1-Bromopentane, reaction with

Synthesis (Freed and Potoski (American Home), 1971 Freed, 1973 Kleemann et al., 1999,) Dezocine is prepared through the following sequence The condensation of 1-methyl-7-methoxy-2-tetralone with 1,5-di-bromopentane by means of NaH or potassium tertbutylate affords 1 -(5-bromopentyl)-1 -methyl-7-methoxy-2-tetralone this product is cyclized with NaH to give 5-methyl-3-methoxy-5,6,7,8,9,10,11,12-octahydro-5,11 -methano-benzocyclodecen-13-one i. The ketone i, by reaction with hydroxylamine hydrochloride in pyridine, is converted into its oxime ii, which is reduced with H2 over Raney Ni to a mixture of isomeric amines which were separated by crystallization of the HCI salts giving 5-a-methyl-3-methoxy-5,6,7,8,9,11 a, 12-octahydro-5,11 -methanobenzo-cyclodecen-13p-amine, which is finally cleaved with concentrated HBr. 

The name of the compound is (/ )-2-bromopentane. Reaction of (5)-2-pentanol with PBr3 to form (R)-2-bromopentane occurs with a change in stereochemistry because the configuration at the chirality center changes from S to R. 

In Scheme 1.3, hexanal on reaction with 1,3-propanedithiol gives the 1,3-dithiane derivative 1.8. A strong base such as u-butyllithium abstracts the proton to give the corresponding 2-lithio-1,3-dithiane 1.9, which reacts with 1-bromopentane to give alkylated product 1.10. Treatment of 1.10 with FIgO and BF3 (boron trifluoride) in aqueous THF (tetrahydrofuran) yields the dipentyl ketone (the corey-seebach reaction ). Thus, dithianyllithium (2-lithio-1,3-dithiane) 1.9 is an acyl anion synthetic equivalent. 

Reaction of epichlorohydrin with sodium methanethiolate gave l,3-bi (methylthio)-2-propanol, which was converted to the sodio derivative and methylated to afford l,3-bis(methylthio)-2-methoxypropane. Finally, treatment with LDA (1 equiv.) resulted in elimination of methanol to give l,3-bis(methyl-thio)propene, whereas reaction with 2 equiv. of LDA gave bis(methylthio)allyllithium, which reacted with I bromopentane furnishing l,3-bis(methylthio)-l-octene, which in turn was converted by hydrolysis with mercury(II) chloride to rra/is-2-octenal (Scheme 14). 

BROMOPENTANE (107-81-3) Forms explosive mixture with air (Hash point 90°F/32°C). Violent reaction with strong oxidizers. Incompatible with strong acids. 

There are two major reactions of enolates (1) displacement reactions with alkyl halides or other suitable electrophiles and (2) nucleophilic addition to carbonyl compounds. Reaction of 58 with butanal to give 59 and reaction of 61 with bromopentane to give 62 are simple examples of each process. Enolate anions function as carbon nucleophiles and their reactions are fundamentally the same as those discussed in Section 8.3.C for acetylides. Although there are interesting differences, treating an enolate anion as a carbon nucleophile is very reasonable. 

Diethyl malonate on reaction with sodium metal gives rise to sodium malonic ester which on treatment with ethyl bromide results into the formation of diethyl ester of ethyl malonic acid with the elimination of hydrobromic acid. The resulting ester on further reaction with 2-bromopentane gives the desired eompound, i.e., diethyl ester of ethyl (1-methyl butyl) malonic acid which on subsequent treatment with thiourea forms thiopental with the elimination of two moles of ethanol. Ultimately, the enol-iorm of thiopental when reaeted with a ealeulated amoimt of sodium hydroxide, it gives thiopental sodium. 

The reaction of thieno[2,3-Zi]thiophene (142) with Bu"Li affords a lithium intermediate, whose treatment with elemental sulfur and bromopentane produces sulfide 169. Regioselective iV-sulfonation of the latter was successfully carried out by successive reactions with Bu"Li, SO2 and hydroxylamino-O-sulfonic acid. Selective oxidation of sulfide 170 with potassium peroxymonosulfate afforded sulfone 171 (99JHC249). 

Apart from HCl, HBr, and HI, there are certainly other strong mineral acids, including nitric acid (HNOg pK = -1.3), sulfuric acid (H2SO4 pK = -5.2), and perchloric acid (HCIO4 pK = -4.8). If 1-pentene reacts with any of these acids, the product will be the secondary cation, 16, but the nucleophilic counter-ion changes. When HBr reacts with 1-pentene, the counter-ion is bromide (Br ), which is rather nucleophilic, and the product is 2-bromopentane. However, if nitric acid reacts, the nucleophile is the nitrate anion (NOg"), which is resonance stabilized and is less likely to donate electrons (less nucleophilic). The product of a reaction with nitric acid in which the nitrate anion reacts as a nucleophile with 16 is 17. When 1-pentene reacts with sulfuric acid, the... 

The ether is prepared via the corresponding halide. If the C-0 bond in 163 is disconnected, the logical bond polarization makes O 6- and a donor site Cj, and that of C2 is 6+, or (an acceptor site). In Chapter 25, Table 25.1 indicates that a synthetic equivalent for Cg is an alkyl halide. Therefore, a reasonable disconnection of 163 leads to 2-bromopentane (167) and the nucleophilic methoxide ion. This suggests a Williamson ether synthesis (Section 11.3.2). Can 167 be prepared directly from 1-pentene The answer is yes, by reaction of the alkene with HBr (Chapter 10, Section 10.2). Therefore, the retrosynthesis shown leads to the synthesis shown in which 1-pentene reacts with HBr to give 167, and a subsequent Sn2 reaction with... 

Experimental data suggest that 2-bromopentane reacts with KI in aqueous THF by both 8 2 and SnI mechanisms. However, when the reaction is done in ethanol, the product is formed almost excessively by an Sn2 mechanism. Because ethanol is a polar protic solvent, why is there such a difference in the mechanism of this reaction in two different solvents Only water can ionize... 

Cyanide is a bidentate nucleophile. Draw the product that results from a reaction with 1-bromopentane where carbon is the nucleophile. Draw the product that results from the reaction where nitrogen is the nucleophile. Calculate the formal charge, if any, on both products. Assuming there is a mixture of these two products, suggest a simple way that you might separate them. 

Primary halides, such as 1-bromopentane (15) usually give very poor yields of an alkene when treated with KOH in ethanol. Based on experimental results with primary alkyl halides, assume that primary alkyl halides do not give an alkene under normal E2 conditions. The activation energy required to generate a transition state such as 16 (for an E2 reaction of 15) is so high that the E2 reaction is quite slow relative to another reaction such as substitution. It is not impossible, just slow. Remember that hydroxide and ethoxide are nucleophiles as well as bases, and one can imagine a facile Sn2 reaction at the primary carbon, which is faster than the E2 reaction. If any reaction occurs when 15 reacts with hydroxide in ethanol, it will likely be the 8 2 product, 1-pentanol via reaction with hydroxide, or 1-ethoxypentane via reaction with ethoxide. If any alkene is formed, it is usually a very minor product. 

The retrosynthetic analysis shown for 220 allows the total synthesis. Catalytic hydrogenation of223 gives 1-pentene (see Chapter 19, Section 19.3.2), which reacts with HBr to give 2-bromopentane (Chapter 10, Section 10.2). The reaction of 2-bromopentane and magnesium metal, followed by reaction with carbon dioxide and aqueous hydrolysis, leads to the requisite carboxylic acid. Reaction of the carboxylic acid with thionyl chloride leads to the acid chloride, which reacts with dimethylamine to give 222. 

Now, let s draw the forward scheme. In the presence of peroxides, the reaction of 1-pentene with HBr produces 1-bromopentane (via anfe -Markovnikov addition). Subsequent reaction with acetylide [produced from ethylene as shown by bromination (Br2), double elimination and deprotonation (excess NaNH2)] provides 1-heptyne. Reduction to the alkene (H2 / Lindlar s catalyst) followed by anP-Markovnikov addition (HBr / peroxide) yields 1-bromoheptane. This primary alkyl bromide can then undergo an Sn2 reaction when treated with acetylide (prepared above), giving the... 

Now let s draw the forward scheme. The 3° alcohol is converted to 2-methylpropene using strong acid. Anti-Markovnikov addition of HBr (with peroxides) produces l-bromo-2-methylpropane. Subsequent reaction with sodium acetylide (produced from the 1° alcohol by dehydration, bromination and double elimation/deprotonation as shown) produces 4-methyl-1-pentyne. Deprotonation with sodium amide followed by reaction with 1-bromopentane (made from the 2° alcohol by tosylation, elimination and anfi -Markovnikov addition) yields 2-methyl-4-decyne. Reduction using sodium in liquid ammonia produces the E alkene. Ozonolysis followed by treatment with dimethylsulfide produces an equimolar ratio of the two products, 3-methylbutanal and hexanal. 

A complication of such reactions is competition from elimination reactions rather than substitution (see Section 18.5). (a) Predict the possible products from the reaction of 2-bromopentane with sodium hydroxide, (b) What can be done to favor the... 

When the temperature was slowly raised, no reaction was observed until 20° C, at which time polymerization occurred. In confirmatory experiments, 1-bromopentane reacted quantitatively with Mg in 1 min at -78° C. The resulting Grignard reagent did not react with subsequently added ... 

Table I. Reaction of 1-Bromopentane with Various Nucleophiles under PTC Conditions ...

Treatment of RuCl3 xH20 with Hacac gives tra i-[Ru(acac)2Cl2] (the first trani-bis(acac) complex to have been made). The complex anion is a precursor to a range of Ru, Ru, and Ru tra 5 -bis(acac) complexes including tra w-[Ru (acac)2L2] where L = MeCN or pyrazine (pyz) the cis analogs result from direct reaction between [Ru(acac)3] and MeCN or pyz (see also Section 5.5.3.4.1). The reaction of [Ru(acac)3] with molten 1,3-diaminobenzene yields complexes (8)-(10). Their formation involves Ru-mediated oxidative di- and trimerization of 1,3-diaminobenzene. Structural data for [Ru(acac)3] and [Ru(3-Bracac)3] (H-3-Bracac = 3-bromopentane-2,4-dione)... 

In order to simplify the problem and have a better understanding of the reaction mechanism, we designed a model reaction of difunctional polystyryllithium that was prepared by initiating styrene with lithium naphthalenide and then reacted with 1-bromopentane in... 

Phenylpiperidine has been prepared by warming aniline with 1,5-dibromopentane 4,8 heating 5-anilino-l-bromopentane 6 the dehydration of 5-anilino-l-pentanol over alumina 7 the electrolytic reduction of N-phenylglutarimide 8 the catalytic hydrogenation of l-phenyl-3-hydroxypyridinium chloride 9 the action of bromobenzene on piperidine in the presence of lithium 10 the reaction of fluorobenzene, 1-methylpiperidine, and phenyl-lithium 11 the action of diphenylsulfone on piperidine in the presence of sodamide 12 the diazotization and deamination of l-(2-aminophenyl)piperidine 13 and of l-(4-aminophenyl)piperidine 14 and the present method.18... 

TABLE 27. Reaction of PhO (3) with 1-bromopentane (1) under various phase-transfer catalytic (0.01) conditions (water 110°C)... 

In a 5-I. flask, placed on a steam bath and fitted with a mechanical stirrer, a separatory funnel, a thermometer well (Note 1) and a calcium chloride tube, is placed 182 g. (7.5 moles) of magnesium turnings. To this is added a crystal of iodine and 100 cc. of a solution of 1133 g. (7.5 moles) of 2-bromo-pentane (Note 2) in 750 g. of -butyl ether (Note 3). The stirrer is started and the flask is heated with steam until the reaction starts. This may take from fifteen minutes to one hour, but the flask must be watched quite closely because the reaction, when once started, is very vigorous and evolves a large amount of heat. As soon as the reaction has started, 750 g. of w-butyl ether is added and then the balance of the solution of 2-bromo-pentane in w-butyl ether is added at such a rate that the temperature is kept at 50-60°. External cooling is used in order to allow more rapid addition of the 2-bromopentane. After addition is complete (about three hours), the mixture is heated on a steam bath for one hour. 

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