γ‐ and δ‐Lactams through Palladium‐Catalyzed Intramolecular Allylic Alkylation: Enantioselective Synthesis, NMR Investigation, and DFT Rationalization

Abstract

The Pd-catalyzed intramolecular allylic alkylation of unsaturated amides to give γ- and δ-lactams has been studied in the presence of chiral ligands. Ligand (R)-3,5-tBu-MeOBIPHEP (MeOBIPHEP = 6,6'-dimethoxybiphenyl-2,2-diyl)bis(diphenylphosphine)) afforded the best results and allowed the cyclization reactions to take place in up to 94:6 enantiomeric ratio. A model Pd-allyl complex has been prepared and studied through NMR spectroscopic analysis, which provided insight into the processes responsible for the observed enantiomeric ratios. DFT studies were used to characterize the diastereomeric reaction pathways. The calculated energy differences were in good agreement with the experimentally observed enantiomeric ratios.

Mechanistic Investigation of the Ruthenium–N‐Heterocyclic‐Carbene‐Catalyzed Amidation of Amines with Alcohols

“…[26] Among the most-successful of these latter approaches are the M0x family of functionals reported by Truhlar and co-workers; herein, we chose the M06 functional, which has been optimized with a particular focus on organometallic systems and has been used successfully in an earlier study. [27] All of the structures were optimized in the gas phase and the single-point solvation energy was calculated for the optimized structures by using a standard Poisson-Boltzmann solver with suitable parameters for benzene as the solvent (dielectric constant: e = 2.284, probe radius: r = 2.600 ). Gibbs free energies were obtained from the vibrational-frequency calculations for the gas-phase geometries at 298 K and 383 K. All of the transition states were characterized by the presence of one negative vibrational frequency.…”

Silver‐Free Two‐Component Approach in Gold Catalysis: Activation of [LAuCl] Complexes with Derivatives of Copper, Zinc, Indium, Bismuth, and Other Lewis Acids

“…High‐resolution mass spectra were obtained by electrospray ionization with a TOF instrument (MicrOTOFq Bruker spectrometer). N ‐Allylbenzylamine42 and N ‐benzylbut‐3‐en‐1‐amine43 were prepared by following reported procedures. Compounds 3 ,44 4 ,45 5 ,46 6 ,46 7 ,40 8 ,40 10 ,47 11 ,48 13 ,20 14 a / 14 b ,20 17 a / 17 b ,21 18 ,49 19 ,49 20 ,24c 22 ,24c methyl 2‐methyl‐3‐oxobutanoate,50 methyl 1‐oxo‐1,2,3,4‐tetrahydronaphthalene‐2‐carboxylate,51 and methyl 1‐oxo‐2,3‐dihydro‐1 H ‐indene‐2‐carboxylate,52 were already described.…”

Nucleophilic Aliphatic Substitution

“…13 Product studies, examee ining the effect of various ligands on the palladium atom, solvent effects, substituent effects, the effect of temperature, the effect of changing the leaving group, NMR (nuclear magnetic resonance spectroscopy) studies of model η 3 -allylpalladium complexes, and DFT/MO6 calculations with a polarized Boltzmann SCRF (self-consistent reaction field) model in solution all indicate that these reactions occur via a reversible ionization step with KOAc, followed by a rate-and enantio-determining S N 2 C−C bond formation step in a syn-configured η 3 -allylpalladium complex with a (R)-3,5t-Bu- (6,6-dimethoxybiphenyl-2,2-diyl) An allylic substitution has been accomplished by allowing two different substrate catalyst complexes to react together in a "dual catalytic" system. 14 The reaction occurs de after the allyl carbonate is converted into a substrate-palladium metal catalyst complex and reacted with a vanadium metal-propargyl alcohol catalyst complex, giving the allylic substitution product.…”

“…PhSeCl reacts with 6-methylhept-5-en-2-ol and a base (trimethylamine is best), giving 98.8% of the phenyl selenoethers, (13) and (14). 132 The reactions are thought to occur via a phenylselenonium ion intermediate, which undergoes an intramolecular attack of the OH group.…”