XY–ZH Systems as potential 1,3-dipoles. Part 8. Pyrrolidines and Δ<sup>5</sup>-pyrrolines (3,7-diazabicyclo[3.3.0]octenes) from the reaction of imines of α-amino acids and their esters with cyclic dipolarophiles. Mechanism of racemisation of α-amino acids and their esters in the presence of aldehydes
Imines of α-aminoacidesters with aromatic, heterocyclic, and aliphatic aldehydes generate azomethine ylides stereospecifically by a prototropic shift on heating in toluene. The azomethine ylides undergo cycloaddition to N-phenylmaleimide, maleic anhydride, and p-naphthoquinone via an endo-transition state to give racemic, single diastereoisomeric, cycloadducts. α-Aminoacids undergo analogous cycloadditions
Michael adducts of imines of α-aminoacidesters are converted into a mixture of two stereoisomeric pyrrolidines by benzyltrimethylammonium methoxide (BTAM) apparently by a 5-endo-trigcyclisation.
X=Y-ZH systems as potential 1,3-dipoles. The stereochemistry and regiochemistry of cycloaddition reactions of imines of α-amino-acid esters.
作者:Ronald Grigg、James Kemp
DOI:10.1016/s0040-4039(00)93177-0
日期:1980.1
The stereochemistry and regiochemistry of cycloadditions of α-aminoacidesterimines is dependent both on imine structure and on the reactivity of the dipolarophile. Phenylglycine imines undergo competing dipole stereomutation and cycloaddition with some dipolarophiles.