Gold-catalyzed bis-cyclization of 1,2-diol- or acetonide-tethered alkynes. Synthesis of ?-lactam-bridged acetals: a combined experimental and theoretical study
作者:Benito Alcaide、Pedro Almendros、Roco Carrascosa、Ramn Lpez、Mara I. Menndez
DOI:10.1016/j.tet.2012.03.028
日期:2012.12
alkyn-1,2-diols or alkynyl acetonides, readily prepared from imines of (R)-2,3-O-isopropylideneglyceraldehyde, were used as starting materials for the regio- and diastereospecific catalytic bis-oxycyclization reaction in the presence of a gold/acid binary system. Interestingly, in contrast to the gold-catalyzed reactions of N-tethered terminal alkynes, which lead to the corresponding 6,8-dioxabicyclo[3
由(R)-2,3- O-异亚丙基甘油醛的亚胺容易制得的2-氮杂环丁酮系链的炔基1,2-二醇或炔基丙酮化物被用作原料的区域和非对映异构催化双氧环化反应的起始原料金/酸二元体系的存在。有趣的是,与N系链末端炔烃的金催化反应(其生成相应的6,8-二氧杂双环[3.2.1]辛烷衍生物(近端加合物))相反,在相同条件下,取代的炔二醇和丙酮化物的反应通过独家的7- end / 5- exo生成7,9-dioxabicyclocyclo [4.2.1] nonane衍生物(远端加合物)作为唯一产品通过氧原子最初攻击外部炔烃碳而进行双-氧环化。而且,该方法的温和性允许掺入1,3-二炔部分作为反应性伴侣,对内部的炔基部分表现出优异的化学选择性。为了确认该机械方案,已经进行了使用氘化氘的标记研究。此外,进行密度泛函计算以深入了解双氧环化反应的机理。