Chelation-Assisted Substrate-Controlled Asymmetric Lithiation-Allylboration of Chiral Carbamate 1,2,4-Butanetriol Acetonide
作者:Adeem Mahmood、Hamad Alkhathlan、Saima Parvez、Merajuddin Khan、Sohail Shahzad
DOI:10.3390/molecules20069890
日期:——
The lithiation of 2-(2,2-dimethyl-1,3-dioxolan-4-yl)ethyl diisopropylcarbamate (1) is achieved freely by sec-butyllithium in diethylether with high lk-diastereoselectivity: the bicyclic chelate complexes 3a and 3b are reacted with electrophiles to form optically active precursors 4a and 4b with >95% diastereoselectivity. In addition, tertiary diamines can undergo an external complexation in contest
2-(2,2-二甲基-1,3-二氧戊环-4-基)乙基二异丙基氨基甲酸酯 (1) 通过仲丁基锂在乙醚中以高 lk-非对映选择性自由实现锂化:双环螯合物 3a 和 3b 为与亲电试剂反应形成光学活性前体 4a 和 4b,非对映选择性 >95%。此外,叔二胺可以与内部氧配体竞争进行外部络合,从而提高立体选择性。1,2金属化物重排后,锂化氨基甲酸酯与反式烯基-9-BBN衍生物进一步反应,得到关键中间体α-取代的烯丙基硼烷7。随后醛的烯丙基硼化反应以良好的收率得到(Z)-反高烯丙基醇8,并且优秀的博士