Alkyl halides oxidation

Matteson and coworkers have described the deprotonation and alkylation of bis(l,3,2-dioxaborin-2-yOmethane (11). Deprotonation with LiTMP yields the stabilized anion, which can be alkylated with a variety of primary alkyl halides. Oxidation under basic conditions then unmasks the carbonyl group. Matteson has also described the deprotonation of some substituted boronic esters (12 X = SPh, SiMei). - The alkylated products derived from (12 X = SPh) can be treated with A/-chlorosuccinimide under mild basic conditions to yield either the monothioacetals or the acetals. Boron-stabilized carbanions can also be generated by transmetallation of the organostannanes. ... 

Systems for which Pd(II)-Pd(IV) cycles are consistent with model reactions involve alkyl halide oxidative addition or oxidation by strong inorganic oxidants. Thus, the reaction of Scheme 10 may be explained by a process very similar to that for Scheme 9 but involving alkyl halide (RT) addition modeled by formation of 27 and its decomposition to 28, cyclization and repetition of this process, and subsequent elimination of norbomene.t In this proposal the sequence for the alkylation of the ortho positions of the aryl group in the intermediate Pd(QH4—C7Hio-C,C )L,2, involving... 

In the presence of base, the C—H bond adjacent to the nitrogen atom is involved in the formation of cyclopaUadated intermediate C. In the second stage of the catalytic cycle the alkyl halide oxidatively adds to the Pd center with the generation of a Pd species (D). Reductive elimination followed by norbomene expulsion gives 2-alkyl-N-paUadaindole (F) which upon 1-protonation delivers the final 2-alkylated IH-indole product. 

Phenyl-2-oxazolin-5-one undergoes ready 4,4-substitution with activated alkyl halides. " Oxidation of the a,a-dialkylated hippuric acids obtained from hydrolysis of the oxazolinones then yields symmetrical ketones (Scheme 17). 

This direct sulphonation should be compared with the indirect methods for the preparation of aliphatic sulphonic acids, e.g., oxidation of a thiol (RSH -> RSOjH), and interaction of an alkyl halide with sodium sulphite to give the sodium sulphonate (RBr + Na,SO, -> RSO,Na + NaBr). 

In contrast to alkylations with most of the alkyl halides, the reactions of anions with ethylene oxide in organic solvents such as diethyl ether and THE... 

In Grignard reactions, Mg(0) metal reacts with organic halides of. sp carbons (alkyl halides) more easily than halides of sp carbons (aryl and alkenyl halides). On the other hand. Pd(0) complexes react more easily with halides of carbons. In other words, alkenyl and aryl halides undergo facile oxidative additions to Pd(0) to form complexes 1 which have a Pd—C tr-bond as an initial step. Then mainly two transformations of these intermediate complexes are possible insertion and transmetallation. Unsaturated compounds such as alkenes. conjugated dienes, alkynes, and CO insert into the Pd—C bond. The final step of the reactions is reductive elimination or elimination of /J-hydro-gen. At the same time, the Pd(0) catalytic species is regenerated to start a new catalytic cycle. The transmetallation takes place with organometallic compounds of Li, Mg, Zn, B, Al, Sn, Si, Hg, etc., and the reaction terminates by reductive elimination. 

Oxidative addition of alkyl halides to Pd(0) is slow. Furthermore, alkyl-Pd complexes, formed by the oxidative addition of alkyl halides, undergo facile elimination of /3-hydrogen and the reaction stops at this stage without undergoing insertion or transmetallation. Although not many examples are available, alkynyl iodides react with Pd(0) to form alkynylpalladium complexes. 

The most interesting and difficult cross-coupling is alkyl-alkyl coupling, because oxidative addition of alkyl halides having /i-hydrogen is slow. In addition, easy elimination of /d-hydrogen is expected after the oxidative addition. 

The reaction of an alkyl halide with lithium is an oxidation-reduction reac tion Group I metals are powerful reducing agents... 

Grignard reagents react with ethylene oxide to yield primary alcohols containing two more carbon atoms than the alkyl halide from which the organometallic compound was prepared... 

Pyrrolethiols, readily obtained from the corresponding thiocyanates by reduction or treatment with alkali, rapidly oxidize to the corresponding disulfides. They are converted into thioethers by reaction with alkyl halides in the presence of base. Both furan- and thiophene-thiols exist predominantly as such rather than in tautomeric thione forms. 

Enby 6 is an example of a stereospecific elimination reaction of an alkyl halide in which the transition state requires die proton and bromide ion that are lost to be in an anti orientation with respect to each odier. The diastereomeric threo- and e/ytAra-l-bromo-1,2-diphenyl-propanes undergo )3-elimination to produce stereoisomeric products. Enby 7 is an example of a pyrolytic elimination requiring a syn orientation of die proton that is removed and the nitrogen atom of the amine oxide group. The elimination proceeds through a cyclic transition state in which the proton is transferred to die oxygen of die amine oxide group. 

One-electron oxidation of carboxylate ions generates acyloxy radicals, which undergo decarboxylation. Such electron-transfer reactions can be effected by strong one-electron oxidants, such as Mn(HI), Ag(II), Ce(IV), and Pb(IV) These metal ions are also capable of oxidizing the radical intermediate, so the products are those expected from carbocations. The oxidative decarboxylation by Pb(IV) in the presence of halide salts leads to alkyl halides. For example, oxidation of pentanoic acid with lead tetraacetate in the presence of lithium chloride gives 1-chlorobutane in 71% yield ... 

In this, the first serious and successful work on the structure of a complex alkaloid, there was naturally at first some confusion between Moquinoline and the better-known quinoline. The 6 7-dimethoxy-woquinolinecarboxylic acid was thought to be a dimethoxycinchoninic acid. It known, however, that quinoline benzylchloride on oxidation furnished formylbenzylanthranilic acid, CjH4(COOH)—N(C,H,)—CHO, whereas various papaverine alkyl halides gave what were presumed to be... 

At-Phenyltriflamide is a useful reagent for the mdd oxidation of alkyl halides to carbonyl compounds through a multistep one-pot procedure [II2] (equation 56)... 

This reaction gives good results for a variety of activated and unactivated alkyl halides [112] Oxidation of 2-bromoketones with iV-phenyltriflamide was used m a one pot synthesis of pyrazines by the sequence of reactions shown m equation 57 [II3] The procedure was successfully applied to the synthesis of deoxyaspergilhc acid [II4 ... 

In 1974, Hegedus and coworkers reported the pa]ladium(II)-promoted addition of secondary amines to a-olefins by analogy to the Wacker oxidation of terminal olefins and the platinum(II) promoted variant described earlier. This transformation provided an early example of (formally) alkene hydroamination and a remarkably direct route to tertiary amines without the usual problems associated with the use of alkyl halide electrophiles. 

Variations and Improvements on Alkylations of Chiral OxazoUnes Metalated chiral oxazolines can be trapped with a variety of different electrophiles including alkyl halides, aldehydes,and epoxides to afford useful products. For example, treatment of oxazoline 20 with -BuLi followed by addition of ethylene oxide and chlorotrimethylsilane yields silyl ether 21. A second metalation/alkylation followed by acidic hydrolysis provides chiral lactone 22 in 54% yield and 86% ee. A similar... 

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