Concise Synthesis of Chromene/Chromane-Type Aryne Precursors and Their Applications

Abstract

The gram-scale synthesis of 5,6-, 6,7-, and 7,8-chromene/chromane-type aryne precursors and their applications in regioselective transformation to other functional derivatives is reported. Chromene/chromane-type arynes are generated under mild conditions, which can further undergo [2 + 2], [3 + 2], and [4 + 2] cycloaddition reactions, nucleophilic addition reactions, and σ-insertion reactions to produce structurally novel substituted chromenes and chromanes. The excellent regioselectivity of the reaction is facilitated by the oxygen-containing guiding groups at the ortho-position of the triple bond, which can be removed or switched to other functional groups including alkenyl, aryl, heteroaryl, and arylamino groups.

Nitronate-aryne cycloaddition as a concise route to stereochemically complex fused benzisoxazolines and amino alcohols

“…The observed regioselectivity of the cycloaddition is consistent with the distortion model, where the nucleophilic O -terminus of the dipole interacts with the most electrophilic carbon of an aryne. 14,17…”

The Versatile and Strategic O-Carbamate Directed Metalation Group in the Synthesis of Aromatic Molecules: An Update

“…To triflate tertiary ArOAms, it is necessary to cleave the ArOAm to form a ArOH before applying a triflating agent. 245,250,251 The synthetic significance of introducing triflates ortho to TMS lies in the preparation of arynes. A typical procedure involves OAm-directed regioselective C-silylation via ortholithiation, removal of the directing OAm group, triflylation, and fluoride-mediated activation.…”

“…This transformation is limited to secondary ArOAms. To triflate tertiary ArOAms, it is necessary to cleave the ArOAm to form a ArOH before applying a triflating agent. ,, …”

“…A typical procedure involves OAm-directed regioselective C-silylation via ortho -lithiation, removal of the directing OAm group, triflylation, and fluoride-mediated activation. It enabled the preparation of a benzyne, ,,, thienobenzyne, , indolyne, pyridine, and chromene-type aryne precursors, for example. The structures of selected arynes ( 198 – 200 ) are shown in Scheme .…”

“…To triflate tertiary ArOAms, it is necessary to cleave the ArOAm to form a ArOH before applying a triflating agent. 245 , 250 , 251 …”