Organocatalytic Asymmetric [2 + 4] Cycloadditions of 3-Vinylindoles with ortho-Quinone Methides

Regio- and chemoselective synthesis of flavanone isosteres via multicomponent reactions: synergistic role of hydrogen bonding and solvent effects

Given the prevalence and significance of flavanones, we present a regio- and chemoselective approach for the synthesis of flavanone isosteres. This method is facilitated by the synergistic effects of hydrogen bonding and solvent interactions. Notably, this novel multicomponent reaction employs commercially available starting materials, operates without the need for catalysts, and achieves high levels of regio- and chemoselectivity under mild conditions. The protocol exhibits excellent tolerance for complex substrates, including those derived from Linagliptin and Cholesterol. Furthermore, this robust synthetic method not only surpasses the limitations of traditional approaches but also aligns with the principles of green chemistry.

Asymmetric Brønsted Acid Catalyzed Cycloadditions of ortho-Quinone Methides and Related Compounds

This review summarizes recent developments in the area of Brønsted acid catalyzed, enantioselective cycloadditions of ortho-quinone methides, ortho-quinone methide imines as well as heterocyclic indole- and pyrrole-based methides. In a straightforward and single-step transformation complex polycyclic N- and O-heterocyclic scaffolds are accessible, with typically good yields and excellent stereocontrol, from simple benzyl and heterobenzyl alcohols upon acid-catalyzed dehydration. The transient precursors are hydrogen-bonded to a chiral Brønsted acid which controls the enantioselectivity of the process.

1 Introduction

2 Cycloadditions of ortho-Quinone Methides

2.1 Brønsted Acid Catalyzed Processes

2.2 Cooperative Brønsted Acid/Transition-Metal-Catalyzed Processes

3 Cycloadditions of ortho-Quinone Methide Imines

4 Cycloadditions of Indolyl-3-methides

5 Cycloadditions of Indolyl-2-methides

5.1 Brønsted Acid Catalyzed Processes

5.2 Cooperative Brønsted Acid/Transition-Metal-Catalyzed Processes

6 Cycloadditions of Pyrrolyl-2-methides

7 Cycloadditions of Pyrrolyl-3-methides

8 Conclusions

Acid-promoted formal [3 + 2] cyclization/N,O-ketalization of in situ generated ortho-alkynyl quinone methides: access to bridged 2,3-cyclopentanoindoline skeletons

An acid-catalyzed formal [3 + 2] cyclization/N,O-ketalization of in situ formed ortho-alkynyl quinone methides (o-AQMs) and tryptophol derivatives was developed.