' C11ernistr? . Urliversity of'Briti.\h Colrrrr~bitr. 2036 Mtiirl Mtill, Urliver:\itl\ Ctlrrlplrs. V n i~c o~r~~e r , B.C., Ctrirtrtltr V6T I Y6Received Novembcr 8, 1982 EIIWARD PIERS and EDWARD H. RUEDICER. Can. J. Chem. 61, 1239( 1983.A total synthesis of the scsquiterpenoid (2)-P-himachalene (2) is described. Treatment of 5.5-dimethyl-2-vinyl-1.3-dioxane (24) with brornoform and aqueous sodium hydroxide in the prcscncc of a phase-transfcr catalyst afforded the dibromocyclopropane 25. When thc latter substance was allowed to react (tctrahydrofuran-hexamethylphosphoranide -95°C) with 11-butyllithium in thc presence of mcthyl iodide, a mixture of the cpirncric products 26 (87-93%) and 27 (7-13%) was produced in high yicld. Compound 26 was convcrtcd via a two-stcp sequcncc (hydrolysis with 88% formic acid, 26 + 28; Wittig reaction with isopropylidcnctriphcnylphosphoranc. 28 + 16) into the bromocyclopropanc 16, which was transformed into the cupratc rcagcnt 17. Rcaction of 3-iodo-2-cyclohexcn-I-one (4) with reagent 17, followed by thcrmolysis (xylene, rcflux) of the resultant product 18 (the title compound), afforded, in quantitative yield, thc dicnonc 12. Methylation of 12 furnished compound 29 which, upon hydrogenation in thc presence of tris(triphcnylphosphine)chlororhodium, gave the kctone 32. Conversion of compound 32 into the corresponding enol phosphate 33. followed by reduction (lithium, cthylamine-tetrahydrofuran, tert-butyl alcohol) of thc latter material. provided (2)-P-himachalcnc (2).
EDWARD PIERS et EDWARD H. RUEDICER. Can. J . Chcm. 61, 1239 (1983).On decrit une synthkse totale dc scsquitcrptne ( 2 ) P-himichalcne (2). LC dimethyl-5.5 vinyl-2 dioxanne-1.3 (24) r6agit avec lc bromoformc dans I'hydroxyde de sodium aqueux cn prCscncc d'un catalyseur dc transfert de phase pour donner le dibromocyclopropane 25. Cc dcrnier reagit (tetrahydrofurannc-hexamCthylphosphoramide, -95°C) avec le 11-butyllithium en prCsencc de I'iodurc de mCthylc cn donnant des produits epimkrcs 26 (87-93%) et 27 (7-13%) avec un fort rendement. On a, en dcux Ctapes, (hydrolysc par I'acide formique h 88'70, 26 + 28; reaction de Wittig avcc I'isopropyllid&ne triphCnylphosphoranc, 28 + 16) transform6 le compost 26 en bromocyclopropane 16 que I'on transforme en cuprate 17. La reaction de l'iodo-3 cyclohexkne-2 one-1 (4) avec la reactif 17 suivie dc la thermolyse (xylknc, reflux) du produit rksultant 18 (Ic composC mentionnC dans le titrc) donne avec un rendement quantitatif la di6none 12. La methylation de cettc dernikre conduit au composC 29 qui par hydrogenation en prCsence du tris(triphCnylphosphine)chlororhodium donne la cCtone 32. La transformation de cette cCtone en phosphate d'Cnol correspondant 33, suivie d'une reduction (lithium, Cthylaminetetrahydrofurannc, alcool (err-butylique) permet d'acceder h la ( 2 ) P-himachalene (2).[Traduit par le journal]