Selective Intermolecular Coupling of Alkynes with Nitriles and Ketones via β,β‘ Carbon−Carbon Bond Cleavage of Zirconacyclopentenes

Takahashi, Tamotsu; Xi, Chanjuan; Xi, Zhenfeng; Kageyama, Motohiro; Fischer, R.; Nakajima, Kiyohiko; Negishi, Ei‐ichi

doi:10.1021/jo980022s

Cited by 99 publications

(45 citation statements)

References 26 publications

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“…On the other hand, oxidative coupling of an aldehyde and an alkyne on the zirconocene(II) is preferred. [11] The intermediate 13 undergoes oxidative coupling to form 11. Hydrolysis of 11 affords the product 4.…”

Section: Methodsmentioning

confidence: 99%

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Coupling Reactions of Zirconate Complexes Induced by Carbonyl Compounds

Yan

You

et al. 2009

Angew Chem Int Ed

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During the past few decades the chemistry of 16-electron organozirconocene complexes has been extensively explored and a tremendous number of applications in synthetic chemistry have been found.[1] However, organozirconate complexes, which usually have an 18-electron configuration with two cyclopentadienyl (Cp) rings, three Zr À C bonds, and alkali counter ions, have rarely been explored in spite of being the supposed intermediates in a number of stoichiometric and catalytic reactions, and able to form CÀC bonds through a successful 1,2-migration of organozirconates. [2][3][4] Our research group has an interest in the above mentioned subjects, and we have recently reported [5] that by adding quinone as an oxidant to a mixture of alkynylzirconates then zirconocenendiyne compounds are afforded: these compounds can be converted into various endiynes through coupling reaction with electrophiles. These results prompted us to further study the chemistry of organozirconate complexes. Herein, we report the coupling reactions of three-membered alkynylzirconates induced by carbonyl compounds. The unique features of this reaction involve the carbonyl compound acting as an electrophile, participating in the reaction with zirconates, and also inducing the coupling of an alkynyl group and an sp 2 -hybridized carbon atom of zirconacyclopropene. To the best of our knowledge, this type of reaction has not been reported. When acyl compounds were used as electrophiles, then functionalized allenes were formed. When aldehydes were used as electrophiles, then dienols were formed. These outcomes are illustrated in Scheme 1.The reaction of zirconate 1 a, which was generated by the treatment of nBuLi with bis(phenylethynyl)zirconocene at room temperature, [6] with chloroformate at 0 8C for five hours afforded allene 3 a in 73 % yield after hydrolysis. Quenching the reaction mixture with DCl in D 2 O provided allene 5 a in a comparable yield with 91 % deuterium incorporation. This result indicates that the zirconium-containing complex 6 a is formed (Scheme 2).Oxazirconacycle 6 a was formed in 74 % yield (based on NMR spectroscopy). The 1 H NMR spectrum of 6 a showed a singlet resonance at d = 5.96 ppm, which was assigned to the protons on the Cp ring. In the 13 C NMR spectrum, the signal for the carbon atoms in the Cp ring appeared at d = 104.5 ppm, and the signal for the allenic-type sp-hybridized carbon atom appeared at d = 198.5 ppm. The carbon signals in Zr À C(Ph) and À C(OEt)O appeared at d = 149.5 and 169.6 ppm, respectively. The allene group is a versatile functionality because it is useful as either a nucleophile or an electrophile as well as a substrate for cycloaddition reactions. This multiple reactivity make allenes as excellent candidates for synthetic manipulation.[7] The reaction described here allowed the efficient synthesis of various substituted allenes. A variety of acyl compounds were subjected to this novel reaction and all reactions afforded analogous products in good to high yields after hydrolysis. Notably, the ac...

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Section: Methodsmentioning

confidence: 99%

“…[11] The intermediate 13 undergoes oxidative coupling to form 11. A plausible reaction mechanism is shown in Scheme 6.…”

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confidence: 99%

Coupling Reactions of Zirconate Complexes Induced by Carbonyl Compounds

Yan

You

et al. 2009

Angew Chem Int Ed

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“…Zirconacyclopentenes 6 are generated in situ by using Takahashi's method [18]. After addition of an aromatic ketone, zirconacyclopentene 6 reacts with the ketone via intermolecular coupling to afford oxazirconacyclopentene 7 [19]. Hydrolysis of oxazirconacyclopentenes 7 with 20% HCl for 3 h afforded indene derivatives in good to excellent yields (scheme 5).…”

Section: One-pot Synthetic Routes To Multiply Substituted Indene Derimentioning

confidence: 99%

New Methods for the Preparation of Multiply Substituted Cyclopentadienes and Related Compounds

2005

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Substituents on cyclopentadienyl ligands significantly influence the reactivity and catalytic efficiency of their transition metal complexes. Therefore, development of synthetic methods for cyclopentadiene derivatives possessing different substituents has been in great demand. In this paper, we report new synthetic methods for multiply substituted cyclopentadienes recently developed in this group. In principle, three types of preparative methods are described. Firstly, zirconacyclopentadienes in the presence of Lewis acids react with aldehydes to afford multiply substituted cyclopentadienes, thus providing a one-pot procedure from two molecules of identical or different alkynes and one molecule of aldehyde; reaction of aluminacyclopentadienes with aldehydes also result in high-yield formation of multiply substituted cyclopentadienes. Secondly, 1,2,3,4-tetrasubstituted 1,4-dilithio-and 1,4-bis(magnesiobromo)-1,3-diene derivatives react with aldehydes or ketones via deoxygenation of the C@O moieties to afford cyclopentadiene derivatives. Thirdly, monolithio reagents, 1,2,3,4-tetrasubstituted 1-lithio-1,3-butadienes, and Grignard reagents, 1,2,3,4-tetrasubstituted 1-magnesiobromo-1,3-butadienes react with aldehydes or ketones to afford cyclopentadiene derivatives upon hydrolysis.

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“…Column chromatography on Al 2 O 3 (petroleum ether / ethyl acetate =10:1) afford 224mg (56%) products as a yellow oil. 1 H NMR (CDCl 3 , Me 4 Si) δ 1.67 (s, 3H), 3.93 (s, 1H), 7. 01-7.18 (m, 12H), 7.20-7.32 (m, 4H), 7.37-7.42 (m, 2H), 7.75 (dd, J=8.1, 1.2 Hz, 2H); 13 C NMR (CDCl 3 , Me 4 Si) δ 31.0, 77.8, 89.2, 99.6, 122.4, 1223.0, 125.8, 126.6, 126.8, 126.9, 127.5, 127.5, 128.1, 128.5, 129.3, 130.0 (bs), 131.2, 139.0, 139.5, 148.4, 156.4 (Z)-2-(4-fluorophenyl)-6-phenyl-3,4-dipropylhex-3-en-5-yn-2-ol (2c) S2 GC yield: 85%.…”

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confidence: 99%

“…Column chromatography on Al 2 O 3 (petroleum ether / ethyl acetate =15:1) afford 244mg (70%) products as a salmon pink oil. 1 H NMR (CDCl 3 , Me 4 Si) δ 0.96(t, J = 7.8 Hz, 3H), 0.97 (t, J = 6.9 Hz, 3H), 1.40-1.55 (m, 2H), 1.59-1.70 (m, 2H), 1.77 (s, 3H), 2.18-2.35 (m, 4H), 3.72 (s, 1H), 6.94-7.00 (m, 2H), 7.11-7.14 (m, 2H), 7.42 (d, J = 5.4 Hz, 1H), 7.45 (d, J = 5.4 Hz, 1H), 7.42-7.46 (m, 2H); 13 C NMR (CDCl 3 , Me 4 Si) δ 13.7, 14.5, 21.7, 23.5, 29.1, 32.8, 35.4, 77.5, 89.4, 97.2, 114.2, 114.5, 119.3, 123.0, 127.4, 127.5, 127.9, 128.0, 130.8, 144.7, 144.7, 153.9, 159.8, 163…”

mentioning

confidence: 99%