Acetic anhydride with alcohols

Normal Fischer esterification of tertiary alcohols is unsatisfactory because the acid catalyst required causes dehydration or rearrangement of the tertiary substrate. Moreover, reactions with acid chlorides or anhydrides are also of limited value for similar reasons. However, treatment of acetic anhydride with calcium carbide (or calcium hydride) followed by addition of the dry tertiary alcohol gives the desired acetate in good yield. 

Another important use of solubility parameters is in interpreting the effects of different solvents on the rates of reactions. In a chemical reaction, it is the concentration of the transition state that determines the rate of the reaction. Depending on the characteristics of the transition state, the solvent used can either facilitate or hinder its formation. For example, a transition state that is large and has little charge separation is hindered in its formation by using a solvent that has a high value of S. The volume of activation is usually positive for forming such a transition state which requires expansion of the solvent. A reaction of this type is the esterification of acetic anhydride with ethyl alcohol ... 

Dialky Itryptaminesfrom Tryptamines. Helv. Chem. Acta, 49,1199 (1966). Heat 82 ml of acetic anhydride with 35 ml of formic acid for 2 hours at 60°. With stirring add dropwise a solution of 100 g of tryptamine in 250 ml of THF. After the addition, cool to room temp (slowly) and let stand for 12 hours. Evaporate the solvents off in vacuo and add water (cold) to precipitate oily formyl tryptamine, which is separated and recrystallized in the minimum amount of aqueous (50%) ethanol (the minimum amount will be under 750 ml). 35 g of the recrystallized formyltryptamine is added to 150 ml of THF and mixed gently and then added to 20 g of LAH (lithium aluminum hydride) in 400 ml of THF. After this addition (which is made dropwise) reflux for 12 hours. Cool to 15° and add 10 ml of water (when decomposing LAH with water or alcohol always add it slowly, dropwise and be careful), then 10 ml of 15% NaOH, and about 30 ml more water or until the bubbling has stopped. Filter, wash the precipitate off with a little THF and evaporate (the filtrate) in vacuo to get the dialkyltryptamine (about 20 g). Recrystallize the residue in about 100 ml of dry methanol and reprecipitate by adding 10 g of anhydrous oxalic acid. 

The ester is prepared from a-trichloromethylbenzyl alcohol, for example, by reaction with acetic anhydride. The alcohol can be prepared by one of the following methods ... 

A different semisynthetic method involves the acylation of an amino alcohol with a peptide ester and the resulting amino alcohol is subsequently oxidized to the aldehyde 40 The acylation of H-Phe[CH2OH] with the peptide ester Z-Ala-Ala-Leu-OMe is carried out in 5% DMF/MeCN with the subtilisin distributed on the surface of macroporous silica gel. The resulting peptide alcohol is oxidized under mild conditions using anhydrous dimethyl sulfoxide and 20-fold excess of acetic anhydride with purification via flash chromatography 40] Z-Phe[CH2OH] has been oxidized under these conditions and the optical rotation indicates little epimerization as compared to literature values 11 40 ... 

Some organics, acetic anhydride, metals, alcohols, wood and its derivatives (see the other tables in this chapter dealing with this compound) Aldehydes, alcohols, unsaturated hydrocarbons Flammable liquids, metals, aldehydes, alcohols, impact, hydrocarbons (unsaturated)... 

Trichlorotrifluoroethane and zinc in diethyl ether or dimethylfor-mamide (DMF) form an organometallic complex with diethyl ether [773] or dimethylformamide [114. This complex reacts with aldehydes similarly as the Grignard reagents to form primarily the expected alcohols. In the presence of acetic anhydride, the alcohol is converted to the corresponding olefin, predominantly with Z configuration. In the case of benzaldehyde, Z- and E- 2-chloro-l-phenyl-3,3,3-trifluoropropene are the products H and I [114]. 

The same is true for the reaction of acetic anhydride with an alcohol. Possible leaving groups from this tetrahedral intermediate are the following. 

PDC with acetic anhydride gives a strong but mild, neutral oxidant It is normally used in dichloromethane at room temperature. Under these conditions secondary alcohols are oxidized to ketones in high yield with 0.6 equiv. of PDC and 3 equiv. of acetic anhydride. With only slightly more PDC (0.7 equiv.) primary alcohols are rapidly and selectively oxidized to aldehydes. (The extra oxidant serves to increase... 

Trihydroxypentane has been made by saponification of 1,2,5-triacetoxypentane with barium hydroxide and by hydrolysis with 0.1 N hydrochloric acid. The triacetoxypentane has been made by the action of potassium acetate and acetic anhydride on 4,S-dibromopentanol-l or 1,2,5-tribromopentane or l-chloro-4,5-diacctoxypentane, but it is most conveniently made by the reaction of acetic anhydride with tetrahydrofurfuryl alcohol. - The present method is a modification of that described by Wilson. ... 

Derivation By heating methyl salicylate with a slight excess of acetic anhydride, adding alcohol, then water, and separating the resulting precipitate. 

CHROMIUM TRIHYDROXIDE (308-14-1) CrH204 A powerful oxidizer. Violent reaction with many materials, including reducing agents (explosion) hydrides, nitrides, and sulfides acetic acid, acetic anhydride acetone, alcohols, alkalis, alkali metals, ammonia, anthracene, arsenic, combustible materials dimethylformamide, ethers, ethyl alcohol fumes (ignition) finely divided metals hydrogen sulfide sulfuric acid organic matter peroxyformic acid, phosphorus, pyridine, selenium, sodium, sulfur, and other oxidizable materials. 

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