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

Iron-Catalyzed Reactions in Organic Synthesis

Ruthenium-Catalyzed Reactions for Organic Synthesis.

Chemistry of Acyl Radicals

The high utility of halogenated organic compounds has prompted the development of a vast number of transformations which install the carbon–halogen motif. Traditional routes to these building blocks have commonly involved multiple steps, harsh reaction conditions, and the use of stoichiometric and/or toxic reagents. In this regard, using transition metals to catalyze the synthesis of organohalides has become a mature field in itself, and applying these technologies has allowed for a decrease in the production of waste, higher levels of regio- and stereoselectivity, and the ability to produce enantioenriched target compounds. Furthermore, transition metals offer the distinct advantage of possessing a diverse spectrum of mechanistic possibilities which translate to the capability to apply new substrate classes and afford novel and difficult-to-access structures. This Review provides comprehensive coverage of modern transition metal-catalyzed syntheses of organohalides via a diverse array of mechanisms. Atte...

Modern Transition-Metal-Catalyzed Carbon–Halogen Bond Formation

Organopalladium intermediates in organic synthesis

Organic syntheses by means of metal complexes. V. Reactions of olefins, carbon tetrachloride, and carbon monoxide catalyzed by metal carbonyls

The 1,5-cyclooctadiene - palladium chloride complex and carbon monoxide react in ethanol to form ethyl 4-cyclooctenecarboxylate. The carbonylation of 1,5-cyclooctadiene catalyzed by palladium chloride has given ethyl 4-cyclooctenecarboxylate and cyclooctanedicarboxylate. It has been found that the monoester can be obtained selectively under certain conditions; the further carbonylation of the monoester gives the diester. Under the same reaction conditions, 1,3-cyclooctadiene gives ethyl 2-cyclooctenecarboxylate in a low yield. Metallic palladium has been found to be the true catalyst and the presence of hydrogen chloride has been found to be essential for the catalysis. It has also been found that the 1, 5-cyclooctadiene - palladium chloride complex can be formed from 1,5-cyclooctadiene, metallic palladium and hydrogen chloride by heating them in an autoclave under nitrogen. It seems likely that the catalytic carbonylation of 1,5-cyclooctadiene proceeds through the formation of the 1,5-cyclooctadiene - pa...

Organic Syntheses by Means of Noble Metal Compounds. XIV. The Carbonylation of Cyclooctadienes

Organic Syntheses by Means of Noble Metal Compounds. XLIX. Oxidation of 3-Hexenedioate to 2,4-Hexadienedioate Catalyzed by Palladium Chloride and Copper (II) Chloride

Tosaku Susuki

Papers

Organic syntheses by means of metal complexes. V. Reactions of olefins, carbon tetrachloride, and carbon monoxide catalyzed by metal carbonyls

Organic Syntheses by Means of Noble Metal Compounds. XIV. The Carbonylation of Cyclooctadienes

Organic Syntheses by Means of Noble Metal Compounds. XLIX. Oxidation of 3-Hexenedioate to 2,4-Hexadienedioate Catalyzed by Palladium Chloride and Copper (II) Chloride

Organic syntheses by means of noble metal compounds XVI. Carbonylation of allene-palladium chloride complexes☆

Free radical reactions in organic electrode processes—IV : Anodic oxidation of cyanide ions in the presence of aromatic hydrocarbons☆