Synthetic methods for γ-lactam and pyrrole derivatives exploiting a three-component coupling strategy

4-Aryloxymethyl-3-pyrrolines and their isomeric pyrrolidines--assembled via a one-pot, three-component coupling of propargylic amines, vinyl sulfones, and phenols--may be elaborated further to provide an easy access to 2,4-disubstituted pyrrole-3-carboxylates and 3,4-disubstituted pyrrolidin-2-ones. The latter were prepared by means of an unprecedented rearrangement process involving hydrogenolysis of 2-aryl pyrrolidine-3-carboxylates, whereas the pyrrole carboxylates arose from aromatization of the corresponding pyrrolines.     

How to Control the Chemoselectivity of the Catalytic Formation of Chiral γ-Lactams or 2,3-Disubstituted Pyrroles by the Choice of Solvent

Summary. The reaction of the unsaturated imine methyl(3-phenylallylidene)amine with ethylene and carbon monoxide in the presence of catalytical amounts of Ru₃(CO)₁₂ leads to the formation of two heterocyclic products. One of the products is a chiral γ-lactam, the other one a 2,3-disubstituted pyrrole derivative, in which only the carbon atom from carbon monoxide is incorporated. The selectivity in the formation of the products may be controlled by the choice of solvent. In general, in nonpolar solvents the formation of the lactam is preferred whereas the use of more polar solvents enhances the yield of the pyrrole. For most of the solvents used there is a linear dependence of the product ratio on the relative permittivity of the corresponding solvent. Typically, polar aprotic solvents do not follow this rule.     

A lactam-derived vinyl boronate as a stable and crystalline reagent for the synthesis of 2-substituted piperidines by Pd-catalyzed coupling reactions

A δ-valerolactam-derived vinyl triflate has been converted into the corresponding vinyl boronate by Pd-catalyzed coupling with bis(pinacolato)diboron, which results in an umpolung. This boronate efficiently couples under Pd catalysis with aryl and heteroaryl bromides to give the corresponding 2-substituted piperidines in excellent yields.     

Oxidation of Poly(dimethylbutadiene) Popcorn Polymer

Poly(dimethylbutadiene) popcorn polymer oxidizes readily in the presence of oxygen at room temperature. Quantitative data are presented for the production of the major volatile product, 2,5-hexanedione, as well as for the secondary products: water, acetic acid, and acetaldehyde. Three reaction mechanisms formerly proposed for polyisoprene oxidation are considered for their applicability to poly(dimethylbutadiene) popcorn oxidation. Of these, one that assumes the formation of a Bevilacquatype peroxyalkoxy radical followed by hydrogen abstraction to form an alcohol group, double bond migration, formation of a peroxide radical adjacent to the alcohol, then elimination of a hydroxy radical and scission, can explain the experimental data.     

Zirconium Borohydride - a Versatile Reducing Agent for the Reduction of Electrophilic and Nucleophilic Substrates

Zirconium borohydride, a potential reducing agent, reduces acids, esters, imines to the corresponding alcohols and secondary amines in good yield at room temperature within two hours. This facile reducing property was taken advantage off in the synthesis of pheromones and some novel chiral precursors for asymmetric synthesis.     

Silica Gel Supported Chromium Trioxide: An Efficient Reagent for Oxidative Cleavage of Oximes to Carbonyl Compounds under Mild Condition

A facile, efficient oxidative deblocking of aldoximes and ketoximes to their corresponding aldehydes and ketones have been achieved by using silica gel supported chromium trioxide.     

New Straightforward Synthesis of β‐Damascenone and β‐Damascone Derivatives from β‐Ionone via Retro‐α‐ionol

β‐Damascenone and β‐damascone derivatives, important fragrant compounds, were directly obtained from β‐ionone by a new way via retro‐α‐ionol.     

Effect of Amines on the Selective Bromination of Some β-Substituted-2-Butenoic Esters

The effect of amines on the selective bromination of some β-substituted-2-butenoic esters is described. The bromination of methyl (Z)-4-t-butyldiphenylsilyloxy-3-methylbutenoate 2 in the presence of DIPEA (N, N-diisopropylethylamine) and the successive treatment of the obtained dibromide with potassium t-butoxide afford the desired Z bromide selectively. But the corresponding E bromide forms exclusively when 2, 6-di-t-butyl-4-methylpyridine is used in the bromination.     

Yb(OTf)3‐Catalyzed Intermolecular Imino Diels–Alder Reaction of 2‐Azetidinone‐Tethered Aryl Imines as Azadienes

Yb(OTf)₃ is an efficient catalyst for the intermolecular imino Diels–Alder reaction of aldimines derived from 2‐azetidinone‐tethered aryl imines and electron‐rich dienophiles to afford the quinoline‐β‐lactams.     

Deprotection of Oximes using Iodosobenzene in the Presence of β‐Cyclodextrin in Water

A mild and efficient method for the regeneration of carbonyl compounds from oximes at room temperature in impressive yields has been developed using iodosobenzene/KBr in the presence of β‐cyclodextrin in water.