Neopentyl halides preparation

The possibility that R-0 fission may occur in advance of attack by halide ion has been demonstrated in the reactions of dineopentyl phenyl phosphite or neopentyl diphenyl phosphite with alkyl halides. In these cases the Michaelis-Arbuzov intermediates cannot be isolated but the neopentyl halides which are formed are contaminated with varying amounts of rearrangement product (t-pentyl halide) (Table IV). These results may explain the formation of mixtures of isomeric halides (9,10,11) in certain applications of Rydon s method for alkyl halide preparation (12). S i fission of the R-0 bond appears to be encouraged by the electron-attracting effect of phenoxy-substituents (Figure 3). 

Preparation of Phosphines from Metallated Phosphines. - Alkali metal-free phosphide anions have been shown to be formed under synthetically useful conditions in the equilibria between primary or secondary phosphines with the Schwesinger bases (23). Techniques have been developed for the preparation of alkali metal diphenylphosphide reagents in high purity, as evidenced by P nmr studies. The same paper reports a study of the course of the reactions between potassium diphenylphosphide and a series of aryl-, n-alkyl- and neopentyl-halides. The results provide the first evidence of the involvement of single electron transfer (SET) processes in the reactions of alkyl halides. This pathway is dominant in the case of neopentyl-type iodides, but plays only a minor role in the related reactions of neopentyl-type bromides and chlorides. No evidence was adduced of the involvement of SET processes in the reactions of unhindered... 

Thioethers (sulfides) can be prepared by treatment of alkyl halides with salts of thiols (thiolate ions).7S2 R may be alkyl or aryl. As in 0-35, RX cannot be a tertiary halide, and sulfuric and sulfonic esters can be used instead of halides. As in the Williamson reaction (0-12), yields are improved by phase-transfer catalysis.753 Instead of RS ions, thiols themselves can be used, if the reaction is run in benzene in the presence of DBU (p. 1023).754 Neopentyl bromide was converted to Me3CCH2SPh in good yield by treatment with PhS in liquid NH3 at -33°C under the influence of light.755 This probably takes place by an SrnI mechanism (see p. 648). Vinylic sulfides can be prepared by treating vinylic bromides with PhS in the presence of a nickel complex,756 and with R3SnPh in the presence of Pd(PPh3)4.757 R can be tertiary if an alcohol is the substrate, e.g,758... 

New quasiphosphonium halides derived from neopentyl diphenyl-phosphinite and dineopentyl phenylphosphonite are reported and it is shown that the attachment of phenyl groups to phosphorus provides enhanced stability. The products, Ph2P(0R)MeX (X = Cl, Br, or I) and PhP(0R)2MeX (X = Br or I) (R = Me3CCH2), are resistant to moist air and can be handled in the open laboratory for the purpose of X-ray diffraction studies (1). The rate of initial reaction between the ester and an alkyl halide increases with the number of phenyl substituents on phosphorus from the diphenyl-phosphinite an adduct with chloromethane can be prepared. 

The cyclization in Step B is an improvement of Butler s procedure for the synthesis of which employs less convenient reagents, KNH and l-bromo-3-chloroacetone acetal. Beside the acetals derived from neopentyl glycol, those derived from ethanol, 1,3-propanediol and 2,4-pentanediol have been synthesized by the present method. The second part of Step B involves the formation and the electrophilic trapping of cyclopropenyl anion 2, which is the key element of the present preparations. Step B provides a simple route to substituted cyclopropenones, but the reaction is limited to alkylation with alkyl halides. The use of lithiated and zincated cyclopropenone acetal, on the other hand, is more general and permits the reaction with a variety of electrophiles alkyl, aryl and vinyl halides, Me3SiCl, Bu3SnCl, aldehydes, ketones, and epoxides. Repetition of the lithiation/alkylation sequence provides disubstituted cyclopropenone acetals. 

Fairly bulky alkyl substituents such as neopentyl and (trimethylsilyl)methyl are also introduced by this method (equation 2) . Unsymmetrical compounds have also been prepared from the appropriate halide and Grignard reagents. For example the synthesis of and 2 has been reported (equations 3 and 4). 

Hudson, H. R., Kow, A., Roberts, J. C. Quasiphosphonium intermediates. Part 3. Preparation, structure, and reactivity of alkoxyphosphonium halides in the reactions of neopentyl diphenylphosphinite, dineopentyl phenylphosphonite, and trineopentyl phosphite with halomethanes and the effect of phenoxy-substituents on the mechanism of alkyl-oxygen fission in Michaelis-Arbuzov reactions. J. Chem. Soc., Perkin Trans. 2 1983, 1363-1368. 

Treatment of lV-methanesulfonyl-l,4-dihydFopyridine with n-butyllithium, followed by benzyl bromide, leads to the corresponding lV-l-(2-phenylethyl)sulfonyl-l,4-dihydropyridine in low yield. The sulfonamide shown in Scheme 131 (entry c) has proved a valuable c -isoprenoid synthon which allows the two-step C -homologation of allyl halides. This synthon was used for the remarkable two-step stereoselective synthesis of nerol from 3-methyl-2-butenyl chloride (Scheme 131, entry c). Finally, the a-chloro dicarbanion of 4-(a-chlon>methanesulfonyl)morpholine is readily availabl on reaction with 2 equiv. of n-butyllithium in THF, and it leads to the corresponding dimethyl derivative with no detectable monoalkylated product or starting sulfonamide on methylation. Intramolecular versions of these reactions allow the low yield synthesis of neopentyl cyclopropanesulfonate (scheme 131, entry d) and the efficient preparation of cyclopropanesulfomorpholine (scheme 131, entry e). ... 

Michaelis and Kaehne isolated a product with saltlike properties from the reaction of triphenyl phosphite and methyl iodide. This observation has been confirmed by Arbuzov and Sazonova (30) and by Landauer and Rydon (206,284), who used this salt as a reagent for the preparation, in excellent yields, of alkyl halides, including neopentyl iodide, from the corresponding alcohols. The course of this reaction... 

Highly syndiotactic polypropylene was prepared by Natta and co-Workers with homogeneous catalysts formed from VCU or from vanadium triacetylacetonate, aluminum dialkyl halide, and anisole at -48 to -7 8 °C. No isotactic fractions formed. This led to the development of many effective soluble catalysts. The catalyst components and the conditions for their preparation are quite important in maintaining control over syndiotactic placement. For the most effective soluble catalyst the ratio of AIR2X to the vanadium compound must be maintained between 3 and 10. The organic portion of the organoaluminum compound can be either methyl, ethyl, isobutyl, neopentyl, phenyl, or methylstyryl. " In addition to VCI4 and to vanadium triacetylacetonate, various other vanadates can be used, like [ VO(OR)/ l3 c], where x = 1,2, or 3 The exact nature of the vanadium... 

Syntheses of dialkylthallium halides with bulky alkyl groups such as trimethyl-silylmethyl and neopentyl have been described, these compounds are dimeric. (Acyloxy)arylthallium compoimds have been prepared from organotin compounds, reactions (40), (41). ... 

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