Chloroformates reactions

Azoles containing a free NH group react comparatively readily with acyl halides. N-Acyl-pyrazoles, -imidazoles, etc. can be prepared by reaction sequences of either type (66) -> (67) or type (70)->(71) or (72). Such reactions have been carried out with benzoyl halides, sulfonyl halides, isocyanates, isothiocyanates and chloroformates. Reactions occur under Schotten-Baumann conditions or in inert solvents. When two isomeric products could result, only the thermodynamically stable one is usually obtained because the acylation reactions are reversible and the products interconvert readily. Thus benzotriazole forms 1-acyl derivatives (99) which preserve the Kekule resonance of the benzene ring and are therefore more stable than the isomeric 2-acyl derivatives. Acylation of pyrazoles also usually gives the more stable isomer as the sole product (66AHCi6)347). The imidazole-catalyzed hydrolysis of esters can be classified as an electrophilic attack on the multiply bonded imidazole nitrogen. 

The mixture was heated to reflux for 24 hours. The chloroformic reaction mixture was washed with water, and then dried over anhydrous sodium sulfate. The chloroform was evaporated off and the oil obtained was fractionally distilled under a pressure of 0.2 mm Hg. The fraction distilling at 140°C to 160°C, being the desired product indicated above, was collected and crystallized. Yield 94 g (32% of theory) MP 7B°C (after recrystallization in petroleum ether). 

An early method developed for the assay of detergents based upon the sodium salts of the higher homologues of the alkanesulphonic acids,21 involved treatment of an aqueous solution of the detergent with methylene blue in the presence of chloroform. Reaction takes place between the ionic dyestuff (which is a chloride) and the detergent ... 

The cyclobutanone (255) reacted with acid to furnish the keto-acid (259). Upon esterification, ketalization and reduction, (259) was converted to the alcohol (260). Mesylation of the alcohol (260) and then treatment of the mesylate with NaN3 in DMSO provided the azide (261). The azide (261) was then transformed to the urethane (262) by reduction and ethyl chloroformate reaction. The urethane (262) was deketalized by acid, nitrosated by N204—NaOAc and decomposed by NaOEt—EtOH to give the ketone (263) 89). The ketone (263) served as a starting material for the synthesis of veatchine (264)90). 

An extremely mild method for the synthesis of nitrate esters from easily oxidized or acid-sensitive alcohols involves the decomposition of a nitratocarbonate (29). The nitratocar-bonate is prepared in situ from metathesis between a chloroformate (reaction between phosgene and an alcohol) and silver nitrate in acetonitrile in the presence of pyridine at room temperature. Under these conditions the nitratocarbonate readily decomposes to yield the corresponding nitrate ester and carbon dioxide. Few examples of these reactions are available in the literature and they are limited to a laboratory scale. 

For nonquantitative -C-NMR techniques, this could be the extent of the analysis possible. However, the combination of F-NMR with C-NMR allowed us to quantitatively calculate the isomer composition and to investigate solvent effects on isomer formation. Figure 17.5 illustrates these concepts. Two possible isomers (structures in Figure 17.5) can be formed from the reaction of 3-fluorophthalic anhydride with 4-fluoroaniline. Upon formation of the amic acid based on 3-fluorophthalic anhydride with 4-fluoroaniline, two isomers were found in both NMP and chloroform reactions as shown by the F-NMR spectra in Figure 17.5a and b, respectively. Two signals were observed for each type of fluorine atom, labeled as Fi and F2 for the anhydride and amine fluorine atoms respectively. Ortho and meta isomers were formed in a ratio of 4.75 1 in solution in NMP, while the same ratio was 1.04 1 in chloroform, where the product precipitated. The major isomer was the ortho in each case as determined by C-NMR of the chloroform prepared amic acid (Table 17.1). 

Synthesis (Kleemann et al. 1999, Janssen (Janssen), 1973 Janssen et al. (Janssen), 1973, Stokbroekx et al., 1973, Niemegeers et al., 1974) ) Treatment of 2-oxo-3,3-diphenyl-tetrahydrofuran, synthesized by treatment of diphenyl-acetic acid ethyl ester with ethylene oxide, with HBr(gas) yields bromo derivative i, which is then converted into butyryl chloride derivative ii by means of thionyl chloride in refluxing chloroform. Reaction of derivative ii with dimethylamine in toluene affords dimethyl (tetrahydro-3,3-diphenyl-2-furylidene)ammonium bromide, which is then condensed with 4-(4-chlorophenyl)-4-piperidinol by means of Na2C03 and Kl in refluxing 4-methyl-2-pentanone to provide loperamide. 

Azoles containing a free NH group react comparatively readily with acyl halides. yV-Acyl-pyrazoles, -imidazoles, etc. can be prepared by reaction sequences of either type (75) — (76) or type (79)—>(80) or (81). Such reactions have been carried out with benzoyl halides, sulfonyl halides, isocyanates, isothiocyanates and chloroformates. Reactions occur under Schotten-Baumann conditions or in inert solvents. 

There are several types of chiral derivatizing reagents commonly used depending on the functional group involved. For amines, the formation of an amide from reaction with an acyl halide [147,148], chloroformate reaction to form a carbamate [149], and reaction with isocyanate to form the corresponding urea are common reactions [150]. Carboxyl groups can be effectively esterified with chiral alcohols [151-153]. Isocynates have been used as reagents for enantiomer separation of amino acids, iV-methylamino acids, and 3-hydroxy acids [154]. In addition to the above-mentioned reactions, many others have been used in the formation of derivatives for use on a variety of packed and capillary columns. For a more comprehensive list, refer to References 155-159. 

With an amino acid-derived chiral auxiliary employed in the chloroformate, reaction of silyl enol ethers with isoquinolinium salts showed not only regiospecificity, but some stereoselectivity as well (Equation 61) <1999SL1154>. The addition of ketene silyl acetals to an W-acylpyridinium salt containing a chiral 2,2-dimethylox-azolidine at C-3 gave 1,4-dihydropyridines with excellent stereoselectivity <2002JA8184>. 

Chitin hydrogels, partially deacetylated, degradation, 182-184 Chloroformates, reaction with polysaccharides, 191,193-195... 

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]. 

Chloroform Reactions.—This ready giving up of its chlorine is also shown by the reactions of chloroform with alkalies, with ammonia and with amines. With alkalies chloroform yields salts of formic acid. This reaction consists in a replacement of all of the chlorine by hydroxyl yielding a tri-hydroxy methane. As we have previously discussed. 

Phenol Chloroform (]) Reaction with formaldehyde. Discussed in Sec. 32.7. 

When lithium aluminum hydride was applied, besides reduction of the C-4—N-5 double bond, the ester group was converted to a hydroxymethyl group. S By reaction with dry formic acid under reflux conditions, the pyrroloquinazoline-2-carboxylates 63 yielded the 6-formyl-5,6-dihydro derivatives 65. S The formyl group was transformed into a methyl group by diborane. S The NH group of the dihydro derivatives 64 was acylated by ethyl chloroformate. Reaction with ethyl acrylate and acrylonitrile involved a Michael addition.The ethoxycarbonyl moiety in position 2 and on the side chain in position 6 was hydrolyzed to a carboxylic group by the action of potassium hydroxide in aqueous methanol and was reduced to a hydroxymethyl group by lithium aluminum hydride in ether. 

Cyclopropyl-2,3-dihydro-17f-benzo[/ ][l,5]diazepin-2-ones 2, obtained in one step from 1,2-phenylenediamines 1, give allylic bromides 3 when treated with A-bromosuccinimide in refluxing chloroform. Reaction with Af-chlorosuccinimide under the same conditions resulted in chlorination at C3 without attack of the cyclopropane. ... 

These cannot be elementary. The fractions are usually 1/2 or 3/2 and indicate a radical chain reaction. An example is the bromination of trichloromethane (chloroform reaction 2.18) the kinetic expression is given by equation (2.19). 

Chloroform, reaction with 1-octene to give l,l,3-trichloro- -nonane, 45, 104... 

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