Palladium‐Catalyzed Insertion of α‐Diazoesters into Vinyl Halides To Generate α,β‐Unsaturated γ‐Amino Esters

As easy as 1, 2, 3 : A palladium‐catalyzed three‐component coupling generates α,β‐unsaturated γ‐amino acids in a single step (see scheme). The reaction is believed to involve migration of a vinyl substituent to a highly electrophilic palladium carbene. Unlike previous synthetic approaches, this synthesis provides access to γ‐amino acids with non‐natural side chains.

     

Palladium‐Catalyzed Carbon–Carbon Bond Formation and Cleavage of Organo(hydro)fullerenes

Palladium can tailor fullerenes : Palladium catalysts enable a number of C? H bond transformations of organo(hydro)fullerene. In addition to anticipated coupling reactions (C? H bond allylation and arylation), an unexpected new C? H bond dimerization reaction and C? C bond‐cleavage reaction were also uncovered.

     

Regioselective Synthesis of β‐Aryl‐ and β‐Amino‐Substituted Aliphatic Esters by Rhodium‐Catalyzed Tandem Double‐Bond Migration/Conjugate Addition

Rhodium–phosphite catalysts were found to effectively mediate double‐bond migrations within unsaturated esters. Once the double‐bond is in conjugation with the carboxylate group, they also catalyze the Michael addition of carbon and nitrogen nucleophiles. In the presence of these catalysts, unsaturated carboxylates enter a dynamic equilibrium of positional and geometrical double‐bond isomers. The conjugated species are continuously removed through 1,4‐additions with formation of β‐amino esters or β‐arylated products, depending on the nucleophile employed. The applicability of both protocols to a range of substrates, such as fatty esters of different chain lengths and double‐bond positions, and several nucleophiles including arylborates and primary and secondary amines, is demonstrated.     

Gram-Scale Synthesis of Nickel(II) Norcorrole: The Smallest Antiaromatic Porphyrinoid

Small is beautiful: A ring-contracted sister of porphyrin, norcorrole, has been synthesized efficiently as a stable molecule by a nickel-templated strategy. The norcorrole complex is stable but exhibits a distinct antiaromatic character according to the Hückel rule. Oxidation of the norcorrole complex provides an aromatic oxacorrole complex.     

Cover Picture: Palladium‐Catalyzed Carbon–Carbon Bond Formation and Cleavage of Organo(hydro)fullerenes (Chem. Eur. J. 19/2009)

An unexpected C? H bond dimerization reaction and C? C bond‐cleavage reaction in organo(hydro)fullerenes have been discovered. In their Communication on page 4760 ff. , K. Itami and M. Nambo describe the use of Pd catalysts for a number of interesting reactions of such fullerenes.

     

Synthesis of Fluorinated Dienes by Palladium‐Catalyzed Coupling Reactions

The synthesis of partly fluorinated 1,3‐ and 1,4‐dienes by palladium‐catalyzed coupling makes these compounds available on the laboratory scale. Several catalyst systems were tested to maximize the yields and minimize the by‐products. The molecular structures of 1,1,2,4,4‐pentafluorobutadiene, chloro(N,N′‐tetramethylethylenediamine)(trifluorovinyl)zinc, PCy₂R, and P(O)Cy₂R (Cy=cyclohexyl, R=2‐(1‐naphthyl)phenyl) were elucidated by X‐ray crystallography.