RHODIUM COMPLEX-CATALYZED DESILYLATIVE CYCLOCARBONYLATION OF 1-ARYL-2-(TRIMETHYLSILYL)ACETYLENES - A NEW ROUTE TO 2,3-DIHYDRO-1H-INDEN-1-ONES

Under water gas shift reaction conditions, 1-aryl-2-(trimethylsilyl)acetylenes undergo Rh-catalyzed desilylative cyclocarbonylation to give 2,3-dihydro-1H-inden-1-ones and trimethylsilanol. A wide variety of functional groups, such as methoxy, chloro, acetyl, ethoxycarbonyl, cyano, and trifluoromethyl, are tolerated on the aromatic ring under the reaction conditions. The products were obtained in good to excellent yield whether the substituent on the aromatic ring was electron-donating or electron-withdrawing. The cyclizations of substrates bearing a meta substituent on the aromatic ring regiospecifically gave 5-substituted-2,3-dihydro-1H-inden-1-ones except when the meta substituent was a methoxy group. The desilylative cyclocarbonylation is an alternative to the conventional preparation of 2,3-dihydro-1H-inden-1-ones, an intramolecular Friedel-Crafts acylation. A possible mechanism for the process is described.