ChemInform Abstract: Unusual [1,2]- and [1,3]-M(CO)5 Shifts in Fischer Carbene Complexes: [4 + 3] and [3 + 3] Annulation Reactions of Furan and Pyrrole Rings.

✍ Scribed by Jose Barluenga; Miguel Tomas; Eduardo Rubio; Jose A. Lopez-Pelegrin; Santiago Garcia-Granda; Monica Perez Priede

• Publisher: John Wiley and Sons
• Year: 2010
• Weight: 40 KB
• Volume: 30
• Category: Article
• ISSN: 0931-7597
• DOI: 10.1002/chin.199931056

✦ Synopsis

Unusual [1,2]-and [1,3]-M(CO) 5 Shifts in Fischer Carbene Complexes: [4 + 3] and [3 + 3] Annulation Reactions of Furan and Pyrrole Rings.

-New [3 + 3] and [4 + 3] cyclizations of activated imines derived from furan-, benzofuran-, pyrrole-, and indole-2-carboxaldehydes with alkynyl or alkenyl carbene complexes (II) or (XIV) are reported. Regarding the metal there are only minor variations, all related to yields, when shifting from chromium to tungsten complexes. The type of cyclization depends on the structure of the imine and on the type of unsaturation of the carbene complex. Cycloadducts of type (VII) and (IX) show unexpectedly high thermal and hydrolytic stability. Refluxing in toluene in the absence or presence of CO leads to indolizine (VIII) or bispyrrole (X), whereas diluted HCl is required for hydrolysis to give aldehydes like (XI). -(BARLUENGA,