DFT study of the mechanism of benzocyclobutene formation by palladium-catalysed C(sp3)-H activation: role of the nature of the base and the phosphine.

Christos E. Kefalidis , Olivier Baudoin (1) , Eric Clot (2)

1 ICBMS - Institut de Chimie et Biochimie Moléculaires et Supramoléculaires
2 ICGM ICMMM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier

DFT(B3PW91) calculations of the mechanism of the intramolecular C(sp(3))-H arylation of 2-bromo-tert-butylbenzene to form benzocyclobutene catalysed by Pd(PR(3)) (R = Me, (t)Bu) and a base (acetate, bicarbonate, carbonate) show that the preferred mechanism is highly dependent on the nature of the phosphine and the base used in the calculations. With the experimental reagents (P(t)Bu(3) and carbonate) the rate-determining step is C-H activation with the base coordinated trans to the C-H bond. An agostic interaction of a geminal C-H bond with respect to the bond to be cleaved induces a lowering of the activation barrier.

Domaines: Chimie organique

Christos E. Kefalidis, Olivier Baudoin, Eric Clot. DFT study of the mechanism of benzocyclobutene formation by palladium-catalysed C(sp3)-H activation: role of the nature of the base and the phosphine.. Dalton Transactions, 2010, 39 (43), pp.10528-35. ⟨10.1039/c0dt00578a⟩. ⟨hal-00691421⟩