Synthesis of chiral 1,4-dihydropyridines by diastereoface-selective asymmetric addition to nicotinic amides

Gold(I)-Catalyzed Nucleophilic Allylation of Azinium Ions with Allylboronates

Gold(I)-catalyzed nucleophilic allylations of pyridinium and quinolinium ions with various allyl pinacolboronates are reported. The reactions are completely selective with respect to the site of the azinium ion that is attacked, to give various functionalized 1,4-dihydropyridines and 1,4-dihydroquinolines. Evidence suggests that the reactions proceed through nucleophilic allylgold(I) intermediates formed by transmetalation from allylboronates. Density functional theory (DFT) calculations provided mechanistic insight.

Intramolecular cation-pi interaction in organic synthesis

Controlling molecular conformation is a significantly important issue in a wide variety of organic reactions because the ground state structure is significantly responsible for the transition one. As observed in enzymes and proteins, the cation-pi interaction plays a key role in the formation of the tertiary structure and the biochemical processes. Therefore, the cation-pi interaction would be a promising conformation-controlling tool not only in large molecules, but also in small molecules due to its stronger interaction force. This article describes the utility of the intramolecular cation-pi interaction in various organic syntheses with evidence for the existence of the cation-pi interactions.

Preparation of new nitrogen-bridged heterocycles. 53. Syntheses of 3-(benzylthio)thieno[3,4-b]indolizine derivatives and their intramolecular arene-arene interactions

Various ethyl 1-arylcarbonyl-3-[(un)substituted methylthio]thieno[3,4-b]indolizine-9-carboxylates were synthesized in good yields by a novel methodology in which the S-alkylation of 5-arylcarbonyl-4-ethoxycarbonylmethyl-3-(1-pyridinio)thiophene-2-thiolates with alkyl or benzyl halides, the 1,5-dipolar cyclization of the resulting pyridinium salts in the presence of a base, and the aromatization were performed. In the X-ray analyses of some 3-(benzylthio)thieno[3,4-b]indolizine-9-carboxylates, a gauche and two anti conformers in relation to the exocyclic sulfide linkage were found. Interestingly, all of the 3-(benzylthio)thieno[3,4-b]indolizine derivatives showed significant high-field shifts (delta up to 0.3 ppm) for the 5- and 6-proton signals compared with those of the 3-methylthio derivatives in the (1)H-NMR spectra and exhibited a definite absorption band near 425 nm in their UV spectra, indicating an intramolecular arene-arene interaction between the thieno[3,4-b]indolizine and the phenyl ring.

Face-selective addition to a cation-pi complex of a pyridinium salt: synthesis of chiral 1,4-dihydropyridines

Selective shielding of one side of the pyridinium face by way of intramolecular cation-pi complex formation enabled nucleophiles to attack only from the non-shielded side, and consequently, chiral 1,4-dihydropyridines were produced stereoselectively with up to 99% de. The structure of the cation-pi complex was elucidated by 1H NMR studies and X-ray analysis.