Journal of Molecular Catalysis A: Chemical 329 (2010) 96–102 Contents lists available at ScienceDirect Journal of Molecular Catalysis A: Chemical journal homepage: www.elsevier.com/locate/molcata Palladium–diphosphine complexes as catalysts for allylations with allyl alcohol Jimmy A. van Rijn, Angela den Dunnen, Elisabeth Bouwman ∗ , Eite Drent Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 Leiden, The Netherlands article info Article history: Received 13 May 2010 Received in revised form 18 June 2010 Accepted 23 June 2010 Available online 1 July 2010 Keywords: Catalysis Allylation Palladium Allyl alcohol Phosphines Phenol abstract Several palladium complexes with bidentate phosphine ligands were tested for their activity in the O- allylation of phenols with allyl alcohol. The use of C 3 -bridged bidentate phosphine ligands results in very high selectivity for O-allylation. The reactions do not require stoichiometric amounts of additives to control the chemoselectivity. Especially, catalysts with gem-dialkyl substituted C 3 -bridged bidentate phosphine ligands perform very well, resulting in a (equilibrium) conversion of ∼50% of phenol with a selectivity of 99% for O-allylation. The use of diallyl ether as the allylating agent results in a significant increase in phenol conversion while maintaining high selectivity for O-allylation. Apart from Pd(OAc) 2 as catalyst precursor, Pd(dba) 2 was also employed, making it possible to use other types of phosphine or phosphite ligands. With the palladium catalytic system not only phenol, but also aliphatic alcohols can be allylated, as well as aromatic and aliphatic amines. © 2010 Elsevier B.V. All rights reserved. 1. Introduction In the context of the development of an environmentally benign catalytic route to epoxy resins, O-allylation of phenols is a highly desirable reaction [1]. Allyl phenyl ethers can be epoxidized to obtain glycidyl ethers, which are currently produced in the epoxy resin industry via the conventional epichlorohydrin route with the co-production of stoichiometric amounts of chloride-containing waste. Allylation reactions of phenols are mostly performed with allylating agents such as allyl chloride or allyl acetate and sto- ichiometric amounts of base are added to induce selectivity for O-allylation [2,3]. Numerous allylation reactions, generally known as the Tsuji–Trost reaction, using palladium catalysts have been reported [4–6]. Regarding atom efficiency, it would be desirable to use allyl alcohol as the allylating agent. Several palladium systems have been reported to be able to use allyl alcohol as an allylating agent [7–11]. However, in the cases where phenols are used as the substrate, stoichiometric amounts of base are necessary to induce chemoselectivity towards O-allylation, inevitably resulting in inor- ganic waste [9]. In the absence of base, C-allylation occurs [10],a feature also observed with ruthenium-based systems [12]. We have developed a catalytic system based on ruthenium that catalyzes both O- and C-allylation of phenols; we have shown that the O- allylated products are reversibly formed, while C-allylated products are produced irreversibly [13]. For this ruthenium-based system a large variety of bidentate phosphine ligands has been used [13,14]. ∗ Corresponding author. Tel.: +31 71 527 4550; fax: +31 71527 4761. E-mail address: bouwman@chem.leidenuniv.nl (E. Bouwman). Apart from the observation that selectivity of the reaction is time- dependent, the role of the ligand appeared to be of great importance for the activity as well as the selectivity; it was shown that with only minor changes in the ligand-structure dramatic effects on both activity and selectivity were accomplished. Restricted coor- dination space at the ruthenium center favors the formation of the O-allylated product, which could be achieved using ligands that either have a large bite angle [13] and/or form kinetically stable chelates [14]. For palladium however, the use of Pd(OAc) 2 for the allylation of phenol-type substrates has only been reported with monodentate phosphine ligands [8–10]. In this paper a palladium system with a selection of bidentate phosphine ligands is reported (Fig. 1); the activity and selectivity for O-allylation as a function of the ligand is discussed. 2. Experimental 2.1. General All reactions were performed under an argon atmosphere using standard Schlenk techniques. Solvents were dried and distilled using standard procedures and were stored under argon. The phos- phine ligands with phenyl substituents (dppm, dppe, dppp, dppb and PPh 3 ) and triphenylphosphite were commercially available and used as received. Pd(OAc) 2 and Pd(dba) 2 were purchased from Strem Chemicals. The ligands dppdmp [15] and dppdep [16] were earlier described in literature. The ligands o-MeOdppp [17], o-MeOdppdmp [18], p-MeOdppp [19], o-Medppp [20] and trisani- sylphosphine [21] were a gift from Shell Global Solutions and used as received. Allyl-1,1-d 2 alcohol was synthesized as reported [22]. 1381-1169/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.molcata.2010.06.023