Carbonyl compounds hydroxylation

Two aldehydes two ketones or one aldehyde and one ketone may be formed Let s recall the classes of carbonyl compounds from Table 4 1 Aldehydes have at least one hydrogen on the carbonyl group ketones have two carbon substituents—alkyl groups for example—on the carbonyl Carboxylic acids have a hydroxyl substituent attached to the carbonyl group... 

The type of alcohol produced depends on the carbonyl compound Substituents present on the carbonyl group of an aldehyde or ketone stay there—they become sub stituents on the carbon that bears the hydroxyl group m the product Thus as shown m Table 14 3 (following page) formaldehyde reacts with Grignard reagents to yield pri mary alcohols aldehydes yield secondary alcohols and ketones yield tertiary alcohols... 

Study of the mechanism of this complex reduction-Hquefaction suggests that part of the mechanism involves formate production from carbonate, dehydration of the vicinal hydroxyl groups in the ceUulosic feed to carbonyl compounds via enols, reduction of the carbonyl group to an alcohol by formate and water, and regeneration of formate (46). In view of the complex nature of the reactants and products, it is likely that a complete understanding of all of the chemical reactions that occur will not be developed. However, the Hquefaction mechanism probably involves catalytic hydrogenation because carbon monoxide would be expected to form at least some hydrogen by the water-gas shift reaction. 

Alkaline solutions of mononitroparaffins undergo many different reactions when stored for long periods, acidified, or heated. Acidification of solutions of mononitro salts is best effected slowly at 0°C or lower with weak acids or buffered acidic mixtures, such as acetic acid—urea, carbon dioxide, or hydroxyl ammonium chloride. If mineral acids are used under mild conditions, eg, dilute HCl at 0°C, decomposition yields a carbonyl compound and nitrous oxide (Nef reaction). 

Hydroxypyrroles. Pyrroles with nitrogen-substituted side chains containing hydroxyl groups are best prepared by the Paal-Knorr cyclization. Pyrroles with hydroxyl groups on carbon side chains can be made by reduction of the appropriate carbonyl compound with hydrides, by Grignard synthesis, or by iasertion of ethylene oxide or formaldehyde. For example, pyrrole plus formaldehyde gives 2-hydroxymethylpyrrole [27472-36-2] (24). The hydroxymethylpyrroles do not act as normal primary alcohols because of resonance stabilization of carbonium ions formed by loss of water. 

In a prostaglandin synthesis a carbonyl group was protected as an oxime in which the hydroxyl group was protected against Collins oxidation by the phenylthiome-thyl-group. The phenylthiomethyl group is readily removed to give an oxime that is then cleaved to the carbonyl compound. ... 

The oxidation of a hydroxyl group by an aluminum alkoxide-catalyzed hydrogen exchange with a receptor carbonyl compound is known as the Oppenauer oxidation. For oxidation of steroidal alcohols the reaction is generally... 

When only one carbonyl or hydroxyl group is to be blocked in a multifunctional compound, the choice of the protecting group will be determined by the ease with which the group can be introduced selectively into the parent molecule. 

Alkenes are reduced by addition of H2 in the presence of a catalyst such as platinum or palladium to yield alkanes, a process called catalytic hydrogenation. Alkenes are also oxidized by reaction with a peroxyacid to give epoxides, which can be converted into lTans-l,2-diols by acid-catalyzed epoxide hydrolysis. The corresponding cis-l,2-diols can be made directly from alkenes by hydroxylation with 0s04. Alkenes can also be cleaved to produce carbonyl compounds by reaction with ozone, followed by reduction with zinc metal. 

Reactions 11-22-11-26 involve the introduction of a CH2Z group, where Z is halogen, hydroxyl, amino, or alkylthio. They are all FriedeI-Crafts reactions of aldehydes and ketones and, with respect to the carbonyl compound, additions to the C=0 double bond. They follow mechanisms discussed in Chapter 16. 

In 1991, Li and Chan reported the use of indium to mediate Barbier-Grignard-type reactions in water (Eq. 8.49).108 When the allylation was mediated by indium in water, the reaction went smoothly at room temperature without any promoter, whereas the use of zinc and tin usually requires acid catalysis, heat, or sonication. The mildness of the reaction conditions makes it possible to use the indium method to allylate a methyl ketone in the presence of an acid-sensitive acetal functional group (Eq. 8.50). Furthermore, the coupling of ethyl 2-(bromomethyl)acrylate with carbonyl compounds proceeds equally well under the same reaction conditions, giving ready access to various hydroxyl acids including, for example, sialic acids. 

As indicated in Chapter 3, compounds with fluorines bound directly to a carbon bearing a hydroxyl group are usually very unstable relative to the carbonyl compound plus HF. Nevertheless trifluoromethanol has been prepared, but it spontaneously loses HF at temperatures above -30 °C. Its fluorine and carbon NMR data are given in Scheme 5.8 and 5.11, and they resemble the respective data of trifluoromethyl ethers. 

The simultaneous protection of two hydroxyl groups by condensation of sugars with carbonyl compounds to give 1,3-dioxolanes or 1,3-dioxanes is also applicable to D-glucuronic acid. Principally, for the preparation of O-alkylidene-a-D-glucofuranuronic acid derivatives, two methods are available 1, direct condensation of 2 or 4 with... 

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