Methyl chloroformate, hydrolysis

Hudson et a/.151,152 have concluded that the bimolecular solvolysis of ethyl chloroformate involves heterolysis of the carbon-chlorine bond and not heterolysis of the carbon-oxygen bond. Their data shows that the hydrolysis of ethyl chloroformate is a second-order reaction in water/acetone mixtures, methyl chloroformate reacting about 2.2 times as fast in 65% water/acetone at 50°C. Hydroxide ion accelerates the reaction (3.1 x 107 in 18% water/ acetone and 3.4 x 108 in 85% water/acetone) and catalysis by hydroxide ion was observed with pure water as solvent by Hall118. There is some disagreement about the value for the hydrolysis rate coefficient for ethyl chloroformate in water and in other solvents (Table 21). To date, the data of Queen153 (for pure water), Kivinen92 (for ethanol) and Liemiu101 (for methanol) must be considered the most accurate. 

As with most of the synthetic polysaccharides, complete methylation189 of the polyxylose was difficult. The fully methylated polymer was soluble in petroleum ether (30-60°) containing 6% of chloroform. Hydrolysis of the methylated xylan gave tri-, di-, and mono-O-methyl-D-xyloses, together with D-xylose, in the molar ratio of 31 33 19 5. The tri-O-methyl-D-xylose fraction contained 38% of 2,3,5-tri-O-methyl-D-xylose, the remainder being the 2,3,4-trimethyl ether. The dimethyl ethers included the 2,5-,... 

The dioxole 658 gave, after treatment with f-BuLi in THF at —78 °C, the related reagent 65 9857,969 (Scheme 172). This anion reacts with aldehydes and ketones to give adducts 660 which, after acidic hydrolysis, gave enols of a-oxo aldehydes 66 1969, reacting also with methyl chloroformate to yield the ester 662857. 

Reduction of pyridine with zinc dust in acetic anhydride gave a mixture of dihydro compounds 141a and 177 (see below), which were converted into 4,4 -bipyridyl by oxidative hydrolysis.193 4-Substituted pyridines gave the bipyridyl (142 R = i-Pr, <-Bu) by similar reduction in methyl chloroformate.104... 

Measurements of methyl chloroform or 1,1,1-trichloroethane (CH3CCI3) showed that this compound was significantly unsaturated in the equatorial Pacific Ocean (Butler et al., 1991). Loss rates were supported roughly by known hydrolysis rates and the authors calculated that —6% of atmospheric CH3CCI3 is removed by consumption in the oceans. With this exception, most of the chlorofluorocarbons were originally thought to be stable in the water column. 

The second Matsuo synthesis (233) was initiated with methyl 3-(2,2-dimethoxyethyl)-4-methyl-4-pentenoate (357) prepared (234) from carvone (239). Hydrolysis with lithium hydroxide followed by iodolactonization (I2-KI-NaHC03) and reduction with tri-n-butyl tin hydride in the presence of azobisisobutyronitrile in benzene under reflux afforded 358. The carbo-methoxy group was introduced with methyl chloroformate and LDA in quantitative yield, and reductive animation of 359 with methylamine and sodium cyanoborohydride gave the lactone 360. Heating of 360 with 10% Pd/C in decalin gave cerpegin (118) in 81% yield (Scheme 42) (233). 

More recently, a strategy based on the reaction of l,2-anhydro-3,4 5,6-di-O-isopropylidene-D-mannitol (74) with the lithiated silyl dithioacetal has been reported [87]. As a result, the alcohol 75 was formed which under acylation with methyl chloroformate furnished carbonate 76 (Scheme 19), converted further to the lactone 77. Direct transformation of dithioacetal 77 into the corresponding ketone failed, despite the different methods used [88]. It succeeded in two steps procedure, involving its conversion into dimethylketal, followed by hydrolysis [89], to afford 78, being the known precursor of KDO [90]. 

ORIGIN/INDUSTRY SOURCES/USES not a natural product formed by the anaerobic biodegradation of trichloroethylene and by the hydrolysis of 1,1,1-trichloroethane manufacturer of polyvinylidene copolymers and methyl chloroform flexible films for food packing (Saran and Velon wraps) flame retardant coatings for fiber and carpet backing in pipes coating for steel pipes adhesive applications... 

The anhydrous compound is not appreciably hygroscopic, is readily soluble in acetone and amyl alcohol, and insoluble in benzene, toluene, xylene and chloroform it is also readily soluble in absolute methyl or ethyl alcohol, but a trace of water causes immediate hydrolysis with the formation of an opalescent precipitate. 

Of the alkyl esters, methyl esters are the most useful because of their rapid hydrolysis. The acid is refluxed with one or two equivalents of methanol in excess alcohol-free chloroform (or dichloromethane) containing about O.lg of p-toluenesulfonic acid (as catalyst), using a Dean-Stark apparatus. (The water formed by the... 

Trimethylsilyl l//-azepine-f-carboxylate (4), prepared in 71 % yield by treating methyl 17/-azepine-1 -carboxylate with iodotrimethylsilane in chloroform at 20°C, with methanol in pentane solution at — 78 °C undergoes slow hydrolysis to the bright-yellow 17/-azepine-l-carboxylic acid (5),9 which is also obtained, as the potassium salt, by the action of potassium /ert-butoxide on ethyl 17/-azepine-l-carboxylate.139 The acid is stable at —78°C for several days but in chloroform solution at 20 °C undergoes decarboxylation to 17/-azepine (6) accompanied by some decomposition. 17/-Azepine is stable for a few hours at — 78 C and has been characterized by 3H and l3CNMR spectroscopy. 

The method is very useful for the synthesis of physiologically interesting a-mcthylamino acids, e.g., methyl dopa from the 3,4-dimethoxybenzyl derivative. The excellent stereoselection achieved in the process, however, is caused by the preferential crystallization of one pure diastereomerfrom the equilibrium mixture formed in the reversible Strecker reaction. Thus, the pure diastcrcomers with benzyl substituents, dissolved in chloroform or acetonitrile, give equilibrium mixtures of both diastereomers in a ratio of about 7 347. This effect has also been found for other s-methylamino nitriles of quite different structure49. If the amino nitrile (R1 = Bn) is synthesized in acetonitrile solution, the diastereomers do not crystallize while immediate hydrolysis indicates a ratio of the diastereomeric amino nitriles (S)I(R) of 86 1447. 

Alkyl esters are efficiently dealkylated to trimethylsilyl esters with high concentrations of iodotrimethylsilane either in chloroform or sulfolane solutions at 25-80° or without solvent at 100-110°.Hydrolysis of the trimethylsilyl esters serves to release the carboxylic acid. Amines may be recovered from O-methyl, O-ethyl, and O-benzyl carbamates after reaction with iodotrimethylsilane in chloroform or sulfolane at 50—60° and subsequent methanolysis. The conversion of dimethyl, diethyl, and ethylene acetals and ketals to the parent aldehydes and ketones under aprotic conditions has been accomplished with this reagent. The reactions of alcohols (or the corresponding trimethylsilyl ethers) and aldehydes with iodotrimethylsilane give alkyl iodides and a-iodosilyl ethers,respectively. lodomethyl methyl ether is obtained from cleavage of dimethoxymethane with iodotrimethylsilane. 

In this series, too, replacement of the N-methyl by a group such as cyclopropylmethyl leads to a compound with reduced abuse potential by virtue of mixed agonist-antagonist action. To accomplish this, reduction of 24 followed by reaction with tertiary butylmagnesium chloride gives the tertiary carbinol 27. The N-methyl group is then removed by the classic von Braun procedure. Thus, reaction with cyanogen bromide leads to the N-cyano derivative (28) hydrolysis affords the secondary amine 29. (One of the more efficient demethylation procedures, such as reaction with ethyl chloroformate would presumably be used today.) Acylation with cyclopropylcarbonyl chloride then leads to the amide 30. Reduction with lithium aluminum hydride (31) followed by demethylation of the phenolic ether affords buprenorphine (32).9... 

A large number of polyfructosans that have been reported from time to time by different authors have been investigated by Schlubach and his associates. In order to obtain polysaccharides of constant optical rotation, 100 to 300 precipitations from aqueous solution by the addition of alcohol were necessary. Fifty to 150 precipitations from chloroform solution with petroleum ether were required for purification of the acetate derivatives. These were methylated according to the procedure of Haworth and Straight,24 and upon hydrolysis partially methylated fructoses were obtained. 

Methylation was carried out according to the procedure of Haworth and Streight.24 Trimethylphlein has m. p. 172°, [o ]d20 = — 57.7° (c = 1.0, chloroform), average molecular weight 3280. Upon hydrolysis, 1,3,4-trimethyl-D-fructose resulted accompanied by a small amount of dimethyl-D-fructose which could be accounted for by the slightly low... 

Schlubach, Knoop and Liu85 investigated the structure of irisin by hydrolysis of the methylated polysaccharide. The acetyl derivative was converted to methylirisin by one treatment with dimethyl sulfate and sodium hydroxide in acetone solution. It was obtained as a white powder having [a]D20 = — 63.2° (c = 2.14, chloroform), m. p. 188-190°. 

It has been mentioned that the mixture of trimethyl-D-fructoses from the acid hydrolysis of hexamethyl-di-D-fructose anhydride III, which are now known to be the 3,4,6- and 1,4,6-trimethyl-D-fructoses, shows a specific rotation near that of pure 3,4,6-trimethyl-D-fructose it is to be inferred accordingly that these two trimethyl-D-fructoses do not differ greatly in rotation. Montgomery76 has synthesized 1,4,6-tri-methyl-D-fructose and found its rotation in chloroform to be [a] d = + 29.7°, a value approximating that of 3,4,6-trimethyl-D-fructose (+ 27.7° in the same solvent). Pertinent also are the respective rotations of the acetone condensation products from these two trimethyl-D-fructoses. Montgomery found that 3,4,6-trimethyl-D-fructose under-... 

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