Trimethylsilyl-4-bromomagnesio-l-butyne

1 -Trimethylsilyl-4-bromomagnesio-l-butyne (activation of magnesium by dry stirring) [38] 

Magnesium turnings (1.27 g, 52 mmol) are stirred in an argon atmosphere for 48 h in a 100 ml three-necked round-bottomed flask [12]. Dry THF (20 ml) is added, followed dropwise by a solution of 4-bromo-Ttrimethylsilyl-1-butyne (2.56 g, 12.5 mmol) in dry THF (20 ml). After the initial exothermic reaction has subsided, the mixture is stirred at room temperature for 1 h. 

The yield of a subsequent copper-catalysed reaction with 2-cyclohexenone was 81%. 

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