Heptyl bromide, reaction

Worked Example 8.18 Consider the reaction between pyridine and heptyl bromide, to make 1-heptylpyridinium bromide. It is an equilibrium reaction with an equilibrium constant K = 40. What is the rate constant of back reaction k if the value of the forward rate constant k = 2.4 x 103 dm3 mol 1 s ... 

For the preparation of heptyl /7-nitrophenyl ether, potassium />-nitrophenoxide (20 g) was boiled under reflux, with rapid stirring, with heptyl bromide (25 g) and cyclopentanone (60 g). Formation of a thick slurry of potassium bromide began in 30 min and the reaction was complete in 2.5 h. After cooling, the mixture was taken up in ether, shaken with sodium hydroxide solution, and worked up as usual. The ether was formed in 89 % yield. Most of the cyclopentanone is recovered. 

Gowenlock and co-workers have shown that the n-heptyl bromide/ sodium reaction leads to cyclohexane [115] whereas the perfluoroheptyl iodide/sodium system does not lead to perfluorocyclohexane [116]. 

Reaction of the ArC,o unit with 1-pentynylmagnesium bromide occurred smoothly in tetrahyrofuran containing cuprous chloride without formation of alienic impurities. An analogous type of route was used for the synthesis of 1,3-dimethoxy-5-[(ZZ)-pentadec-8,11-dienyl]benzene, (15 2)-cardol dimethyl ether (ref. 105). For the synthesis of (15 2)-urushiol, 1,2-dihydroxy-3-[(ZZ)-penta-dec-8.11-dienyl]benzene and its dimethyl ether, 7-(2,3-dimethoxyphenyl)heptyl bromide and the corresponding 2,3-dihydroxy compound, obtained by demethylation with boron tribromide, have been used (ref. 149). 

Methyl iodide has been used as a mercaptan-blocking group in studies on keratin fibers [87]. Other monofunctional alkyl halides, including benzyl chloride, heptyl bromide, and dodecyl bromide, have also been reacted with reduced keratin fibers [8]. Hall and Wolfram [88] have used this reaction... 

Preparation by reaction of heptyl bromide with 5-allyl-2,4-dihydroxyacetophenone in the presence of potassium carbonate and potassium iodide in refluxing methyl ethyl ketone (77%) [2671], (40%) [2678,2679]. 

It is liquid-liquid reactions involving phase transfer catalysts which generally benefit from the use of ultrasound. Sonication produces homogenisation - i. e. very fine emulsions - which greatly increase the reactive interfacial area and allows faster reaction at lower temperatures. Davidson has reported an example of this with the ultrasonically enhanced saponification of wool waxes by aqueous sodium hydroxide using tetra n-heptyl ammonium bromide as a PTC [124]. 

The submitters have also prepared 5,5-dimethyl-2-heptyl-tetrahydrofuran (n 1.4360) by a similar dehydration of 2-methyl-2,5-undecanediol obtained from the reaction of methyl-magnesium bromide and 7-undecanoic lactone. 

Phase-transfer agents are the most popular catalysts for the Halex reaction with alkaline fluorides. All types of transfer agents have been claimed tetraalkyl-ammonium halides (refs. 34, 48), Aliquat 336 (ref. 49), branched pyridinium halides (eventually supported on a polymer) (refs. 50 to 53), tetraalkylphosphonium chlorides (refs. 42, 54 - 57) or bromides (ref. 12), crown-ethers (refs. 58, 59) eventually associated with Ph4PBr (refs. 43, 60), tris-(dioxa-3,6-heptyl)amine (TDA-1) (ref. 61) or polyethyleneglycols (PEG) (ref. 62). 

Attempts to extend this methodology to a-sulfinyl derivatives of other esters have been only moderately successful. As shown in Scheme 14, ester (215) may be deprotonated by r-butylmagnesium bromide and added to aldehydes, although not to ketones. The intermediate P-hydroxy-a-sulfinyl esters, in each case a mixture of diastereomers, are reduced to obtain diastereomeric mixtures of -hydroxy esters. The diastereomeric ratio of these materials does not reveal the degree of asymmetric induction in the original aldol reactions, because of the unknown stereochemistry of the desulf urization step. Aldols (216) were converted by a three-step process into secondary alcohols (217), which were found to have isomeric purities of 33.5% enantiomeric excess for R = Ph and 80% enantiomeric excess for R = n-heptyl. 

The stereoselectivity of the reaction of 1 -alkynylzinc bromides 130 (R == heptyl or Ph) with various chiral a-benzyloxy aldehydes 131 (R = Me, /-Pr or PhCH20CH2) to yield the alcohols 132 depends on the nature of the substituents R and R Regiospecific propargylation with acylsilanes is exemplified by the reaction of the organozinc bromide 133 (from 2-octynyl bromide and zinc dust in THF) with benzoyltrimethylsilane, followed by desilylation, to yield only the alcohol 134 . 

Acyl cyanides are versatile synthetic intermediates and are generally prepared by the reaction of acid chlorides, acid bromides, and occasionally acid anhydrides with metal cyanides. It has now been found that the very reactive acyl iodides, used either preformed or generated in situ, are useful substrates for the preparation of ap-unsaturated and other acyl cyanides. Aryl acyl cyanides are obtained from the flash vacuum pyrolysis of 3-azido-l,2,4-oxadiazoles, and ethoxalyl cyanide from the reaction of di-n-heptyl sulphide with 2,3-dicyano-oxiran-2,3-dicarboxylate. The chemistry of acyl cyanides has been reviewed. ... 

Alkylation of pyrrole magnesium bromide and chloride with y-chloro-butyronitrile gives 2- and 3-cyanopropylpyrrole (2 >3). The isomer distribution is similar to those observed in reactions with butyl chloride, heptyl chloride and 8-methoxybutyl chloride. It is concluded that the constitution of pyrrole magnesium chloride is the same in tetrahydrofuran as in ether s. 

---