Alder Reaction of 1, 2,4,5-Hexatetraene Tetramethyl Paracyclophane-4,5,12,13-tetracarboxylate

Submitted by Henning Hopf, Ingrid Bohm, and Jurgen Kleinschroth1 

Caution Propargyl bromide is poisonous and should be handled in a well-ventilated hood. For a warning regarding the use of benzene, see Ref. 2. 

The checkers dried the ether by distillation from sodium benzophenone ketyl immediately before use. 

The submitters initiated Grignard formation by adding a few milliliters of a solution of 142.8 g (1.2 mol) of propargyl bromide in 560 mL of anhydrous ether. If the reaction does not begin, they suggest that the flask be heated with a warm stream of air from a heat gun.  

The checkers found that the addition time varied from ca. 1 to 4 hr, depending on the temperature of the cooling bath and the extent to which it was stirred. 

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