Enantioselective Cycloisomerization of 1 6-Enynes Catalyzed by Chiral DiphosphaneЦPalladium Complexes.код для вставкиСкачать
COMMUNICATIONS Chivn. So(. 1983, 105. 5939: L. Hofinann. H. Werner. J. Organonie~.Cheni. 1983. 2.5s. C41 , H. Werner. W. Paul, A q e i r . Cltem. 1984. 96.68: Angeii-. Cliem h i . Ed D i g / . 1984. 23. 58: W. A. Herrmann, J. Rohrmann. A. Schifer. J Orgunoine~.Cliem 1984. 265. C1: .I. H. Shin. G . Parkin. 0rgunomerallic.s 1995. 14. 1104. R. Okazaki. N. Kumon. N. Inamoto. J Am. Chem. SOC.1989. 111. 5949. K.Okuma, Y. Komiya. I Kaneko, Y Tachibana. E. Iwata. H. Ohta. Bull. Chei77. SOC.Jpn 1990. 63. 1653: P. T. Meinke. G. A. Krafft, J. Am. C l i ~ n iSuc . 1988. 110. 86'71 : M Segi. S. Nakajima. S. Suga, S. Mural. S. Ryu. A. Ogdwa, N. Sonoda. ilitd. 1988. 110, 1976; G. Erker. R. Hock. R. Notle. /hid. 1988, 110. . C/iem. 1988. 1. 53: 624: J. Nakaydma, K. Akimoto. M. Hoshino. J. P l i ~ s Org. G. W. Kirby. A. N. Tretheway. J. Clieni. Soc. Chem. Conimrm. 1986. 1152; R. Okazaki. A. Ishii. N. tnamoto. ihid. 1986. 71. and references therein. N. Tokitoh. N. Takeda. R. Okazdki, J. Am. Citein Soc. 1994, 116. 7907. N. Tokitoh. N. Takeda. T. Imakubo, M. Goto. R. Okazaki. Cli~ni.LrJrr.1992. 1599; Bull. Chem. Soc. Jpn. 1995, 68, 2757. TbtCHSe, 4 was prepared by the reaction of TbtCHN, with (C,H,),TiSe,[li~ in the presence of a catalytic amount of CuCl at room temperature. 4 was obtained as an inseparable mixture of compounds with different numbers of selenium atoms. the average number of which was determined to be 5.1 by elemental analysis. A. Shaver, J. M. McCall, Organomerol/ics 1984. 3. 1823. Compound 7 gradually decomposes to TbtCHO and MesNCSe at room temperature. S. Watanabe, T.Kawashirna, R. Okazaki. unpublished results. The structures of l a and Ib in solution were determined by ' H ( ' H i nuclear Overhauser effect (NOE) experiments, !he results of which were similar to those for TbtCHS. For rotational isomerization of sterically congested. substituted benzenes, see: J. Siegel. A. Gutierrez. W. B. Schweizer. 0.Ermer. K. Mislow. J. A m . C/i@t77. SOC.1986, 108. 1569: J. S. Lomas, V. Bry-Capdeville. J. Chem. SOC.Perkin T,.uns. 2 1994. 459. and references therein. G. Erker. R. Hock, C. Kriiger. S. Werner, F. G Kllrner, U. Artschwager-Perl. Angew Chem. 1990. 102. 1082; Angew. Chem. In!. Ed. Engl 1990. 29. 1067 M = 968.16. trtclinic, space Crystallographic data for 3a: C,,H,,O,SeSi,W. group Pi, (I =12.859(3). b =16.680(7), r =11.748(6),&. Y =107.67(3), =97.32(3), ;.=95.50(3)', V=2357(1)A3. Z = 2. pcrlcd=1.364gcm-'. LI = 34.09 c m - ' . The final cycle of full-matrix least-squares refinement was 3.000(0] and 415 variable parameters based on 2776 observed reflections [ I i with R (R,) = 0.054 (0.032). Further details of the crystal structure investigation may be obtained from the Director of the Cambridge Crystallographic Data Centre. 12 Union Road. GB-Cambridge CB2 1EZ (UK), on quoting the full journal citation. F. H Allen, 0. Kennard. D G. Watson. L. Bramrner. A. G . Orpen, R. Taylor. J. Chrni. Soc. Perkm Trans. 2 1987, S1. P. R. Brooks, J. A. Counter. R. Bishop. E. R. T. Tiekink. Acru Crcsrullogr. Sect. C 1991. 47. 1939. K. Okuma. K. Kojima. I. Kaneko. Y. Tsujimoto, H Ohta, Y. Yokomori, J Climni. Soc. Perkin Trans. 1 1994. 2151. the construction of a stereogenic center offers an economical access to optically active five-membered cdrbo- and heterocycles, which occur abundantly in natural products. To date, only two examples of asymmetric induction have been reported utilizing 1) optically active carboxylic acids in conjunction with Pdor31and 2) chiral phosphanes for the double stereodifferentiation of optically active ~ubstrates.'~] We now demonstrate that chiral diphosphane-Pd complexes effectively catalyze this interesting cycloisomerization, furnishing 1,4-dienes in medium to high enantioselectivities. Although phosphane ligands reduce the rate of the cyclization, they are crucial for smooth conversion and for minimizing side reactions. Pd complexes with (S,S)-(R,R)-TRAP ligands 4['] were found to be particularly effective for the cyclization of l a (R = SiMe,) at room temperature [Eq. (a), Table 11. In- PhSd2 1 f \ / ' i I Ar M e P 4 Table 1. Enantioselective cycloisomerization of 1.6-enynes l a (R lyzed by TRAP-palladium complexes [a]. Entry TRAP 4 (Ar)[b] [c] Yield [YO] Enantioselective Cycloisomerization of 1,6-Enynes Catalyzed by Chiral Diphosphane-Palladium Complexes Andreas Goeke, Masaya Sawamura, Ryoichi Kuwano, and Yoshihiko Ito" PhSd2 1 2 3 4 5 4a(C6H,) 4 b (p-CH30CbH,) 4 c (p-CIC,H,) 4d (p-FC,H,) 4 e (p-F,CC,H,) 6 4f (m-F,CC,H,) 4 g (3,5-(CF,)>C,Hd 4 h (2-fury]) 7 8 77 71 66 70 72 66 If1 24kI 61 60 76 Product 2 a ee ["h] [d] = SiMe,) cata- Config. [el 36 (R) 34 (R) 41 40 48 58 14 76 kl 10 10 4 (R) (R) ( R) ( R )[fl ( R )[gl (R) (R) (R) The cycloisomerization of 1.6-enynes in the presence of Pd', acetic acid, and phosphane ligands reported by Trost opened elegant pathways to 1,3- and 1,4-dienes, which are difficult to produce using other methods. 1,3-Dienes with exocyclic double bonds are suitable for Diels-Alder reactions.''. 21 Of particular interest is the formation of the Alder-ene type 1,4-diene, since [a] Reactions were carried out in benzene at 40°C for 5 h ; la:[Pd,(dbd),] .CHCI,:4:HOAc = 100:2.25:8.3:180, [b] (S,S)-(R,R)-configurated TRAPs were used. [c] Yield after purification by chromatography. [d] Determined by HPLC with Chiralcel OJ. [el Assigned based on elution behavior on chiral HPLC analogous to that of 2e (Table 2. entry 5). [fl 25 "C for 12 h. [g] 0" C for 24 h with 2.7 equiv of acetic acid; starting material was recovered. ['I creasing the electron-withdrawing ability of the ligand P-aryl substituents (4a, 4 b < 4c, 4d < 4e) resulted in higher selectivities and also higher reactivities. With 4 e cyclization occurred even at 0 "C (76% ee, 24% yield), whereas the reaction with 4 a did not occur at this temperature. On the other hand, ligands 4f-h did not lead to better results. For the meta-substituted TRAPs 4 f and 4g, steric bulk is assumed to account for these Prof. Dr. Y Ito, Dr. A. Goeke. R. Kuwano Department of Synthetic Chemistry and Biological Chemistry Faculty of Engineering. Kyoto University Sakyo-ku. Kyoto 606-01 (Japan) Fax: Int. code +(75)753-5668 Dr. M. Sawamura Department of Chemistry, School of Science The University of Tokyo, Hongo. Bunkyo-ku. Tokyo 113 (Japan) results. I n addition. optically active cis-chelating phosphanes 5~1ch ;IS CHI RAPHOS,[61 DIOP,"] BPPFA,ls1 and PPFA['] only led t o selectivities of 6- 15 '/o ee with conversions of 56-85 %. Moreover. with BINAPl9l and the electron-donating EtTRAP"'] no conversion occurred even at 80 "C. Neither isomerization to the constitutional isomer 3 nor racemization, which may be responsible for low enantiomeric excesses of the cyclization products, b a s observed on treatment of 2 with [Pd(PPh,),] under the reaction conditions. The regioselective formation of 1,4-dienes 2 can be explained by the relative ease of the b-elimination of H, over H, in the proposed palladium(ir) intermediate B. The j-elimination of Ha, however. is affected by steric and electronic factors and leads to mixtures of 1.4- (2) and 1.3-dienes (3) in most cases.['* 31 When a silylallyl serves as the alkene component, the 1,4-dienes are formed selectively due to the kinetically enhanced acidity of the CH group z to silicon. The configuration of the double bond in 2 was always E ( E : Z > 50: I ) , indicating that the cis-[!elimination took place out of the sterically less congested conformation. Although the reaction mechanism remains highly speculative, we believe the trans-chelation of the TRAP ligands to the palladium atom to be essential for the enantioselectivitydetermining step. This premise is supported by the observation of only two doublets at 6 = 21.4 and 38.3 (J = 455 Hz) in the 31PNMR spectrum (81 MHz, C,D,, 4a as ligand, 30°C) of the catalyst system under conditions similar to the reaction conditions described in Tdbk 1. Results of the cycloisomerization of various 1,6-enynes (1 ai) with (S.S)-(R,R)-p-CF,C,H,-TRAP (&) are summarized in Table 2. The replacement of one of methyl substituents of the Table 2. Eniintiosclective cycloisomerization of 1.6-eneynes 1 catalyzed by the palladium complex oI' /I-CF,C,H,-TRAP 4e [a] Entry 1 2 [el 3 If1 4 5 6 'k1 8 9 10 R (I) SiMe, ( I a) SiMe,Ph ( I b) CH,SiMe, ( l c ) C,H,SiMe, ( I d ) Me(le) Et ((€1-1 f) Et ((Z)-If) C,H,, (Ig) CH,Ph ( 1 h) CH,CHMe, ( l i ) T[C] 0 0 25 35 35 35 35 35 35 35 2.3[b] Yield 298.2 >98:2 3.5.1 >15:1 24 8.1.1 8.9: I >15:1 6.8: 1 5:1 >15:1 [%I ee[%][c] (Config.) [d] 27 68 71 71 74 66 73 75 80 k1] See Experimental Procedure; reaction time 24 h. [b] Determined by ' H N M R spectroscopy [c] Determined for all compounds by HPLC using Chiralcel OJ For the determination of the w value. 3 was removed by treatment with an excess of i\'-phenylnialeimide in CH,CI,. [d] Assigned based on elution behavior on chiral HPLC an;dogous 10 that of 2 ( R = Me). [el Reaction time 48 h. [fl Reaction time 20 h. [g] % - E = 96 4. silicon atom with a phenyl group had only a limited influence on both the reactivity and enantioselectivity (entries 1,2). The preferential formation of 1,4-dienes in substrates bearing a silylallyl group was extinguished in substrates having a homoallyl ( I c, entry 3) or an even more remote silyl group (1 d, entry 4), leading to some 1 .3-diene formation. Interestingly, when steric congestion was relieved by placing the silyl group on a remote position. the enantioselectivity increased considerably, peaking at 95% re. However. steric reasons alone cannot account for this observation. since ee values obtained with substrates having aikyl or phenyi substituents at the homoallylic position (1 g-i) were lower (entries 8-10), It is important t ) note that the product of (Z)-1f has opposite configui-atio : to that of substrate (E)-lf (entries 6, 7). Therefore, the use , )f diasteriomerically pure enynes is a prerequisite for obtainin: high enantioselectivities. The enantioselectivity was also sensitive tog ards the sulfonamide groups. The idea of stabilizing the confoi-mation of intermediate A by the introducing bulkier sulfonamide groups was not tenable. since the selectivities continuously decreased (data not shown). Moreover, the reaction of an enyne carrying a methanesulfonamide group (R = SiMe,) proceeded with very low enantioselectivity (0 "C 11 % ee). This low selectivity may indicate that the substituent on the sulfonamide group may be primarily electronic. Experimental Procedure A solution of [Pd,(dba),] CHCI, (2.2 mg. 2.25 mol%) (db'i = dihenzylideneacetone) and p-CF,C,H,-TRAP 4e (8.6 mg, 8.1 mol "A) in toluene (0.5 mL) was stirred under N, at 25 C for 30 min. Acetic acid was added (15mg). and after 5 min I c (31 .0 mg, 0.093 mmol. entry 3 in Table 2) was added, and the mixture was stirred for 20 h. The solvent was evaporated in vacuo and the residue purified by preparative thin-layer chromatography (silica gel, hexane!EtOAc 5/11 affording 2c and 3c as a mixture (2c:3c = 3.5:1.21.1 mg. 68%). For thedetermination oftheenantioselectivity 3 e was removed by stirring the above mixture in CH,CI, ( I mL) with phenyl maleimide (ca. 10 equiv) Purification by preparative thin-layer chromatography (sllica gel. hexane/EtOAc 5:l) afforded pure 2 c (95% co (R). Chiralcel OJ. [.]A3 = 31.9 ( c = 0.31 in CHCI,). + Received: September 30. 1995 [Z8437IE] German version: A n g e ~Cherti. 1996, /(IN. 686-687 Keywords: asymmetric syntheses . complexes with phosphorus ligands cyclizations * enynes * palladium compounds - [ I ] For a review: a) B. M. Trost in Siudres in Nuturd Produc! Chemistr~.S/ereo.\elecriiv Sjnthesis. Vo/ 8 (Ed. : Atta-ur-Rahman). Elsevier. Amsterdam. 1991, pp 277-282: h) B. M. Trost. Arc. Chem. Re$. 1990, 23. 34-42.  a) B. M . Trost, G. J. Tanoury, M. Lautens, C. Chan, D. T MacPherson. J. An?. Chem. Sot. 1994. 116.4255-4267: b) B. M. Trost. D. L. Romero, F. Rise. ihrd. 1994, 116.4268-4278. c) B. M.Trost, M. Lautens. C. Chan. D. J. Jebaratnam. T. Mueller. ihrd. 1991. 113. 636-644; d ) B. M. Trost. M Lautens. hid 1985, 107. 1781-1783.  B M. Trost, D. C. Lee, F. Rise. Tetrahedron LL'II. 1989, 30. 651 --654.  B. M. Trost. B. A. Czeskis. Tetruhedron Lert. 1994, 35. 21 I -214.  (R,R)-(S,S)-TRAP = (R,R)-2.2"-Bis[(S)-I-(diarylphosphanyl)ethyl]-l .1"biferrocene a) M . Sawamura, H . Hamashima. M. Suganiira. R. Kuwano. Y. Ito, Orgunorneta//ics. 1995. 14,4549-4558; b) M Sawamura, H Hamashima, Y Ito. Terrahedron: Asymmetrr 1991. 2, 593-596.  CHIRAPHOS = 2,3-bis(diphenylphosphanyl)butane: M Fryzuk. B. J Bosnich, J. An?. Chern. Soc 1977, 99, 6262 -6267.  DIOP = 2,3-O-isopropylidene-2.3-dihydroxy-l.4-his(diphenylphosphanyl)butane: H. B. Kagan. T.-P. Dang, J. Am. Chem So<. 1972. 94. 6429.~6433.  BPPFA = N.N-dimethyl-l-[1.2-bis(diphenylphosphanyl)ferrocenyl]ethylamine. PPFA = 1 -[1 -(dimethylamino)ethy1]2-(diphenylphosphanyl)ferrocene. T. Hayashi. T. Mise. M. Fukushima. M. Kagotani. N. Nagashima. Y. Hamada, A. Matsumoto. S. Kawakami, M Konishi. K. Kimamoto. M . Kumada. Bull. Chem. Soc. Jpn. 1980, 83. 1138 - 1 I51  BINAP = 2.2'~bis(diphenylphosphanyl)-l.l'~binaphthyl. A Miyashita. A. Yasuda. H. Takaya. K. Toriumi. T Ito. T. Souchi. R. Noyori. J Ani. Chmr Sot.. 1980. 102. 7932-7934. [lo] R. Kuwano, M. Sawamura. J. Shirai, M. Takahashi. Y. Ito. ~ ~ ~ / r - u h ~Lrrr. ~~/ron 1995,36. 5239-5242 [I 11 Allylsilane has already been used in an asymmetric intramolecular Heck reaction: L. F. Tietre. R Schimpf. Angeii.. Chem. 1994. 106. 1138 1139. Angrii.. Chmi. / n ! . Ed. Engl 1994. 33. 1089-1090.  For the determination of both the enantiomeric excess and xbsolute configuration. the sulfonamide group was converted into a trrr-but[)xycarhonyl (Boc) group [Li,'NH,, -78 C: (Boc),O,'Et,N]. The optical rotaiim of the resulting carbamate ([&' = + 12.9 (c = 0.35 in CHC1.J W;IS compared %ith the rcported value for the (S)-configurated carbainate ( > 96% cc) ([I];' = - 37.3 (< = 0 55 in CHCI,). W. Oppolzer. T. N. Birkinshaw. G. Bernardinelli. .litruhcdron Lc,f/.1990. 31. 6995-6998).