Dialkyl-, preparation reactions

Slightly unconventional modifications have been applied, occasionally with advantage, to otherwise conventional preparative reactions. Thus, the Michael-Becker reaction between dibromomethane and sodium dialkyl phosphites in solvents containing liquid ammonia is aided by exposure of the reaction mixtures to ultraviolet radiation. Dialkyl arylphosphonates are obtained in very high yield from the reaction between trialkyl phosphites and aromatic hydrocarbons when carried out in the presence of trisodium phosphate in an electrochemical system (see Organophosphorus Chemistry , Vol. 12, p. 105). The bond between phosphorus and aromatic carbon is also formed when aryl halides react with the P(0)H function in the presence of a combination of tetrakis-... 

Oehler, R., Zimmermatm, V., and Jager, G., Preparation of Zinc Dialkyl Dithiophosphates. Reaction and Reaction Products, Erdoel Kohle, Erdgas, Petrochemie, Vol. 40, No. 2,1987, p. 87. 

Dialkylative cyclization reactions have been used to prepare bridged, spiro, and fused bicyclic sulfoienes. Reaction of 3-alkyl- and 3-chloro-3-sulfolenes (124a-d) with 1,3-diiodopropane, in the presence of 2 equivalents of base, initially furnishes intermediate anion (125). Intramolecular alkylation then takes place either at the a-position to deliver the bridged product (126) or at the y-position for the fused bicycle (127) [25] (Scheme 6.37). 

Ando et at, found the photochemical reaction to be the most useful method to date for the preparation of sulphoniumcyclopentadienylides (7) from diazocyclopentadiene and a variety of dialkyl sulphides. Reaction with di-t-butyl sulphide afforded a mixture of sulphides, which probably resulted from rearrangements of an initially formed ylide (8). With allyl ethyl sulphide, diazocyclopentadiene gave a 13% yield of the addition product (9) and a 31% yield of a product (10) resulting from initial ylide formation... 

Triethyl phosphite is a colourless mobile liquid, insoluble in water. Trialkyl phosphites are valuable intermediates in the preparation of many organophosphorus compounds they readily form dialkyl esters of alkylphosphonic acids by the Arbusov reaction (p. 311). 

Formation of esters of inorganic acids (Section 15 9) Alkyl nitrates dialkyl sulfates trialkyl phos phites and trialkyl phosphates are examples of alkyl esters of inor game acids In some cases these compounds are prepared by the direct reaction of an alcohol and the inorganic acid... 

In the preparation of hydroperoxides from hydrogen peroxide, dialkyl peroxides usually form as by-products from the alkylation of the hydroperoxide in the reaction mixture. The reactivity of the substrate (olefin or RX) with hydrogen peroxide is the principal restriction in the process. If elevated temperatures or strongly acidic or strongly basic conditions are required, extensive decomposition of the hydrogen peroxide and the hydroperoxide can occur. 

Synthesis. Dialkyl peroxides are prepared by the reaction of various substrates with hydrogen peroxide, hydroperoxides, or oxygen (69). They also have been obtained from reactions with other organic peroxides. For example, dialkyl peroxides have been prepared by the reaction of hydrogen peroxide and alkyl hydroperoxides with alMating agents, eg, RX and olefins (33,66,97) (eqs. 24—27). 

DiaLkyl peroxides may be prepared by reaction of alcohols or alkyl trifluoromethanesulfonates with organomineral peroxides of siUcon, tin, and germanium (44,108), where Q = Sn and Ge ... 

Such copolymers of oxygen have been prepared from styrene, a-methylstyrene, indene, ketenes, butadiene, isoprene, l,l-diphen5iethylene, methyl methacrjiate, methyl acrylate, acrylonitrile, and vinyl chloride (44,66,109). 1,3-Dienes, such as butadiene, yield randomly distributed 1,2- and 1,4-copolymers. Oxygen pressure and olefin stmcture are important factors in these reactions for example, other products, eg, carbonyl compounds, epoxides, etc, can form at low oxygen pressures. Polymers possessing dialkyl peroxide moieties in the polymer backbone have also been prepared by base-catalyzed condensations of di(hydroxy-/ f2 -alkyl) peroxides with dibasic acid chlorides or bis(chloroformates) (110). 

Thermally unstable cycHc trioxides, 1,2,3-trioxolanes or primary o2onides are prepared by reaction of olefins with o2one (64) (see Ozone). Dialkyl trioxides, ROOOR, have been obtained by coupling of alkoxy radicals, RO , with alkylperoxy radicals, ROO , at low temperatures. DiaLkyl trioxides are unstable above —30° C (63). Dialkyl tetraoxides, ROOOOR, have been similarly produced by coupling of two alkylperoxy radicals, ROO , at low temperatures. Dialkyl tetraoxides are unstable above —80°C (63). 

An important use of dialkyl succinates is in the preparation of dialkyl succinyl succinates (35,53—56), which are intermediates in the manufacture of quinacridone pigments. The reaction is carried out in the presence of alkaU metal alkoxides (eq. 2). 

Diorgano Sulfites. Symmetrical or mixed dialkyl sulfites ate prepared by the stepwise reaction of thionyl chloride either with two molecules of an alcohol or with stoichiometric quantities of two alcohols in pyridine (105). 

Heating the adduct of ethylene oxide and sulfur dioxide with primary alcohols in the presence of alkaH hydhdes or a transition-metal haHde yields dialkyl sulfites (107). Another method for the preparation of methyl alkyl sulfites consists of the reaction of diazomethane with alcohoHc solutions of sulfur dioxide (108). 

R Tl compounds, eg, methyl [3003-15-4], ethyl [687-82-1], isobutyl [3016-08-8], and phenyl [3003-04-1] thaHium(III), are usuaHy prepared by the reaction between a dialkyl or diarylthaHium haHde and an organolithium reagent in ether (16) ... 

Complexes of titanium, such as 2,6-(RNCH2)2NC H2TiCl2, prepared by reaction of TiCl with 2,6((CH2)3Si)RNCH2)2NC H2, can react with various Grignard reagents to prepare conformationady rigid diamide mono- and dialkyl titanate complexes (218,219). 

Where X is Br or Q, the free acids may be obtained by acidification of the alkaline solution, but where X is I, the acids must be isolated as salts to avoid reduction of the arsonic acids by HI. Rather than using alkyl haUdes, alkyl or dialkyl sulfates or alkyl arenesulfonates can be used. Primary alkyl haUdes react rapidly and smoothly, secondary haUdes react only slowly, whereas tertiary haUdes do not give arsonic acids. AHyl haUdes undergo the Meyer reaction, but vinyl hahdes do not. Substituted alkyl haUdes can be used eg, ethylene chlorohydrin gives 2-hydroxyethylarsonic acid [65423-87-2], C2H2ASO4. Arsinic acids, R2AsO(OH), are also readily prepared by substituting an alkaU metal arsonite, RAs(OM)2, for sodium arsenite ... 

A number of compounds of the types RBiY2 or R2BiY, where Y is an anionic group other than halogen, have been prepared by the reaction of a dihalo- or halobismuthine with a lithium, sodium, potassium, ammonium, silver, or lead alkoxide (120,121), amide (122,123), a2ide (124,125), carboxylate (121,126), cyanide (125,127), dithiocarbamate (128,129), mercaptide (130,131), nitrate (108), phenoxide (120), selenocyanate (125), silanolate (132), thiocyanate (125,127), or xanthate (133). Dialkyl- and diaryUialobismuthines can also be readily converted to secondary bismuthides by treatment with an alkali metal (50,105,134) ... 

A large number of pyridazines are synthetically available from [44-2] cycloaddition reactions. In one general method, azo or diazo compounds are used as dienophiles, and a second approach is based on the reaction between 1,2,4,5-tetrazines and various unsaturated compounds. The most useful azo dienophile is a dialkyl azodicarboxylate which reacts with appropriate dienes to give reduced pyridazines and cinnolines (Scheme 89). With highly substituted dienes the normal cycloaddition reaction is prevented, and, if the ethylenic group in styrenes is substituted with aryl groups, indoles are formed preferentially. The cycloadduct with 2,3-pentadienal acetal is a tetrahydropyridazine derivative which has been used for the preparation of 2,5-diamino-2,5-dideoxyribose (80LA1307). 

Carbon-sulfur bonds can be formed by the reaction of elemental sulfur with a lithio derivative, as illustrated by the preparation of thiophene-2-thiol (201) (700S(50)104). If dialkyl or diaryl disulfides are used as reagents to introduce sulfur, then alkyl or aryl sulfides are formed sulfinic acids are available by reaction of lithium derivatives with sulfur dioxide. 

For the characterization of 1,3-dialkyl-diaziridines, derivatives can be prepared with phenyl isocyanate. The reaction products (47) are... 

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