Cross-coupling reactions alkynylsilane

Synthetic reactions involving activation of alkenyl- and arylsilanes by copper salts have also been reported. A copper-mediated system is effective in the cross-coupling reaction of aryl- and heteroarylsilanes with aryl halides under Pd-free conditions (Equation (13)).66 Alkenyl- and arylsilanes as well as alkynylsilanes undergo homocoupling in the presence of Cul and air.65,65a Functionalized alkenyl- and arylsilanes bearing a coordination site in the vicinity of silicon (e.g., 7) are easily activated by copper salts even at room temperature (Scheme 5).67,67l 67e 68 q-jle organocoppers such as 8 are useful for carbon-carbon bond-forming reaction with carbon electrophiles. 

Successful extensions to sp-carbon cross-coupling reactions with vinyl triflates are exemplified by the synthesis of the enyne 32 [Eq, (15)]. It is noteworthy that this reaction is compatible with the presence of alkynylsilanes, emphasizing the different behavior of organosilicone and organotin derivatives [25]. 

We have found that alkynylsilanes are smoothly converted into alkynylcopper compounds by treatment with CuCl in l,3-dimethyl-2-imidazohdinone (DMI) the copper reagents can be isolated in good yields [563]. This study was the first example of preparation and isolation of organocopper compounds by use of organosilicon reagents. The Si-Cu transmetalation is applicable to the synthesis of alkynyl ketones by Cu-catalyzed alkynylation of acid chlorides (Scheme 10.217). We have also shown that a Cu-mediated system is effective in the cross-coupling reaction between arylsilanes or heteroarylsilanes and aryl hahdes [564]. 

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]. 

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

---