Construction of 2-pyridones via oxidative cyclization of enamides: access to Pechmann dye derivatives

An efficient protocol for the construction of structurally diverse 2-pyridone derivatives from imines and α,β-unsaturated acid chlorides in a single operation is reported.

Cu-Catalyzed highly regioselective 1,2-hydrocarboxylation of 1,3-dienes with CO2

A novel Cu-catalyzed highly regioselective 1,2-hydrocarboxylation of terminal 1,3-dienes with CO2 to synthesize 2-benzyl-β,γ-unsaturated acid derivatives has been developed.

Investigation on Reaction Sequence and Group Site of Citric Acid with Cellulose Characterized by FTIR in Combination with Two-Dimensional Correlation Spectroscopy

Cotton fabrics are prone to wrinkles and can be treated with citric acid (CA) to obtain good anti-wrinkle properties. However, the yellowing of the CA-treated fabrics is one big obstacle to the practical application of citric acid. The changing sequence order of CA anhydride and unsaturated acid (the reason for yellowing), such as aconitic acid (AA), has not been investigated. Herein, Fourier transform infrared (FTIR) spectroscopy, two-dimensional correlation spectroscopy (2Dcos), and Gaussian calculation were employed to characterize the reaction mechanism between CA with cellulose. FTIR spectra of the CA-treated fabrics heated under different temperatures were collected and further analyzed with 2Dcos. The results indicated the changing sequence order: 1656 cm−1→1784 cm−1→1701 cm−1, (“→” means earlier than), i.e., unsaturated acid→anhydride→ester. Moreover, a change of Gibbs free energy (ΔG) showed that trans-AA (ΔG = −22.10 kJ/mol) is more thermodynamically favorable to be formed than CA anhydride 1 (ΔG = −0.90 kJ/mol), which was proved by Gaussian computational modeling. By taking cellobiose as a model of cellulose, the ΔG results proved that O(6)–H(6) on the glucose ring is the most likely hydroxyl to react with anhydride originated from CA or AA, especially with the terminal carbonyl group.

Friedel–Crafts Chemistry. Part 53. Divergent and Diversity-Oriented Synthesis of Condensed Indole Scaffolds via Friedel–Crafts Ring Closure Approach

A series of indole-fused medium-sized N-heterocyclic systems 10a–h were prepared from laboratory-synthesized indole-based esters 9a–h via intramolecular Friedel–Crafts cyclizations induced by both trifluoromethanesulfonic acid and AlCl3/CH3NO2 catalysts under suitable conditions. The synthetic sequence to precursors 9a–h that started from simple N-methylindole-2-carboxylic acid involved conversion to aminoindoles 2a, b, reaction with α,β-unsaturated acid chlorides to yield acyclic amides 5a–d, ring closure to tricyclic lactams 6a–d, and carbonyl reduction to respective pyrido and azepino tricyclic amines 7a–d, which finally underwent N-alkylations with α- or β-haloesters to produce the required ester precursors. The structures of synthesized compounds without stereochemical implications are established using both spectral and analytical data.

An Intramolecular Diels–Alder Furan (IMDAF) Approach towards the Synthesis of Isoindolo[2,1-a]quinazolines and Isoindolo[1,2-b]quinazolines

An efficient approach to bridged pentacyclic nitrogen heterocycles via the tandem acylation/intramolecular Diels–Alder furan (IMDAF) reaction of 2-furylquinazolinones is described. Reactions of α,β-unsaturated acid anhydrides with 2-furyl-2,3-dihydroquinazolin-4-ones give 6b,9-epoxyisoindolo[2,1-a]quinazolines in average yields. In this case, the exo-IMDAF reactions proceed with excellent diastereoselectivity giving five stereogenic centers and three new rings in one synthetic step. Isomeric 2,4a-epoxyisoindolo[1,2-b]quinazolines are obtained by one-pot, three-component condensation reactions of allylamine, isatoic anhydride and furaldehydes involving the same IMDAF­ reaction as the key step. Some useful transformations including halogenation, hydrogenation, Prilezhaev epoxidation, and esterification of the synthesized epoxyisoindoloquinazolines are also demonstrated.