Chloroformic acid esters phenol chloroformates

Solid esters are easily crystallisable materials. It is important to note that esters of alcohols must be recrystallised either from non-hydroxylic solvents (e.g. toluene) or from the alcohol from which the ester is derived. Thus methyl esters should be crystallised from methanol or methanol/toluene, but not from ethanol, n-butanol or other alcohols, in order to avoid alcohol exchange and contamination of the ester with a second ester. Useful solvents for crystallisation are the corresponding alcohols or aqueous alcohols, toluene, toluene/petroleum ether, and chloroform (ethanol-free)/toluene. Carboxylic acid esters derived from phenols are more difficult to hydrolyse and exchange, hence any alcoholic solvent can be used freely. Sulphonic acid esters of phenols are even more resistant to hydrolysis they can safely be crystallised not only from the above solvents but also from acetic acid, aqueous acetic acid or boiling n-butanol. 

Table IV gives the Rf values determined under these conditions. Figure 3 shows the chromatograms of the reaction products of the re-esterification of a number of plasticizers. It is obvious that the method is suitable for identifying the alcohol components of all frequently used ester types. Difficulties have been met with phenolic components although they are present primarily in phosphoric acid esters. To identify these, evaporate to dryness a few drops of the reaction mixture of an alkaline saponification and mix this with a bit of the precipitated alkali salt. Add this residue to 10 to 20 drops of chloroform and gradually evaporate it repeat...

Combination of silicon hydrides with catalytic amounts of a ruthenium(II) complex in tetrahydrofuran, chloroform or benzene has afforded a new reducing system capable of efficient reduction of a,p-unsatu-rated carboxylic acids, esters, amides, etc. Addition of a weak proton source, such as a sterically hindered phenol significantly increases reaction rates. The ruthenium mixture was found to exhibit the same regioselectivity observed with the above-described palladium systems. 

Ethyl chloroformate/triethylamine Carboxylic acid aryl esters from carboxylic acids and phenols... 

Nitrobenzene, m-Dinitrobenzene o-Nitro phenol N-Nitramines Oxonium fluoroborate Trialky I oxonium salt Trialkyloxonium fluoroborate Pyrylium fluoroborate Carboxylic acid esters HCOOC H, p-Nitro-phenyl formate Isopropenyl acetate Chloroformic acid esters Ethyl chloroformate Methyl trichloroacetate Ethyl malonate Orthoformic acid esters, Ethyl orthoformate (RCO) O (CH COhO,... 

The acylpalladium complex formed from acyl halides undergoes intramolecular alkene insertion. 2,5-Hexadienoyl chloride (894) is converted into phenol in its attempted Rosenmund reduction[759]. The reaction is explained by the oxidative addition, intramolecular alkene insertion to generate 895, and / -elimination. Chloroformate will be a useful compound for the preparation of a, /3-unsaturated esters if its oxidative addition and alkene insertion are possible. An intramolecular version is known, namely homoallylic chloroformates are converted into a-methylene-7-butyrolactones in moderate yields[760]. As another example, the homoallylic chloroformamide 896 is converted into the q-methylene- -butyrolactams 897 and 898[761]. An intermolecular version of alkene insertion into acyl chlorides is known only with bridgehead acid chlorides. Adamantanecarbonyl chloride (899) reacts with acrylonitrile to give the unsaturated ketone 900[762],... 

Trimethylsilyl trichloroacetate, K2CO3, 18-crown-6, 100-150°, 1-2 h, 80-90% yield.This reagent silylates phenols, thiols, carboxylic acids, acetylenes, urethanes, and /3-keto esters, producing CO2 and chloroform as byproducts. 

Proton donors alcohols, carboxylic acids, phenols, and chloroform Proton acceptors amines, ethers, sulfoxides, amides, esters, and alcohols... 

The solvents most commonly employed are water, ethyl and methyl alcohol, ether, benzene, petroleum ether, acetone, glacial acetic acid also two or three solvents may be mixed to get the desired effect as described later. If you still cannot dissolve the compound, try some of these chloroform, carbon disulfide, carbon tetrachloride, ethyl acetate, pyridine, hydrochloric acid, sulfuric acid (acids are usually diluted first), nitrobenzene, aniline, phenol, dioxan, ethylene dichloride, di, tri, tetrachloroethylene, tetrachloroethane, dichloroethyl ether, cyclohexane, cyclohexanol, tetralin, decalin, triacetin, ethylene glycol and its esters and ethers, butyl alcohol, diacetone alcohol, ethyl lactate, isopropyl ether, etc. 

Alcohols and phenols can be attached to support-bound alcohol linkers as carbonates [467,665,666], although few examples of this have been reported. For the preparation of carbonates, the support-bound alcohol needs to be converted into a reactive carbonic acid derivative by reaction with phosgene or a synthetic equivalent thereof, e.g. disuccinimidyl carbonate [665], carbonyl diimidazole [157], or 4-nitrophenyl chloro-formate [467] (see Section 14.7). The best results are usually obtained with support-bound chloroformates. The resulting intermediate is then treated with an alcohol and a base (DIPEA, DMAP, or DBU), which furnishes the unsymmetrical carbonate. Carbonates are generally more resistant towards nucleophilic cleavage than esters, but are less stable than carbamates. Aryl carbonates are easily cleaved by nucleophiles and are therefore of limited utility as linkers for phenols. 

The use of these efficient reagents should usually be confined to the drying of amines (soda lime, barium oxide or calcium oxide may also be employed), potassium hydroxide is somewhat superior to the sodium compound. These bases react with many organic compounds (e.g. acids, phenols, esters and amides) in the presence of water, and with some common solvents (e.g. chloroform) so that their use as desiccants is very limited. 

Phenylis Salicylas, Phenyl Salicylate, Salol, C13H10O3, is the salicylic ester of phenyl, and occurs as a white, crystalline powder, odorless and almost tasteless, nearly insoluble in water, soluble in 10 parts alcohol, and very soluble in ether, chloroform, and oils. On warming with an alkali, it splits up into salicylic acid 60, and phenol 40, frequently repeated, in compressed tablets or in cachets, or suspended by mucilage of acacia or of tragacanth. 

The combined 0.1 N HCl fractions are adjusted to pH 9 with 1 N aqueous ammonia followed by reextraction of the alkaloids three times into chloroform, each time with one-half volume of chloroform. The combined chloroform layers are dried over Na2S04 and then evaporated to dryness at 30°C in vacuo with a water aspirator. Many of the dendrobatid alkaloids have appreciable volatility, and evaporation in vacuo must be done carefully. The resulting alkaloid residue is dissolved in methanol so that 100 (A corresponds to 100 mg of original wet weight of skin, then stored at -20°C in glass vials with Teflon-lined caps. This alkaloid fraction contains mainly alkaloids, but traces of fatty acid methyl esters, steroids, and environmental artifacts, such as phthalates and phenolic antioxidants, often are present as minor contaminants. 

SBSE can be successfully used in the analysis of environmental samples [93-97] and for food analysis [98, 99]. PDMS is the most commonly used polymer, primarily because of its thermal stability and durability. SBSE has been modified by application of derivatization with different reagents (acetic anhydride, BSTFA, etc) [100-104]. This approach is suitable for the extraction of compounds requiring derivatization. The use of multistep derivatization with several extraction elements (each reaction is performed on a different stir bar) allows efficient extraction, desorption, and chromatographic analysis of compounds with different functional groups (e.g., phenols, steroids, amines, thiazoles, ketones). Acetic anhydride (ester formation), ethyl chloroformate (reaction of acids and amines), tetraethyloborane, and sodium bis-trimethylotrifluoroacetamide have been used for extraction and simultaneous derivatization [105]. 

Phenol is liable to undergo extensive oxidation during nitration so that carefully controlled conditions are required it forms 40% o- and 13% p-nitrophenolA solvent like chloroform or acetic acid is recommended. The nitration of p-cresol is carried out in benzene and acetic acid solution at 0°, the product being 3-nitro-4-hydroxytoluene (77%). The nitration of ra-cresol is discussed under method 491. Benzene is oxidized and nitrated (oxynitration) to 2,4-dinitrophenoI (72%) or to picric acid (2,4,6-trinitrophenol) by the action of mercuric nitrate in nitric acid. Aromatic alcohols like / -phenylethanol are nitrated as the esters to avoid oxidation products... 

Active ester formation by the mixed anhydride method is accompanied by the side reaction of esterification at the carbonate moiety of mixed anhydride 51 which generates mixed carbonate 52 (Scheme 12).This decreases the yields, but is more of a nuisance than an obstacle as the side products do not interfere with crystallization of the esters as the former are soluble in the crystallizing solvent. More mixed carbonate is formed from derivatives of the hindered amino acids and proline none is formed from a-unsubstituted acids. A-Hy-droxysuccinimide gives rise to much less byproduct than 4-nitrophenol other phenols generate intermediate amounts. Less byproduct is generated when the reagent is isopropyl chloroformate. The impurity can be readily removed from a solution of the ester by adsorption of the compounds on reverse-phase chromatography beads followed by separation by selective displacement. ... 

None of these methods has achieved popularity, but a unique variant of the carbonates provides a general method that is simple and efficient. Mixed carbonates 58 formed from isopropenyl chloroformate and substituted phenols or hydroxylamines react at room temperature with N -protected acids 23 in the presence of A-methylmorpholinet or a catalytic amount of 4-(dimethylammo)pyridinet giving active esters 24 in exceptionally high yield (see Table 13) with conconnitant liberation of acetone (Scheme 14). Compounds prepared using the non-aromatic base require purification on a silica gel column. 

One of the early efforts at a systematic study of carbonyl systems in acid solvents has historical importance. Murty and Seshadri published a series of papers describing their Raman investigations of solutions of carbonyl compounds in various solvents (1471-1476). Among the carbonyl bases were esters, aldehydes, and carboxylic acids. The solvents included phenol, various alcohols, water, chloroform, ethers, and carbon tetrachloride. 

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