Available online at www.sciencedirect.com Journal SCIENC ofOrgano metallic Chemistry ELSEVIER Journal of Organometallic Chemistry 690 (2005)59225928 www.elsevier.com/locate/jorganchem Stereoselective [3+2+2] cycloaddition utilizing optically active binuclear Fischer carbene complexes with alkynes aDepartment of Chemistry,GraduateSchoolof Science,OsakaPrefecture University,Sakai,Osaka 599-8531,Japan b Kyoto Pharmaceutical University,Misasagi,Yamashina, Kyoto 640-8412, Japan Received 10 June 2005; received in revised form 22 July 2005; accepted 22 July 2005 Available online 31 August 2005 Abstract The reaction of optically active α,β-unsaturated binuclear Fischer carbene complexes with alkynes gave planar chiral cyclohepta- triene chromium complexes via [3+2+2] cycloaddition with high diastereoselectivity. @ 2005 Elsevier B.V. All rights reserved. Keywords: Fischer carbene; Cycloaddition; Planar chirality; Arene chromium complex 1.Introduction chromium complex [5]. The advantage of these chiral Fischer carbene complexes are that a chiral auxiliary The Fischer carbene complex is one of the most ver- can be introduced close to the reaction site effectively satile organometallic reagents for organic synthesis [1] blocking one face of the aα,β-unsaturated double bond In recent years, a number of novel reactions using of the carbene complex.As a continuation of our studies Fischer carbene complexes have been reported [2]. One on asymmetric reactions utilizing the planar chirality of of the major classes of reactions utilizing α,β-unsatu- arenechromiumcomplex,weexaminedtheasymmetric rated Fischer carbene complexes is cycloaddition reac- variation of the [3+2+2] cycloaddition reaction devel- tions, which provides four-, five-, and six-membered oped by Barluenga utilizing chiral binuclear Fischer car- carbo- or heterocyclic compounds, and important ad bene complexes. vances have been reported [1]. Recently, Barluenga developed interesting [3+2+2] cycloaddition reactions of α,β-unsaturated Fischer carbene complexes with alky- 2. Results and discussion nes giving seven-membered carbocyclic compounds [3]. For the asymmetric variation of these reactions, various Initially,we examined the reaction of binuclear chiral Fischer carbene complexes have been developed Fischer carbene complex 1a ([a)-3400 (c 0.001, to date [4]. On the other hand, we have developed the CHCl3) with 1-pentyne (2a) (3.0 equiv) in the presence newentryofopticallyactiveo,β-unsaturatedbinuclear of a stoichiometric amount of Ni(cod)2 (1.1 equiv). The Fischer carbene complexes with planar chirality of arene resulting solution was stirred for 2 h at -10 C and then warmed to 20 C over 2 h. It was found that bis-tricar- bonylchromium-coordinated7-arylcycloheptatriene * Corresponding authors. Fax: +81 72 254 9931 (K. Kamikawa)/+81 derivative 3aa ([α]+40 (c 0.08, CHCl3))was obtained 75 595 4763 (M. Uemura). E-mail addresses: [email protected] (K. Kamikawa), via the [3+2+2] cycloaddition in 47% yield with high [email protected] (M. Uemura). diastereoselectivity (dr =>98:<2) (Table 1, entry 1). 0022-328X/S - see front matter @ 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2005.07.089 5923 K.Kamikawa et al./Journal of Organometallic Chemistry690(2005)5922-5928 Table 1 Stereoselective [3+2+2] cyclization reaction utilizing chiral binuclear Fischer carbene complexes (OC)3Crn. (OC)3C Cr(CO)5 R1 R1 H R? H R2 OMe Ni(cod)2 R2 MeO "Cr(CO)3 CHCN Cr(CO)3 MeO Cr(CO)3 R2 R2 2 1 3 4 1a, R1 = OMe 2a, R2 = Pr (OC)Cr 1b, R1 = Me 2b, R2 = Ph H 82 1c, R1 = CI 2c, R2 = MeSi 1d, R1 = Br MeO R2 5 Entry Complex 1 Product 3 Yield (%) of 3 Product 4 Product 5 Acetylene 2 Yield (%) of 4 dr (3/4) Yield (%) of 5 1a 2a 3aa 47 >98/<2 - 2 1a 2b 3ab 28 >98/<2 5ab 25 1a 3 2c 3ac 27 4ac 27 1/1 5ac 10 45 1b 2a 3ba 67 >98/<2 1c 2a 36 6/16 6 1d 2a 41 91/9 When phenylacetylene (2b) was used as the alkyne, hept- Thediastereomers were confirmed to be 3ac and 4ac atriene chromium c