Lanthanide triflate complexes of the type [Ln(OTf)(3)] (Ln=La, Sm, Nd, Yb, Lu) serve as effective, recyclable catalysts for the rapid intramolecular hydroalkoxylation (HO)/cyclization of primary/secondary and aliphatic/aromatic hydroxyalkenes in imidazolium-based room-temperature ionic liquids (RTILs) to yield the corresponding furan, pyran, spirobicyclic furan, spirobicyclic furan/pyran, benzofuran, and isochroman derivatives. Products are straightforwardly isolated from the catalytic solution, conversions exhibit Markovnikov regioselectivity, and turnover frequencies are as high as 47 h(-1) at 120 degrees C. The ring-size rate dependence of the primary alkenol cyclizations is 5>6, consistent with a sterically controlled transition state. The hydroalkoxylation/cyclization rates of terminal alkenols are slightly more rapid than those of internal alkenols, which suggests modest steric demands in the cyclic transition state. Cyclization rates of aryl-functionalized hydroxyalkenes are more rapid than those of the linear alkenols, whereas five- and five/six-membered spirobicyclic skeletons are also regioselectively closed. In cyclization of primary, sterically encumbered alkenols, turnover-frequency dependence on metal-ionic radius decreases by approximately 80-fold on going from La(3+) (1.160 A) to Lu(3+) (0.977 A), presumably reflecting steric impediments along the reaction coordinate. The overall rate law for alkenol hydroalkoxylation/cyclization is v approximately k[catalyst](1)[alkenol](1). An observed ROH/ROD kinetic isotope effect of 2.48 (9) is suggestive of a catalytic pathway that involves kinetically significant intramolecular proton transfer. The present activation parameters--enthalpy (DeltaH(++))=18.2 (9) kcal mol(-1), entropy (DeltaS(++))=-17.0 (1.4) eu, and energy (E(a))=18.2 (8) kcal mol(-1)--suggest a highly organized transition state. Proton scavenging and coordinative probing results suggest that the lanthanide triflates are not simply precursors of free triflic acid. Based on the kinetic and mechanistic evidence, the proposed catalytic pathway invokes hydroxyl and olefin activation by the electron-deficient Ln(3+) center, and intramolecular H(+) transfer, followed by alkoxide nucleophilic attack with ring closure.

Lanthanide triflates, Ln(OTf)(3), serve as efficient catalysts for the intramolecular hydroalkoxylation (HO)/cyclization of primary/secondary and aliphatic/aromatic hydroxyalkenes in room temperature ionic liquids (RTILs). Cyclizations are effective in the formation of five- and six-membered oxygen heterocycles with Markovnikov-type selectivity. Reaction rates exhibit first-order dependence on [Ln(3+)] and [substrate].

Lanthanide trifluoromethanesulfonates, Ln(OTf) 3 (OTf (-) = trifluoromethanesulfonate), serve as effective precatalysts for the rapid, regioselective, intermolecular acylation of activated arenes. This contribution probes mechanism and metal ionic radius effects in the catalytic lanthanide triflate-mediated acylation of anisole with acetic anhydride. Kinetic studies of Ln(OTf) 3 (Ln = La, Eu, Yb, Lu)-mediated anisole acylation with acetic anhydride in nitromethane reveal the rate law nu approximately k 3 [Ln (3+)] (1)[acetic anhydride] (1)[anisole] (1). Eyring and Arrhenius analyses yield Delta H++ = 12.9 (4) kcal.mol (-1), Delta S++ = -44.8 (1.3) e.u., and E a = 13.1 (4) kcal.mol (-1) for Ln = Yb, with the negative Delta S++ implying a highly organized transition state. The observed primary kinetic isotope effect of k H/ k D = 2.6 +/- 0.15 is consistent with arene C-H bond scission in the turnover-limiting step. The proposed catalytic pathway involves precatalyst formation via interaction of Ln(OTf) 3 with acetic anhydride, followed by Ln (3+)-anisole pi-complexation, substrate-electrophile sigma-complex formation, and turnover-limiting C-H bond scission. Lanthanide size effects on turnover frequencies are consistent with a transition state lacking significant ionic radius-dependent steric constraints. Substrate-Ln (3+) interactions using paramagnetic Gd (3+) and Yb (3+) NMR probes and factors affecting reaction rates such as arene substituent and added LiClO 4 cocatalyst are also explored.

Polymeric (CuS t Bu)∞ (1) undergoes reaction with trialkylphosphines to form the cuprous thiolato phosphine complexes [(CuS t Bu)4(PR3)2] (R = Me (2a), Et (2b)) in high yield. In contrast to 2b, in polar solvents (CH2Cl2, tetrahydrofuran), complex 2a is in equilibrium with the ion pair Cu(PMe3)4 +Cu5(S t Bu)6 - (3) and other species such as (CuS t Bu) x (PMe3)2 (x = 6 (4), 8 (5)). Clusters 2−4 were isolated analytically pure and fully characterized in solution by multinuclear nuclear magnetic resonance (NMR) spectroscopy and in the solid state by single-crystal X-ray diffraction and 31P magic angle spinning NMR spectroscopy, while the structure of compound 5 was determined by single-crystal X-ray diffraction. Thermal analysis (TGA/DTA) and examination of the volatile byproducts suggest stepwise phosphine loss and C−S bond cleavage by isobutene elimination as the predominant thermolysis pathways of this new Cu2S precursor class.

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