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45.29.1.1.5.1 Variation 1: By Cyclotrimerization of Alkynes

DOI: 10.1055/sos-SD-045-01385

Tobe, Y.; Takeda, T.Science of Synthesis, (2010451336.

ω-Chloro terminal alkynes 113 (with n methylene groups; n=29) are trimerized using a Ziegler-type catalyst prepared from titanium(IV) chloride and triisobutylaluminum, giving a mixture of 1,3,5- and 1,2,4-tris(chloroalkyl)benzenes 114 and 115, respectively (Scheme 29).[‌68‌] Substitution with sodium acetylide gives the corresponding trialkynylbenzenes 116 and 117, which are treated once again with the Ziegler-type catalyst to give a mixture of [n.n.n](1,3,5)-, [n.n.n](1,2,4)-, and probably [n.n.n](1,2,4)(1,3,5)cyclophanes 118, 119, and 120, respectively, from which the 1,3,5-isomer can be isolated by separation by gasliquid chromatography, column chromatography (alumina), or recrystallization in 110% yields.

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