Dialkyl lead chloride

Waste waters containing low concentrations of soluble organic lead in the presence of high concentrations of other diverse ions such as Cl pose a particularly difficult treatment problem. Generally, organic lead exists in solution as the tri- or dialkyl lead chloride species. These salts are not amenable to the conventional methods used to remove inorganic lead, viz., those of pH adjustment followed by settling. The technique of chemical conversion of the... 

Trialkyl-lead hydrides and dialkyl-lead dihydrides were made by reducing the corresponding chlorides with lithium aluminium hydride at low temperature (- 78°)36p 37.38,... 

Inefficiencies ia the reaction with POCl leads to alternative production of trialkyl phosphates by employing the sodium alkoxide rather than the alkyl alcohol itself Dialkyl aryl phosphates are produced ia two steps. The low molecular weight alcohol iavolved (eg, butyl) first reacts with excess POCl. The neutral phosphate ester is then completed by the iatermediate chloridate reacting with excess sodium arylate ia water. 

Acylation of norephedrine (56) with the acid chloride from benzoylglycolic acid leads to the amide (57), Reduction with lithium aluminum hydride serves both to reduce the amide to the amine and to remove the protecting group by reduction (58), Cyclization by means of sulfuric acid (probably via the benzylic carbonium ion) affords phenmetrazine (59), In a related process, alkylation of ephedrine itself (60) with ethylene oxide gives the diol, 61, (The secondary nature of the amine in 60 eliminates the complication of dialkylation and thus the need to go through the amide.) Cyclization as above affords phendimetra-zine (62), - Both these agents show activity related to the parent acyclic molecule that is, the agents are CNS stimulants... 

As a result of alkylation LAB is obtained with a clearly changed composition in comparison with the use of chloroparaffin. With respect to the dialkyl-tetralin content, values are obtained which are comparable to LAB from the HF alkylation process (same olefin base) (Table 11). Another important difference is the 2-phenylalkane content. The isomer distribution depends on the catalyst. The reaction between straight /z-chloroparaffins or n-olefins with benzene in the presence of aluminum chloride leads to the same isomer distribution. In both cases the 2-phenylalkane content is predominant compared to the 3-, 4-, and 5-phenylalkanes. If hydrogen fluoride is used as catalyst the 2-phenylalkane... 

Mikolajczyk and coworkers have summarized other methods which lead to the desired sulfmate esters These are asymmetric oxidation of sulfenamides, kinetic resolution of racemic sulfmates in transesterification with chiral alcohols, kinetic resolution of racemic sulfinates upon treatment with chiral Grignard reagents, optical resolution via cyclodextrin complexes, and esterification of sulfinyl chlorides with chiral alcohols in the presence of optically active amines. None of these methods is very satisfactory since the esters produced are of low enantiomeric purity. However, the reaction of dialkyl sulfites (33) with t-butylmagnesium chloride in the presence of quinine gave the corresponding methyl, ethyl, n-propyl, isopropyl and n-butyl 2,2-dimethylpropane-l-yl sulfinates (34) of 43 to 73% enantiomeric purity in 50 to 84% yield. This made available sulfinate esters for the synthesis of t-butyl sulfoxides (35). 

Compounds 118 could be produced from the reaction of dialkyl esters of 3-monosubstituted-l,2-alkadienephosphonic acids with methylselenenyl chloride. It was established that, along with 118, 2,3-adducts were also formed [113]. Use of phenylsulphenyl chloride in this reaction leads exclusively to the formation of 2,5-dihydro- l,2-oxaphosphole-2-oxide derivatives 117 (Scheme 48) [113, 114]. 

The reaction of dialkyl esters of 1,2-alkadienylphosphonic and phosphinic acids with methyl and phenylsulphenyl chloride, leads exclusively to 2,5-dihydro-l,2-oxaphosphole-2-oxide derivatives [113-115],... 

A resonance-stabilized lithium salt generated from a y-substituted a,P-unsaturated carboxylate derivative has been found to undergo displacement of chloride from dialkyl chlorophosphites leading (on oxidation) to the formation of P-keto-8-carboxyphosphonates (Equation 4.2 7).71... 

Sulfenyl chlorides and halogens react with 1,2-alkadienylphosphonic acids to afford phosphorus-containing heterocydes [72], However, the electrophilic addition of dialkyl 4-methyl-2,3,5-hexatrien-2-yl phosphonates with sulfenyl or selenyl chloride afforded 2-thienyl methylphosphonates or the seleno analogues [73, 74]. The conjugate addition of sulfenyl or selenyl chloride with the 2,4-diene moiety in the starting allene leads to the formation of the five-membered skeleton (Scheme 10.69). 

Guanidines have been prepared by the reaction between an amine, or an amine salt, and a host of other reagents, such as a thiourea in the presence of lead or mercuric oxide [83, 157, 158], carbodi-imides [140, 174, 175],calcium cyanamide [176, 177], isonitrile dichlorides [178—180], chloroformamidines [181], dialkyl imidocarbonates [182], orthocarbonate esters [183], trichloro-methanesulphenyl chloride [184], and nitro- or nitroso-guanidines [185-188]. Substituted ureas can furnish guanidines, either by treatment with amines and phosphorus oxychloride [189], or by reaction with phenylisocyanate [190] or phosgene [191]. 

The action of 1% methanolic hydrogen chloride on 1,2-O-iso-propylidene -3,5-di - O - p-tolylsulfonyl-D-xylofuranose (65) leads,81 after boiling for three hours under reflux, to 2,5-anhydro-3-0-p-tolylsulfonyl-D-xylose dimethyl acetal (66). The structure of 66 was demonstrated by conversion into the disulfonate 67 this was prepared independently from a 2,5-anhydro-D-xylose dialkyl dithio-acetal72 (48) by p-toluenesulfonylation followed by exchange of the acetal group in methanol in the presence of mercury salts. 

Dialkyl dithioacetal derivatives of ketoses, such as D-fiuctose and L-sorbose, me inaccessible directly from the parent sugars, the ketose undergoing extensive decomposition under the conditions employed for mercaptaladon of aldoses. Such derivatives can, however, be prepared by indirect methods. Acetylation of D-fiuctose [40] and L-soibose with acetic adiydride and zinc chloride [41] leads to good yields of acyclic pentaacetates in which foe ketose carbonyl is not involved in a cyclic acetal. Subsequent treatment of these acetylated derivatives with thiols affords foe acetylated dialkyl dithioacetals in satisfactory yields, and conventional deacetylation affords foe unprotected dialkyl dithioacetals [40,41]... 

Peroxide may also be removed by shaking with an aqueous solution of sodium sulphite or with solid tin(n) chloride (see 11. Propan-2-ol) or by passage through a column of alumina. It is worthy of note that all dialkyl ethers have a tendency to form explosive peroxides and they should be routinely tested before further purification leading to a final distillation process is attempted. 

Although systematic investigations are lacking, alkyl chlorides or alkyl bromides and tellurium do not lead to isolable dialkyl tellurium dihalides. Cyclohcxyl bromide and tellurium reacted at 160°, but dicyclohexyl tellurium dibromide could not be isolated from the reaction mixture4. However, when the reaction was carried out in the presence of an amine, dimethylformamide, or dimethyl sulfoxide, adducts of dicyclohexyl tellurium dibromide were obtained in approximately 50% yield4. 

Olefinic esters may be obtained directly by the Knoevenagel reaction. Alkyl hydrogen malonates are used in place of malonic acid. Decarboxylation then gives the ester directly as in the preparation of ethyl 2-heptenoate (78%) and methyl m-nitrocinnamate (87%). Alkyl hydrogen malonates are readily available by partial hydrolysis of dialkyl malonates. The use of malonic ester in the condensation leads to olefinic diesters, namely, alkylidenemalonates such as ethyl heptylidenemalonate (68%). A small amount of organic acid is added to the amine catalyst since the salts rather than the free amines have been shown to be the catalysts in condensations of this type. Various catalysts have been studied in the preparation of diethyl methylenemalonate. Increased yields are obtained in the presence of copper salts. Trimethylacetalde-hyde and malonic ester are condensed by acetic anhydride and zinc chloride. Acetic anhydride is also used for the condensation of furfural and malonic ester to furfurylidenemalonic ester (82%). ... 

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