Alcohols direct

Diasterocontrolled hydrogenation of allylic alcohols directed by the -OH group... 

Another even more significant use of methyl alcohol can be as a fuel in its own right in fuel cells. In recent years, in cooperation with Caltech s Jet Propulsion Laboratory (JPL), we have developed an efficient new type of fuel cell that uses methyl alcohol directly to produce electricity without the need to first catalytically convert it to produce hydrogen. 

Unlike the addition of concentrated sulfuric acid to form alkyl hydrogen sulfates this reaction is carried out m a dilute acid medium A 50% water/sulfuric acid solution is often used yielding the alcohol directly without the necessity of a separate hydrolysis step Markovmkov s rule is followed... 

Most other oxidizing agents, such as chromium trioxide (0rO3) in aqueous acid, oxidize primary alcohols directly to carboxylic acids. An aldehyde is involved as an intermediate in this reaction but can t usually be isolated because it is further oxidized too rapidly. 

Although halide ions (particularly I and Br ) are strong nucleophiles, they are not strong enough to carry out substitution reactions with alcohols directly. 

The conversion of alcohols directly into the structurally related hydrocarbons by ionic hydrogenation can provide a means of synthesis for compounds that would be extremely difficult or impossible to obtain by other methods. A good example is the synthesis of 2-terr-butyladamantane (12, R = Me). This interesting, highly strained compound may be synthesized in moderate overall yield by a conventional multiple-step route.149 Alternatively, it is obtained in 90% isolated yield upon treatment of a dichloromethane solution of the readily available 2-/c/7-bulyI -2-adamantanoI (11, R = Me)150 and one equivalent of either tri-n-hexylsilane151152 or triethylsilane153 with trifluoroacetic acid at room temperature (Eq. 16). 

When the reaction of DMFL with alcohols, cyclohexane, or a-methylstyrene is initiated by triplet senitization, the outcome is virtually the same as it is for the direct irradiation. Thus ethers are formed in high yield with the alcohols, direct insertion accounts for the major product in cyclohexane, and the olefin cyclopropanation is stereospecific. 

Strong oxidising agents such as acidified potassium permanganate are used for getting carbo Qrlic acids from alcohols directly. CrOs in anhydrous medium is used as the oxidising agent for the isolation of aldehydes. 

BKC115>. Amides derived from aromatic carboxylic acids and benzotriazole were reported to form 2-aryl-5,6-dihydro-4//-l,3-oxazines with 3-aminopropanol in excellent yields when subjected to microwave irradiation in the presence of SOCI2 <2004JOC811 >. Imidates have often been applied to cyclize 1,3-amino alcohols directly to 5,6-dihydro-l,3-oxazine derivatives <1996ACS922, 2004JHC69, 2004JHC367>. 

An attempt to dehydrate the alcohol directly would lead to rearrangement of the R intermediate. The major product would be (CH,)2C=C(CHj)2. To avoid this, pyrolyze the acetate ester of this alcohol. 

The epoxidation of enones using chiral phase transfer catalysis (PTC) is an emerging technology that does not use transition metal catalysts. Lygo and To described the use of anthracenylmethyl derivatives of a cinchona alkaloid that are capable of catalyzing the epoxidation of enones with remarkable levels of asymmetric control and a one pot method for oxidation of the aUyl alcohol directly into... 

The tartaric acid scaffold also led to the design of one of the most effective and general methods to generate enantiomerically enriched substituted cyclopropyhnethanol derivatives. Indeed, the chiral dioxaborolane ligand 19, prepared from tetramethyltartramide and butylboronic acid, is a superb chiral additive in allylic alcohol-directed cyclopropanation reactions (equation 83) . The best procedure requires the use of the soluble bis(iodomethyl)zinc DME complex . The reaction affords high yields and enantiomeric... 

The axial allylic alcohol directs the chromium-promoted epoxidation of the alkene. 

Looking first at alcohol-directed reductions62, it is apparent that there have been many studies of the reduction of allylic and homoallylic alcohols using both the neutral and cationic reduction complexes based on rhodium, iridium etc. In the case of cyclic substrates where an alcohol is located on one side of a ring, the hydrogen is simply delivered cis to the alcohol function63. This is illustrated by key reduction steps in the synthesis of monensin (Scheme 5)64 and the marine natural product arenarol (Scheme 6)65. In each... 

The formation of higher alcohols directly in one step from smaller alcohols via the Guerbet reaction was investigated by passing the alcohol... 

Aldehydes. Fluorinated aldehydes are unknown. It has been observed that the reduction of a fluoro acid yields the alcohol directly, and also that the oxidation of a fluoro alcohol does not stop short of the acid.88... 

Ethers For the synthesis of ether, the Williamson ether synthesis is considered as the best method. It involves the SN2 reaction between a metal alkoxide and a primary alkyl halide or tosylate. The alkoxide needed for the reaction is obtained by treating an alcohol with a strong base like sodium hydride. An alternative procedure is to treat the alcohol directly with the alkyl halide in the presence of silver oxide, thus avoiding the need to prepare the alkoxide beforehand. 

Answer A method of converting primary or secondary alcohols directly to the corresponding alkyl bromide involves the treatment of the alcohol with PBr3 as shown below. 

The Fischer esterification converts carboxylic acids and alcohols directly to esters by an acid-catalyzed nucleophilic acyl substitution. The net reaction is replacement of the acid —OH group by the —OR group of the alcohol. 

In practice, alcohols can always be obtained from the reduction (in a second step) of the products obtained from oxidative cleavage reactions. However, when ozone is used as the cleavage reagent it is possible to obtain alcohols directly without the need to isolate intermediate products. 

Sodium acetylide adds to the carbonyl group of conjugated olefinic aldehydes to give olefinic acetylenic alcohols. Direct addition of acetylene to aldehydes and ketones is catalyzed by copper acetylide (ethynylation ). ... 

Syntheses of alkyl phenyl ethers, C,H, OR, are carried out by refluxing aqueous or alcoholic solutions of alkali phenolates with alkyl halides the yields vary with the nature of the alkyl halides (40-80%). The reactive halogen in benzyl halides is easily replaced by an alkoxyl group (95%). ° The choice of a solvent is sometimes important. Thus, in the preparation of the alkyl ethers of o- and p-hydroxybiphenyl from a mixttire of the phenol, alkyl halide, and powdered potassium hydroxide, high yields are obtained using acetone as a solvent, whereas, with alcohol as solvent, only small yields are obtained. Triarylmethyl chlorides react with alcohols directly (97%). ... 

The hydrides can also he used to form primary alcohols from either terminal or internal olefins. The olefin and hydride form an alkenyl zirconium, Cp2ZrRCl, which is oxidized to the alcohol. Protonic oxidizing agents such as peroxides and peracids form the alcohol directly, hut dry oxygen may also he used to form the alkoxide which can he hydrolyzed (234). 

The oxidation of allylic alcohols directly to methyl carboxylates has been reported using MnOj and sodium cyanide in methanol. 

Introduction. The action of halogens on saturated open chain hydrocarbons, as for example, pentane or hexane, gives several monohaJogen derivatives. Since the separation of the isomeric monohalides is difficult in the laboratory, they are usually prepared from alcohols. Direct halogenation is used industrially. The cyclic hydrocarbons, such as cyclohexane and benzene, jdeld only one monohalide. The present experiment illustrates direct bromination of a hydrocarbon. Chlorination is more difficult it is described in the latter part of the text (page 229). The catalyst used for bromination is iron other substances which can be used for the same purpose are anhydrous aluminum chloride and pyridine. 

Other carboxylic acids such as 55 have been used to make corresponding diastereoisomeric esters. The choice of aromatic substituent in 55 is made on the basis of the greater anisotropy of the three fused aromatic rings in 55 with respect to phenyl. It has recently been possible to assign configuration to a pair of enantiomeric alcohols directly from the H NMR spectra of their esters with 55. The discussion goes beyond the scope of this text, but for details the work of Fukushi et al. 1 Takahashi et a/.18 and Seco et al 9 should be consulted. 

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