Dinuclear [Cu(2)(R-pybox)(2)][X](2) [X = PF(6), R-pybox = 2,6-bis[4'-(S)-isopropyloxazolin-2'-yl]pyridine (S,S)-(i)Pr-pybox (1), 2,6-bis[4'-(R)-phenyloxazolin-2'-yl]pyridine) (R,R)-Ph-pybox (2), 2,6-bis[4'-(S)-isopropyl-5',5'-difeniloxazolin-2'-yl]pyridine (S,S)-(i)Pr-pybox-diPh (3); X = OTf, (R,R)-Ph-pybox (4)] and mononuclear complexes [Cu(R-pybox)(2)][PF(6)] [R-pybox = (S,S)-(i)Pr-pybox (5), (R,R)-Ph-pybox (6)] have been diastereoselectively prepared by reaction of [Cu(MeCN)(4)][PF(6)] or CuOTf.0.5C(6)H(6) and the corresponding pybox ligand. The reaction of CuX (X = I, Br, Cl) with substituted pybox in a 2:1 molar ratio allows us to synthesize tetranuclear complexes [Cu(4)X(4)(R-pybox}(2)] [R-pybox = (S,S)-(i)Pr-pybox, X = I (7), Br (8); (R,R)-Ph-pybox, X = I (9), Br (10), Cl (11); (S,S)-(i)Pr-pybox-diPh, X = I (12), Cl (13)]. Dinuclear complexes [Cu(2)(mu-Cl)(R-pybox)(2)][CuCl(2)] [R-pybox = (S,S)-(i)Pr-pybox (15), (R,R)-Ph-pybox (16)] have been prepared by reaction of CuCl with (i)Pr-pybox or Ph-pybox in 3:2 molar ratio. The structures of the complexes 1, 2, 7, 15, 16 and that of the polymeric species [Cu(4)(mu(3)-Br)(3)(mu-Br)((i)Pr-pybox)](n) (14) have been determined by single-crystal X-ray diffraction analysis. Diffusion studies using (1)H and (19)F-DOSY experiments provide evidence that the different nuclearity of compounds 1 and 5 is maintained in the solution state and confirm that these ionic compounds exist in solution as stable, discrete, cationic complexes. The complexes 1-4, 6, 9, 10, and 16 as well as the previously reported [Cu(2){(S,S)-(i)Pr-pybox}(2)][OTf](2) have been assayed as catalysts in the enantioselective synthesis of propargylamines. The dinuclear complexes [Cu(2){(R,R)-Ph-pybox}(2)][X](2) (2, 4) were found to be the most efficient catalysts (up to 89% e.e.).

The reaction of lithium enolates of achiral N-protected glycine esters with chiral alkoxyalkenylcarbene complexes of chromium provided the corresponding Michael adducts with either high anti or syn selectivity depending on the nature of the nitrogen protecting group, and high diastereofacial selectivity when carbene complexes containing the (-)-8-phenylmenthyloxy group were employed. Subsequent oxidation of the metal-carbene moiety followed by deprotection of the amine group and hydrolysis of both carboxylic esters afforded enantiomerically enriched 3-substituted glutamic acids of natural as well as unnatural stereochemistry. Alternatively, when the deprotection step was performed previously to the oxidation, cyclic aminocarbene complexes were formed, which finally led to optically active 3-substituted pyroglutamic acids.

The reaction of o-alkynylbenzaldehydes 1 with different alcohols, silylated nucleophiles 5, electron-rich arenes 10, and heteroarenes 12 in the presence of the reagent IPy(2)BF(4), at room temperature, gave functionalized 4-iodo-1H-isochromenes 2, 6, 11, and 13 in a regioselective manner. When alkynes 16 and alkenes 19 and 20 were used as nucleophiles, a regioselective benzannulation reaction took place to form 1-iodonaphthalenes 17 and 1-naphthyl ketones 18, respectively. Moreover, the latter process has been adapted to accomplish the synthesis of indole, benzofuran, and benzothiophene derivatives (23, 27, and 28, respectively). The three patterns of reactivity observed for the o-alkynylbenzaldehyde derivatives with IPy(2)BF(4) stem from a common iodinated isobenzopyrylium ion intermediate, A, that evolves in a different way depending on the nucleophile present in the reaction medium. A mechanism is proposed and the different reaction pathways observed as a function of the type of nucleophile are discussed. Furthermore, the reaction of the o-hexynylbenzaldehyde 1 b with styrene was monitored by NMR spectroscopy. Compound III, a resting state for the common intermediate in the absence of acid, has been isolated. Its evolution in acid media has been also tested, thereby providing support to the proposed mechanism.

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The reaction of electron-deficient alkenes with alkoxyalkynyl Fischer carbene complexes (FCCs) represents a straightforward route to a new type of captodative (donor-acceptor) alkynylcyclopropanes, which have been prepared in moderate to high yields and in a diastereoselective manner. Some studies regarding the employment of additives to facilitate the recovery of the metal moiety after the reaction are also described. Finally, the first example of a cyclopropanation reaction through employing Fischer carbene complexes under microwave irradiation is presented; this method proved to be an advantageous alternative to the thermal reaction.