Organic synthesis via transition metal complexes, part 107 - Enaminone substituents attached to cyclopentadienes: 3E/3Z stereochemistry of 1-metalla-1,3,5-hexatriene intermediates (M = Cr, W) as a functional criterion for the formation of cyclopentadienes and six-membered heterocycles, respectively

Reactions of NH-enaminones 2 with [2-(1-cycloalkenyl)ethynyl]carbene comple xes 7 (M = W, Cr) gave tetrahydropentalenes, tetrahydroindenes, and hexahyd roazulenes 8a-i, in which the NH-enaminone moiety is attached to the cyclop entadiene unit. The reaction involved formation of (3E)-1-metalla-1,3,5-hex atriene intermediates, which underwent pi cyclization faster than 3E/3Z iso merization. Tungsten complexes 12 and 13 were characterized as reaction int ermediates. Compounds 8 are potentially bidentate ligands with respect to c oordination both of the cyclopentadienyl and the enaminone moieties.