Methyl carbon hydroxylation

Reactions of the Hydroxyl Group. The hydroxyl proton of hydroxybenzaldehydes is acidic and reacts with alkahes to form salts. The lithium, sodium, potassium, and copper salts of sahcylaldehyde exist as chelates. The cobalt salt is the most simple oxygen-carrying synthetic chelate compound (33). The stabiUty constants of numerous sahcylaldehyde—metal ion coordination compounds have been measured (34). Both sahcylaldehyde and 4-hydroxybenzaldehyde are readily converted to the corresponding anisaldehyde by reaction with a methyl hahde, methyl sulfate (35—37), or methyl carbonate (38). The reaction shown produces -anisaldehyde [123-11-5] in 93.3% yield. Other ethers can also be made by the use of the appropriate reagent. 

An ethyl carbonate, prepared and cleaved by conditions similar to those described for a methyl carbonate, was used to protect a hydroxyl group in glucose. ... 

We do not know if the vinylic alcohol is actually an intermediate or whether a hydride-71 complex of it rearranges directly to the aldehyde as probably happens in the palladium-catalyzed oxidation of ethylene to acetaldehyde. The formation of 4% 2-methyl-2-phenylpropanal is unexpected. This product must arise from a reversed addition of the phenylpalladium group followed by a hydrogen transfer from the hydroxyl-bearing carbon to the palladium, followed by reductive elimination of a hydridopalladium group. An alkyoxypalladium intermediate has been proposed (39). 

Only 2-methyl-2-butanol is a tertiary alcohol (three alkyl substituents on the hydroxyl-bearing carbon) ... 

Because two of the alkyl groups on the hydroxyl-bearing carbon are the same (methyl), only two, not three,different ketones are possible starting materials ... 

The proposed mechanism for photocatalytic degradation of the /V-(l-mcthylcthyl) group involves reaction of an hydroxyl radical with either a methinyl or the methyl carbon, which via the corresponding hydroperoxide subsequently leads to formation of the acetamido and formylamino (via aminopropionaldehyde) products, respectively... 

Sodium dichromate hydroxylates tertiary carbons [620] and oxidizes methylene groups to carbonyls [622, 623, 625, 626, 631] methyl and methylene groups, especially as side chains in aromatic compounds, to carboxylic groups [624, 632, 633, 634, 635] and benzene rings to quinones [630, 636, 637] or carboxylic acids [638]. The reagent is often used for the conversion of primary alcohols into aldehydes [629, 630, 639] or, less frequently, into carboxylic acids or their esters [640] of secondary alcohols into ketones [621, 629, 630, 641, 642, 643, 644] of phenylhydroxylamine into nitroso-benzene [645] and of alkylboranes into carbonyl compounds [646]. 

FIGURE 9.50 UV light is required for conversion of plant (ergesterol) and animal (7-dehydrocholesterol) forms of the provitamin to the vitamin. The plant form differs from the animal form, in that the side-chain contains a double bond and an extra methyl carbon. UV light results in conversion of both forms of provitamin to vitamin D, and D3, respectively. (The side-chain double bond of D2 is not reduced in the body, but it can be artificially reduced in the laboratory, where the product is called vitamin D4.) Hydroxylation is shown for Dj, but not for D2. 

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