Alkyl iodides, preparation

Nickel catalysed cross-coupling of a dialkylzinc with an alkyl iodide preparation of ( )-ethyl 12-acetoxy-2-dodecenoate34... 

Reagents AgN02, dry sand, alkyl iodide prepared by reacting the alcohol with iodine and phosphorus, saturated NaN02 solution, 40% NaOH, dilute H2SO4. 

A special apparatus (Fig. Ill, 40,1) renders the preparation of iodides from alcohols a very simple operation. The special features of the apparatus are —(i) a wide bored (3-4 mm.) stopcock A which considerably reduces the danger of crystallisation in the bore of the tap of the iodine from the hot alcoholic solution (ii) a reservoir B for the solid iodine and possessing a capacity sufficiently large to hold all the alkyl iodide produced (iii) a wide tube C which permits the alcohol vapour fix)m the flask D to pass rapidly into the reservoir B, thus ensuring that the iodine is dissolved by alcohol which is almost at the boiling point. An improved apparatus is shown in Fig. Ill, 40, 2, a and b here a... 

The small capacity apparatus is especially recommended for the use of students the consumption of iodine by a large class of students is not unreasonably high. Larger apparatus, e.g., 60 ml. and 100 ml. capacity holding 100 g. and 200 g. respectively of iodine, are generally preferred for routine preparations of alkyl iodides the bolt-head flask should then be of 250 or 500 ml. capacity. Thus for n-butyl iodide a typical preparation would employ 120 g. (148-5 ml.) of n.butyl alcohol, 21 75 g. of red phosphorus, and 200 g. of iodine. 

Higher alkyl ethers are prepared by treating the sodium derivative of the phaiol (made by adding the phenol to a solution of sodium ethoxide in ethyl alcohol) with the alkyl iodide or bromide (Williamson synthesis), for example ... 

In the total synthesis of zearaienone (451), the ester 450 was prepared by the carbonylation of the crowded aryl iodide 448. The alkyl iodide moiety in the alcohol molecule 449 is not attacked[306]. Methyl trifluoromethacrylate (453) was prepared by the carbonylation of 3,3,3-trifluoro-2-bromopropylcne (452), The carbonylation in the presence of alkylurea affords 454. which is converted into the trifluoromethyluracil 455[307],... 

Alkyl ketones can be prepared by the carbonylation of alkyl iodides in the presence of organoboranes. The carbonylation of iodocyclohexane with 9-octyl-9-BBN at 1 atm gives cyclohexyl octyl ketone in 65% yield[386]. This reaction is treated in Section 1.1.3.3. Methyl o-methylacetoacetate (919) is obtained by the reaction of the 2-bromopropionate 918, which has a /9-hydrogen, with CO and Me4Sn. PhjAs as a ligand gives better results than Ph3P[771]. 

The reaction of perfluoroalkyl iodides with alkenes affords the perfluoro-alkylated alkyl iodides 931. Q.a-Difluoro-functionalized phosphonates are prepared by the addition of the iododifluoromethylphosphonate (932) at room temperature[778], A one-electron transfer-initiated radical mechanism has been proposed for the addition reaction. Addition to alkynes affords 1-perfluoro-alkyl-2-iodoalkenes (933)[779-781]. The fluorine-containing oxirane 934 is obtained by the reaction of allyl aicohol[782]. Under a CO atmosphere, the carbocarbonylation of the alkenol 935 and the alkynol 937 takes place with perfluoroalkyl iodides to give the fluorine-containing lactones 936 and 938[783]. 

Chlorination of alkanes is less exothermic than fluonnation and bromination less exothermic than chlorination Iodine is unique among the halogens m that its reaction with alkanes is endothermic and alkyl iodides are never prepared by lodmation of alkanes... 

Other preparations of trifluoromethanesulfonic acid kiclude oxidation of methyltrifluoromethyl sulfide under a variety of conditions (10,11). Perfluorosulfonyl fluorides have also been prepared by reaction of fluoroolefkis with sulfuryl fluoride (12,13). Chinese chemists have pubflshed numerous papers on the conversion of telomer-based alkyl iodides to sulfonyl fluorides (14,15) (eqs. 8 and 9) ... 

Alkyl esters of trifluoromethanesulfonic acid, commonly called triflates, have been prepared from the silver salt and an alkyl iodide, or by reaction of the anhydride with an alcohol (18,20,21). Triflates of the 1,1-dihydroperfluoroalkanols, CF2S020CH2R can be prepared by the reaction of perfluoromethanesulfonyl fluoride with the dihydroalcohol in the presence of triethylamine (22,23). Triflates are important intermediates in synthetic chemistry. They are among the best leaving groups known, so they are commonly employed in anionic displacement reactions. 

Magnesium alkyls can also be prepared by reaction of alkyl iodide and a calcium—magnesium ahoy in ether. 

Isoxazolium salts can be prepared by reaction with alkyl iodides or sulfates, although the low basicity of isoxazoles and their sensitivity to nucleophilic attack may necessitate special care. Isoxazolium salts containing bulky Af-substituents can be prepared by the reaction of isoxazoles with alcohols in the presence of perchloric acid. For example, the reaction of 3,5-dimethylisoxazole (53) with some alcohols in the presence of 70% perchloric acid gave isoxazolium salts, (54a) in 29%, (54b) in 57% and (54c) in 82% yield 79AHC(25)147, 68JOC2397). Attempts to quaternize 3,5-dimethyl-4-nitroisoxazole failed 71JCS(B)2365). 

Other methods for the preparation of esters are the action of alcohol on the acid chloride or anhydride (see Reactions, p. 75), or by boiling up the dry powdered silver salt of the acid with the alkyl iodide,... 

Ethylmalonic Acid.—Like acetoacetic ester (see p. 83), diethylmalonate contains the gioup CO.CHj.CO. By the action of sodium or sodium alroholate, the hydrogen atoms of the methylene group are successively replaceable by sodium. The sodium atoms are in turn replaceable by alkyl or acyl groups. Thus, in the present preparation, ethyl malonic ester is obtained by the action of ethyl iodide on the monosodium compound. If this substance be treated with a second molecule of sodium alcoholate and a second molecule of alkyl iodide, a second radical would be in roduced, and a compound formed of the general formula... 

Cradally, dais allows orgatiozitic reagents to be prepared from less reactive aryl bromides and secondary or tertiary alkyl bromides.. Alternatively, orgatiozitic iodides can be prepared by means of a paliadiurniOj-catalyzed reaction between alkyl iodides and Et2Zn iSdaeme 2.25) [53-56],... 

Of preparative importance is the substitution of chloride or bromide or iodide, since the more reactive alkyl iodides are better substrates for further transformations. Alkyl iodides often are difficult to prepare directly, which is why the conversion of readily accessible chlorides or bromides via a Finkelstein reaction is often preferred. 

Differences in solubility of the reactants may for example be utilized as follows. Sodium iodide is much more soluble in acetone than are sodium chloride or sodium bromide. Upon treatment of an alkyl chloride or bromide with sodium iodide in acetone, the newly formed sodium chloride or bromide precipitates from the solution and is thus removed from equilibrium. Alkyl iodides can be conveniently prepared in good yields by this route. Alkyl bromides are more reactive as the corresponding chlorides. Of high reactivity are a-halogen ketones, a-halogen carboxylic acids and their derivatives, as well as allyl and benzyl halides. 

Haller and Louvrier have prepared a number of homologues of camphor by heating the ketone in benzene solution with sodamide and alkyl iodides. The following are the characters of a number of these —... 

Other iV-alkyl-m-toluidines may be prepared by practically the same procedure. The submitters report that -propyl, iso-propyl, and w-butyl derivatives are obtained readily from m-toluidine and the appropriate alkyl iodides (rather than the bromides). In these cases the alkylation is effected by placing the sealed bottle in a beaker of water which is wanned gradually to 70-80° and kept in a warm place until the reaction is completed usually several days are required. 

Between sulfur dioxide radical anions, dithionite, and sulfoxylate/sulfite there exists a pH-dependent equilibrium465 (equation 86). Therefore, dithionite has been used as a source of sulfoxylate in order to prepare sulfinate and hence sulfones. Alkylation with triethyl oxonium fluoroborate leads to ethyl ethanesulfinate, alkyl iodides lead to symmetrical sulfones466 (equation 87). 

---