Alkynylsilane Cross-Couplings - The Sila-Sonogashira-Hagihara Reaction

Alkynylsilane Cross-Couplings-The Sila-Sonogashira-Hagihara Reaction 

Organosilicon compounds are useful reagents in modem organic chemistry that are readily available, inexpensive, and robust Their use in acetylene chemistry has classically been limited to protective groups for terminal acetylenes (Section 9.2.2.5). Owing to the weakly polarized character of the C-Si bond, alkynylsilanes are stable to the amine base used in the Sonogashira reaction and will thus not react under 

This tactic has been adopted for the construction of a wide range of internal acetylenes and could also be employed for the synthesis of 1,3-diynes from chloroaUcynes, which often fail under the Cadiot-Chodkiewicz conditions [329]. 

Significantly higher yields were, however, achieved in the absence of a Pd catalyst for this procedure and hence sparked interest in Pd-free variants of the sila-Sonogashira-Hagihara reaction. A simple, but efficient system used the inexpensive and readily available CuCl/PPhj combination for the catalytic cross-coupling of alkynylsilanes with aryl iodides [322]. 

An interesting variant of the sila-Sonogashira-Hagihara reaction avoiding any transition metal catalysts has more recently been reported by Portella et al [332]. The catalytic cycle was implemented under fluoride activation while replacing 

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