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A one-pot protocol is described which allows direct access to azaindoles from amino-halopyridines and ketones.

An improved method for the synthesis of tethered ruthenium(II) complexes of monosulfonylated diamines is described, together with their application to the hydrogenation of ketones and aldehydes. The complexes were applied directly, in their chloride form, to asymmetric ketone hydrogenation, to give products in excess of 99% ee in the best cases, using 30 bar of hydrogen at 60 °C, and to the selective reduction of aldehydes over other functional groups.

The asymmetric hydrogenation of complex heterocyclic ketones 1 in the presence of the novel catalyst RuCl2[(S)-Xyl-P-Phos][(S)-DAIPEN] and a base afforded the corresponding alcohols 2 in good enantiomeric purity. The outcome of the reaction depended on the substitution pattern of the ketone and the stoichiometry of the base. After optimization of the reaction conditions, the pure alcohols 2a and 2b were isolated in good yield (>70%) and enantiomeric purity (>93% ee) and used as key intermediates for the synthesis of the pharmaceutically active 3,6,7,8-tetrahydrochromeno[7,8-d]imidazoles 3a and 3b.

A rapid and convenient method for the synthesis of a wide range of 2-substituted 7-azaindole derivatives from methyl ketones and 2-amino-3-halopyridines is given.

The reaction of propargylic alcohols with carboxylic acid, or phenol derivatives, in the presence of the precatalyst [RuCl(cod)(C 5 Me 5 )] leads selectively to a variety of alkylidenecyclobutenes through head-to-head dimerization of propargylic alcohol. The first step is the formation of a cyclobutadiene-ruthenium intermediate resulting from the head-to-head coupling of two molecules of propargylic alcohol. On protonation with strong acids (HPF 6 , HBF 4 ) dehydration of the cyclobutadiene complex leads to formation of an alkylidenecyclobutenyl-ruthenium complex. The X-ray structure of one such complex, [RuCl(C 5 Me 5 )(η 4 -R'CCH-CH-C=CR 2 )] (R' = cyclohexen-1-yl, CR 2 = cyclohexylidene) has been determined. Carboxylate is added at the less substituted carbon of the cyclic allylic ligand. DFT/B3LYP calculations confirm that the intermediate arising from head-to-head coupling of alkyne to the RuClCp* species yields the cyclobutadiene-ruthenium complex more easily with propargylic alcohol than with acetylene.

The precatalyst [Cp*RuCl(cod)] promotes the head-to-head cyclodimerization of propargylic alcohols and the formation of novel alkylidene cyclobutenes (see scheme; Cp*=C5 Me5 , cod=1,5-cyclooctadiene) by addition of carboxylic acid to the Ru(η4 -cyclobutadiene) intermediate and dehydration.

Chiral dipyridylamines have been synthesized by N-arylation reactions, and the applicability of those compounds to the copper-catalyzed asymmetric allylic oxidation of cyclohexene was demonstrated.

The precatalyst [Cp*RuCl(cod)] promotes the head-to-head cyclodimerization of propargylic alcohols and the formation of novel alkylidene cyclobutenes (see scheme; Cp*=C5 Me5 , cod=1,5-cyclooctadiene) by addition of carboxylic acid to the Ru(η4 -cyclobutadiene) intermediate and dehydration.

International audience; The reaction of a variety of alkynes with N2CHSiMe3, in the presence of Cp*RuCl(cod) as the catalyst precursor, leads to the general formation of functional conjugated dienes. This selective formation results from the ruthenium-catalyzed creation of two carbon−carbon double bonds in a single step under mild conditions. Terminal alkynes produce 1,4-bistrimethylsilylbuta-1,3-dienes with Z stereoselectivity for the less hindered double bond whereas disubstituted alkynes favor E-configuration for the same double bond. Diynes react also as monoalkynes, and only one triple bond is transformed to give disilylated dienynes. The reaction can be applied to the in situ desilylation in methanol and formation of monosilylated dienes. The catalytic formation of 1,4-bisfunctional buta-1,3-dienes can also take place with N2CHCO2Et and N2CHPh. The reaction can be understood by addition of two carbene units to triple bonds. An initial [2 + 2] addition of the Ru═CHSiMe3 bond with the alkyne triple bond leads to an alkenyl ruthenium-carbene species capable of coordinating a second carbene unit to produce conjugated dienes.

The asymmetric hydrogenation of complex heterocyclic ketones 1 in the presence of the novel catalyst RuCl2[(S)-Xyl-P-Phos][(S)-DAIPEN] and a base afforded the corresponding alcohols 2 in good enantiomeric purity. The outcome of the reaction depended on the substitution pattern of the ketone and the stoichiometry of the base. After optimization of the reaction conditions, the pure alcohols 2a and 2b were isolated in good yield (>70%) and enantiomeric purity (>93% ee) and used as key intermediates for the synthesis of the pharmaceutically active 3,6,7,8-tetrahydrochromeno[7,8-d]imidazoles 3a and 3b.

A new iron(III) halide-promoted aza-Prins cyclization between γ,δ-unsaturated tosylamines and aldehydes provides six-membered azacycles in good to excellent yields. The process is based on the consecutive generation of γ-unsaturated-iminium ion and further nucleophilic attack by the unsaturated carbon−carbon bond. Homoallyl tosylamine leads to trans-2-alkyl-4-halo-1-tosylpiperidine as the major isomer. In addition, the alkyne aza-Prins cyclization between homopropargyl tosylamine and aldehydes gives 2-alkyl-4-halo-1-tosyl-1,2,5,6-tetrahydropyridines as the only cyclic products. The piperidine ring is widely distributed throughout Nature, e.g., in alkaloids,1 and is an important scaffold for drug discovery, being the core of many pharmaceutically significant compounds.2,3 The syntheses of these type of compounds have been extensively studied in the development of new drugs containing six-membered-ring heterocycles.4 Reactions between N-acyliminium ions and nucleophiles, also described as amidoalkylation or Mannich-type condensations, have been frequently used to introduce substituents at the R-carbon of an amine.5 There are several examples that involve an intramolecular attack of a nucleophilic olefin into an iminium cation for the construction of a heterocyclic ring system.6 Traditionally, the use of hemiaminals or their derivatives as precursors of N-acyliminium intermediates has been a common two-step strategy in these reactions.6a Among this type of cyclization is the aza-Prins cyclization,7 which uses alkenes as intramolecular nucleophile. However, cy† X-ray analysis. E-mail address: malopez@ull.es. (1) (a) Fodor, G. B.; Colasanti, B. Alkaloids: Chemical and Biological PerspectiVes; Pelletier, S. W., Ed.; Wiley: New York, 1985; Vol. 23, pp 1-90. (b) Baliah, V.; Jeyarama, R.; Chandrasekaran, L. Chem. ReV. 1983, 83, 379-423. (2) Watson, P. S.; Jiang, B.; Scott, B. Org. Lett. 2000, 2, 3679-3681. (3) Horton, D. A.; Bourne, G. T.; Smythe, M. L. Chem. ReV. 2003, 103, 893-930. (4) Buffat, M. G. P. Tetrahedron 2004, 60, 1701-1729 and references therein. (5) Speckamp, W. N.; Moolenaar, M. J. Tetrahedron 2000, 56, 3187- 3856 and references therein. (6) (a) Hiemstra, H.; Speckamp, W. N. In ComprehensiVe Organic Synthesis; Trost, B. M., Fleming, O., Heathcock, C. H., Eds.; Pergamon: New York, 1991; Vol. 2, pp 1047-1081. (b) Speckamp, W. N.; Hiemstra, H. Tetrahedron 1985, 41, 4367-4416. (7) (a) Dobbs, A. P.; Guesne, S. J. J.; Hursthouse, M. B.; Coles, S. J. Synlett 2003, 11, 1740-1742. (b) Dobbs, A. P.; Guesne, S. J. J.; Martinove, S.; Coles, S. J.; Hursthouse, M. B. J. Org. Chem. 2003, 68, 7880-7883. (c) Hanessian, S.; Tremblay, M.; Petersen, F. W. J. Am. Chem. Soc. 2004, 126, 6064-6071 and references therein. (d) Dobbs, A. P.; Guesne, S. J. Synlett 2005, 13, 2101-2103. ORGANIC

C2-symmetric and unsymmetrically substituted 2,2′-dipyridylamines have been synthesized by sequential Buchwald–Hartwig aminations of halo-pyridines. The X-ray crystal structure of a copper dichloride complex bearing a C2-symmetric 2,2′-dipyridylamine reveals details of the binding properties of the ligand and the coordination geometry at the metal center. In preliminary experiments the use of the new nitrogen chelates in asymmetric catalysis has been demonstrated.

International audience; The reaction of a variety of alkynes RCCH with a variety of carboxylic acids R1CO2H, in the presence of 5% of RuCl(COD)C5Me5, selectively leads to the dienylesters (1E,3E)-RCH1=CH2-CH3=C(R)(O2CR1). The reaction also applies to amino acid and dicarboxylic acid derivatives. It is shown that the first step of the reaction consists of the head-to-head alkyne coupling and of the formation of the metallacyclic biscarbene-ruthenium complex (C5Me5)(Cl)Ru:C(R)-CH=CH-C:(R), isolated for R = Ph and catalyzing the formation of dienylester. D-labeled reactions show that the alkyne protons remain at the alkyne terminal carbon atoms and carboxylic acid protonates the C1 carbon atom. QM/MM (ONIOM) calculations, supporting a mixed Fischer-Schrock-type biscarbene complex, show that protonation occurs preferentially at the carbene carbon C1 adjacent to Ru, in the relative cis position with respect to the Ru-Cl bond, to give a mixed C(1)alkyl-C(4)carbene complex in which the C4 carbene is conjugated with the noncoordinated C2=C3 double bond. This 16-electron intermediate has a weak stabilizing agostic C-H bond. This most stable isomer appears to have a C4 center more accessible to the nucleophilic addition which accounts for the experimentally observed product.