在釕金屬上鄰位-3-(5-烯-1-已炔)酚的分子內環化及其相關反應之研究

Abstract

The intramolecular cyclization of 1,5-enyne mediated by CpRu(PPh3)2Cl leading to the formation of chromane ring derivatives is described. For the enyne compound 2a-2c with different substitution on the aromatic ring, the reaction takes place at the propargylic alcohol first giving the vinylidene intermediate which could undergo an intramolecular cyclization to yield the cyclic oxocarbene complexes (5a-c and 5a’ and 5c’). Moreover, the cyclization may proceed via a vinylidene intermediate which was not observed in our system. Modifications of various substituents at Cb by the use of different alkyl halides can be readily achieved in mild condition. For the chromane ring derivatives 9, the two allyl groups underwent ring closing metathesis reaction in the presence of Grubb’s catalyst and yielded the tricyclic product 10. Additionally, photolysis of 7, 8 or 9 results in dissociation of a PPh3 ligand from the metal center which is accompanied with filling in the vacant site by the counter anion, iodide, to form neutral complexes 11, 12 or 13. Besides, both substituents at Cb and oxygen-free aromatic ring of the chromane moiety participate well, with reaction time and product selectivity as a function of the steric and electronic character. These chemical reactions and their mechanism are corroborated by structure determinations of three ruthenium complexes using single crystal X-ray diffraction analysis.