Chloride intermediate

Alkyltin Intermedia.tes, For the most part, organotin stabilizers are produced commercially from the respective alkyl tin chloride intermediates. There are several processes used to manufacture these intermediates. The desired ratio of monoalkyl tin trichloride to dialkyltin dichloride is generally achieved by a redistribution reaction involving a second-step reaction with stannic chloride (tin(IV) chloride). By far, the most easily synthesized alkyltin chloride intermediates are the methyltin chlorides because methyl chloride reacts directiy with tin metal in the presence of a catalyst to form dimethyl tin dichloride cleanly in high yields (21). Coaddition of stannic chloride to the reactor leads directiy to almost any desired mixture of mono- and dimethyl tin chloride intermediates ... 

The other commercially important routes to alkyltin chloride intermediates utilize an indirect method having a tetraalkjitin intermediate. Tetraalkyltins are made by transmetaHation of stannic chloride with a metal alkyl where the metal is typicaHy magnesium or aluminum. Subsequent redistribution reactions with additional stannic chloride yield the desired mixture of monoalkyl tin trichloride and dialkyltin dichloride. Both / -butjitin and / -octjitin intermediates are manufactured by one of these schemes. 

General Reaction Chemistry of Sulfonic Acids. Sulfonic acids may be used to produce sulfonic acid esters, which are derived from epoxides, olefins, alkynes, aHenes, and ketenes, as shown in Figure 1 (10). Sulfonic acids may be converted to sulfonamides via reaction with an amine in the presence of phosphoms oxychloride [10025-87-3] POCl (H)- Because sulfonic acids are generally not converted directiy to sulfonamides, the reaction most likely involves a sulfonyl chloride intermediate. Phosphoms pentachlotide [10026-13-8] and phosphoms pentabromide [7789-69-7] can be used to convert sulfonic acids to the corresponding sulfonyl haUdes (12,13). The conversion may also be accompHshed by continuous electrolysis of thiols or disulfides in the presence of aqueous HCl [7647-01-0] (14) or by direct sulfonation with chlorosulfuric acid. Sulfonyl fluorides are typically prepared by direct sulfonation with fluorosulfutic acid [7789-21-17, or by reaction of the sulfonic acid or sulfonate with fluorosulfutic acid. Halogenation of sulfonic acids, which avoids production of a sulfonyl haUde, can be achieved under oxidative halogenation conditions (15). 

Alcohol attack generates an unstable intermediate that undergoes nucleophilic attack by CL at carbon. Compare electrostatic potential maps of methanol, thionyl chloride intermediate, and phosphorus trichloride intermediate. What features of these maps are consistent with an electrophilic reactive intermediate ... 

The most efficient processes in Table I are for steel and alumintim, mainly because these metals are produced in large amounts, and much technological development has been lavished on them. Magnesium and titanium require chloride intermediates, decreasing their efficiencies of production lead, copper, and nickel require extra processing to remove unwanted impurities. Sulfide ores produce sulfur dioxide (SO2), a pollutant, which must be removed from smokestack gases. For example, in copper production the removal of SO, and its conversion to sulfuric acid adds up to 8(10) JA g of additional process energy consumption. In aluminum production disposal of waste ciyolite must be controlled because of possible fiuoride contamination. 

Hydrocarbonylation. The hydrocarbonylation reaction can be applied to the synthesis of a-arylpropanoic acids of the NSAIDS type.239 For this synthesis to be effective, selective carbonylation of the more-substituted sp2 carbon is required. Although many carbonylation conditions are unselective, PdCl2(PPh3)2 with /2-toluenesulfonic acid and LiCl achieves excellent selectivity. The selectivity is thought to involve the formation of a benzylic chloride intermediate. 

Plasma processes have been successfully demonstrated for production of metals from their oxides and chlorides intermediates. Reducing agents are, of course, to be used. Thus, a plasma-based process involving reduction of tantalum chloride in hydrogenous atmosphere has been claimed to yield highly pure metal powder suitable for making of porous capacitor of high capacitance. 

When the flowsheet is complex and involves numerous process steps, a low-energy efficiency will result. The metals titanium and magnesium are difficult to reduce, and their production involves chloride intermediates which are produced from the oxide raw materials. Titanium requires magnesium or sodium as the reducing agent, and these metals are themselves obtained by electrolytic processes which are energy-intensive. Another feature which may add to the complexity of the process flowsheet is the need to separate impurities and by-products using special processes this is the case with copper, lead, and nickel. 

The mechanism of the formation of compound 67 has been studied by Higa and Krubsack [41] in detail, as shown in Scheme 15. Namely, the initial step of the reaction of the cinnamic acid derivative 66 with thionyl chloride is an electrophilic addition of thionyl chloride across the double bond of cin-namoyl chloride to form the sulfinyl chloride intermediate (66a), which is then converted to 68 by the Pummerer reaction. Dehydrochlorination of 68... 

FIGURE 4.62 Oxidative dehalogenation of halothane to form areactive acid chloride intermediate and structures of other anesthetics that can form similar reactive metabolites. 

Reactions of chiral silanes with chiral aldehydes exhibit matching and mismatching characteristics (Eqs. 9.56 and 9.57) [48]. The additions proceed through an acyclic transition state, which favors syn adducts. The matched (M)/(R) pairing of Eq. 9.56 proceeds by way of a favorable Felkin-Anh arrangement to afford the syn,syn homopropargylic alcohol product. However, if the silanes possess an a-hydrogen, a vinylic chloride intermediate is formed, as shown in Scheme 9.13. Subsequent treat-... 

Reaction of the transient zinc intermediates with various electrophiles yielded the acetylenic substitution products and only minor amounts of allenes (Table 9.49). Reactions with aldehydes were non-selective, affording mixtures of stereo- and regioisomeric adducts. However, prior addition of ZnCl2 resulted in the formation of the homopropargylic alcohol adducts with high preference for the anti adduct, as would be expected for an allenylzinc chloride intermediate (Table 9.50). 

The use of DMF to accelerate the formation of acid chlorides from carboxylic acids has been reviewed previously,4 and is believed to occur via an imidoyl chloride intermediate.5... 

In contrast to oxidative dechlorination, the hydrolytic dechlorination of chloramphenicol replaces a Cl-atom with a OH group to yield a (monochlo-ro)hydroxyacetamido intermediate. The latter, like the dichloro analogue, also eliminates HC1, but the product is an aldehyde that is far less reactive than the oxamoyl chloride intermediate. Chloramphenicol-aldehyde undergoes the usual biotransformation of aldehydes, namely reduction to the primary alcohol 11.41 and dehydrogenation to the oxamic acid derivative 11.40 (Fig. 11.7). 

There are many heterocyclic molecules in which 1,3,4-thiadiazoles are fused to other ring systems. For example, Molina et al. developed a procedure for building a thiadiazole ring on to a properly substituted imidazole moiety (Scheme 29). Reaction of l-amino-2-methylthio-4-phenylimidazole (161) with triphenylphosphine dibromide in dry benzene furnished the 2-methylthio-4-phenyl-l-triphenylphosphoranylidenamino imidazole (162) in a 95% yield. With aroyl chlorides at elevated temperature, this gave the 2-aryl-6-phenylimidazo[2,l-Z ][l,3,4]thiadiazoles (164) in yields between 50% and 70% via the imidoyl chloride intermediate (163) which could be isolated and shown to cyclize to the thiadiazole. The method developed for the imidazole ring was also applicable to the thiadiazolotriazine ring system <88H(27)1935). 

Mitotane, or o,p -DDD, is an oral medication used in the treatment of adrenocortical carcinoma. Chemically it is an isomere of DDT. Following its metabolism in the adrenal cortex to a reactive acyl chloride intermediate, mitotane covalently binds to adrenal proteins, specitically inhibiting adrenal cortical hormone production. The drug accumulates in fat tissue. It is eliminated mainly by the kidneys with a half-life of 18-159 days. Common side effects include anorexia, nausea, lethargy, sleepiness and skin problems. 

In the thiomaltose series the same approach was used for the synthesis of 4,4 -dithiomaltotriosides (48a,48b) (Scheme 16) [43]. However the sequence of reactions is much longer since the chloride intermediate (46) was formed in 83% yield only when the peracetylated 4-thiomaltose (45) was used, and the 1,4-dithiomaltose peracetate (47b) was obtained via the corresponding S-benz-oyl analogue (47 a). Under these conditions the 4,4 -dithiomaltotriosides were obtained in 20% overall yield from the 4-thio-)3-maltose peracetates (45). 

Electrophilic cyclodimerization (to 26) also results when (25) is subjected to Bischler-Napieralski conditions (POCI3, reflux), presumably through reaction of pyrazole with the imino chloride intermediate (78JHC1339). 

Stabilizer Synthesis. The selected alkyltin chloride intermediate reacts with either a carboxylic acid or a mercaptan in the presence of an appropriate base, such as sodium hydroxide, to yield the alkyltin carboxylate or alkyltin mercaptide heat stabilizer. Alternatively, the alkyltin chloride can react with the base to yield the alkyltin oxide, which may or may not be isolated, for subsequent condensation with the selected carboxylic acid or mercaptan. 

Aromatic acid chlorides are decarbonylated to aryl chlorides when they are heated to 300-360 C with palladium on carbon. The reaction proceeds by way of an aroylpalladium chloride, then to an arylpalla-dium chloride and finally through a reductive elimination to the aryl chloride. If the reaction is conducted in the presence of a reactive alkene under mild conditions the aroylpalladium chloride intermediate will sometimes acylate the alkene, as noted in Section 4.3.5.3.I. More usually, however, decarboxylation is more rapid than acylation, especially at higher temperatures (>100 C), and decarbonylation occurs. The... 

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