Benzotriazole-Assisted Aromatic Ring Annulation: Efficient and General Syntheses of Polysubstituted Naphthalenes and Phenanthrenes.
(Benzotriazol-1-ylmethyl)benzenes and -naphthalenes 1a-f, easily accessible from benzyl bromides and benzotriazole, readily undergo lithiation and subsequent 1,4-addition to alpha,beta-unsaturated aldehydes and ketones. Intramolecular cyclization of the products, induced by acetic acid-hydrobromic acid or polyphosphoric acid (PPA), followed by simultaneous dehydration and debenzotriazolylation furnishes a wide range of polysubstituted naphthalenes 7a-f and of phenanthrenes 9 and 11 in moderate to good yields in one-pot procedures. If compounds 1 are first lithiated and reacted with electrophiles, the resulting alkylation products undergo similar annulation reactions with alpha,beta-unsaturated carbonyl compounds to provide the more highly substituted naphthalenes 6a,b and phenanthrenes 10a,b in moderate overall yields.
Katritzky
Alan R.
AR
Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200.
Zhang
Guifen
G
Xie
Linghong
L