Tandem Cyclization in Ruthenium Vinylidene Complexes with Two Ester Groups

The reaction of [Ru]-Cl ([Ru] = Cp(PPh3)2Ru) with o-ethynyl-substituted methyl benzoate, followed by a sequential deprotonation and electrophilic alkylation reactions by further reacting with base and various alkyl haloacetates, respectively, generated several disubstituted ruthenium vinylidene complexes. In the deprotonation reactions of these disubstituted vinylidene complexes containing two ester groups, tandem cyclizations of the ligand is accompanied with a methanol elimination to generate a new organometallic product containing a three-ring indenofuranone ligand, which structure has been confirmed by a single-crystal X-ray diffraction analysis. Facile protonation and methylation are observed in these indenofuranone complexes. Additionally, for the simple furyl complex containing an O-benzyl group, a 1,3-migration of the benzyl group is observed to yield a lactone product and a Claisen rearrangement is also observed in analogous complexes with O-allyl or O-propargyl groups.