title: Studies in chlorin chemistry. II. A versatile synthesis of dihydrodipyrrins.
abstract: [reaction: see text] Dihydrodipyrrins are key building blocks for the synthesis of hydroporphyrins, many of which have important biological activity. The title compounds were prepared in stereo- and regioselective fashion by a three-step sequence consisting of (1) Pd(0)-catalyzed coupling-cyclization of 2-iodopyrroles with gamma-alkynoic acids to afford enelactones of the desired substitution pattern, (2) methylenation at the lactone carbonyl group employing the Petasis reagent, and (3) in situ enol-ether hydrolysis and amination of the resultant 1,4-diketone to close the pyrroline ring (nine examples). Yields for each step were generally high, although in substrates not blocked by geminal substitution aromatization to a dipyrromethane is a competing side reaction.
authors.affiliation: Burke Chemical Laboratory, Dartmouth College, Hanover, New Hampshire 03755, USA.
authors.forename: William G
authors.initials: WG
authors.lastname: O'Neal
authors.forename: William P
authors.initials: WP
authors.lastname: Roberts
authors.forename: Indranath
authors.initials: I
authors.lastname: Ghosh
authors.forename: Peter A
authors.initials: PA
authors.lastname: Jacobi
mesh_terms: D008968:Molecular Conformation; D011166:Porphyrins / Q000138:chemical synthesis*
chemical_list: D011166:Porphyrins