitropropane, as seen from the extremely low enolization equilibrium constant of acetone ( E = 0.9 x 10-7, Guthrie and Cullimore, 1979 Guthrie, 1979) and its low CH acidity (pK = 19.1 0.5, Guthrie et al., 1982). ... 

Double bonds in conjugation with the carbon-hetero multiple bond also lower addition rates, for similar reasons but, more important, may provide competition from 1,4 addition (p. 977). Steric factors are also quite important and contribute to the decreased reactivity of ketones compared with aldehydes. Highly hindered ketones like hexamethylacetone and dineopentyl ketone either do not undergo many of these reactions or require extreme conditions. 

These results show for the first time, the reactivity of the double bond C = N with the 2 diazopropane that constitutes an efficient route for the preparation of new heterocyclic systems. In all cases, the reaction is peris-elective only the double bond C = N is affected diazo carbon attacks the quaternary carbon of the imidate 60 and not the double bond C = O (substrates 60b and 60c). Indeed, diazopropane reacts with ketones with inverse regioselectivity (with regards to imidates 60) to yield oxadiazoUnes [32,33] (Scheme 14). 

Ketophosphonium salts are considerably more acidic than alkylphosphonium salts and can be converted to ylides by relatively weak bases. The resulting ylides, which are stabilized by the carbonyl group, are substantially less reactive than unfunctionalized ylides. More vigorous conditions are required to bring about reactions with ketones. Stabilized ylides such as (carboethoxymethylidene)triphenylphosphorane (Entries 8 and 9) react with aldehydes to give exclusively trans double bonds. 

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