Beilstein J. Org. Chem.2010,6, No. 57, doi:10.3762/bjoc.6.57
alkyne protecting groups triisopropylsilyl and hydroxymethyl (HOM) and on the polartagging with the hydroxymethyl moiety for an easy chromatographic separation of the products. This paper provides an update of this synthetic route. For the deprotection of HOM protected alkynes, γ-MnO2 proved to be
better than (highly) activated MnO2. The use of HOM as an alkyne protecting group is accompanied by carbometalation as a side reaction in the alkynyl–aryl coupling. The extent of carbometalation can be distinctly reduced through substitution of HOM for 1-hydroxyethyl. The strategy of polartagging is
-diiodobenzene a better procedure is presented together with the finding that 1,4-dialkyl-2,3-diiodobenzene, a constitutional isomer of 1,4-dialkyl-2,5-diiodobenzene, is one of the byproducts.
Keywords: alkyne protecting group; carbometalation; C–C coupling; phenyleneethynylene; polartagging; Introduction
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Graphical Abstract
Scheme 1:
Synthesis of oligoPPEs by a unidirectional (a) or bidirectional (b) repeating unit by repeating uni...