Acid-Catalyzed Decomposition of O-Silylated α-Diazo-β-hydroxy Esters: Access to Mixed Monosilyl Acetals

Synthesis of Functionalized Indoles by an Iridium-Catalyzed N-H Insertion Cascade: Nucleophilic Cyclization of Naphthylamines with α-Diazocarbonyl Compounds

A novel iridium-catalyzed [3 + 2] annulation of naphthylamines and α-diazocarbonyl compounds was developed for the rapid assembly of densely functionalized indoles. This new catalytic process represents the first example of a cascade intramolecular nucleophilic cyclization by the N-H insertion of amines. Various naphthylamines and α-diazocarbonyl compounds could be obtained in high yields with excellent functional group tolerance. The reaction affords valuable indole derivatives, enabling expedient access to novel heterocyclic analogues not easily accessible by other methods.

Rhodium(I)-Catalyzed O-H Insertions on O-Protected α-Diazo-β-Hydroxyesters

The X-H insertion reaction constitutes a powerful tool to create diversity through the diazo decomposition of diazocarbonyl compounds. However, until now, X-H insertion on α-diazo-β-aryl-β-hydroxyester scaffolds, readily prepared by aldol-type addition, remained a challenge for the organic chemist. We report herein the first O-H insertions on O-protected α-diazo-β-aryl-β-hydroxyesters, providing straightforward access to a wide range of α,β-dioxygenated esters through modulation of the alcohol and of the aryl substituent. The key feature to achieving this transformation is the use of Rh(I) catalysts, which proved to be crucial to favor the targeted O-H insertion product over the competing 1,2-H and 1,2-Ar migration products. Overall, 32 O-H insertion products have been prepared, in moderate to good yields, with a diastereoisomeric ratio up to 7.5:1 in favor of the syn diastereoisomer.