Copper-Catalyzed Highly Enantioselective Cyclopentannulation of Indoles with Donor–Acceptor Cyclopropanes

Abstract

A highly diastereo- and enantioselective BOX/Cu(II)-catalyzed C2,C3-cyclopentannulation of indoles with donor-acceptor cyclopropanes has been developed on the basis of asymmetric formal [3 + 2] cycloaddition of indoles. This reaction provides rapid and facile access to a series of enantioenriched cyclopenta-fused indoline products and can be further extended to the construction of tetracyclic pyrroloindolines. The synthetic potential of the reaction was demonstrated in a four-step synthesis of the core structure of borreverine.

Ein neues goldenes Zeitalter in der Chemie Donor‐Akzeptor‐substituierter Cyclopropane

“…Um dies zu verhindern, war die zusätzliche Zugabe eines Bisoxazolin/ Zn II -Komplexes notwendig (Tabelle 6, Nr. [63] Racemische Vinylcyclopropane kçnnen zudem mithilfe des Pd 0 -(S,S)-DACH-Trost-Komplexes durch asymmetrische formale [3+2]-Cycloadditionen mit prochiralen Michael-Verbindungen in spiro-anellierte Cyclopentane 57 d überführt werden (Tabelle 6, Nr. [59] Bei Untersuchungen der Reaktion von Aminocyclopropanen mit Silylenolethern wurde eine solche Ringçffnung ebenfalls beobachtet.…”

Indole‐derived Donor‐acceptor Cyclopropanes

“…reported cyclopropanation of arylethenes via Cu(II)‐catalyzed reaction with α‐bromocarbonyl compounds . Using this approach, they synthesized IDDA cyclopropane 39 (Scheme ) with a yield that is identical to that obtained in the Rh 2 (OAc) 4 ‐catalyzed reaction between the same alkene 38 and diazomalonate …”

“…Xie, Tang, and coworkers used dynamic kinetic asymmetric [3+2]‐cycloaddition between pyrroloindole 74 and (2‐indolyl)cyclopropane‐1,1‐diester 39 for simple access to the tetracyclic core of alkaloid borreverine (Scheme ) …”

Copper(II) Trifluoromethanesulfonate

“…A highly diastereo-and enantioselective [3 + 2] cycloaddition of indoles with donor-acceptor cyclopropanes has been developed using Cu(OTf) 2 and chiral bis(oxazoline)s (eq 50). 44 The reaction provides easy access to a series of cyclopentafused indoline products with excellent diastereoselectivities (up to >50/1 dr) and enantioselectivities (up to 96% ee). The title compound proved to be an efficient catalyst in the 1,3-dipolar cycloaddition between acryloyl-1,3-oxazolidin-2one and diphenyl nitrone (eq 51).…”