aspects of the intramolecular Diels-Alder reaction on perhydro-1,3-benzoxazines derivedfrom (-)-8-aminomenthol bearing α,β-unsaturated amides and the dienic component attached at C-2 are described. The thermal cyclization of 2-(2'-furyl) derivatives 2, 6, and 7 exclusively afforded mixtures of exo adducts. The product selectivity was highly dependent on the solvent of the reaction. In CH2Cl2, the
2-(2′-Furfuryl)-N-acryloyl tetrahydro-1,3-benzoxazine 2a participates in diastereoselective intramolecular Diels-Alderreaction in very mild conditions leading to two diastereoisomeric exo-adducts with good diastereoselectivity. Chromatographic separation of both adduts, and further elimination of the menthol appendage allows to prepare enantiopure iso-indoline derivatives in excellent chemical yields.
A Short Diastereoselective Synthesis of Enantiopure Highly Substituted Tetrahydroepoxyisoindolines
作者:Rafael Pedrosa、Celia Andrés、Javier Nieto
DOI:10.1021/jo991544q
日期:2000.2.1
Diastereoselectiveintramolecular Diels−Alder reaction on 3-allyl-2-furyl- or 3-furfuryl-2-vinyl-substituted chiral perhydro-1,3-benzoxazines derivedfrom (−)-aminomenthol is described. The [4 + 2]...