Friedel-Crafts allenylation

Friedel-Crafts reaction remains unexplored, possibly due to the difficulty of the cycloalkyne formation. A mild, versatile, and efficient method for the one-step synthesis of substituted dihydro- and tetrahydroisoquinolines has been developed by the FeCl3-6H20-catalyzed intramolecular allenylation/cyclization reaction of benzylamino-substituted propargylic alcohols, representing the first example of the intramolecular Friedel-Crafts reaction of propargylic alcohols (Scheme 8) [24, 25]. FeCls, InCls, and Yb(OTf)3 also exhibit good catalytic activity for the reaction. 

Propargylic silyl ethers 588 undergo intramolecular Friedel-Crafts alkylation to afford 4-allenyl isochromans 589 in excellent yield (Equation 243) <2001JOC4635>. 

An intramolecular Friedel-Crafts alkylation of propargyl silyl ethers 22 gives 4-allenylisochromans presumably via an allenyl cation (Scheme 22) <01JOC4635>. 

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