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Palladium‐Catalyzed Annulation of Aryl‐1,2‐diols and Propargylic Carbonates. Theoretical Study of the Observed Regioselectivities
Author(s) -
Labrosse JeanRobert,
Lhoste Paul,
Delbecq Françoise,
Sinou Denis
Publication year - 2003
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200300071
Subject(s) - chemistry , regioselectivity , oxyanion , structural isomer , aryl , palladium , medicinal chemistry , density functional theory , annulation , catalysis , stereochemistry , computational chemistry , organic chemistry , alkyl
Methyl 1‐methylprop‐2‐ynyl carbonate reacts with 3‐ and 4‐substituted benzene‐1,2‐diols to give 2,3‐dihydro‐3‐methyl‐2‐methylidene‐1,4‐benzodioxines, as a mixture of regioisomers in the case of methoxy‐substituted diphenol, and a single regioisomer for the nitro‐ and the formyl‐substituted diphenols. The oxyanion which attacks first corresponds to the less acidic hydroxy function, and the attack of the second oxyanion on the η 3 ‐allylpalladium intermediate is directed toward the more substituted carbon atom. In order to explain the regioselectivity of the cyclization, a theoretical study based on density functional theory (DFT) has been performed. The first step implies an equilibrium between the two oxyanions. The regioselectivity of the second step is due to a subtle balance between the nature of the phosphane, the bulkiness, and the electronic properties of the substituents. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)