Pauson-Khandreactions are carried out with different substituted aromatic enynes, yielding tricyclic cyclopentenones related to natural products such as chromenes. Enynes are easily obtained in a two-step approximation from the corresponding salicylaldehydes. The reaction is promoted by dissolved TMANO (trimethylamine N-oxide) and/or 4 A molecular sieves. This new way of induction for the Pauson-Khand
[GRAPHICS]The Pauson-Khand reaction still has a relatively low scope with respect to the used carbon skeleton, while yields are low in many other cases. We have observed that the addition of molecular sieves improves yields remarkably, Experimental protocol is extremely easy, and it has been applied to several substrates including the less favorable ones.