Inexpensive reagents for the synthesis of amides from esters and for regioselective opening of epoxides
作者:A. Solladie-Cavallo、M. Bencheqroun
DOI:10.1021/jo00048a011
日期:1992.10
Lithium aluminum amides [LiAl(NHR)4], 6a-6d, easily prepared in Et2O or THF from 1 equiv of LiAlH4 and 5 equiv of amine, proved to be efficient reagents for the synthesis of secondary amides from esters (approximately 100% with unhindered amines and 92% with tBuNH2). They also open aryl epoxides with very high regioselectivity to give 97-98% of the beta-amino-alpha-arylethanols (corresponding to the SN2 mechanism).
Enantioselective Synthesis of Both Enantiomers of a Isoproterenol Analogue and of Di-<i>O</i>-pivaloylepinephrine
An asymmetric synthesis of the analogue 4a of isoproterenol and of di-o-pyvaloylepinephrine 3 which provides bothenantiomers in optically pure state is reported. The key step of the method is the highly diastereo-selective reduction (using DIBAL or DIBAL/ZnCl2) of a β-ketosulfoxide 7 which leads, as desired, to the (S)- or the (R)-configuration at C(1) (Schemes 4 and 5).