TITANOCENE-CATALYZED CYCLOCARBONYLATION OF O-ALLYL ARYL KETONES TO GAMMA-BUTYROLACTONES

A method for the transformation of o-allyl aryl ketones to gamma-butyr olactones using a catalytic amount of Cp2Ti(PMe3)(2) or Cp2Ti(CO)(2) i s described. This catalytic ''hetero Pauson-Khand''-type process proce eds via the carbonylation of an oxatitanacycle followed by thermally-i nduced reductive elimination to form a gamma-butyrolactone and to rege nerate the catalyst. We have investigated the scope and limitations of this catalytic methodology. Our results are consistent with the view that the key step in this catalytic cycle is formation of a charge tra nsfer complex or involves reversible electron transfer between the cat alyst and the substrate.