Bases Sodium methoxide

For the synthesis of phlhaloeyanines with some special central metals (c.g., silicon), phthalonitriles are not sufficiently reactive. Using the respective isoindolinediimine which shows a higher reactivity may be of advantage. The isoindolinediimine derivative can be prepared by treating the phthalonitrile with gaseous ammonia and a catalytic amount of a base (sodium methoxide) in methanol. 

OS 77] [R 4b] ]P 57] The migration of the base, sodium methoxide, was enhanced by electrophoretic force [12], This led to faster mixing than by diffusion only. As a consequence, the conversion rate was increased. 

Dehydrohalogenation of this compound can be accomplished under E2 conditions by treatment with base. Sodium methoxide in methanol would be appropriate, for example, although almost any alkoxide could be employed to dehydrohalogenate this tertiary bromide. 

Note that the deprotonation of the strong acid nitromethane (pKa = 10) is accomplished using the relatively weak base sodium methoxide (NaOMe). 

Octamethylnaphthalene. The definitive paper on the preparation of octamethyl-naphthalene (2, 168, ref. 11b) has now been published. The conversion of (3) to (4) with dimsylsodium is essentially quantitative. Isobutyric acid has been identified as a second product. Use of other bases (sodium methoxide in methanol, sodium hydride) was unsuccessful. 

But orientation in E2 elimination is not always Saytzeff, particularly when compounds other than alkyl halides are involved. To see the various factors at work here, let us take, as a simple example, elimination from the 2-hexyl halides brought about by the strong base sodium methoxide. The iodide, bromide, and... 

Organometallic or mixed halide-organometallic diketonates of Si, Ge, Sn, Pb, Ti, Zr, Sb can be synthesized in the presence of base (sodium methoxide, pyridine, triethylamine, ammonia) (Equations (15) and (16)) ... 

Access to key materials for synthesis in this group has been possible for some years by reaction of acrolein with 2-methyl-3-pentanone in presence of p-toluenesulfonic acid, distilling off the water formed during the reaction, and leading to 2,6,6-trimethyl-2-cyclohexenone (690). Alternatively, 2-methyl-3-pentanone reacts with methyl acrylate in the presence of base (sodium methoxide/ methanol in xylene) to give 92% of the diketone 691 (probably as the enol). ... 

Synthesis of polycyclic compounds. 2,2 -Bisbramomethyldiphenyl (1) reacts with 1 mole of triphenylphosphine to give the phosphonium salt (2), which is converted into the ylide (3) on treatment with base (sodium methoxide). The ylide (3) is not isolated but undergoes intramolecular C-alkylation to form the phosphonium salt (4). This salt on treatment with phenyllithium gives the ylide (5). This ylide is readily transformed into phenanthrene or 9-substituted phenanthrenes.3... 

Athene synthesis. A new synthesis of alkenes involves treatment of dilithium ethynylbis(trialkylborates) (1) with cyanogen bromide and a base (sodium methoxide). If cyanogen bromide and sodium methoxide are used in equimolecu-lar amounts, franr-alkenes (2) are formed mainly. When 3 eq. of cyanogen bromide and 1 eq. of base are used, tri- and tetrasubstituted alkenes, (3) and (4), are formed. 

Finally, we can expect to find an ever-increasing consumption of sodium in the preparation of strong bases. Sodium methoxide has been rather extensively used in a variety of base-catalyzed reactions, especially in the pharmaceutical field. There are a number of reactions for which a stronger base is required. Sodium hydride and sodamide, both intrinsically cheap, should find many applications here. Even the somewhat more expensive sodium borohydride is expected to become popular as a cheaper replacement for the familiar lithium aluminum hydride. 

Oxiranes (1, 315-316). The original method of Corey has been modified to provide a one-pot process. Dimethylsulfoniikm methylide is prepared in situ by reaction of dimethyl sulfide with dimethyl sulfate in CH3CN followed by addition of base (sodium methoxide). Addition, of the carbonyl compound leads to the oxirane and dimethyl sulfide, which can t e recycled (equation I). Yields are generally higher than those obtained by the original method. 

A recent innovation is the use of the 2-(a-pyridyl)ethyl function as a protecting group. It is stable even to 2N-sodium hydroxide or concentrated ammonia, conditions under v ich carboxylic acid esters are readily cleaved [7], and, in this respect, offers an advantage over the /3-cyanoethyl group. A strong base, sodium methoxide, is required for its removal. 

The conjugate bases listed m Table 1 7 that are anions are commonly encountered as their sodium or potassium salts Thus sodium methoxide (NaOCH3) for example is a source of methoxide ion (CH30 ) which is the conjugate base of methanol... 

Similarly sodium methoxide (NaOCHj) is a suitable base and is used m methyl alco hoi Potassium hydroxide m ethyl alcohol is another base-solvent combination often employed m the dehydrohalogenation of alkyl halides Potassium tert butoxide [K0C(CH3)3] is the preferred base when the alkyl halide is primary it is used m either tert butyl alcohol or dimethyl sulfoxide as solvent... 

Again, the basic catalyst is typically sodium methoxide, although other bases such as phenoxides (8) and basic anion-exchange resias (9) have also been used. The reaction usiag sodium methoxide is performed at 4.9 MPa (48 atm) and 120°C (10). 

An acidimetric quantitative determination is based on treatment of the hydantoia with silver nitrate and pyridine ia aqueous solution. Complexation of the silver ion at N-3 Hberates a proton, and the pyridinium ions thus formed are titrated usiag phenolphthaleia as an iadicator. In a different approach, the acidity of N-3—H is direcdy determined by neutralization with tetrabutylammonium hydroxide or sodium methoxide ia dimethylformarnide. 

The reactions of trialkylboranes with bromine and iodine are gready accelerated by bases. The use of sodium methoxide in methanol gives good yields of the corresponding alkyl bromides or iodides. AH three primary alkyl groups are utilized in the bromination reaction and only two in the iodination reaction. Secondary groups are less reactive and the yields are lower. Both Br and I reactions proceed with predominant inversion of configuration thus, for example, tri( X(9-2-norbomyl)borane yields >75% endo product (237,238). In contrast, the dark reaction of bromine with tri( X(9-2-norbomyl)borane yields cleanly X(9-2-norbomyl bromide (239). Consequentiy, the dark bromination complements the base-induced bromination. 

The Guerbet reaction can be used to obtain higher alcohols 2-propyl-1-heptanol [10042-59-8] from 1-pentanol condensation and 6-methyl-4-nonanol from 2-pentanol (80—83). Condensations with alkah phenolates as the base, instead of copper catalyst, produce lower amounts of carboxyhc acids and requke lower reaction temperatures (82,83). The crossed Guerbet reaction of 1-pentanol with methanol in the presence of sodium methoxide catalyst afforded 2-heptanol in selectivities of about 75% (84). 

The DAG conversion to L-ascorbic acid also can occur by a base-catalyzed mechanism. Methyl 2-oxo-L-gulonate (methyl DAG) is converted, on treatment with sodium methoxide, to sodium-L-ascorbate, which is then acidified to L-ascorbic acid. Various solvent systems have been evaluated and reported (46). 

Strong bases such as methan olic potassium hydroxide, sodium methoxide, or 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU), cause epimerization at the C-2 carbon or shift the beta-gamma double bond into conjugation with the lactone carbonyl (Fig. 4) (25,26). 

In theory two carbanions, (189) and (190), can be formed by deprotonation of 3,5-dimethylisoxazole with a strong base. On the basis of MINDO/2 calculations for these two carbanions, the heat of formation of (189) is calculated to be about 33 kJ moF smaller than that of (190), and the carbanion (189) is thermodynamically more stable than the carbanion (190). The calculation is supported by the deuterium exchange reaction of 3,5-dimethylisoxazole with sodium methoxide in deuterated methanol. The rate of deuterium exchange of the 5-methyl protons is about 280 times faster than that of the 3-methyl protons (AAF = 13.0 kJ moF at room temperature) and its activation energy is about 121 kJ moF These results indicate that the methyl groups of 3,5-dimethylisoxazole are much less reactive than the methyl group of 2-methylpyridine and 2-methylquinoline, whose activation energies under the same reaction conditions were reported to be 105 and 88 kJ moF respectively (79H(12)1343). 

After the initial claim of the synthesis of an oxirene (by the oxidation of propyne Section 5.05.6.3.1) this system reappeared with the claim 31LA(490)20l) that 2-chloro-l,2-diphenyl-ethanone (110) reacted with sodium methoxide to give diphenyloxirene (111), but it was later shown (52JA2082) that the product was the prosaic methoxy ketone (112 Scheme 97) (the formation of 111 from 110 would be an a-elimination carbene-type reaction). Even with strong, nonnucleophilic bases, (110) failed to provide evidence of diphenyloxirene formation (64JA4866). 

Either acid or base catalysis may be employed. Alkaline catalysts such as caustic soda or sodium methoxide give more rapid alcoholysis. With alkaline catalysts, increasing catalyst concentration, usually less than 1% in the case of sodium methoxide, will result in decreasing residual acetate content and this phenomenon is used as a method of controlling the degree of alcoholysis. Variations in reaction time provide only a secondary means of controlling the reaction. At 60°C the reaction may takes less than an hour but at 20°C complete hydrolysis may take up to 8 hours. 

Methyldihydrostrychnidinium-A acetate is produced in much small amount in the hydrogenation ( internal alkylation) reaction and w isolated as the iodide, m.p. 345-350°, and converted to the chloric which on treatment with sodium methoxide gave methoxymethyltetr hydrostrychnidine (c in the above list) with some des-base-D, and < thermal decomposition yielded dihydrostrychnidine-A. These and oth reactions of des-base-D are regarded as best accounted for by formu (XVIII). ... 

Both des-bases yield mono- and di-metho-salts, and the latter ( digestion with sodium methoxide in methyl alcohol give the better yiel... 

A variety of conditions has been used to prepare oxiranes from trans-hxomo-hydrins. In general, bromohydrins are heated in a solution of 5-10% methanolic potassium hydroxide for 30 min to 8 hr. Longer reflux times are required for bromohydrins which are not anti-coplanar, e.g., diequatorial bromohydrins. A 5 % solution of potassium acetate in boiling ethanol can be used to cyclize steroidal bromohydrins containing base sensitive groups. The use of 1.1 equivalents of sodium methoxide per equivalent of steroid in methanol solution is especially recommended for 9a-bromo-l lj5-hydroxy steroids. 

The bases most commonly used to effect rearrangement are hydroxides, alkoxides, alcoholic sodium bicarbonate and, in some instances, amines. In the rearrangement of a series of l,l-dibromo-2-keto-alkanes, where a direct comparison has been made between triethylamine and sodium methoxide, the amine has given slightly better results ... 

Miller et al. [9] hypothesized rules on the regioselectivity of addition from the study of the base-catalyzed addition of alcohols to chlorotnfluoroethylene. Attack occurs at the vinylic carbon with most fluorines. Thus, isomers of dichloro-hexafl uorobutene react with methanol and phenol to give the corresponding saturated and vinylic ethers The nucleophiles exclusively attack position 3 of 1,1-dichloro-l,2,3,4,4,4-hexafluoro-2-butene and position I of 4,4-dichloro-l,l,2,3,3,4-hexafluoro-1-butene [10]. In I, l-dichloro-2,3,3,4,4,4-hexafluoro-l-butene, attack on position 2 is favored [J/] (equation 5) Terminal fluoroolefms are almost invariably attacked at tbe difluoromethylene group, as illustrated by the reaction of sodium methoxide with perfluoro-1-heptene in methanol [/2J (equation 6). 

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