Reaction with butyl bromide

If the group R is a hydroxyalkyl group - phosphonate polyols are obtained. One example is the transformation of tris (dipropylene glycol) phosphite in phosphonate polyol, at 160-180 °C, by the following reactions with butyl bromide [5] (reaction 18.25 with a catalytic quantity of butylbromide). 

In the absence of strongly polar co-solvents 2-lithiothiophene displays moderate reactivity in alkylations and the reactions have to be carried out at elevated temperatures in the region of 50 °C. Careful control of the temperature is therefore not necessary if the reaction is carried out on a modest scale. The reactivity of 2-lithiothiophene in alkylations can be enhanced enormously by addition of a small amount of HMPT (5-10vol.%) in this case the reaction with butyl bromide proceeds smoothly at 20 °C and is complete within 15 minutes. The organometallic derivative can also be rendered more reactive by adding an equivalent amount of /-BuOK dissolved in THF. Subsequent reaction with butyl bromide proceeds smoothly at —10 to 0 °C. The procedure below can also be applied to prepare other non-volatile alkylthiophenes. We expect secondary alkyl halides to react much less easily dehydrohalogenation may be an important side-reaction, or even the dominant process. 

In many cases the more easily and more cheaply available open-chain S,S-acetals, such as H2C(SCH3)2 and H2C(SC2H5)2, can be used as starting compounds instead of 1,3-dithianes. We found that the abstractions of a methylene proton from 1,3-dithiane and H2C(SCH3)2 or H2C(SC2Hs)2 by BuLi and the subsequent reactions with butyl bromide proceeded with comparable rates. Differences arise, however, when the alkyl derivatives have to belithiated. Whereas the lithiation of 2-alkyl-1,3-dithianes by BuLi seems to proceed cleanly [1], the open-chain derivatives... 

Functionalization reactions with butyl bromide and trimethylchlorosilane (bis-silylation). 

For the reaction of butyl bromide with tin, to give BuaSnBr and BugSnBrg (approximately equimolar), tetrabutylammonium iodide was found to be the best catalyst, and the mechanism was proposed (41) to be as follows. 

An alternative approach to reduce the levels of impurity (VII) would be to have a "transient" existence of the lithio species, so that it reacts instantaneously with trialkyl borate to form the aryl boronate, prior to being quenched by any extraneous proton source to form (VII). Thus, the preparation of boronic acid (II) was improved by changing the order of the reagents. The slow addition of n-butvl lithium also controls the exotherm of the reaction. There was no reaction observed between n-butyl lithium and triisopropyl borate (to form any butyl boronic acid), nor was there any formation of 2-butyl derivative of (VII) formed by reaction between butyl bromide and the lithio species. The reaction is veiy fast and as soon as the addition of n-butyl lithium is completed the reaction is finished. This indicates a rapid transmetallation and instantaneous boronation of the lithio species. The reaction is very much a... 

Introduction of an ester (Scheme 19) was achieved by reaction of the free OH-2 with tert-butyl bromoacetate in DMF in the presence of K2C03 in 72% yield. From which the corresponding free acid 73 was obtained in quantitative yield. Propargylation of OH-2 was also performed by reaction with propargyl bromide in the presence of NaH which led to diynes 74 and... 

In an extension of this work, the reuse of the polymeric catalyst was addressed and several new PE-poly(alkene) glycol copolymers were prepared [68]. Commercially available oxidized polyethylene (CO2H terminated, both high and low molecular weight) was converted to the acid chloride and reacted with Jeffamine D or Jeffamine EDR, and subsequently converted to the tributylammonium bromide salt with butyl bromide. These new quaternary salts were shown to catalyze the nucleophihc substitution of 1,6-dibromohexane with sodium cyanide or sodium iodide. While none of the polymeric quaternary salts catalyzed the reaction as well as tetrabutylammonium bromide, the temperature-dependent solubility of the polymers allowed removal of the polymer by simple filtration. 

Figure 6. SEC profiles of PI-6-PS-6-PI triblock copolymer chains end-capped with butyl bromide group (SI44) before and after the coupling reaction in n-hexane, with the self-assembly as well as in THF without the self-assembly.

The rate of alkylation of enolate ions is strongly dependent on the solvent in which the reaction is carried out.43 The relative rates of reaction of the sodium enolate of diethyl M-butylmalonatc with -butyl bromide are shown in Table 1.2. 

The hydrotalcite-1ike material catalyzes organic reactions in which the interlayer Cl" anions play the role of catalyst. The material catalyzed the halide-exchange reactions between benzyl chloride with butyl bromide or butyl iodide in toluene. The hydrota1cite-1ike material also catalyzes a disproportionation of trimethoxysilane to give silane and tetramethoxysilane. 

Sn2 reactions provide an interesting example of the utility of electrostatic potential maps in rationalizing an experimental result, while challenging conventional wisdom . It is well established that a nucleophile such as bromide reacts much faster with methyl bromide than it does with ter/ -butyl bromide. The reason normally cited is that while the transition state for the Sn2 reaction with methyl bromide is uncrowded , that for the corresponding reaction with tert-hutyl bromide is sterically crowded . However, this interpretation does... 

The mechanochemical reactions of aluminum were investigated under two reaction conditions, namely, during and after the milling. The active source may be different in the two reactions. However, high temperature, high pressure, and nascent surface appeared not to be active factors in this case, because preactivated aluminum was observed to react with butyl bromide even after the termination of milling. 

In the meantime, the reactivity of milled aluminum correlated well with the intensity of exoelectron emission. Such an emission decayed with time after termination of milling, along with the suppression of the chemical reaction. The aluminum, which had entirely lost electron emission activity, did not react with butyl bromide at all. Alkyl halides capture free electrons. The emission intensity of the free (unused) electrons under butyl bromide atmosphere was less than 20% of that under benzene atmosphere. In other words, exoelectrons are captured with butyl bromide more easily than with benzene. Butyl bromide has much stronger electron affinity than benzene. 

One equivalent of NaOEt in EtOH deprotonates diethyl malonate completely to give the sodium enolate A (Figure 13.36). This enolate is monoalkylated upon addition of an alkylating reagent such as BuBr, and a substituted malonic ester C is formed. During the alkylation reaction, the substituted malonic ester C reacts to a certain extent with some of the enolate A, resulting in the butylated enolate B and unsubstituted neutral malonic ester. It is for this reason that the reaction mixture contains two nucleophiles—the original enolate A and the butylated enolate B. The alkylation of A with butyl bromide is much faster than that of B, since A is less sterically hindered than B. The main product is therefore the product of monoalkylation. Distillation can be used to separate the main product from small amounts of the product of dialkylation. 

Butylation of ethyl phenylacetate, /-butyl phenylacetate, and ethyl 2-phenylhexanoate has also been accomplished with -butyl bromide and sodium hydride in refluxing monoglyme in 64%, 66%, and 56% yields, respectively.6 In contrast to the sodium amide reactions above, however, careful fractionation of the crude products was required to obtain pure products. 

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