Preparation of an Indolylfulgimide‐Adamantane Linker Conjugate with Nitrile Anchoring Groups through Palladium‐Catalyzed Transformations

Abstract

AbstractWe report the preparation, through palladium‐catalyzed transformations, of the indolylfulgimide linker conjugate 1, containing an adamantane core and nitrile anchoring groups. The ethynylene‐linker 12 for the final Sonogashira coupling was prepared through palladium‐mediated cyanation of an iodo‐substituted precursor with Zn(CN)2. The synthesis of the 6‐bromo‐substituted indolylfulgimide coupling partner 2 was accomplished in seven steps. Model studies using phenylacetylene and the 5‐bromo‐substituted indole 13 were conducted to find conditions that would prevent homocoupling of the ethynylene linker 12 in the final Sonogashira coupling step. The use of Pd(PhCN)2Cl2 and [(tBu)3PH]BF4 in the presence of diisopropylamine, together with CuI as additive, proved to be most efficient. Finally, the photochromic properties of conjugate 1 and indolylfulgimide 2 were studied.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)