Alkyls from alkyl halides

A wide class of aiyl-based quaternary surfactants derives from heterocycles such as pyridine and quinoline. The Aralkyl pyridinium halides are easily synthesized from alkyl halides, and the paraquat family, based upon the 4, 4 -bipyridine species, provides many interesting surface active species widely studied in electron donor-acceptor processes. Cationic surfactants are not particularly useful as cleansing agents, but they play a widespread role as charge control (antistatic) agents in detergency and in many coating and thin film related products. 

Anilides and a-Naphthalides. The Grignard reagents prepared from alkyl halides react with phenyl isocyanate (CgHjN=C=0) or with a-uaphthy l isocyanate (C,oH, N=C=0) to yield addition products that are converted by hydrolysis into anihdes and a-naphthalides respectively RX + Mg —> RMgX... 

Alkyl mercuric halides. Grignard reagents, prepared from alkyl halides, react with a mercuric halide that contains the same halogen as the reagent to form alkyl mercuric halides ... 

The higher homologues of propyne, e.g. 1-decyne, can be obtained in a similar way. Starting from 1-butyne and its homologues, alkylation with alkyl halides leads to 1-alkynes with a branched substituent. 

We now have a new problem Where does the necessary alkene come from Alkenes are prepared from alcohols by acid catalyzed dehydration (Section 5 9) or from alkyl halides by dehydrohalogenation (Section 5 14) Because our designated starting material is tert butyl alcohol we can combine its dehydration with bromohydrm formation to give the correct sequence of steps... 

Phosphorus ylides are prepared from alkyl halides by a two step sequence The first step is a nucleophilic substitution of the 8 2 type by triphenylphosphme on an alkyl halide to give an alkyltriphenylphosphonium salt... 

Because nitriles can be prepared from alkyl halides by nucleophilic substitution with cyanide ion the overall process RX RC=N RCH2NH2 leads to primary amines that have one more carbon atom than the starting alkyl halide... 

Synthesis of primary amines from alkyl halides with hexamelhylenetelramines. 

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. 

Primaty amines may be prepared from alkyl halides using phthalimide. This is called the Gabriel amine synthesis. 

The 1-alkyl-diaziridines can easily be hydrolyzed to alkyl hydrazines. Hence alkyl hydrazines are easily available from Grignard reagents and thus from alkyl halides. The three last examples of Table XII show the yield of alkyl hydrazine calculated on the diazirine used. The reaction has preparative interest because the alkylation of hydrazine with alkyl halides only gives monoalkyl hydrazines in exceptional cases. ... 

Alkynes can be prepared by the elimination of HX from alkyl halides in much the same manner as alkenes (Section 7.1). Treatment of a 1,2-dihaloaJkane (a vicinal dihalide) with excess strong base such as KOH or NaNH2 results in a twofold elimination of HX and formation of an alkyne. As with the elimination of HX to form an alkene, we ll defer a discussion of the mechanism until Chapter 11. 

Thiols are usually prepared from alkyl halides by Snj2 displacement with a sulfur nucleophile such as hydrosulfide anion, SH. 

Strategy We ve seen two methods for preparing carboxylic acids from alkyl halides ... 

Thiol (s), 652, 667-668 disulfides from, 668 electrostatic potential map of, 75 from alkyl halides, 667 hybridization of, 20 naming, 667 odor of, 667 oxidation of, 668 pKa of, 604... 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

ATRP catalysts may be used to generate radicals and thus alkoxyamines can be produced from alkyl halides in high yield (Scheme 9.21).174 The alkoxyaminc 102 was obtained in 92% yield 174 whereas reaction of TEMPO with PMMA under ATRP conditions is reported to provide a macromonomer (Section 9.7.2.1). 

In all the desulphonylation reactions discussed in Sections III.B and III.C the sulphur is lost from the starting sulphone and is reduced in the process simultaneously, the former carbon-sulphur bond is either reduced to a C—H bond or is converted into a C=C bond. The reactions described in this section have the common thread that the sulphur atom is lost with reduction at sulphur, but the carbon atom is converted directly into a carbonyl group. Formally, these reactions offer a route from alkyl halides to aldehydes or ketones. 

It might be mentioned that matters are much simpler for organometallic compounds with less-polar bonds. Thus Et2Hg and EtHgCl are both definite compounds, the former is a liquid and the latter is a solid. Organocalcium reagents are also known, and they are formed from alkyl halides via a single electron transfer (SET) mechanism with free-radical intermediates. "... 

Primary amines can be prepared from alkyl halides by the use of hexamethylenetetramine followed by cleavage of the resulting salt with ethanolic HCl. The method, called the Delepine reaction, is most successful for active halides such as allylic and benzylic halides and a-halo ketones, and for primary... 

For a review of formation of nitrates from alkyl halides, see Boguslavskaya, L.S. ... 

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