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Selective Palladium-Catalyzed Cocyclotrimerization of Arynes with Dimethyl Acetylenedicarboxylate: A Versatile Method for the Synthesis of Polycyclic Aromatic Hydrocarbons†
journal contribution
posted on 2000-09-16, 00:00 authored by Diego Peña, Dolores Pérez, Enrique Guitián, Luis CastedoBenzyne (1a) and the substituted derivatives 4,5-difluorobenzyne (1b) and 3-methoxybenzyne (2)
undergo chemoselective palladium-catalyzed [2 + 2 + 2]-cocyclotrimerization with dimethyl
acetylenedicarboxylate (DMAD) to afford the corresponding phenanthrenes and/or naphthalenes.
The major products are phenanthrenes if Pd(PPh3)4 is used as the catalyst, naphthalenes if
Pd2(dba)3 is used. When the method is applied to polycyclic arynes 3−6, which are generated from
the corresponding o-trimethylsilylaryl triflates, the same reactivity pattern is observed: the reaction
can be selectively directed either toward the cocyclization of one molecule of aryne and two molecules
of alkyne or to the reaction of two molecules of aryne with one molecule of alkyne, by appropriate
choice of the palladium catalyst. The synthesis of polycyclic aromatic compounds 33−39 using this
methodology is reported.