Synthesis of Siloles and Germoles via Double trans Addition to 1,3-Diynes

4 SYNTHESIS OF SILOLES AND GERMOLES VIA DOUBLE TRANS ADDITION TO 1,3-DIYNES 

The silole skeleton can be constructed by double trans hydrosilylation of 1,3-diynes. It was realized by using a cationic ruthenium complex as the catalyst in 2007 [18], The reaction of l,4-diphenylbuta-l,3-diyne and diphenylsilane (PhaSiHa, 3 equiv) in 

Silafluorene exhibited superior reactivity for the double trans hydrosilylation, giving spirocyclic silole in 79% yield. The use of diethylsilane and methyl(phenyl)silane as hydrosilylation agents was unsuccessful. 

A variety of symmetrical and unsymmetrical 1,3-diynes underwent double trans hydrosilylation with silafluorene to furnish spirocyclic siloles (Table 20.4). A range of heteroatom functionalities, including halogens, silicon, and boron, on the phenyl rings survived unscathed under the reaction conditions. l-Phenyl-4-(4-vinylphenyl)buta-1,3-diyne furnished the corresponding silole with the vinyl group remaining intact. 

On the other hand, hexa-2,4-diyne failed to react, suggesting that 1,3-diynes with the 1- and 4-carbons, connected to sp carbons, are suitable substrates for the present silole-forming reaction. 

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