Silahelicenes, which contain two silole moieties in a helically chiral structure, were synthesized by a chiral Ir-catalyzed intermolecular [2+2+2] cycloaddition of tetraynes with diynes along with a Ni-mediated intramolecular [2+2+2] cycloaddition. The photophysical properties of the obtained highly enantiomerically enriched silahelicenes (up to 93% ee) were also measured.

The Rh-catalyzed hydroarylative and hydrovinylative cyclization of diynes with aryl ketones or enones gave monocyclic 1,3-dienes. Enynes also underwent the same reaction and chiral products were obtained with high ee using a chiral Rh catalyst. Carbonyl-directed activation of aromatic and vinylic C-H bonds is likely the initial step in the present transformation.

Cycloaddition reactions O 0070Rhodium-Complex-Catalyzed [2 + 2 + 2] Cycloaddition of Diynes and Carbonyl Compounds. -In the presence of Rh(I)/BINAP catalysts, 1,6-and 1,7-diynes undergo [2 + 2 + 2] cycloaddition with carbonyl compounds to give fused pyran derivatives. However, the cycloadducts resulting from 1,6-diynes are not stable and ring opening yields enones such as (IV) and (V). Using chiral catalysts the formation of enantio--enriched products is possible. -(TSUCHIKAMA, K.; YOSHINAMI, Y.; SHIBATA*, T.; Synlett 2007Synlett , 9, 1395Synlett -1398 Dep. Chem., Sch. Sci. Eng., Waseda Univ., Shinjuku, Tokyo 169, Japan; Eng.) -Jannicke 42-036

The first synthesis of silahelicenes (IV), which have helical chirality including silole moieties, is reported.

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