有機スズヒドリドの機能制御に基づく官能基, 立体および位置選択的還元反応

抄録

Novel types of tin hydrides were developed by the introduction of a halogen substituent or a ligand on the tin atom. These modified tin hydrides achieved chemoselective reduction between carbonyl groups and other functionalities such as organic halides, epoxides, imines and enones. In the reaction with epoxy ketones, two types of tin hydrides Bu₃SnH-Bu₄NF and Bu₂SnFH-HMPA systems reduced only the carbonyl moieties with high syn- and anti-selectivities, respectively. Whereas, when Bu₂SnIH -HMPA was used, the reduction of epoxide groups took place to give 3-hydroxy ketone, where the carbonyl groups were tolerated. The high nucleophilicity of Sn-I bond toward epoxides is responsible for the selectivity. Tin chloride hydride complex, Bu₂SnClH-HMPA was revealed to reduce imines over carbonyl groups. In the reduction of conjugated enone, Bu₂SnFH afforded 1, 2-reduction predominantly to give allylic alcohol. On the other hand, Bu₂SnIH promoted the selective 1, 4-reduction of enones even in the presence of aldehydes. When a mixture of an enone and PhCHO was treated with Bu₂SnIH, the first resulting tin enolate subsequently reacted with co-existent PhCHO to give an aldol product.