5-Hexenyl chloride

The first experimental hint for a finite lifetime of an alkyl halide anion radical in homogeneous etheral solution was provided by Garst and coworkers in 1977. From the reduction of 5-hexenyl chloride, bromide and iodide with disodium tetraphenylethylene in 2-methyltetrahydrofuran (MTHF) at 20°C they concluded that radical anions R-X Na were involved and that the order of their stability was R-I Na" >R-Br Na > R-CrNa. ... 

The reactivity order of alkylhalides that is tertiary > secondary > primary suggests the reaction does not proceed via mechanism but via radical or car-bocation like mechanism. To discriminate between the two mechanisms 1,1-dimethyl-5-hexenyl chloride is reacted with tributyltin hydride (which involves radicals) and with the lithium di-n-butyl-9-BBN ate complex. It is well known that 5-hexenyl radicals undergo cyclization to give cyclopentylmethyl radicals [31], whereas hexenyl cation cyclizes to cyclohexyl cation [32]. As reduction with ate complex (Chart 25.13) affords none of the cyclopentyl derivatives, thus rules out the radical mechanism. 

Eisch, Behrooz and Galle196 give compelling evidence for the intervention of radical species in the desulphonylation of certain acetylenic or aryl sulphones with metal alkyls having a lower oxidation potential at the anionic carbon. The primary evidence presented by these workers is that the reaction of 5-hexenylmagnesium chloride outlined in equation (85) gives a mixture of desulphonylation products, in accord with the known behaviour of the 5-hexenyl radical, in which the cyclopentylmethyl radical is also formed. 

A5-hexenyl substituent, extensive cyclization occurs to yield the cyclopentylcarbinyl product from the yields of uncyclized and cyclized products for A5-hexenylmercury chloride, the rate constants for equation 50 have been estimated (vide supra). The SH2 reaction 49 has also been invoked to be the key step in the alkylation of -substituted styrenes by a free-radical addition-elimination sequence, namely96... 

The acid-catalysed ring-closure of divinyl ketones to cyclopentenones (equation 6), the Nazarov reaction6-8, represents a conrotatory electrocyclization of 4jr-cyclopentadienyl cations. The conrotatory course of the reaction was confirmed for the case of the dicyclo-hexenyl ketone 7, which yielded solely the tricyclic ketone 8 on treatment with phosphoric acid (equation 7)3b. Cycloalkanocyclopentenones 10 with c/s-fused rings are obtained from the trimethylsilyl-substituted ketones 9 (n = 1, 2 or 3) and iron(III) chloride and... 

Many examples exist for Pd-catalyzed cross-couplings of alkenylzirconocenes with simple carbocyclic aryl or alkenyl halides, whereas few precedents are seen for the coupling of alkenylzirconocenes with heteroaryl halides. Undheim and coworkers reported a Pd-catalyzed cross-coupling of 2,4-dichloropyrimidine with alkenylzirconocene [50]. Hydrozirconation of hexyne readily took place at room temperature with zirconocene chloride hydride in benzene. The resulting hexenylzirconocene chloride (76) was then coupled with 2,4-dichloropyrimidine at the more electrophilic 4 position, giving rise to 2-chloro-4-[( )-l-hexenyl]pyrimidine (77). 

Photolysis of methylpyridinium chloride in water or methanol affords derivatives of the rare 6-azabicyclo[3.1.0]hexenyl system (296, 297) azabicyclohexenyl ions (298, 299) and methylazoniabenzvalene (300) are implicated as intermediates (Scheme 220) (72JA3283). A similar mechanism might explain the isomerization of 3,5- to 2,4-lutidine-d2 on irradiation in acidic D20. 

Wunderlich and Knochel recently published the alkylation of diaryliron compounds by alkyl iodides or benzyl chloride 1 (entry 33) [77]. The reaction works well with 98% pure FeCl2 2LiCl but not with 99.998% pure metal salt. Addition of other transition metal salts showed that nickel contained in the FeCl2 of 98% purity is the likely catalyst. Alkylarenes 3 were obtained in 65-88% yield. The method tolerates ester, nitrile, fluoride, or chloride substituents. Although the use of 5-hexenyl iodide did not provide a cyclized product, the initial formation of radicals cannot be excluded safely. 

A -oxocenes increase as the 5-substituent of a 5-hexenyl acetal is varied from H to SiMej to SPh. As shown in Scheme 62, the Cjs-nonisoprenoid metabolite ( )-laurenyne 190) was synthesized using this method [111b]. Thus, mixed acetal precursor 188 was treated with 2 equiv of stannic chloride in dichloromethane at 0 °C for 1.5 h followed by 0-desilylation to produce oxocene 189 as the sole cyclic ether product in 37% yield. 

Effect of acetate/chloride ratio on relative amount of hexenyl acetates... 

All reactions run at 115°C. for 15 min. using NaOAc in HOAc. Acetate/Chloride Ratio, 2.45 product 100% hexenyl acetates. 

Methyl-4-(6-phenyl-l-hexenyl) carbamate (5 grams) in 400 milliliters of 40 per cent sodium hydroxide solution was refluxed for two hours. The reaction mixture was then steam distilled and the distillate extracted several times with ether, The ether extracts were dried over anhydrous sodium sulfate, filtered, and the solvent removed by evaporation. The resulting product, a p/m-allyl-gamma-phenylpropylamine, was converted to the hydrochloride addition salt by the addition of ethereal hydrogen chloride. 

Eight- and nine-membered cyclic ethers are also generated via type-III reactions by treating the 5-hexen-l-ol acetals with Lewis acids. 8-endo Cyclization of 5-hexenyl methoxyethoxymethyl ether in the presence of two equivalents of tin(IV) chloride forms a 2 1 mixture of chlorinated and unsaturated 1 -oxycyclooctanes 11 and 1232. Vinylsilane undergoes an 8-endo Prins cyclization. After O-desilylation, oxocene 13, which is used as a precursor in a laurenyne synthesis, is obtained in 37% yield33. 

Zinc stearate (I) reacts with 4-chloro-2-hexene to yield hexenyl stearate and zinc chloride, which is a strong catalyst for this esterification reaction as well as for the degradation reaction that yields hexadiene and... 

This reaction was clarified with hexenyl stearate (I) at 60°C during the reaction between zinc stearate and 4-chloro-2-hexene in tetrahydro-furan. During this reaction, zinc stearate reacts immediately with 2 mol of model compound, and kinetic laws do not suggest the presence of CIZnOCOR as an intermediate product in the substitution reaction. Nevertheless, such an organometallic compound was suggested by Frye and Horst (9) and also by Anderson and McKenzie (10) who assumed that such compounds accounted for the ligand exchange between cadmium chloride and barium carboxylate. 

Similarly, fused and spiro cyclopropane systems 31 and 33 can also be synthesized by the reaction of appropriate cycloalkenyl cobaloximes 30 and 32 with free radical precursors such as toluenesulfonyl iodide (Scheme 11). The thermal and photochemical reactions of hexenyl cobaloximes 34 with a large excess of CCI4 gives mainly the pentachloroheptane 35 (path A). On the other hand, the photochemical reactions in the presence of low concentration of CCI4 gives mainly the cyclopentyl methyl chloride 36a through homolysis of the C-Co bond followed by cyclization of the hexenyl radical and chlorine atom abstraction (path B). However,... 

Later Olah et al. showed that the trans-chloride 605 with SbFj—SO Fl yield a 3-cyclohexenyl cation 606, but not the ion 520 thus, just as under solvolytk conditions, ion 520 is formed only when cr-participation is possible in the transition state of ionisation. In the same paper it was pointed out that ion 520 could be generated from the alcohol if freshly distilled SbFj in SOjFQ (—78 "C) was used the admixtures of proton acids, the authors maintain, favour the opening of the cyclopropane ring before ionization. The ionization of 3-methyl- 607 and 3-phenyl-cis-bicyclo[3,l,0]hexanol-3 608 in SbFj—SOjFCl results in the 3-methyl-cyclo-hexenyl ion 609 and the 3-methyl-l-phenylcyclopentenyl ion 610. That the ionization of tertiary substrates results in classical tertiary carbocations rather than trishomocyclopropenyl ions appears to be due to the hindrance in passing from the conformation of the bath to the chair which is indispensable for the formation of a delocalized ion. 

The cyclization of 4-substituted 5-hexenyl iodides proceeds well, leading to cyclopentylz-inc iodides that can be trapped with various electrophiles such as 3-iodo-2-cyclohexenone, iodine, acid chlorides, allylic halides, and ethyl propiolate (carbocupration) (Scheme 1) Various substitution patterns allow a successful cyclization. Also, a range of functional groups like esters or nitriles are tolerated in the ring closure (Scheme 8). 

N-Trimethoxysilylpropyl-N,N,N-trimethyl ammonium chloride 35154-45-1 2-Hexenyl isovalerate cis-3-Hexenyl isovalerate... 

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