Synthesis of cyclic chiral α-amino boronates by copper-catalyzed asymmetric dearomative borylation of indoles

Abstract

A copper(i)-catalyzed dearomative borylation of <i>N</i>-alkoxycarbonyl protected indole-3-carboxylates has been developed. The boron addition in this reaction occurred regioselectively at the 2-position of indoles followed by diastereoselective protonation, affording the corresponding stable cyclic chiral α-amino boronates (2-borylindolines) in moderate to good yields with excellent diastereo- and enantioselectivities. The product <b>2c</b> could be used as a versatile precursor to undergo subsequent stereoselective transformations, delivering highly functionalized 2,3,3-trisubstituted chiral indolines.