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Efficient Preparation of Photoswitchable Dithienylethene‐Linker‐Conjugates by Palladium‐Catalyzed Coupling Reactions of Terminal Alkynes with Thienyl Chlorides and Other Aryl Halides
Author(s) -
Zastrow Marc,
Thyagarajan Sujatha,
Ahmed Saleh A.,
Haase Paul,
Seedorff Sabine,
Gelman Dmitri,
Wachtveitl Josef,
Galoppini Elena,
RückBraun Karola
Publication year - 2010
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200900503
Subject(s) - linker , sonogashira coupling , photochromism , aryl , chemistry , coupling reaction , conjugate , catalysis , halide , palladium , acetylene , combinatorial chemistry , photochemistry , adamantane , polymer chemistry , organic chemistry , alkyl , computer science , operating system , mathematical analysis , mathematics
Three photochromic dithienylethene‐linker‐conjugates with an adamantane core containing different spacer lengths and footprint areas with carboxylic anchoring groups are synthesized. The synthetic routes start either from the ethynylene‐linker 5 or the iodo‐substituted linker 8 . Reaction conditions for the final Sonogashira coupling step between ethynylene‐linker 5 with the chloro‐substituted dithienylethene 4 in the presence of [PdCl 2 (CH 3 CN) 2 ]/X‐Phos and Cs 2 CO 3 or K 3 PO 4 are optimized using 2‐chloro‐5‐methylthiophene ( 9 ) and triethylsilylacetylene or triisopropylsilylacetylene ( 10a , 10b ,) as model compounds. Experimental conditions are found to suppress the activation of the C(sp)Si bond in TIPS‐acetylene 10b , a reaction leading to a subsequent cross‐coupling reaction to form by‐product 12 . Furthermore, activation of the C(sp)Si bond in the presence of the fluorinated backbone of the chloro‐substituted dithienylethene 4 can also be prevented. The photochromic properties of the conjugate 3 and its precursor dithienylethene 7b are also investigated.