Applications of Bifunctional Organocatalysts on ortho‐Quinone Methides

Abstract

ortho-Quinone methides are important structures, having a cyclohexadiene core bearing an exocyclic alkylidiene and carbonyl functionality at the ortho-position, and are widely used as essential intermediates in organic synthesis. These reactive intermediates are also used as important building blocks for the construction of a variety of heterocycles by hetero Diels-Alder, electrocyclization reactions. Moreover, ortho-quinone methides are a class of electrophiles, serving as Michael acceptors leading to conjugate additions with various nucleophiles. In general, ortho-Quinone methides have transient existence and are highly reactive in nature. ortho-Quinone methides have been generated in situ from stable precursors using either Brønsted acids or Brønsted bases. In the last few years, ortho-quinone methides have been explored as imperative class of substrates in various bifunctional organocatalysts mediated asymmetric conjugate additions, cycloannulation, acyl-transfer reaction, thiolation and hydrophosphination reactions. This review illustrates recent advancements of asymmetric transformations of ortho-quinone methides with bifunctional H-bonding organocatalysts.[a] S.

Synthetic route optimization of Sumepirin antiepileptic drug candidate

“…It makes possible to investigate the possibility of functionalization of this scaffold via meta-quinon methide intermediate. The reactivity of orto-and para-quinon methides intermediates is well studied in non-heterocyclic aromatic structures [7,8]. But we can barely find any data on its heterocyclic analogs.…”

Recent Advances in Organocatalytic Asymmetric Cycloaddition Reactions Through Ortho‐Quinone Methide Scaffolds

“…Recent comprehensive reviews by Osipov [4i] and Gao [4j] have also respectively documented the main progress in o ‐QMs as key intermediates in cascade heterocyclizations and Diels−Alder reactions involving in situ generated o ‐QMs, highlighting the power and potential of this strategy in organic synthesis and natural product total synthesis. In 2019, the application of different bifunctional H‐bonding organocatalysts on o‐ QMs for asymmetric transformations was also illustrated by Pan [10e] . Despite the impressive contributions described in these reviews, a timely summarization of recent advances is extremely valuable due to the rapid development in this research field.…”

Catalytic Asymmetric [4 + 2] Cycloaddition of ortho-Alkenyl Naphthols/Phenols with ortho-Quinone Methides: Highly Stereoselective Synthesis of Chiral 2,3,4-Trisubstituted Chromans

“…The catalytic asymmetric [4 + 2] cycloaddition of o -QMs have provided direct and highly efficient synthetic strategies to construct the bioactive benzopyran derivatives, such as coumarins, chromenes, and chromans. ,− Given the abundance and importance of trisubstituted chromans I , it is highly desirable to enable access to these chromans by the organocatalytic asymmetric biomimetic [4 + 2] cycloaddition of o -QMs with linear-substituted ortho -alkenyl phenols. As part of our continuing interest on the Brønsted acid-catalyzed reactions and inspired by the biosynthetic strategies for chiral chromans, we herein report our preliminary result on the biomimetic [4 + 2] cycloaddition of ortho -alkenyl naphthols/phenols with in situ -generated o -QMs, catalyzed by the readily available monomeric flexible chiral phosphoric acids .…”