| Abstract
| - Variously substituted linear enediynes phosphines oxides possessing the double bond at either theterminal or internal position and with the phosphine oxide appended onto the alkyne or the alkeneterminus have been prepared. Their cobalt(I)-mediated cyclizations produce the η4-complexedtricyclic compounds in high yields. The endo/exo selectivity depends on both the position of thephosphine oxide on the enediyne and the position of the double bond in the tether. With chiralphosphine oxides, a certain degree of induction was observed, and depending on the substituentson the phosphorus atom, the diastereoselectivity can reach 74%. Up to now, it is the highest levelreported 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 siteof the substituent have been suggested to explain the observed selectivities.
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