Palladium(0)-catalyzed tandem cyclization of allenenes is described. Treatment of allenenes with an aryl halide, potassium carbonate, and catalytic [Pd(PPh(3))(4)] in dioxane afforded tri- or tetracyclic heterocycles in moderate to good yields through insertion of arylpalladium(II) halide into the allenic moiety, intramolecular carbopalladation, and aromatic C--H bond activation. The substituent on the olefin terminus has proven to be essential for the success of the tandem cyclization. The reaction with heterocyclic aryl halides such as iodopyrazine or 4-bromo-1-methylindole afforded tri- or tetracyclic heteroaromatic products in good yields.

Thermal [2 + 2] cycloaddition of allenes with an additional multiple bond is described. By simply heating the allenenes or allenynes having a three-atom tether in an appropriate solvent such as dioxane or DMF, the distal double bond of the allenic moiety regioselectively participates in the cycloaddition to form bicyclo[4.2.0]oct-5-ene derivatives in good to excellent yields. In all the reactions of allenenes, the olefin geometry was completely transferred to the cycloadducts. While the reaction of terminal allenes afforded bicyclic cyclobutane derivatives as a single isomer, the cycloaddition of some internal allenes with axial chirality yielded a diastereomeric mixture of cycloadducts. These results are in good accordance with the stepwise mechanism through a biradical intermediate with a coplanar allyl radical.

Die Benzhydrylgruppe ist der Schlüssel: Die effiziente Alkylierung 3‐substituierter Aziridin‐2‐carboxylate gelingt nur bei N‐Benzhydryl‐geschützten Aziridinen, und sie verläuft mit vollständiger Retention der Konfiguration an der 2‐Position. Sequenzielle katalytische asymmetrische Aziridinierung und Aziridinalkylierung wurden für die Synthese von BIRT‐377 (siehe Formel) eingesetzt.

Formation of 3-pyrrolines from simple unactivated allenes bearing a protected amino group under basic conditions is described. Treatment of alpha-amino allenes with potassium carbonate in DMF under reflux in the absence of any transition-metal catalysts gave the corresponding 3-pyrrolines in good to excellent yields, by 5-endo-trig mode cycloisomerization. The reaction of internal allenes with an axial chirality afforded the corresponding 3-pyrrolines in a stereoselective manner.

Squaring the circle: A route to bicyclo[4.2.0]octane derivatives has been developed by the [2+2] cycloaddition of allenenes or allenynes. The thermal intramolecular [2+2] cycloaddition of simple allenes 1 with an additional multiple bond leads to direct and regioselective formation of the distal adducts 2 in good to excellent yields.

Theo rganocatalytic aerobic oxidation of electron-deficient a-fluoroalkyl alcohols at room temperature is described. Ther esulting fluoroalkyl ketones are versatiles ynthetic intermediates for av ariety of fluorine-containingm olecules.T his otherwise difficult transformation has now been accomplished by the reactionofa-fluoroalkylalcohols with N-oxyl radicals,c atalytically generated from 9-azabicyclo[3.3.1]nonan-3-one N-oxyl/nitrogeno xide (keto-ABNO/NO x )a nd oxygeni na cetic acid (AcOH), affording the corresponding fluoroalkyl ketones in high yield. This operationally simple reaction can be performed under mild conditions,a nd was applied to aw ide range of alcohols( 20 examples), thus demonstrating ah igh functional group tolerance.M oreover, am odified one-pot protocol based on this method was able to convert an aldehyde to atrifluoromethyl ketone on ag ram scale.

Two novel palladium(0)-catalyzed cyclizations of allenenes are described. Treatment of allenenes such as N-(1-alkyl-2,3-butadienyl)-N-allylsulfonamide with an aryl halide and K(2)CO(3) in the presence of a catalytic amount of Pd(PPh(3))(4) in dioxane affords 2,3-cis-pyrrolidines in a stereoselective manner. In sharp contrast, cyclization of the same allenenes using catalytic Pd(2)(dba)(3) x CHCl(3) in the presence of allyl methyl carbonate in CH(3)CN leads to stereoselective formation of a 3-azabicyclo[3.1.0]hexane framework in moderate yields.

The design and synthesis of structurally variable, nonplanar N-oxyl radical catalysts and their application to the aerobic oxidation, etherification, and acetoamidation of benzylic C-H bonds are described. The catalytic oxidation of C-H bonds represents a powerful tool to synthesize oxygenated functional molecules from simple hydrocarbons in a straightforward way. Electron-deficient N-oxyl radical catalysts, such as phthalimidoyl N-oxyl (PINO) radical, generated from N-hydroxyphthalimide (1), have attracted much attention because of their applications in the oxidation of C-H bonds with high bond dissociation energy (BDE). However, a few sites in 1 are available for structural modifications and improvements of the catalytic performance. By replacing one carbonyl group in 1 with a trifluoromethyl (CF 3 )-substituted sp 3 -carbon, we generated an additional tunable site and a nonplanar backbone, while retaining the desirable electronwithdrawing properties and increasing the lipophilicity with respect to 1. We synthesized a variety of Nhydroxy pre catalysts containing such a CF 3 moiety, and investigated their utility in the aerobic oxidation of benzylic C-H bonds. Precatalysts with electron-withdrawing substituents, such as trifluoroethoxy and the acetophenone moieties, afforded higher yields than a corresponding methoxy-substituted analogue. The introduction of substituents at the aromatic ring was also effective, as evident from the performance of 7-CF 3 and 4,5,6,7-tetrafluoro precatalysts. Especially the combination of trifluoroethoxy-and 4,5,6,7-tetrafluoro substitution afforded a superior performance. These catalyst systems exhibited high functional group tolerance during the aerobic oxidation of C-H bonds, and benzylic etherification and Ritter-type reactions could be carried out at room temperature when a selected precatalyst and N-bromosuccinimide (NBS) were used.