Cyclohexanone reaction with

Formation of a 1,2-disubstituted hydrazine by acid hydrolysis of an appropriately substituted pyrazolidine has been noted (67HC(22)l), but the most interesting ring fission of pyrazolidines involves the N(l)—N(2) bond of 1-phenylpyrazolidines (421). If, instead of phenylhydrazone, compound (421) is used in the Fischer indole synthesis, N- aminopropylin-doles are formed (73T4045). Scheme 39 shows the reaction with cyclohexanone. 

Common reagents such as lithium diisopropylamide (LDA see Chapter 11, Problem 5) react with carbonyl compounds to yield lithium enolate salts and diisopropylamine, e.g., for reaction with cyclohexanone. 

Oxidation of 4-methylcyclohexanone by addition of nitric acid at about 75°C caused a detonation to occur. These conditions had been used previously to oxidise the corresponding alcohol, but although the ketone is apparently an intermediate in oxidation of the alcohol, the former requires a much higher temperature to start and maintain the reaction. An OTS report, PB73591, mentions a similar violent reaction with cyclohexanone [1], Presence of nitrous acid is essential for the smooth oxidation of cycloalkanones with nitric acid to a, rw-hcxanedioic acids. Because high-purity nitric acid (free of nitrous acid) is now commonly available, addition of a little sodium or potassium nitrite to the acid is necessary before its use to oxidise cycloalkanones [2],... 

These alkoxytitanium homoenolates show high propensity for equatorial attack in their ir reactions with substituted cyclohexanones (Table 6). The basic trend of their chemical behavior is similar to that of simple titanium alkyls [35]. Chemo-selectivity of the reagent 19 is also noteworthy. The alkoxytitanium homoenolate reacts preferentially with an aldehyde even in the presence of a ketone Eq. (32). A notable difference of rate between the reaction with cyclohexanone and that with 2-methylcyclohexanone was also observed, the latter being far less reactive toward the homoenolate. 

He also obtd, by using larger amts of 30% H202 in a reaction with cyclohexanone in ether 1, l-Di(hydroperoxycyclohexyl) peroxide,... 

A new, direct route to 0,S-acetals is based in part on the ability of trimethylsilyl triflate to mediate synthesis of 0,0-acetals from carbonyl compounds and silyl ethers (10, 439). Thus reaction of 1 1 mixtures of a silyl ether and phenylthiotrimethylsilane with an aldehyde in the presence of catalytic to stoichiometric amounts of trimethylsilyl triflate can give 0,S-acetals in 37-93% yield. Acetone is amenable to this 0,S-ketalization, but reactions with cyclohexanone result mainly in 0,0-ketals. 

The stabilization of carbanions by the 1,2,5-thiadiazole system is indicated in the facile formation of the phosphorane (110) by treatment of the phosphonium salt (109) with cold aqueous base. The resonance-stabilized phosphorane reacts readily with aldehydes but fails to enter into a reaction with cyclohexanone. 

The sulfur ylide 3.45 on reaction with cyclohexanone gives oxirane 3.64, while the phosphorus ylide 3.65 gives the alkene 3.66. 

In a paper emphasizing the preparative value, Schulz and Kluge described the a-hydroxylation of ketones in good yields by using 2 equivalents of triarylarainium salts in moist acetonitrile [172]. In contrast to the oxidative functionalization of 68, 70 and 72 the reaction with cyclohexanone (64) and methyl isopropyl ketone (80) was run in the presence of a hindered pyridine base. Thus, mechanistically, it cannot rigorously be stated whether ends or the enolates are oxidized (cf Sect. 3.2). 

A related reductive cyclisation has been developed by Schafer et al. in which the cathodic cyclisation of A-(oxoalkyl)pyridinium salts led to indolizidine and quinolizidine derivatives <95AG(E)2007, 03EJO2919>. Electrolyses of the pyridinium salts were carried out in a divided beaker-t5q)e cell at a mercury pool cathode under constant current, using 1 M aqueous sulfuric acid as the electrolyte. In this way, cyclisation of cyclopentanone 129 to the isomeric quinolizidines 130 and 131 was achieved in high yield and with excellent diastereoselectivity (Scheme 38). The stereochemical course of the reaction with cyclohexanone 133 was not as well defined, with three of the four possible diastereoisomers being given in a ratio of 10 21 26 (for 134,135 and 136 respectively). 

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