Anisole 4 + 2 Annulation

As depicted below, a procedure for the iodocyclization of acetoxy-containing 2-(l-alkynyl)anisole and subsequent direct palladium-catalyzed earbonylatiori/lactonization was reported as an efficient entry to naturally occurring eoumestan and coumestrol <05IOC9985>. A novel Pd(II)-mediated cascade carbonylative annulation of substituted o-hydroxyphenylacetylenes to give benzo[fo]furan-3-carboxylie adds was achieved in a one-pot reaction <050L2707>. 

Two decades after the first example of annulation of the imidazole moiety (Nispen et al. 1980) to bond c of quinoxaline under the action of dilifhium salt 43, a new procedure has been suggested in which the initial compounds are quinoxali-nones 59 (Banish and Spergel 2001 Chen et al. 2001, 2002a Hazeldine et al. 2005). Protected iV-(4-methoxybenzyl)quinoxalinones 60 are introduced into the reaction with TsMIC in THF in the presence of NaH, which leads to imidazo-quinoxaline 61 in high, sometimes quantitative, yields. The protective group is removed under the action of trifluoroacetic acid (TFA), anisole and trifluoromethanesulfonic acid (TfOH). This method is simple and enables the... 

---