Halides, primary, conversion into

Amines are powerful nucleophiles which react under neutral or slightly basic conditions with several electron-accepting carbon reagents. The reaction of alkyl halides with amines is useful for the preparation of tertiary amines or quaternary ammonium salts. The conversion of primary amines into secondary amines is usually not feasible since the secondary amine tends towards further alkylation. 

Perhaps the most useful reaction of carboxylic acids is their conversion into esters. There are many methods for accomplishing the transformation, including the S -2 reaction of a carboxylate anion with a primary alkyl halide that we saw in Section 11.3. 

Substrates suitable for oxidative conversion into carbonyl compounds are alkenes, primary or secondary alcohols, and benzyl halides. Polystyrene-bound alkenes have been converted into aldehydes (with the loss of one carbon atom) by ozonolysis followed by reductive cleavage of the intermediate ozonide (Entry 1, Table 12.3). 

The conversion of (primary) pyrazinamines into the corresponding halogenopyrazines by one-pot diazotization and treatment with halides has proven reasonably satisfactory for making some chloro-, bromo-, or fluoropyrazines to date, iodopyrazines... 

Another C-O bond roactioa of Alcohols is their conversion into alkyl halides (Section 10.7). Tertiary alcohols arc readily converted into alkyl halides by treatiBom with either KCl or HBr otO C. Primary and secondary alcohols are much more rvsistanl to acid, however, and arc hrat converted into lioUdea by tikfauueni with either SOCl o> PDvj. 

Reaction of sodium acetylides with alkyl halides permits conversion of smaller alkynes into larger ones. Practically, the reaction is limited to the use of primary halides because of the great tendency for secondary and tertiary halides to undergo a side reaction, elimination this point will be discussed further (Sec. 8.12) after we have learned something about the nature of acetylides. 

Conversion of a primary alcohol into alkyl halides by S 2 reactions with SOCI2 and PBrj. 

Primary phosphorothiosulphenamides may be acylated, and with sodium ethoxide they are converted into trialkyl phosphorothionates. Other reactions of phosphorothiosulphenamides include the loss of sulphur upon treatment with sodium, and translocation of the amino-function when treated with thiophosphoryl halides. Treatment of the acyl chloride (71) with ethyleneimine gives an amide which undergoes ready conversion into the isocyanate (72). ... 

The smooth transformation of a primary amine into the corresponding alkyl halide allows a simple conversion of a primary amine into the corresponding alcohol. Normally the stereoconfiguration of the leaving group remains intact, which allowed stereochemical assignments in the terpene series ( ). 

A new one-pot procedure for the direct conversion of primary alcohols into the corresponding nitriles avoids drawbacks associated with previous methodology (Scheme 28). Nitriles are prepared from halides in good yield via the use of polymer-supported cyanide. ... 

The conversion of primary amines into thiols and thioethers via pyridinium salts (64) has recently been reported (Scheme 39). Alkyl halides have been... 

Two papers this year have described the use of chromate ions for the conversion of alkyl halides or alcohols into aldehydes or ketones (Equation 4). The reaction can be conducted in HMPA in the presence of a crown ether, and although yields are good for allylic and benzylic halides (ca. 80%) they are not so high for saturated halides. " The chromate ion, however, can be supported on an insoluble polymer matrix as the tetra-alkylammonium salt and this both enhances the nucleophilicity of the ion and simplifies the work up procedure. Using the polymer-supported reagent a variety of primary and secondary alcohols were oxidized to the corresponding aldehyde or ketone in excellent yield (ca. 90%). ... 

In Summary Several reagents oxidize primary alcohols and aldehydes to carboxylic acids. A haloalkane is transformed into the carboxylic acid containing one additional carbon atom either by conversion into an organometaUic reagent and carbonation or by displacement of halide by cyanide followed by nitrile hydrolysis. 

Metallic Pd is a good catalyst for the conversion of the primary azide 34 into the nitrile 35 in the presence of a hydrogen acceptor such as diphenylacety-lene[33]. By this method, organic halides can be converted into nitriles without increasing the carbon number. Reaction of the azidoformate 36 with an allylic... 

A more general method for preparation ofa-amino acids is the amidotnalmatesynthesis, a straightforward extension of the malonic ester synthesis (Section 22.7). The reaction begins with conversion of diethyl acetamidomalonate into an eno-late ion by treatment with base, followed by S 2 alkylation with a primary alkyl halide. Hydrolysis of both the amide protecting group and the esters occurs when the alkylated product is warmed with aqueous acid, and decarboxylation then takes place to vield an a-amino acid. For example aspartic acid can be prepared from, ethyl bromoacetate, BrCh CCHEt ... 

The conversion of primary and secondary alcohols into alkyl halides via imidazolides can be achieved by five different routes ... 

The alkyl halides react with cyanide to produce alkyl cyanides. But this reaction has rarely been employed to obtain the increased length of the chain because of the long reaction times and poor yields. However, the use of DMSO as a solvent has simplified the procedure and improved the yields for the conversion of primary and secondary alkyl chlorides into cyanides, without any rearrangement. 

A convenient one-pot procedure for the conversion of alcohols into primary amines has been reported. The alcohol is converted into the corresponding alkyl halide by the action of bromotrichloromethane/triphenylphosphine and the product is treated successively with sodium azide, triethyl phosphite, hydrochloric acid and sodium hydroxide (equation 20)55, cf. equation 14. 

The simple procedure for the carbonylation of allyl halides has been extended in the high yielding solid-liquid two-phase conversion of allyl phosphates into amides (60-80%) under the influence of a rhodium carbonyl cluster in the presence of primary or secondary amines (Scheme 8.8). A secondary product of the reaction is the allylamine, the concentration of which increases as the pressure of the carbon monoxide is reduced, such that it is the sole product (ca. 80%) in the absence of carbon monoxide [28],... 

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