α-Deprotonated allyl ethers: Conformational mobility and conformational preferences
作者:Christian Margot、Paola Maccaroni、Frédéric Leroux、Manfred Schlosser
DOI:10.1016/s0040-4020(98)00774-1
日期:1998.10
tert-Butyllithium is best suited to accomplish a hydrogen/metal exchange at the α-position of γ-alkyl branched allyl ethers. Rapid torsional equilibration occurs at the γ-terminus of the deprotonated allyl unit while the alkoxy group at the α-site has to occupy the exo position in order to minimize steric repulsions. The introduction of an alkoxy group into the terminal position of a γ-branched 2-alkenyllithium
叔丁基锂最适合在γ-烷基支链烯丙基醚的α-位完成氢/金属交换。快速扭转平衡发生在去质子化的烯丙基单元的γ末端,而α位的烷氧基必须占据exo位置,以最大程度地减少空间排斥。在γ-支化的2-链烯基锂的末端位置引入烷氧基会稍微降低扭转异构化的势垒(降低几千卡/摩尔)。