Alkyl cyclohexyl iodide

In a variation of the scheme above, alkylation of p-hydroxy-benzoic acid with cyclohexyl iodide affords the cyclohexyl ether, 55. (Under alkaline reaction conditions, the ester formed concurrently does not survive the reaction.) Acylation of the acid chloride obtained from 55 with the preformed side chain (56) gives cyclomethycaine (57). ... 

Benzoxazinones 141 and 143 have been reacted in a reductive radical alkylation using triethylborane as the alkyl radical source <2004SL2597>. Triethylborane could also be used in catalytic amount with isopropyl, tert-h xVj, or cyclohexyl iodide as the alkylating agent. Zinc with copper iodide could also he used as initiator (Scheme 8). 

The addition of functionalized alkyl radicals to protonated heteroaromatics was more difficult (because the radicals could not be generated by H-atom abstraction), but a recent development holds promise to resolve this problem. Generation of a methyl radical in the presence of an alkyl iodide sets up a relatively rapid equilibrium as indicated in Scheme 85. This equilibrium will favor any more highly substituted alkyl radical over methyl, and further, this latter radical will be significantly more nucleophilic. Thus when methyl radicals are generated in the presence of cyclohexyl iodide and a protonated quinaldine, die... 

The second key to success in making sure that the alkyl radical behaves well is to use a reactive radical trap. In fact, this is a major limitation of intermolecular radical carbon-carbon bond-forming reactions for the trapping of alkyl radicals only electrophilic alkenes (attached to electron-withdrawing groups such as -CN, -CC Me, -COMe) will do. This is a limitation, but nonetheless, cyclohexyl iodide adds to all these alkenes with the yields shown and the rate of addition to most of these alkenes is 103 to 104 times that of addition to 1-hexene. 

Dialkyl telluriums, diaryl telluriums, and alkyl aryl telluriums are converted to triorgano telluronium salts on reaction with alkyl halides. These alkylations proceed easily with methyl, ethyl, and propyl iodide, allyl bromide cyclohexyl iodide, ethyl bromoace-tate , and even bromobenzene and iodobenzene -... 

Tertiary and cyclic alkyl halides (cyclohexyl iodide), secondary alkyl chlorides and primary and secondary tosylates cannot be used in these intermolecular alkylations. This is also the case with dibro-moethane and 2-bromo-2-nitropropane, which both lead instead to a,3-dithianylalkanes resulting from the oxidative coupling of the carbanion. 

AlIyl ligands of the nickel(I) complexes also couple with ordinary nonallylic organic halides. Alkyl, alkenyl, and aryl halides are equally employable as substrates the Ti-methallylnickel complex (CXVIII), for example, couples in A, A -dimethylformamide (DMF) with methyl iodide (90% yield), methyl bromide (90%), cyclohexyl iodide (91%), tert-b iXy iodide (25%), iodo-benzene (98 %), vinyl bromide (70 %), benzyl bromide (91 %), phenyl a-chloro-methyl ester (50%), p-bromophenacyl bromide (75%), and chloroacetone (46%) (Corey and Semmelhack, 1967). 

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]. 

Cyclohexyl bromide, for exfflnple, is converted to cyclohexene by sodium ethoxide in ethanol over 60 times faster than cyclohexyl chloride. Iodide is the best leaving group in a dehydrohalogenation reaction, fluoride the poorest. Fluoride is such a poor leaving group that alkyl fluorides are rarely used as starting materials in the preparation of alkenes. 

The results of the alkylation of 6 377a 426-427 429 are summarized in Table XI. In addition to the above factors, the regioselectivity of electrophilic attack on 518 was strongly affected by the structure of the alkylating agents, e.g., methyl iodide, ethyl bromide, cyclohexyl bromide, and rm-butyl bromide. 

In some systems it is necessary to add a large amount of salts to obtain polymers with low polydispersities. This happens when salts participate in ligand/anion exchange (special salt effect) and when they enhance ionization of covalent compounds through the increase of ionic strength. The special salt effect may either reduce or enhance ionization. Strong rate increases observed in the polymerization of isobutyl vinyl ether initiated by an alkyl iodide in the presence of tetrabutylammonium perchlorate or triflate can be explained by the special salt effect [109]. The reduction in polymerization rate of cyclohexyl vinyl ether initiated by its HI adduct in the presence of ammonium bromide and chloride can be also ascribed to the special salt effect [33]. The breadth of MWD depends on the relative rate of conversion of ion pairs to covalent species and is affected by the structure of the counterions. 

Second, if tin(II) catecholate is ligated by an optically active dialkyl tartrate, it will react with an allylic bromide or iodide and an aldehyde, in the presence of Cul as catalyst, to give the optically active homoallylic alcohol. The enantioselectivity is highest when the alkyl groups of the tartrate are bulky (t-butyl or cyclohexyl). Aromatic aldehydes give higher enantioselectivities than do aliphatic aldehydes, and the reaction is also successful with a-carbonylketones 74... 

Oxidation. Oxidation of alkyl halides by DMSO requires high temperatures (100-150°), and yields are relatively low except for primary iodides (1, 303). Epstein and Ollinger11 find that halides can be oxidized to carbonyl compounds by DMSO at room temperature (4-48 hours) in the presence of silver perchlorate as assisting agent. Chlorides are relatively unreactive, but bromides and iodides are oxidized relatively easily. Yields are higher with primary halides than with secondary halides. Cyclohexyl halides are oxidized to only a slight extent to cyclohexanone, the main product being cyclohexene, formed by elimination. 

Most of the useful iodine transfer radical reactions arise from the addition of alkyl iodides, which have been activated by one or more adjacent carbonyl or nitrile substituents, to unactivated olefins. This both labilizes the initial iodide, facilitating chain initiation, and helps ensure that the atom transfer step is exothermic. The requisite iodides are typically synthesized by deprotonation with EDA or NaH, followed by iodination with I2 or A-iodosuccinimide. Cyclization of an iodoester yields primarily lactone product, proceeding through the intermediacy of the I-transfer products as shown in Scheme 5 [19]. Reactions in which a-iodoesters cyclized with alkynes also proved efficient. Similar ketones yielded less synthetically useful mixtures of cyclopentyl and cyclohexyl (arising from 6-endo transition states) products. 

Secondary alkyl bromides (e.g., isopropyl bromide) react less readily and higher temperatures are required. To avoid any decomposition of the lithiated thioacetal or its reaction with THF, the alkylations are usually carried out with the iodides [1]. Cyclopentyl bromide (reaction carried out at + 10°C) and LiCH(SCH3)2 gave the expected product in a moderate yield [3]. With cyclohexyl bromide the predominant reaction is dehydrobromination [1]. 

It is of interest to note that by substituting alkyl bromides for cyclohexyl bromide the corresponding a-phenyl-a-alkyl-acetonitriles are obtained, which may be hydrolysed to the a-phenylaUphatic acids thus with ethyl iodide a-phenyl-butyronitrile is produced, hydrolysed by ethanolic potassium hydroxide to a-phenylbutyric acid. 

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