This paper describes a novel synthesis of trienes by treatment of trans-2-alkenyl triphenylphosphonium bromides with BuLi in THF solution. Compounds, 5,7,9-tetradecatriene, 1,6-diphenyl-1,3,5-hexatriene, and 2,6,11,16-tetramethyl-2,6,8,10,14-hexadecapentaene were prepared in the yields of 40%, 9%, and 46%, respectively. Cross-coupling of trans-2-heptenyltriphenylphosphonium bromide and trans-3-phenyl-2-propenyltriphenylphosphonium bromide gave a mixture of 5,7,9-tetradecatriene (10.6%), 1,6-diphenyl-1,3,5-hexatriene (0.5%), and 1-phenyl-1,3,5-decatriene (9.4%)

Hayashi, Nobuyuki

Tsuboi, Sadao

Ye, Xuan

Okayama University Scientific Achievement Repository

Journal of the Faculty of Environmental Science and Technology, Okayama UniversityVol 5, No.1. pp. 153-158, February 2000A Novel Synthesis ofSymmetric TrienesXuan Ye, Nobuyuki Hayashi, and Sadao Tsuboi*(Received November 21 . 1999)This paper describes a novel synthesis of trienes by treatment of trans-2-alkenyltriphenylphosphonium bromides with BuLi in THF solution. Compounds,5,7,9-tetradecatriene, 1,6-diphenyl-l,3,5-hexatriene,and 2,6,11,16-tetramethyl-2,6,8,10,14-hexadecapentaene were prepared in the yields of 40%, 9%, and 46%,respectively. Cross-coupling of trans-2-heptenyltriphenylphosphonium bromide andtrans-3-phenyl-2-propenyltriphenylphosphonium bromide gave a mixture of5,7,9-tetradecatriene <I0.6%), 1,6-diphenyl-l,3,5-hexatriene (0.5%), andI-phenyl-l,3,5-decatriene (9.4%).INTRODUCTIONThe formation of carbon-carbondouble-bond from alkyl halides and phosphinewas found by Wittig. 1.2 Phosphorus ylidsformed by alkyl halide andtriphenylphosphine react with an aldehyde orketone to give alkenes.3 Poulain and Noiret4reported a synthesis of symmetrical Z-olefinsfrom alkyl phosphonium salts via an auto-RESULTtrans-2-Heptenol (la) and Geraniol (lb)were brominated. The trans-2-heptenylbromide (2a), Geranyl bromide (2b), andtrans-3-phenyl-2-propenyltriphenyl bromide(2c) were treated with triphenyl phosphine to*Depanmeut of EuviroDmeutal Chemistry aud MaterialsOkayama University. Okayama 700-8530, Japan.a-mail: stsuboi6@c.c.okayama-u.ac.jpoxidation process. However, to our knowledgethe synthesis of trienes by the couplingreactions ot' phosphonium salts in thepresence of base has never been reported. Inthis paper we report the formation ofcarbon-carbon double bonds by the reactionsof alkenyl phosphoranes and theirprecursors, phosphonium salts.give phosphonium compounds 3a, 3b, and 3c.The treatment of phosphonium salts withBuLi gave symmetric trienes 5a, 5b, and 5c inthe yields of 9-46%, as shown in Scheme 1.153154 1. Fac. Environ Sci. and Tech., Okayama Univ. 5 (1) 2000Schemel.yvOHR ~ ------'~R'la: R =n-C4~' R' =HIb: R = (CH3hC = CHCH2CH2R'=CH32a: R =n-C4H9, R' =H2b: R = (CH3hC = CHCH2CH2R'=CH3yield 83%63%R'R2a: R = n-C4~' R' = H2b: R = (CH3hC = CHCH2CH2R'=CH32e: R=Ph, R'=HJa: R = n-C4H9, R' = H yield 85%Jb: R = (CH3hC = CHCH2CH2 75%R'=CH33e: R = Ph, R' = H 92%R'RR'BuLi, THFRJa: R = n-C4H9, R' = HJb: R = (CH3hC = CHCH2CH2R'=CH33e: R =Ph, R' = H4a: R = n-C4H9, R' = H4b: R = (CH3hC = CHCH2CH2R'=CH34e: R = Ph, R' = HRHR'RH R'4a: R =n-C4~' R' =H4b: R = (CH3hC = CHCH2CH2R'=CH34c: R = Ph, R' = HSa: R = n-C4~' R' = H yield 40%5b: R = (CH3)2C = CHCH2CH2 46%R'=CH35c: R=Ph,R'=H 9%x. YE et al. S~\'mmetric Trielles 155A cross·coupling reaction of phosphonium Scheme 2. Poulain and Noiret4 reported abromides 3a and 3c in the presence of BuLi. synthesis of symmetrical Z.olefins from alkylgave triene compounds 5a, 5c, and 6 in 10.6%, phosphonium salts via an auto·oxidation0.5%, and 9.4% yields, respectively, as shown in process.Scheme 23a+3cBuLi, THF5a + 5c + Ph10.6% 0.5% 6, 9.4%HBase----t..~ RCH=PPh3 ---........~ RCH=CHRAll experiments ofpreparation of symmetricaltrienes were carried out under an atmosphere ofnitrogen. Triphenylphosphine was found in themixture of products. The process happenedduring present experiments is not anauto·oxidation. The mechanism of thereaction is suggested that nucleophilicalkenyl phosphorane 4a-c attacked alkenylphosphonium bromides 3a-c to form theintermediate 7, which eliminated protonand triphenylphosphonium bromide to givetrienes 5a-c, as shown in Scheme 3.Scheme 3.RCH=CHR + BuR5 a- c+ 2PPh3 + LiBr7BuLi3a - cRI156 1. Fac. Environ. Sci. and Tech., Okayama Univ. 5 (1) 2000EXPERIMENTAL SECTIONThe melting points and boiling points are with ice water. The mixture was extracted withuncorrected. Mass spectra were measured on a ether (20ml x 3). 'The organic layer was washedShimadzu model GC-MS QP 5000 at 70 eV. IH with saturated NaCI solution, and dried overand 13C NMR spectra were performed on a anhydrous MgS04. After evaporation of theVarian Gemini 200 NMR spectroscopy. IR solvent the crude product was purified on a silicaspectra were determined on a JASCO model gel column chromatography, giving 0.889g (63%FT-IR 5000 apparatus. tans-2-Heptenol, yield) of2b: bp 112-115 'C /3mmHg.Cinnamyl alcohol, Geraniol and Cinnamyl tra.ns-2-Heptenyltriphenylphosphoniumbromide are commercially available from TCI Bromide (3a).6 To a 25 ml 2-necked round flask(Thkyo Chemical Industry Co'>. under an atmosphere ofnitrogen, were added 15trans-2-Heptenyl Bromide (2a).5 To a 25 ml ml of Benzene, 0.774g (4.4 mmon oftwo-necked round flask under an atmosphere of trans-2-heptenyl bromide and 1.15g (4.4 romoDnitrogen, was added 0.918g (3.39 romoD of of triphenylphosphine. The mixture was stirredphosphorus tribromide. The flask was cooled to for 24 hr at room temperature under darkness.O"C on ice-water bath. An ether solution of White crystals were filtrated, and washed withtrans-2·heptenol 1.03g (9.23 mmon in 12.4 ml ether. Recrystallization from ethanol gave 1.45gether was dropped and the mixture was stirred (85% yield) of 3a: mp 168 - 170 "C; IH NMRat same temperature for 6 hr. The mixture was (200 MHz, CDCh) 0 0.781 (t, 3H, J = 6.7 Hz),quenched with ice water and extracted with 1.048 - 1.218 Un, 4ID, 1.860 - 1.980 Un, 2H),ethyl acetate. The organic layer was washed 4.680 - 4.790 (dd, 2H), 5.170 - 5.360 Un, 1H),with saturated NaCI solution, dried over 5.380 Un, IH), 7.620 - 7.890 Un, 15H).anhydrous MgS04. After evaporation of the trans-2,7-Dimethyl-2-octadienyltriphenylpho-solvent, the crude product was purified on a sphonium bromide (3b) was prepared as shownsilica gel column chromatography, giving 1.35g in the preparation ofcompound 3a: 75% yield; IR(82% yield) of2a. (KBr, em"l) 2916, 2886, 1437, 1114, 1073, 752,Geranyl Bromide (2b). Th a 25 ml two-necked 716, 685, 547; IH NMR (200 MHz, CDCh) 0 1.32round flask under an atmosphere of nitrogen, - 1.86 (m, 9H), 1.82 - 1.97Un, 4H), 4.56 - 4.67were added 10 ml of dry ether and 1.00g (6.48 (dd, 2H), 4.88 (br, IH), 5.09 - 5.13 (q, IH), 7.68mmon of Geraniol, then cooled to O"C with - 7.19 Un, 15).ice-water bath. Then, 0.67g (2.4 mmon of trans-3-Phenyl-2-propenyltriphenylphosphon-phosphorus tribromide was added dropwise and ium bromide (3d was prepared as shown in thethe mixture was stirred for 1 hr at O"C. The preparation of compound 3a: 92% yield. Anal.temperature rose to room temperature. The Calc for C27HuBrP : C, 70.6%; H, 5.26%. Found:mixture was stirred for 32 hr and then quenched C, 70.06%; H, 5.27%.1. Kirby, A. J.; Warren, A. G. " The OrganicChemistry ofPhosphorus" , Elsevier 1976.x. YE et al. Symmetric Trielles5,7,9-Tetradecatriene (5a). To a 5 ml two-necked round flask under an1b a 5 ml two-necked round flask under an atmosphere of nitrogen were added 0.375gatmosphere of nitrogen were added 0.275g (0.58 (0.77 mmoI) of CinnamyltriphenylphosphoniummmoI) of 3a, 2.5 ml of THF, and 0.36 ml (0.57 bromide and 2.5 ml of THF, 0.48 ml (0.77mmol) of BuLi (1.6 MIL). The mixture was mmol) of BuLi (1.6 MIL) at 0 t. The mixturestirred at 0 t ~ room temperature for 24 hr was stirred at 0 t for 3 hr, and then at roomand 5 ml of 5% HCI was added. The mixture temperature for 24 hr. Then 3 ml of 5% HCI waswas extracted with hexane (10 ml x 3). The added. The mixture was extracted with hexaneorganic layer was washed with saturated NaCI (10 ml x 3). The organic layer was washed withsolution, dried over anhydrous MgS04. After saturated NaCI, and dried over anhydrousevaporation of the solvent, the crude product MgS04. After evaporation of the solvent, thewas purified on a silica gel column crude product was purified on a silica gel columnchromatography ( hexane as an eluent ), giving chromatography ( hexane as an eluent ), giving22 mg (40%) yield of 5a: GC-MS (70 eV) mlz 192 16 mg (9% yield) of 5c: GC-MS (70 eV) mlz 232(M+), 163, 149, 135, 121, 107,93. IH NMR (200 (M+), 215, 202, 178,135,141, 128, 115.MHz, CDCh) 00.887 (t, 6H), 1.345 (m, 8H), Reaction of 3a and 3c in the presence of BuLi.2.083 (q, 4H), 5.103 - 5.720 (ro, 2H), 5.960 - 1-Phenyl-l,3,5-decatriene (6).6.130 (m, 4H). To a 5 ml two'necked round flask under an2,6,1l,15-Tetramethyl-2,6,8,10,14-hexadecapen- atmosphere of nitrogen were added 0.43gtaene (5b).7 (0.98 mmol) of 3c, 0.55g (1.2 mmol) of 3a, 15To a 20 ml two-necked round flask under an ml of THF and 1.36 ml (2.18 mmol) of BuLiatmosphere of nitrogen were added 0.661g (1.3 (1.6 MIL) at 0 "C. The mixture was stirred atmmol) of Geranyltriphenylphosphonium 0 "C for 2 hr, and then at room temperaturebromide, 10 ml of THF, and 1.22 ml (1.33 mmol) for 18 hr. Then 5 ml of 5% HCI was added. Theof BuLi. (1.6 MIL) at room temperature. The mixture was extracted with hexane (10 ml x 3).mixture was heated to reflux temperature for 0.5 The organic layer was washed with saturatedhr and then 3 ml of 5% HCI was added. The NaCI, dried over anhydrous MgS04. Aftermixture was extracted with hexane (10 ml x 3). evaporation of the solvent, the crude productThe organic layer was washed with saturated was purified on a silica gel columnNaCI, dried over anhydrous MgS04. After chromatography (hexane as an eluent), givingevaporation of the solvent, the crude product 20 mg (9.4% yield) of 6, 12.2 mg (10.6% yield)was purified on a silica gel column of 5a, and 6 mg (0.5% yield) of 5c.chromatography (hexane as an eluent), giving81.3 mg (46% yield) of 5b: GC-MS (70 eV) mlz REFERENCES272 (M+), 218, 160, 135, 133.1,6-Diphenyl-l,3,5-hexatriene (5c).157158 1. Fac. Environ. Sci. and Tech., Okayama Univ. 5 (1) 20002. Wittig G.; Geissler, G. Ann. Chem. 1953, 580,44.3. Vollhardt, K P. C. Synthesis 1975, 765.4. Poulain, S; Noiret, N; Patin, H. ThtrahedronLett. 1996, 37, 7703.5. Dawson, M. D.; Derdzinski, K; Hobbs, D.P.;Yasuda, D. J. Org. Chem. 1984, 49, 5265.6. Barlow, L.; Pattenden, G. J. Chem. Soc.Perkin ']}ans 1, 1976, 1029.7. Okuma, K; Koda, G.; Okumura, S.; Ohno, AChem. Lett., 1996, 609.

A Novel Synthesis of Symmetric Trienes

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