P-8 イリジウムサレン錯体を触媒とするα-スピロシクロプロピルラクトンの合成法の開発(ポスター発表の部)

概要

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1,4-Cycloheptadiene skeletone can be seen in many natural products. Although various approaches have been reported, most of them require multi steps. Davies et al. have reported that rhodium-catalyzed reaction of 1,3-dienes and α-alkenyl-α-diazoacetates gives 1,4-cycloheptadiene derivatives in a highly enantioselective manner via cyclopropanation and subsequent Cope rearrangement. Although this is a straightforward approach, the yields of some reactions are unsatisfactory, due to instability of the diazo compound. Recently, Doyle and co-workers reported that cyclopropanation of 1,3-dienes using vinyldiazolactone 1, an equivalent of α-alkenyl-α-diazoacetates, gave alkenyl-α-spirocyclopropyl lactones, which could be converted into 1,4-cycloheptadiene derivatives, in good yields with moderate E- and enantio-selectivity. We have reported that iridium-salen complex 2 is an efficient catalyst for asymmetric cyclopropanation using α-diazoacetate. Thus, we examined the cyclopropanation of 1,3-dienes using 1 in the presence of 2 and found that the reactions gave alkenyl-α-spirocyclopropyl lactones with excellent E- and enantio-selectivity in good yields, irrespective of the substitution pattern of the alkenyl moiety.
天然有機化合物討論会の論文
2008-09-01