versions, Ru18 and Ru20, the yields were even better (98 and 70%, respectively), indicating higher stability of these catalysts. Complexes Ru17-Ru20 were obtained as mixtures of diastereoisomers, a phenomenon previously described by Mauduit et al. in analogous systems. Next, using the benzyland 4-nitrobenzyl-substituted catalysts Ru14 and Ru15, two more complexes Ru21 and Ru22 were successfully synthesised in high yields of 74 and 81%, respectively. In addition, the catalyst possessing the chelating cyclic ether moiety Ru23 was also obtained in 82% yield. Recently, Fogg et al. shed more light on the influence of air and water on the outcome of Z-stereoretentive cross-metathesis (CM) between allylbenzene (2a) and (Z)-2-butene-1,4-diol (3a), as well as selfmetathesis (SM) of methyl oleate using stereoretentive catalysts Ru5 and Ru7. It was found that dithiocatecholate-based catalysts rapidly decompose in solution in the presence of air, by eliminating the alkylidene ligand as O=CHC 6 H 4 -2-OiPr and the formation of atypical four-coordinate Ru(IV)-oxo products, Ru(O)(S 2 C 6 H 2 -3,6-Cl 2 )(NHC). Therefore, we decided to verify whether the introduced structural modifications improved the resistance of our catalysts toward oxygen. We also aimed to explore the potential of selected antioxidants in lowering the oxygen content of the reaction mixture and thus increasing the catalyst's lifetime, eliminating the necessity of using a glovebox. As a model reaction we chose the same cross-metathesis reaction of allylbenzene (2a) with (Z)-2-butene-1,4-diol (3a) as Fogg performed in degassed THF for 4 h under an inert atmosphere and in air (Table ).