Zusammenfassung
Highly reactive titanium on graphite as the reagent of choice promotes intramolecular McMurry-type reactions of acyloxy and acylamido carbonyl compounds affording furans, benzofurans and indoles in good to excellent yields. A variety of reducible groups in the substrates is tolerated (e.g. -F, -Cl, -Br, -I, -CF3, -OMe, -CN, -thiophenyl, -COOR, -CONR2 and strained products such as I can be obtained (by reductive cyclization of acylanilide II), the x-ray analysis of which is reported. The experimental results indicate the possible formation of dianions from the aromatic aldehydes or ketones as reactive intermediates which attack the ester or amide functions in their proximity, rather than a radical path via ketyls.
