A New Synthesis of Sulfur-, Nitrogen- and Oxygen-Containing Eight-Membered Ring Lactams

Synthesis of Benzo[b]azocin-2-ones by Aryl Amination and Ring-Expansion of α-(Iodophenyl)-β-oxoesters

Transformation of β-oxoesters with PhI(OCOCF3 )2 leads to α-(ortho-iodophenyl)-β-oxoesters. These materials are the starting point for the synthesis of 6-carboxybenzo[b]azocin-2-ones by a sequence of aryl amination and ring transformation. This reaction sequence starts with copper-catalyzed formation of N-alkyl anilines from the iodoarenes and primary amines in the presence of K3 PO4 as stoichiometric base. The intermediate products underwent ring transformation by addition of the nitrogen into the carbonyl group of the cycloalkanone, furnishing benzo-annulated eight-membered ring lactams. Under the same reaction conditions, the cyclohexanone and cycloheptanone derivatives gave no aminated products, but ring-transformed to benzofuran derivatives. The title compounds of this investigation contain two points for further diversification (the lactam nitrogen and the carboxylate function), thus, the suitability of this compound class as a scaffold was proven by appropriate functionalizations. The first series of derivatizations of the scaffold was initiated by hydrogenolytic debenzylation of N-benzyl derivative to provide the NH-congener, which could be deprotonated with LDA and alkylated at nitrogen to give further examples of this compound class. Secondly, the ester function was submitted to saponification and the resulting carboxylic acid could be amidated using HATU as coupling reagent to furnish different amides.

Cerium-catalyzed, oxidative synthesis of annulated, tetrasubstituted dihydrofuran-derivatives

Densely functionalized, annulated dihydrofuran derivatives are prepared from β-oxoesters and silylenolethers by a cerium-catalyzed aerobic oxidation.

Facile cyclization in the synthesis of highly fused diaza cyclooctanoid compounds using retrievable nano magnetite-supported sulfonic acid catalyst

Magnetically separable Fe₃O₄–SO₃H nano particles have been prepared and established as an efficient catalyst for the synthesis of dihydrofuran fused cyclooctanoids via the dehydration reaction of dihydroxy cyclooctanoid heterocylces.