Unusual Regioselectivity in the Aldehyde Addition Reactions of Allenyl/Propargyl Zirconium Complexes Derived from γ-(2-Pyridyl)propargyl Ethers: Synthesis of Multisubstituted α-Hydroxyallenes
作者:Guoqin Fan、Xin Xie、Yuanhong Liu、Yuxue Li
DOI:10.1021/om301007z
日期:2013.3.25
different to that of the reactions using propargylic ethers without a pyridyl group reported so far, in which homopropargyl alcohols were formed predominantly. The structure of allenylzirconium intermediate has been confirmed by X-ray crystal analysis which reveals an intramolecular Zr–N coordination. DFT calculations suggest that the smaller steric effect of the pyridine ring compared with the phenyl
trisubstituted allenesfrom propargyl alcohol is provided; the synthesis proceeds via an oxaphosphetane intermediate. Functional groups such as formyl and pyridyl exhibited a degree of tolerance during reaction without any protection. The alcohol dimethylated at the propargyl position afforded two structural isomers, allene and 1,3-diene. The product ratio was considerably influenced by the solvent. Allene was