Asymmetric C-C bond formation using a ruthenium catalyst with chiral counter anion

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Attempt to develop enantiotopic group selective [2+2] cyclization of 1,7-allenyne using a ruthenium catalyst having a chiral counter anion part. Although various phosphate- or sulfate-based anions were employed as a chiral anion part for the asymmetric cyclization, no satisfied results were obtained so far. Investigation of the reaction using chiral alcohol as a chiral anion source was also conducted. As a result, it was found that the use of menthol gave gave the desired cyclized product in moderate enantioselectivity.On the other hand, we also investigated the possibility of chiral ionic liquid as a chiral anion source. Thus, the [2+2] cyclization in the ionic liquid was examined. As a result, [BDMI][PF6] was found to be a suitable solvent for the cyclization. Furthermore, recycling the ionic liquid containing the ruthenium catalyst was possible for up to 10 times.