Topological selectivity in the intramolecular [4+1] pyrroline annulation. Formal total stereospecific synthesis of (+-)supinidine : (+-)-isoretronecano

PIRROLINA

BIBLIOGRAFÍA NACIONAL QUÍMICA

1986

The preparation and cycloadditions of azidodienes 13 and 14 are described in detail. The synthesis of pyrrolines 1 and 2 is reported, and the conditions are revealed to achieve maximum selectivity in their preparation. The topography of the ultimately prepared pyrrolines depends primarily on the substitution parameters of the starting dienes and on the conditions of rearrangement of their respective vinylaziridines 15 and 16. The former parameter is easily controlled through the vinylogous Reformatsky reaction of ethyl 4-bromocrotonate with aldehyde precursors. The latter parameter depends on the choice of thermolytic vs. nucleophilic activation of particular bonds in vinylaziridines 15 and 16. The flexibility and practicality of this method is exemplified by several convergent approaches to substituted pyrrolines 1 and 2 and their conversion to the title pyrrolizidine alkaloids. Stereospecific preparation of saturated pyrrolizidines 35 is also described. A detailed study of the base-catalyzed elimination of β-acetoxy esters was performed, and the stereochemical consequences are reported for the formation of E and Z geometric isomers of dienes 13.

Journal of the American Chemical Society  v. 108, no. 13, 1986. -- p. 3755-62

American Chemical Society

1986

PDF

Inglés

Artículo

DOI: 10.1021/ja00273a033

PDF