Synthesis and Application of Robust Spiro [Fluorene‑9] CAAC Ruthenium Alkylidene Complexes for the "One-Pot" Conversion of Allyl Acetate to Butane-1,4-diol.

A series of a novel CAAC ligands featuring a spiro-fluorene group have been synthesized and complexed with ruthenium alkylidenes, yielding the corresponding Hoveyda-type derivatives as a new family of olefin metathesis catalysts. The novel complexes have been characterized by XRD, HRMS and NMR measurements. The synthetized complexes were tested in catalysis and showed good activity in olefin metathesis, as demonstrated on diethyl diallylmalonate and allyl acetate substrates. The unique backbone in the ligand system with the large, yet inflexible condensed system renders interesting properties to the catalyst, exemplified by the good catalytic performance and improved Z‑selectivity. In addition, the complex can also serve as a hydrogenation catalyst in a consecutive (one-pot) reaction. The latter reaction can convert allyl acetate to butane‑1,4‑diol, a valuable chemical intermediate for biodegradable polybutylene succinate (PBS).