Catalytic, Cascade Ring‐Opening Benzannulations of 2,3‐Dihydrofuran
<i>O</i>
,
<i>O</i>
‐ and
<i>N</i>
,
<i>O</i>
‐Acetals
作者:Joel Aponte‐Guzmán、Lien H. Phun、Marchello A. Cavitt、J. Evans Taylor、Jack C. Davy、Stefan France
DOI:10.1002/chem.201601954
日期:2016.7.18
An Al(OTf)3‐catalyzed intramolecular cascade ring‐opening benzannulation of 2,3‐dihydrofuran O,O‐ and N,O‐acetals is described. The cascade sequence involves the dihydrofuran ring‐opening by acetal hydrolysis, an intramolecular Prins‐type cyclization, and aromatization to generate an array of benzo‐fused (hetero)aromatic systems in up to 95 % yield. This method represents the first example of dihydrofuran
A convergent approachtowardsnonsymmetrical 2,5-diester pyrroles is described. The buildingblocks can be easily assembled in less than four steps allowing for facile construction of diversity. The synthesis uses a rhodium-catalyzed NH insertion, followed by a one-pot deprotection-condensation to yield the desired pyrroles.