2-Bromobutane preparation

Dialkylation of acetylene with 1-bromobutane, prepared in part (/), gives the necessary ten-carbon chain. 

Write a series of equations showing how to prepare cis 5 decene from acetylene and 1 bromobutane as the source of all its carbons using any nec essary organic or inorganic reagents Hint You may find it helpful to review Sec tion 9 6)... 

The sample solution to Problem 17.16(a) showed the preparation of 3-methyl-3-heptene by a Wittig reaction involving the ylide shown. Write equations showing the formation of this ylide beginning with 2-bromobutane. 

This reaction sequence is called the acetoacetic ester synthesis. It is a standard procedure for the preparation of ketones from alkyl halides, as the conversion of 1-bromobutane to 2-heptanone illustrates. 

In the first systematic study on nucleophilic substitutions of chiral halides by Group IV metal anions, Jensen and Davis showed that (S )-2-bromobutane is converted to the (R)-2-triphenylmetal product with predominant inversion at the carbon center (Table 5)37. Replacement of the phenyl substituents by alkyl groups was possible through sequential brominolysis and reaction of the derived stannyl bromides with a Grignard reagent (equation 16). Subsequently, Pereyre and coworkers employed the foregoing Grignard sequence to prepare several trialkyl(s-butyl)stannanes (equation 17)38. They also developed an alternative synthesis of more hindered trialkyl derivatives (equation 18). 

Sodium amide, in alkylation, of di-pbenylmetliane, 48, 80 of ethyl phenylacetate with (2-bromoethyl)benzene, 47, 72 in condensation of 2,4-pentanedione and 1-bromobutane to give 2,4-nonanedione, 47, 92 preparation of, 48, 80 Sodium 2-aminobenzenesulfinate, from reduction of 2-nitrobenzenesul-finic acid, 47, 5... 

Prepd from.. .. A short note on how 1-bromobutane has been prepared, and references to the original literature (journals). 

The Bouveault reaction is the preparation of an aldehyde by a one pot reaction between an organic halide and lithium metal in dimethylformamide. Ultrasound has been found to markedly enhance this reaction when it is performed in tetrahydrofuran [93]. Use of an ultrasonic bath at 10-20 °C affords short reaction times of between 5 and 15 min and generates yields in the range 70-88%. Using this methodology the conversion of 1-bromobutane to pentanal (88%) can be achieved in only 5 minutes. This must be contrasted with the yield of less than 10 % which is obtained under the normal stirred conditions in the same time period. This result confirms that the effect of irradiation goes beyond mere agitation (Eq. 3.11). 

Exercise 23-24 Show how a mixture of amines prepared from 1-bromobutane and an excess of butanamine may be resolved into its components by reaction with the anhydride of 1,4-butanedioic acid, (CH2)2(CO)20, separation of the products through advantage of their solubility properties in acid or base, and regeneration of the corresponding amines (Section 18-10C). Write equations for the reactions involved. 

Cognate preparations. s-Butyl bromide (2-bromobutane). The quantities required are as for butyl bromide but with butan-2-ol (b.p. 99-100 °C) replacing the butan-l-ol. Two to three washings with concentrated hydrochloric acid are necessary, i.e. until the volume of the acid layer remains unchanged on shaking with halide. The yield of s-butyl bromide, b.p. 90.5-92.5 °C, is 150 g (92%). 

Note. (1) Diethyl s-butylmalonate, b.p. 110-120 °C/20 mmHg, is prepared by reacting 2-bromobutane with diethyl malonate. Use the general procedure described for the butyl isomer (Expt 5.133) but extend the period of heating under reflux to 48 hours to complete the alkylation. 

The alkylating agent, 1-bromobutane, is prepared from 1-butene by free-radical (anti-Markovnikov) addition of hydrogen bromide. 

Ylides are prepared by the reaction of an alkyl halide with triphenylphosphine, followed by treatment with strong base. 2-Bromobutane is the alkyl halide needed in this case. 

Dibutyl TeUurium (Hydrazine Method)1 To a stirred mixture of 0.40 g (10 mmol) powdered sodium hydroxide, 0.64 g (5.0 mmol) of finely ground tellurium powder, and 10 m/ dimethylformamide are added, dropwise by syringe under an atmosphere of nitrogen at 50- 60° 0.50 ml (7.1 mmol) 80% hydrazine hydrate. The mixture is stirred for 3 h. A solution of 1.4 g (10 mmol) bromobutane in 2 ml dimethylformamide is added and the mixture heated at 60° for 30 min, then cooled to 20°, and extracted with petroleum ether (30 -60°). The organic phase is separated, washed with water, and dried with anhydrous calcium chloride. The mixture is filtered and the solvent evaporated from the filtrate. The residue is purified by preparative TLC (silica gel, Merck 60 GF 254/hexane) yield 57% b.p. 111-114713 torr. 

Kopecky s synthesis of trimethyldioxetane employed the base-mediated dehydrohalogenation of 2-methyl-2-hydroperoxy-3-bromobutane. Subsequently, this type of eliminative cyclization (14) has been applied to the preparation of scores of dioxetanes. Additionally, many dioxetanes have been prepared by the addition of singlet oxygen to electron-rich olefins which do not possess allylic hydrogens (15), a method discovered first by Bartlett and Schaap... 

Problem 8.33 Show reagents and reactions needed to prepare the following compounds from the indicated starting compounds, (a) Acetylene to ethylidene iodide (1,1-diiodoethane). (b) Propyne to isopropyl bromide, (c) 2-Butyne to racemic 2,3-dibromobutane. (d) 2-Bromobutane to trans-2-butene. (e) n-Propyl bromide to 2-hexyne. (/) 1 -Pentene to 2-pentyne. ... 

All these reactions involve addition of a dialkylcopper reagent [(CHsC C CH CuLi] to an alkyl halide. The dialkylcopper is prepared by treating 1-bromobutane with lithium, followed by addition of Cul ... 

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