Beilstein J. Org. Chem.2008,4, No. 1, doi:10.1186/1860-5397-4-1
compared to macrocycle 1. 3,5-Diiodo-4-methylbenzene (2) was treated with trimethylsilyl(TMS)acetylene under standard Hagihara-Sonogashiracoupling conditions and subsequently deprotected with K2CO3 in MeOH/THF. As expected, the Pd-catalyzed coupling reaction runs under milder conditions and with higher
(model reactions with 4-methylanisole showed that a direct diiodination could not be obtained under the conditions we used; for example, with N-iodosuccinimide and FeCl3 we could obtain cleanly 2-iodo-4-methylanisole). Pd-catalyzed Hagihara-Sonogashiracoupling with 15, deprotection of the
PAH substituents (Scheme 3). Pd-catalyzed coupling of the diiodo compound 14 with the mono protected bisacetylene 20, deprotection of the acetylenes with TBAF and subsequent coupling with an excess of the diiodo compound 5c gave the diiodide 23. Hagihara-Sonogashiracoupling of 23 with an excess of
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Graphical Abstract
Figure 1:
a) Design principle for common discotic liquid crystals; b) Design principle for discotic liquid cr...
Beilstein J. Org. Chem.2007,3, No. 30, doi:10.1186/1860-5397-3-30
the resulting aldehyde under Stork's conditions [11] provided the Z-iodoolefin 5 in a highly stereoselective manner. The Sonogashiracoupling reaction [12] of 5 with TMS-acetylene followed by cleavage of the trimethylsilyl group with K2CO3 afforded (-)-231C. Although the rotation of the natural
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Graphical Abstract
Scheme 1:
Syntheses of (-)-209B, (-)-231C, (-)-233D, and (-)-235B".