17 research outputs found
Phase-transfer-catalysed synthesis of pyrroloindolines and pyridoindolines by a hydrogen-bond-assisted isocyanide cyclization cascade.
A cascade reaction that generates pyrrolo- and pyridoindoline motifs from isocyanide precursors under phase-transfer conditions is described. This transformation proceeds at room temperature in the presence of a quaternary ammonium catalyst and base to generate functionalized products containing an all-carbon quaternary stereocentre. Quantum chemical calculations demonstrated that intramolecular general acid catalysis plays a key accelerating role through stabilization of developing charge in the transition state, and that the reaction is best described as a 5-endo dig cyclization, rather than an anionic 6π electrocyclization. Investigations employing chiral phase-transfer catalysts have given promising selectivities to date
11-Step Total Synthesis of (−)-Maoecrystal V
An expedient, practical, and enantioselective route to the highly
congested <i>ent</i>-kaurane diterpene maoecrystal V is
presented. This route, which has been several years in the making,
is loosely modeled after a key pinacol shift in the proposed biosynthesis.
Only 11 steps, many of which are strategic in that they build key
skeletal bonds and incorporate critical functionalities, are required
to access (−)-maoecrystal V. Several unique and unexpected
maneuvers are featured in this potentially scalable pathway. Reevaluation
of the biological activity calls into question the initial exuberance
surrounding this natural product
Phase-transfer-catalysed synthesis of pyrroloindolines and pyridoindolines by a hydrogen-bond-assisted isocyanide cyclization cascade.
A cascade reaction that generates pyrrolo- and pyridoindoline motifs from isocyanide precursors under phase-transfer conditions is described. This transformation proceeds at room temperature in the presence of a quaternary ammonium catalyst and base to generate functionalized products containing an all-carbon quaternary stereocentre. Quantum chemical calculations demonstrated that intramolecular general acid catalysis plays a key accelerating role through stabilization of developing charge in the transition state, and that the reaction is best described as a 5-endo dig cyclization, rather than an anionic 6π electrocyclization. Investigations employing chiral phase-transfer catalysts have given promising selectivities to date
Phase-transfer-catalysed synthesis of pyrroloindolines and pyridoindolines by a hydrogen-bond-assisted isocyanide cyclization cascade.
A cascade reaction that generates pyrrolo- and pyridoindoline motifs from isocyanide precursors under phase-transfer conditions is described. This transformation proceeds at room temperature in the presence of a quaternary ammonium catalyst and base to generate functionalized products containing an all-carbon quaternary stereocentre. Quantum chemical calculations demonstrated that intramolecular general acid catalysis plays a key accelerating role through stabilization of developing charge in the transition state, and that the reaction is best described as a 5-endo dig cyclization, rather than an anionic 6π electrocyclization. Investigations employing chiral phase-transfer catalysts have given promising selectivities to date