Co-Complexes Derived from Alkene Insertion to Alkyne-Dicobaltpentacarbonyl Complexes: Insight into the Regioselectivity of Pauson−Khand Reactions of Cyclopropenes
作者:Mahesh K. Pallerla、Glenn P. A. Yap、Joseph M. Fox
DOI:10.1021/jo800776z
日期:2008.8.1
Described are the X-ray crystallographic and spectral properties of Co-complexes that were isolated from two Pauson-Khand reactions of chiral cyclopropenes. These are the first examples of isolated Co-complexes derived from the putative alkene-insertion intermediates of Pauson-Khand reactions. The binuclear Co-complexes are coordinated to mu-bonded, five-carbon "flyover" carbene ligands. It is proposed that the complexes result from cyclopropane fragmentation subsequent to alkene insertion. The observation of these metal complexes provides a rationale for the origin of regioselectivity in Pauson-Khand reactions of cyclopropenes.
Diastereoselective Intermolecular Pauson−Khand Reactions of Chiral Cyclopropenes
作者:Mahesh K. Pallerla、Joseph M. Fox
DOI:10.1021/ol051456u
日期:2005.8.1
can increase the scope and utility of intermolecularPauson-Khandreactions. The well-defined chiral environment of cyclopropenes has a powerful influence on the diastereoselectivity of the reactions and leads to the production of a single cyclopentenone in each of the described cases. The cyclopropane ring strongly influences the stereochemistry of reactions at the enone, and the three-membered ring