Studies on a catalytic version of the Matteson asymmetric homologation reaction

Studies of a catalytic asymmetric version of the Matteson reaction between dichloromethylboronates and organolithium reagents have been undertaken. From several different chiral catalytic systems studied, only one based on a mannitol derivative has given substantial asymmetric induction close to that previously achieved with a bis(oxazoline) derivative and ytterbium triflate. More detailed study of the latter reaction revealed that fresh ytterbium triflate actually reduced the level of asymmetric induction, while "aged" ytterbium triflate, or a fresh sample that had been treated with water, brought about improved induction. The implications of these findings are discussed.