220978-56-3Relevant academic research and scientific papers
Improvement of the diastereoselectivity of the cobalt-mediated [2+2+2] cycloaddition of substituted linear enediynes
Slowinski, Franck,Aubert, Corinne,Malacria, Max
, p. 707 - 710 (1999)
The level of the diastereoselectivity of the cobalt-mediated [2+2+2] cyclization of linear enediynes was improved compared to that reported in the literature by substituting the triple or the double bond with ester, phosphine oxide or sulfoxide groups.
Diastereoselective cobalt-mediated [2 + 2 + 2] cycloadditions of substituted linear enediynes phosphine oxides: Scope and limitations
Slowinski, Franck,Aubert, Corinne,Malacria, Max
, p. 378 - 386 (2007/10/03)
Variously substituted linear enediynes phosphines oxides possessing the double bond at either the terminal or internal position and with the phosphine oxide appended onto the alkyne or the alkene terminus have been prepared. Their cobalt(I)-mediated cyclizations produce the η4-complexed tricyclic compounds in high yields. The endo/exo selectivity depends on both the position of the phosphine oxide on the enediyne and the position of the double bond in the tether. With chiral phosphine oxides, a certain degree of induction was observed, and depending on the substituents on the phosphorus atom, the diastereoselectivity can reach 74%. Up to now, it is the highest level reported for such a cyclization in which a stereogenic center is created. Regarding all of our results, two reaction pathways involving an initial coordination of the cobalt moiety on the chelating site of the substituent have been suggested to explain the observed selectivities.
