Protection/Deprotection‐Free Syntheses and Structural Analysis of (Keto‐aryl)diynes

Abstract

Abstract The reactions of precursors 4‐BrC 6 H 4 COR with TMSC≡CH (Sonogashira coupling) followed by in situ deprotection and subsequent dimerization gave thermally stable dimeric keto‐diynes RCOC 6 H 4 (C≡C) 2 C 6 H 4 COR ( 8 – 11 ) as yellow powders in 25–85 % yields without the necessity of carbonyl group protection/deprotection steps. Compounds 8 – 11 were also synthesized by an alternative method that utilized α‐haloalkynes previously obtained directly from TMS‐protected 4‐RCOC 6 H 4 C≡CTMS alkynes. The resulting diynes were characterized by spectroscopic methods and in most cases by X‐ray crystallography. Careful analysis of the crystal data revealed a surprisingly high degree of chain curvature. Moreover, compounds 9 (R = Me) and 10 (R = Et) were extremely flat, which greatly facilitates electronic communication throughout the whole molecule. Deeper analysis of the packing motifs showed 9 to have a great potential for topochemical 1,4‐polymerization.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)