EDWARD PIERS, JOHN R. GRIERSON, CHEUK KUN LAU, and ISAO NAGAKURA. Can. J. Chem. 60,210 (1982). A new, efficient method for the preparation of P-chloro, P-bromo, and P-iodo a$-unsaturated ketones is described. The method involves the reaction of P-diketones or a-hydroxymethylenecycloalkanones with triphenylphosphine dihalides in the presence of triethylamine. With the dichloride and dibromide reagents, the reactions are conveniently carried out in benzene at room temperature, while with triphenylphosphine diiodide the reactions are best performed in refluxing acetonitrile (P-diketones) or in acetonitrile-hexamethylphosphoramide (a-hydroxymethylenecycloalkanones). The reaction of triphenylphosphine diiodide -triethylamine with a series of 4-alkyl-l,3-cyclohexanediones provides mainly or exclusively (depending on the size of the alkyl group) 6-alkyl-3-iodo-2-cyclohexen-I-ones, while reaction of this reagent with 2-hydroxymethylenecyclohexanone and 2-hydroxymethylenecyclopentanone affords stereoselectively and regioselectively (E)-2-iodomethylenecyclohexanone and (E)-2-iodomethylenecyclopentanone, respectively. On decrit une nouvelle methode efficace de preparatton des P-chloro, P-bromo et P-iodo cetones a,P-insaturees. La methode fait intervenir la reaction des P-dicetones ou des a-hydroxymethylenecycloalcanones avec les dihaiogenures de triphenylphosphine en presence de triethylamine. Les reactions ont lieu dans le benzene a la temperature ambiante si on utilise les dichlorures ou les dibromures comme reactifs, tandis qu'avec le diiodure de triphenylphosphine, on obtient de meilleures reactions dans I'acetonitrile au reflux (P-dicetones) ou dans un melange d'acetonitrile-hexamethylphosphoramide (a-hydroxymethylenecycloalcanones). La reaction du diiodure de triphenylphosphine dans la triethylamine avec une serie d'alkyl-4 cyclohexanediones-l,3 conduit principalement ou exclusivement (dependant de la taille du groupe alkyle) aux alkyl-6 iodo-3-cyclohexen-2 ones-1, tandis que ce m6mereactif avec I'hydroxymethylene-2 cyclohexanone et I'hydroxymethylene-2 cyclopentanone conduit de f a~o n stereoselective et regioselective aux iodomethylene-2 cyclohexanone-(E) et iodomethylene-2 cyclopentanone-(E) respectivement. EDWARD PIERS, JOHN R. GRIERSON, CHEUK KUN LAU[Traduit par le journal] Introduction chloride (39), oxalyl chloride (40, 9), and triphenyl-P-Chloro a,P-unsaturated ketones have been phosphine -carbon tetrachloride (41). Of these, known for a long time (1) and, over the years, have the latter two reagents appear to be the best in served as important and versatile intermediates in terms of c~n~e n i e n~e and efficiency. Con~erSion of organic On the other hand, the corre-P-diketones into P-bromo enones has traditionally sponding bromo compounds, although known, do been accomplished by treatment of the not appear to have been used a great deal by substrates with phosphorus tribromide (29,36,42), synthetic organic chemists. Furthermore, prior to although the yield of this Process does not appear to the initiation of ...

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synopsisWhen a small amount of persulfate is dissolved in a relatively concentrated aqueous solution of bromide salts, especially LiBr, liberation of Brz occurs to some extent. This system waa utilized for the graft copolymerization of various acrylatea in wool fibers using diethylene glycol monobutylether as monomer-solubilizer. The grafting waa fairly well performed a t a relatively low temperature (1MO"C.) and without homopolymerization while liberating Br2. This new graft copolymerization has been attributed to the concerted action of the fiber-swelling power of bromide salta, the following redox system, and the mild bromination of some monomers by which the grafting will proceed without homopolymerization.It is known that the bromides of alkali metals or ammonium are well absorbed by protein materials such as wool, silk, or gelatin accompanying its hydration, swelling, or contraction, more or less according to the lyotropic series of cations (Li+ > Na+ > K+ for wool or silk, Li+ > NH4+ > Na+ > K+ for When a small amount of persulfate, in the form of K2SzOs or (NH4)2S20s, is dissolved in relatively concentrated aqueous solutions of these bromides, the liberation of Br2 occurs to some extent. The mechanism of this reaction involves the following redox system:The facility of Br2 liberation was observed to be in the order K+ > NHI+ 2 Na+ > Li+ and decreased with increasing the degree of hydration of bromide.Thus, we attempted to utilize the fiber-swelling action of these bromides and the redox system formed between Br-and S2OS-for the graft copolymerization of vinyl monomers in wool fibers. In order to solubilize vinyl monomers, especially water-insoluble monomers, in the aqueous solutions 3465

EDWARD PIERS, JACQUES BANVILLE, CHEUK KUN LAU, and ISAO NAGAKURA. Can. J. Chem. 60,2965Chem. 60, (1982. Treatment of the P-iodo enones 7-10 with lithium (phenylthio)(cyclopropyl)cuprate provided excellent yields of the corresponding P-cyclopropyl a,P-unsaturated ketones 11-14, respectively. When 3-isopropenyl-2-cyclohexen-I-one (16) was allowed to react with dimethyloxosulfonium methylide in dimethyl sulfoxide -tetrahydrofuran, 3-(I-methy1cyclopropyl)-2-cyclohexen-I-one (17) was produced in 59% yield. Although thermal rearrangement (-425-450°C) of compounds 11 and 17 produced high yields of the annulation products 19 and 22, respectively, similar reactions involving the P-cyclopropyl enones 12 and 13 were not efficient in terms of production of the corresponding bicyclic systems (23,26, and/or 27, respectively). In these cases, predominant (24 + 25 from 12) or significant (28 + 29 from 13) amounts of monocyclic dienones were formed. The annulation product 22 served as a convenient starting material for a new formal total synthesis of the sesquiterpenoid (f)-zizaene (30). Conjugate addition of lithium divinylcuprate to 22 afforded the ketone 36 which was converted by standard methods (via 38 and 39) into the enone 40. Treatment of the latter substance with thiophenol in the presence of tetra-n-butylammonium fluoride gave 41, which was transformed via ketalization (41 -t 42), hydroboration (42 + 43), tosylation (43 -t 44), and oxidation (44 -t 45) into the sulfone 45. When the latter compound was treated with potassium rerr-butoxide in hexamethylphosphoramide, the tricyclic ketal sulfone 46 was produced in 85% yield. Reduction of46 with sodiumamalgam afforded the ketal47, which upon hydrolysis under mild conditions gave the ketone 32. Treatment of the latter substance with sodium methoxide in methanol provided a 1:2 mixture of the epimeric ketones 31 and 32, which had been converted previously by Coates and Sowerby into (+)-zizaene (30). 1Les P-iodo enones 7-10 rtagissent avec le (phtnylthiocyclopropyl) cuprate de lithium e n conduisant respectivement avec I d'excellents rendements aux cttones a$-insaturtes, P-cyclopropyles correspondantes 11-14. Si on laisse reagir I1isopropCnyl-3 cyclohexene-2 one-l(16) avec le methylure de dimCthyloxosulfonium dans le dimethylsulfoxyde -tetrahydrofuranne, on obtient le (methyl-1 cyclopropyl)-3 cyclohexen-2 one-1 (17) avec un rendement de 59%.

Treatment of the β-iodo enones 4 and 26–28 with lithium (phenylthio)(2-vinylcyclopropyl)cuprate (21, mixture of epimers), followed by thermolysis (180 °C, 30–45 min) of the initially formed β-(2-vinylcyclopropyl) enones, provided excellent yields of the seven-membered ring annulation products 25 and 30–32, respectively. In similar fashion, the (E)-2-(iodomethylene)cycloalkanones 8 and 29 were transformed efficiently into the spiro-annulation products 34 and 35 respectively. When compound 36 was treated with bromoform – sodium hydroxide in the presence of a phase-transfer catalyst, the dibromocyclopropane 37 was produced. The latter substance served as the starting material for a sequence of reactions (hydrolysis with hydrochloric acid in methanol, 37 → 38; oxidation with pyridinium chlorochromate, 38 → 39; Wittig reaction with methylenetriphenylphosphorane, 39 → 40; reduction with zinc in acetic acid, 40 → 41) culminating in the stereoselective formation of cis-1-bromo-2,2-dimethyl-3-vinylcyclopropane (41). On the other hand, treatment of compound 37 with n-butyllithium (ether, −90 °C), followed by protonation of the presumed intermediate 43 and hydrolysis of the resultant product 44, provided the bromo alcohol 45 in 70% yield. The latter substance was converted into trans-1-bromo-2,2-dimethyl-3-vinylcyclopropane (47). When the cuprate reagents 42 and 48 (prepared from the bromocyclopropanes 41 and 47, respectively) were allowed to react with the iodo enones 4 and 26, the β-(2-vinylcyclopropyl) α,β-unsaturated ketones 49, 52, 54, and 56 were produced in high yields. The enone 49, upon thermolysis in refluxing n-hexane, underwent facile Cope rearrangement to produce the annulation product 50 quantitatively. In contrast, the homolog 54 was notably resistant to [3,3]-sigmatropic rearrangement and, upon thermolysis in o-xylene, o-dichlorobenzene, or collidine at elevated temperatures produced, in varying ratios, the Cope rearrangement product 55 and the isomerization product 56. Thermal rearrangement (o-dichlorobenzene, 220 °C, sealed tube) of trans-3-(2,2-dimethyl-3-vinylcyclopropyl)-2-cyclohexen-1-one (52) provided the annulation product 51 (59% yield). In contrast, the corresponding homolog 56, under very similar conditions, produced only a minor amount of the annulation product 55. In this case, the major product (trienone 57) was that resulting from a [1,5]-sigmatropic hydrogen migration (ratio of 55/57 ≈ 1:4).