Unsaturated alcohols, oxidation

Sulfation andSulfamation. Sulfamic acid can be regarded as an ammonia—SO. complex and has been used thus commercially, always in anhydrous systems. Sulfation of mono-, ie, primary and secondary, alcohols polyhydric alcohols unsaturated alcohols phenols and phenolethylene oxide condensation products has been performed with sulfamic acid (see Sulfonation and sulfation). The best-known appHcation of sulfamic acid for sulfamation is the preparation of sodium cyclohexylsulfamate [139-05-9] which is a synthetic sweetener (see Sweeteners). 

Adogen has been shown to be an excellent phase-transfer catalyst for the per-carbonate oxidation of alcohols to the corresponding carbonyl compounds [1]. Generally, unsaturated alcohols are oxidized more readily than the saturated alcohols. The reaction is more effective when a catalytic amount of potassium dichromate is also added to the reaction mixture [ 1 ] comparable results have been obtained by the addition of catalytic amounts of pyridinium dichromate [2], The course of the corresponding oxidation of a-substituted benzylic alcohols is controlled by the nature of the a-substituent and the organic solvent. In addition to the expected ketones, cleavage of the a-substituent can occur with the formation of benzaldehyde, benzoic acid and benzoate esters. The cleavage products predominate when acetonitrile is used as the solvent [3]. 

The alcohol-unsaturate couplings developed in our laboratory provide products of carbonyl addition. In contrast, related hydrogen auto-transfer processes provide products of alcohol substitution via pathways involving oxidation-condensation-reduction and the use of preactivated nucleophiles. For recent reviews, see [22-25]. 

In this case, the 2-aminobenzyl alcohol is oxidized to 2-aminobenz-aldehyde, which undergoes an aldol condensation with the ketone to give an 0, /3-unsaturated ketone. This is followed by cyclodehydratisation to form quinoline. An excess of ketone is necessary to act as a sacrificial hydrogen acceptor. 

During the past year, chloroperoxidase (CPO) was found to catalyze the smooth asymmetric epoxidation of functionalized cii-alkenes, such as the unsaturated ester 32. The reaction appears to be limited to 2-alkenes (i.e., methyl group on one side of the alkene), although some branching on the longer alkyl chain is tolerated. Allylic alcohols are oxidized to the corresponding unsaturated aldehydes but without epoxide formation <99TL1641>. 

Keto amides (see Dicarbonyl compounds) Keto esters (see Dicarbonyl compounds) Ketones (see also Dicarbonyl compounds, Unsaturated carbonyl compounds) From alcohols by oxidation... 

A suspension of ca. 6-50 equivalents, typically 5-20 equivalents, of active M11O2 in a ca. 0.02-0.2 M solution of the alcohol in a drya organic solventb is vigorously0 shaken at room temperatured till most of the unsaturated alcohol is oxidized.6... 

An aliphatic alcohol is oxidized with active M11O2, producing an aldehyde that reacts in situ with a stabilized phosphorane. The overall yield of the desired unsaturated ester is 80%. Curiously, the oxidation of the alcohol with M11O2 under the same reaction conditions and in the absence of phosphorane delivers only a 12% of the corresponding aldehyde. 

Because of the mechanism of action of DDQ, sulfides and selenides are expected not to react with DDQ during the mild conditions used in the oxidation of unsaturated alcohols. There is one published example in which an alcohol is oxidized with DDQ in the presence of a selenide.130... 

IOB alone can oxidize some alcohols, but catalysed oxidations are much more efficient. Thus, in the presence of RuCl2(PPh3)2 primary aliphatic alcohols were oxidized cleanly to aldehydes, at room temperature the use of m-iodosylbenzoic acid instead of IOB considerably increased the yields for example, hexanal was formed from hexanol quantitatively (by GC) [19], Another catalytic system involved the use of simple lanthanide salts such as ytterbium triacetate [20]. Cyclic y-stannyl alcohols, readily available from cyclic vinyl ketones and Bu3SnLi, underwent oxidation accompanied by carbon-carbon bond cleavage (Grab fragmentation), when treated with IOB.BF3 and DCC. The products were unsaturated aldehydes or ketones. 

In the first approach shown in Scheme 9, ketoester 77 was alkylated successively with 4-bromobutene and 1,3-dibromopropene. After decarboxylation, 78 was converted into iV-aziridinylimine 79 in good yield. The pivotal radical cyclization reaction proceeded smoothly to produce a mixture of isomeric propellane compounds 80, which was purified after the epoxidation step. For the synthesis of modhephene, the mixture of epoxides was rearranged into the corresponding allylic alcohols 81 and then the allylic alcohols were oxidized, giving a separable mixture of unsaturated ketones 82a and 82b. The major product 82a possessed the correct stereochemistry of the methyl group of modhephene. Since 82a had already been converted into modhephene, a formal total synthesis of dZ-modhephene has thus been completed. The isomeric ratio of 80 reflects the stereoselectivity during the radical cyclization reaction. The selectivity was very close to the ratio reported by Sha in his radical cyclization reaction. ... 

Isolated carbon-carbon multiple bonds are not normally attacked by Jones reagent, but some doublebond isomerization may occur during the preparation of a, -unsaturated aldehydes. Hydroxy-directed epoxidation (presumably via chromate ester formation, followed by oxygen transfer to the double bond) has also been observed in steroidal substrates for axial alcohols (equation 1). Equatorial alcohols undergo oxidation to give the expected enone. 

By using PDC as a suspension in dichloromethane it becomes a selective oxidant for the preparation of aldehydes, saturated or unsaturated. Allylic alcohols are oxidized faster than saturated alcohols, but some ( )/(Z)-isomerization has been observed during the preparation of a,3-unsaturated aldehydes with PDC in dichloromethane. 

Cesium fluoride reacts with epoxides to form cesium alcoholates that can be transformed into a plethora of ethers and esters in good yield, for example, reaction of 12 to give 13. Methyl-ation with iodomethane is common. For sensitive alcohols silver oxide is the base of choice." No elimination to the a,)S-unsaturated sulfoxides was reported, when alcohols 14 were treated w ith iodomethane in dimethylformamide to give ethers 15." ... 

When used in DMF, PDC oxidizes aldehydes and primary alcohols to carboxylic acids. However, allylic primary and secondary alcohols are oxidized only to the a ,j3-unsaturated carbonyl compounds. All these oxidations proceed in high jrield. 

Just as the saturated primary alcohols on oxidation yield first aldehydes and then acids so the ethylene unsaturated primary alcohols yield first the unsaturated aldehydes, just considered, and these on further oxidation yield corresponding unsaturated acids,... 

Both aliphatic and aromatic alcohols, as well a s unsaturated alcohols, are oxidized in the liquid phase with argentic oxide in nitric or acetic acid at temperatures from -10 through 60 °C [5S6]. 

Oxidations with peimanganates are suitable for the preparation of carboxylic acids from saturated and benzylic alcohols. Unsaturated alcohols may suffer cleavage of double bonds. Conventional oxidations are carried out in aqueous media, usually in the presence of alkali hydroxides. Thus... 

---