Haloalkanes alcohols from

Alcohols from Haloalkanes by Acetate Substitution— Hydrolysis Step 1. Acetate formation (Sn2 reaction)... 

Monothioacetals 1,3-Oxathiolanes Thiolactams S extrusion, 59-60, 261 Thiols synthesis from haloalkanes, 169, 269 Thionation of lactones, 110-111 Thiones olefination of, 35 Thionocarbonates. See Carbonothioates Thionolactones, 110-111 Thionyl chloride prepn. of acyl halides, 143 prepn. of carboxylic esters, 347 prepn. of haloalkanes from alcohols, 32 Thiophenoi. See Benzenethiol Thiotosylatc. See Benzenesulfonothioic add... 

Neutral molecules containing the hydroxyl group are seldom employed as nucleophiles, even though the oxygen atom has two non-bonded pairs of electrons. We shall see why this is so later, but, in general, the anions derived from water ( OH), alcohols (RO ) and carboxylic acids (RCOO ) are used in preference to the parent compounds. Anions are usually employed in the synthesis of ethers and ethanoates (acetates) from haloalkanes (Reactions 3.3 and 3.4)... 

In Chapters 11 and 12 we return to the presentation of a new functional group the carbon-carbon double bond. This functional group differs from those seen so far in that it hicks strongly polarized covalent bonds. Instead, its reactivity arises from specitil characteristics of electrons in so-called it bonds. The properties of the.se electrons and their consequences are discussed in the next chapter. Chapter 11 is restricted to a general description of alkenes as a compound class and a presentation of methods of preparation of double bonds. Most of the reactions are ones you have already seen, because the major methods of alkene syntheses are the same elimination reactions of alcohols and haloalkanes that were presented in Chapters 7 and 9. Only some finer details have been added. 

In Summary Alcohols may be prepared from haloalkanes by nucleophilic substitution, provided the haloalkane is readily available and side reactions such as elimination do not interfere. 

Esters from Alcohols and Haloalkane Synthesis CHAPTER 9... 

In this chapter, we looked at alkenes, a compound class characterized by the carbon-carbon double bond. In Chapters 7 and 9, we learned that alkenes are prepared synthetically by elimination reactions of haloalkanes and alcohols, hi this chapter, we examined these reactions in more depth. We saw that the structure of the base determines what products will form in E2 elimination from haloalkanes. Similarly, the stracture of an alcohol undergoing acid-catalyzed dehydration determines what mechanism takes place and how easily it occurs. 

In Summary The hydroxy group in COOH can be replaced by halogen by using the same reagents used to convert alcohols into haloalkanes—SOCI2 and PBrs. The resulting acyl halides are sufficiently reactive to be attacked by carboxylic acids to generate carboxyUc anhydrides. Cyclic anhydrides may be made from dicarboxylic acids by thermal dehydration. 

The alcohol is 3-methyl-2-butanol. (b) The compound is both a ketone and a haloalkane. Identify the hydrocarbon chain and number the chain in the direction that gives the ketone group the lower number. The chain has five carbon atoms the ketone group is on the second carbon atom from one end, and the chlorine atom is on the fourth ... 

Modifying the reaction medium to involve liquid ammonia with metallic lithium, f-butyl alcohol, and white phosphorus, to which is added the haloalkane, is reported to provide the primary alkylphos-phine derived from the haloalkane.19 Similar results are reported for the reaction of red phosphorus with sodium acetylides20 and by treatment of red phosphorus with sodium metal in an organic medium followed by the addition of two equivalents of f-butyl alcohol and the haloalkane.21 The latter approach is noteworthy in that moderate yields (45%) are obtained for primary phosphines derived from secondary haloalkanes (Figure 2.6). Mixtures of tertiary phosphines bearing one or two acetylenic linkages are produced in low yield ( 15%) by the reaction of lithium acetylides with white phosphorus in liquid ammonia followed by addition of a haloalkane.22... 

Sulphonic esters have been obtained from the sulphonyl chlorides in high yields under mild conditions for a range of alcohols and phenols [e.g. 18, 19]. Of particular value is the protection of glycosides possessing a free hydroxyl group and hydroxy-steroids, which are tosylated readily under phase-transfer conditions [20-22]. Alkyl sulphinites have been obtained in a similar manner [23]. Alternatively, preformed tetra-rt-butylammonium sulphonates or their alkali metal salts have also been alkylated with haloalkanes or alkyl fluorosulphonates [24,25]. In contrast with more classical procedures, tosylation of alcohols, which are susceptible to E/Z-isomerism, e.g. Z-alk-2-en-l-ols, occurs with retention of their stereochemistry under phase-transfer catalysis [26]. 

Hydroboration of alkenes in non-ethereal solvent has been reported using diborane generated in situ from a quaternary ammonium borohydride and bromoethane (see Section 11.5). Almost quantitative yields of the alcohols are reported [e.g. 1 ]. As an alternative to the haloalkane, trimethylsilyl chloride has also been used in conjunction with the ammonium borohydride [2]. Reduction of the alkene to the alkane also occurs as a side reaction (<20%) and diphenylethyne is converted into 1,2-diphenylethanol (70%), via the intermediate /ra 5-stilbene. 

When a haloalkane with p-hydrogen atom Is heated with alcoholic solution of potassium hydroxide, there Is elimination of hydrogen atom from p-carbon and a halogen atom from the a-carbon atom. As a result, an alkene is formed as a product. Since p-hydrogen atom is involved in elimination. It Is often called p-elimination. 

S)-2-Amino-3-methylbutanol [(S)-valinol] derived oxazolidinones, i.e., (S)-3-acyl-4-iso-propyl-2-oxazolidinones 1, have been used extensively for the preparation of a-alkylated acids, aldehydes and alcohols. The enolates are formed by deprotonation with lithium diisopropyl-amide or sodium hexamethyldisilazanide at low temperature in tetrahydrofuran. Subsequent addition of a haloalkane gives alkylation, which occurs from the Si-face2. The diastereoselectivities are usually good (>90 10), and the products are usually purified by flash chromatography and/or recrystallization (see Table 10). Additional examples of alkylation of 1 have been published5 l0 12- 20 22-29 39.44.-47,49.57.70-78... 

The ring closure of amino alcohols with C02 to yield cyclic carbamates, was achieved under mild conditions (atmospheric pressure of C02, room temperature), in acetonitrile as solvent and in the presence of triethylamine as the base, using more easily available reactants, such as P(III)-derivatives (Ph3P, (PhO)3P, n-Bu3P, (MeO)3P) and haloalkanes (CC14, CC13CC13) [76]. According to the proposed mechanism, the active species is a phosphonium adduct of the used P(III)-compound with the haloalkane, which activates the intermediate carbamate formed from amino alcohol and C02 at the carbamic moiety to produce a transient species which cyclizes to the final product (Scheme 6.12). 

Scheme 6.12 Proposed mechanism for the synthesis of cyclic carbamates from amino alcohols and C02, using P(lll) reagents and haloalkanes.

Cyclopropen-1-yl sodium derivatives are also readily prepared. Thus reaction of cyclopropene with one equivalent of sodium amide in liquid ammonia leads to 1-sodiocyclopropene which is alkylated by haloalkanes 77,78 reacts with ketones to produce tertiary alcohols and opens epoxides to produce 2-cyclopropenyl-ethanols in moderate to good yields79). Moreover, on reaction with two equivalents of base followed by haloalkane, 1,2-dialkylated species are obtained sequential reactions can also be used to produce unsymmetrically substituted cyclopropenes78). Reaction with a deficiency of sodium amide can also cause addition of the cyclopro-penyl anion to unreacted cyclopropene, leading to products derived from the 2-cyclo-propylcydopropen-l-yl anion and to 1,2-dicyclopropylcyclopropene 77). 

Whereas haloalkanes are widely used for the electrophilic alkylation of a broad variety of nucleophiles, perfluoroalkyl bromides or iodides do not act analogously as electrophilic perfluoroalkylation reagents (Figure 2.7). For example, the reaction of perfluoroalkyl iodides with aliphatic alcoholates does not yield the expected alkyl perfluoroalkyl ether (analogous to the Williamson ether synthesis) but mostly the hydrofluorocarbon resulting from the reduction of the iodide [1]. In contrast, perfluoroalkyl iodides and bromides have been used as preparatively useful electrophilic iodination or bromination reagents [2]. 

The or /io-positions of the benzene ring in 4,4-dimethyl-2-phenyl-4,5-dihydrooxazole 13, prepared from benzoyl chloride and the amino alcohol 12, are activated to such an extent that lithiation is possible. On reaction with an electrophile, e.g. a haloalkane, and followed by hydrolysis, 2-substituted or 2,6-disubstituted benzoic acids 14 or 15 are obtained [78] ... 

It is ab.solutcly necessary to know the.se interconversion patterns, because they provide the framework fttr designing synthetic strategy. Suppose we wish to synthesize an alcohol starling with an alkane. From this chart, we. see immediately that we have no direct method for converting tilkanes to alcohols. We must first itiake a haloalkane and then use it in another reaction to make an alcohol. We set up the proposed synthesis in just that way and insert the specific reagents necessary to carry out the two synthetic steps ... 

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