Intramolecular S _N′-type aromatic substitution of benzylic carbonates at their para-position

The benzylic carbonates, which connect with an active methine through an o-phenylene tether at their meta-position, are cyclized by Pd(η ³- C ₃H ₅)Cp-S-Phos catalyst, yielding 3-methyl-9,10- dihydrophenanthrenes. In the catalytic cyclization, the internal nucleophile attacks not the ortho-carbon but the para-carbon of the benzylic ester. The [3 + 2] cycloaddition of m-(silylmethyl)benzyl carbonates with alkylidene malonates was developed from the palladium-catalyzed intramolecular S _N′- type aromatic substitution.