Synthesis of benzofurans with remote bromide functionality by domino "ring-cleavage-deprotection-cyclization" reactions of 2-alkylidenetetrahydrofurans with boron tribromide.
[reaction: see text] Bromination and subsequent Suzuki reactions of 2-alkylidenetetrahydrofurans, readily available by [3+2] cyclizations, afforded 1'-(2''-methoxyphenyl)-2-alkylidenetetrahydrofurans. Treatment of the latter with boron tribromide and subsequent addition of water resulted in the chemoselective formation of functionalized benzofurans containing a remote bromide functionality. The products are formed by a new domino "ring-cleavage-deprotection-cyclization" reaction. The addition of an aqueous solution of potassium tert-butoxide, rather than water, afforded saturated analogues of calycine by a "ring-cleavage-deprotection-ring-closure-lactonization" reaction.
Bellur
Esen
E
Institut für Chemie, Universität Rostock, Albert-Einstein-Strasse 3a, 18059 Rostock, Germany.
Langer
Peter
P
D001572:Benzofurans / Q000138:chemical synthesis*; D001895:Boron; D001965:Bromides / Q000138:chemical synthesis
D001572:Benzofurans; D001965:Bromides; D001895:Boron