Synthesis of tetraarylallenes via palladium-catalyzed addition-elimination reactions of 1,1,3-triaryl-2-propyn-1-ols with aryl iodides

The palladium-catalyzed reactions of tent-propargylic alcohols with aryl iodides afforded tetraarylallenes in good yields. This reaction involves: (1) oxdative addition of the aryl iodide to Pd(0); (2) arylpalladium intermediate coordination to the carboncarbon triple bond of the 1,1,3-triaryl-2-propyn-l-ol and subsequent regioselective insertion of the alkynol to form (3-hydroxyvinylpalladium species; and (3) (beta-elimination to produce the tetraarylallenes. Generally, the best results are obtained by employing 5 mol% of Pd(TFA)(2), 10 mol% of PPh3, two equivalents of aryl iodide and five equivalents of Et3N in MeCN.