A highly selective Ir-catalyzed borylation of 2-substituted indoles: a new access to 2, 7-and 2, 4, 7-substituted indoles
WF Lo, HM Kaiser, A Spannenberg, M Beller, MK Tse
Index: Lo, Wei Fun; Kaiser, Hanns Martin; Spannenberg, Anke; Beller, Matthias; Tse, Man Kin Tetrahedron Letters, 2007 , vol. 48, # 3 p. 371 - 375
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Citation Number: 28
Abstract
The selective CH-functionalization of 2-substituted indoles is presented. Using bis (pinacolato) diboron (2) in the presence of iridium complexes, a novel catalytic mono- borylation is observed preferentially at the 7-position of the indole. This allows for an efficient synthesis of various 2, 7-di-and 2, 4, 7-trisubstituted indoles, which are otherwise difficult to access. The scope and limitation of the method is demonstrated.
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