Alcohols functional group interconversions

Section 15.1 Functional group interconversions involving alcohols either as reactants or as products aie the focus of this chapter. Alcohols aie commonplace natural products. Table 15.1 summarizes reactions discussed in earlier sections that can be used to prepare alcohols. 

Converting one functional group into another is called functional group interconversion. Our knowledge of oxidation-reduction reactions has greatly expanded our ability to carry out functional group interconversions. For example, an aldehyde can be converted into a primary alcohol, an alkene, a secondary alcohol, a ketone, a carboxylic acid, an acyl chloride, an ester, an amide, or an amine. 

The tandem oxidation processes employing Mn02 continue to be applied to functional group interconversions. A new entry in this area is the direct conversion of activated alcohols to nitriles via an intermediate aldehyde followed by its corresponding imine (eq 104). 52... 

Sn2 reactions are highly useful in organic synthesis because they enable us to convert one functional group into another—a process that is called a funcdonal group trausfonna-tion or a functional group interconversion. With the Sn2 reactions shown in Fig. 6.11, methyl, primary, or secondary alkyl halides can be transformed into alcohols, ethers, thiols, thioethers, nitriles, esters, and so on. Note. The use of the prefix thio- in a name means that a sulfur atom has replaced an oxygen atom in the compound.)... 

Resolution of compounds containing functional groups that are not acidic or basic requires a reversible functional group interconversion involving a chiral resolving agent. For example, the reaction of a racemic alcohol with a chiral carboxylic acid results in a mixture of diastereomeric esters that can be separated. After separation, hydrolysis of the ester regenerates the desired alcohol. To resolve a racemic ketone or aldehyde, a reaction with a chiral diol or a chiral amine could be employed to form diastereomeric acetals or imines, respectively. 

The direct transformation of alcohols to the corresponding amines is of growing interest because alcohols are easily available or accessible by chemical means. Amination of alcohols is usually catalyzed by transition metals at high temperatures and elevated pressures. Unfortunately, there is no enzyme known today that allows this particular functional group interconversion (FGl) in one step. Consequently, a multi-enzyme cascade was set up for the amination of alcohols as demonstrated for various benzylic and cinnamic alcohols under physiological conditions [24] aerobic alcohol oxidation toward the aldehyde was performed via a galactose oxidase originating from Fusarium (NRRL 2903 [25]) followed by an in situ co-TA-catalyzed reductive amination step (Scheme 4.5). 

Here, a functional group interconversion suggests that the alcohol, CgH5CH(OH)CH3, would be a useful intermediate. 

Section 15.1 Functional group interconversions involving alcohols either as reactants or as... 

The selectivity of many reagents and their scope of application have been improved by working in multi-phase systems. Thus dichromate may be used in benzene " or dichloromethane by means of phase-transfer catalysis, and in the latter case aldehydes can easily be obtained from primary alcohols. The reverse type of reaction, namely reduction, can be achieved by cyanoborohydride supported on an anion exchange resin.Other useful functional group interconversions (and removals), RX to RCHO and RX to RH, have been effected with... 

WeVe talked at length about the interconversions of acid derivatives, explaining the mechanism of attack of nucleophiles such as ROH, H20, and NH3 on acyl chlorides, acid anhydrides, esters, acids, and amines, with or without acid or base present. We shall now go on to talk about substitution reactions of acid derivatives that take us out of this closed company of compounds and allow us to make compounds containing functional groups at other oxidation levels such as ketones and alcohols. 

Recent years have also witnessed an increasing interest in the use of halo-genoselenuranes as reagents for interconversions of basic functional groups. As early as 1986 it was reported in a conference communication [68a] that tibe easily available dichloroselenuranes 137 react with alcohols 136 in the presence of equimolar amounts of triphenylphosphine with the clean formation of the corresponding chlorides 138 (Eq. 31). 

B. Functional Groups — Preparation, reactions, and interconversions of alkanes, alkenes, alkynes, dienes, alkyl halides, alcohols, ethers, epoxides, sulfides, thiols, aromatic compounds, aldehydes, ketones, carboxylic acids and their derivatives, amines... 

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