Iodides alkyl, preparation from alcohols

The required xanthates 1 can be prepared from alcohols 5 by reaction with carbon disulfide in the presence of sodium hydroxide and subsequent alkylation of the intermediate sodium xanthate 6. Often methyl iodide is used as the alkylating agent ... 

Direct substitution of F for OH by means of HF has no preparative importance. All the methods of preparing alkyl fluorides from alcohols proceed in principle by way of esters the alcohol is converted into the alkyl chloride, bromide, iodide, or / -toluenesulfonate, and then the halogen atom (see page 204) or the tosyloxy group (see page 229) is replaced by fluorine. 

Preparation.— The 2-alkoxydiazaphospholidines (55), mentioned earlier in this Report, have been prepared from alcohols and their facile conversion into alkyl chlorides, bromides, and iodides with inversion of configuration at carbon has been reported (Scheme 34) a one-pot procedure is suggested for the transformation of an alcohol into an alkyl iodide. Tributyldi-iodophosporane, BU3PI2,... 

Primary, secondary, and terriary alkyl iodides may be prepared from alcohols by treatment with chlorotrimethylsilane in the presence of sodium iodide, without rearrangement, in yields ranging from 78 to 98% (Eq. 6.54) [83]. 

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... 

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. 

There are also useful procedures for preparation of azides directly from alcohols. Reaction of alcohols with 2-fluoro-l-methylpyridinium iodide followed by reaction with lithium azide gives good yields of alkyl azides.75... 

Indole, sodium salt, preparation of, 54, 60 Indole, 1-benzyl, 54, 50, 58 Indoles, iV-alkyl-, 54, 58, 60 Iodides, from alcohols, methyl iodide, and triphenyl phosphite, 51, 47 ... 

Alkylation of alcohols with 2-(methoxyethoxy)methyl chloride (MEMC1, bp 50-52 C/1.7 kPa) (HAZARD carcinogenic) under an assortment of conditions pioneered by Corey still retain favour. These include reaction of the lithium or sodium alkoxide (generated from sodium or potassium hydride) with ME MCI in THF or DME at 0 °C (10-60 min) and reaction of the alcohol with MEMCI in dichloromethane in the presence of /-Pr NEt at room temperature for 3 h. For hindered alcohols, sodium iodide can be added to generate the more reactive 2-methoxyethoxymethyl iodide in situ. Alternatively, reaction of the alcohol with [(2-methoxyethoxy)methyl]triethylammonium chloride (prepared from MEMO and trie thy lamine) in refluxing acetonitrile is recommended for acid-sensitive substrates such as tertiary alcohols [Scheme 4,271],500... 

The sodium or potassium alkoxide prepared from primary and secondary alcohols and sodium hydride or potassium hydride in THF reacts with 2-(trimethyl-silyi)ethoxymethyl chloride (SEMCl, bp 57-59 PC/1 kPa, HAZARD carcinogenic) to give the SEM ethers in good yield [Scheme 4.304]481 Alternatively, the alcohol can be alkylated with SEMC1 in the presence of f-PrjNEt in dichloro-methane at 4013 C [Scheme 4.305].257,525,555 Conversion of the SEMCl to the corresponding iodide in situ using tetrabutylammonium iodide accelerates the reaction ... 

From alcohols. Alcohols can be transformed into phenylselenides in a stepwise manner via mesylation and reaction with lithium phenylselenolate. This procedure offers obvious advantages over the formation of the corresponding bromides or iodides when subsequent reaction with strong nucleophiles, such as organolithium compounds, are necessary to prepare the radical precursors. The diol 8 is converted to the bis(phenylselenide) 9 via the corresponding bis(mesylate) as shown in Scheme 2 [6]. Compound 9 is converted to the radical precursor 11 via reaction with lithium phenylacetylide followed by alkylation with allylbromide and a Pauson-Khand reaction. Such a reaction sequence would not be feasible with an alkyl halide. The cyclization afforded the expected tricyclic compound 12 in 95% yield. 

Thermal decomposition of methyl xanthates is similar to the pyrolysis of acetates for the formation of the double bond. Olefins are obtained from primary, secondary, and tertiary alcohols without extensive isomerization or structural rearrangement. The other products of the pyrolysis of the methyl xanthates are methyl mercaptan and carbon oxy-sulfide. The xanthates prepared from primary alcohols are more difficult to decompose than those prepared from secondary and tertiary alcohols. Over-all yields of 22-51% have been obtained for a number of tertiary alkyl derivatives of ethylene. Originally the xanthates were made by successive treatment of the alcohol with sodium or potassium, carbon disulfide, and methyl iodide. In a modification of this procedure sodium... 

During the endgame of the total synthesis of the stemona alkaloid (-)-stenine, Y. Morimoto and co-workers utilized the Finkelstein reaction to prepare a primary alkyl iodide from a primary alkyl mesylate. The mesylate was prepared from the corresponding primary alcohol with MsCI/EtsN. The resulting primary alkyl iodide was used in the subsequent intramolecular N-alkylation to construct the final perhydroazepine C-ring of the natural product. 

Stone and Shechter have developed high-yield procedures for the preparation of alkyl iodides from alcohols, ethers, and olefins by reaction with a reagent described as 95% orthophosphoric acid in combination with potassium iodide. For the conversion of 1,6-hexanediol into 1,6-diiodohexane, a mixture of 65 g. of P2O5 and 231 g. (135 ml.) of 85% phosphoric acid is stirred mechanically and let cool to room temperature, potassium iodide and 1,6-hexanediol are added, and the mixture is stirred and heated as indicated. The initially homogeneous solution separates into... 

As stated on page 115, the action of hydriodic acid on polyacid alcohols does not yield, as might be expected, the poly-iodine derivatives, but mono-iodine derivatives. Thus from glycerol, isopropyl iodide is obtained from erythrite, normal secondary butyl iodide from man-nite, the normal secondary hexyl iodide. These iodides, as pointed out, may be converted into the corresponding alcohols. The method is of practical value in the preparation of tertiary alcohols from acid-chlorides and zinc alkyls. — Butlerow s synthesis. Compare page 126. 

The secondary alkyl halides can be prepared from the alcohols by the action of the halogen acids or the phosphorus halides. In certain cases they can be made by adding the halogen hydride to unsaturated hydrocarbons. Addition takes place most readily with hydriodic acid. Secondary butyl iodide, for example, can be prepared in this way from butylene and a strong aqueous solution of hydriodic acid —... 

Certain secondary alkyl halides are most readily prepared from polyhydroxy alcohols. The formation of isopropyl iodide from glycerol has been noted (95). Secondary hexyl iodide is... 

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