Research News, Apr 26th, 2012

 Carbonylation of 1-Lithiobutadiene with Carbon Monoxide Followed by Intramolecular Acyllithiation of C=C Double Bond and Intermolecular Acylation with Acid Chloride: Scope, Applications and Mechanistic Aspects

Heng Li, Lantao Liu, Fei Zhao, Congyang Wang, Chao Wang, Qiuling Song, Wen-Xiong Zhang, and Zhenfeng Xi*

 J. Org. Chem. 2012, online 20120423, DOI: 10.1021/jo300631d

 The carbonylation of a 1-lithio-1,3-butadiene derivative with CO gave rise to a butadienyl acyllithio intermediate, which underwent an immediate intramolecular acyllithiation of the C=C double bond affording a lithio cyclopentadienyl enolate. The X-ray structural analysis of the enolate revealed a dimer connected with a “Li2O2” four-membered ring. Subsequent intermolecular acylation of this enolate with acid chlorides afforded β-keto-3-cyclopentenones, γ-keto-2-cyclopentenones or cyclopentadienyl ester derivatives. The stereo- and regio-selectivity of the in situ generated lithio cyclopentadienyl enolate with various acid chlorides was investigated and analyzed, showing that the formation of the above products was significantly dependent on both the substituents on the butadienyl skeleton and the bulkiness of acid chlorides.

背景介紹

2002年，本研究室發現1-锂-1,3-丁二烯與一氧化碳、腈發生新穎反應，分别生成環戊烯酮衍生物和多取代吡啶衍生物 (Org. Lett. 2002, 4, 4627; J. Am. Chem. Soc. 2002, 124, 6238.)。我們推測在該反應中，有機锂部分與分子内存在的碳碳雙鍵産生協同效應，促進分子内有機锂部分對碳碳雙鍵的加成反應。近十年來，我們“基于機理研究和活性中間體的合成化學”研究理念，一直嘗試獲得該反應的中間體信息以理解該反應的機理，并進一步發展新方法。在本工作中，我們成功分離得到了1-锂-1,3-丁二烯與一氧化碳反應産生的環戊二烯基醇锂活性中間體，研究了該中間體發生酰基化時的電子效應和立體效應，合成了一系列酰基化産物。