Synthesis of benzofurans with remote bromide functionality by domino "ring-cleavage-deprotection-cyclization" reactions of 2-alkylidenetetrahydrofurans with boron tribromide |
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Authors: | Bellur Esen Langer Peter |
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Affiliation: | Institut für Chemie, Universit?t Rostock, Albert-Einstein-Strasse 3a, 18059 Rostock, Germany. |
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Abstract: | [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. |
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