 | Alkynylation of Alkynes via Zirconcycles
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| | Zhenqi Zhong, Yuanhong Liu, Kiyohiko Nakajima and Tamotsu Takahashi |
| 1) Catalysis Research Center, Hokkaido Univ.
2) Aichi Univ. Edu. |
| | Conjugated 3-ene-1,5-diynes represent important chemical building blocks, the subunit found in system as diverse as antitumor antibiotics, synthetic polymers and natural products. Recently, we have developed a facile synthetic route for this type of compounds, which is based on the reaction of zirconacylopentene 1 with alkynyl halides. The symmetrical or unsymmetrical cis-3-ene-1,5-diynes 3 were formed in 41-72% yields. Interestingly, it was found that cis-enediynes slowly isomerized to trans-enediynes. For example, when cis-1,3,4,6-tetraphenyl-hex-3-ene-1,5-diyne 3a was dissolved in hexane/acetone (5/1) solution, and stood at room temperature for 15 days, the trans-3a was obtained (43%) in crystal. The crystal structure of trans-3a was determined by X-ray analysis and 13C NMR spectra. |
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