Recent Advances in the Cycloaddition Reactions of 2‐Benzylidene‐1‐benzofuran‐3‐ones, and Their Sulfur, Nitrogen and Methylene Analogues

Abstract

Benzothiophene, benzofuran, indole, and indene derivatives are privileged heterocyclic motifs. These are present in a wide range of bioactive natural products and pharmaceutical drugs and are the subject of materials science research. However, the construction of benzothiophene, benzofuran, indole, and indene frameworks have been long‐standing challenges to organic chemists. In this review, we classify the derivatives of four structures synthesized from 2‐benzylidene‐1‐benzofuran‐3‐one and their analogues in terms of their ring size (from three‐ to ten‐membered) and type (fused or spiro), as well as summarizing the developments of this field. Finally, we discuss the ring opening and 1,4‐addition reactions.

Organocatalytic Strategies for the Development of the Enantioselective Inverse‐electron‐demand Hetero‐Diels‐Alder Reaction

“…[20] Some years later, Liu and Zhang developed the enantioselective synthesis of dehydropiperidine derivatives via an IEDHDAR. The reaction proceeds with high yields, moderate to good diastereoselectivities and excellent enantioselectivities in the presence of different five-and six-membered cyclic 1azadienes [21] and propanal (Scheme 12). [22] Furthermore, the authors suggest a concerted mechanism where the in situ formed enamine reacts with the diene.…”

Asymmetric [3+2] Annulations of Thioaurone and Aurone Derivatives for the Construction of Spiroheterocycles

“…Thus, developing efficient strategies for the construction of such frameworks, especially in an asymmetric catalytic manner, has attracted growing interest of synthetic chemists [2] . The enantioselective cycloaddition reaction of thioaurones, aurones and their derivatives 1 , serving as highly electrophilic two‐atom building blocks, represents one of the most straightforward protocols to access these enantioenriched spiroheterocyclic substances [3] . Among them, the asymmetric [3+2] cycloadditions between compounds 1 and in‐situ generated azomethine ylides under the catalysis of Brønsted bases have been developed [4] .…”

“…[2] The enantioselective cycloaddition reaction of thioaurones, aurones and their derivatives 1, serving as highly electrophilic two-atom building blocks, represents one of the most straightforward protocols to access these enantioenriched spiroheterocyclic substances. [3] Among them, the asymmetric [3 + 2] cycloadditions between compounds 1 and in-situ generated azomethine ylides under the catalysis of Brønsted bases have been developed. [4] In addition, with the activation of chiral Lewis base catalysts [including N-hetereocyclic carbenes (NHCs), amines and phosphines], unsaturated carbonyl compounds as well as allenoates, could participate in asymmetric [3 + 2] [5] or [4 + 2] [6] annulations, furnishing diverse spiroheterocyclic compounds, usually with high levels of stereoselectivity (Scheme 1a).…”

Michael/Michael Addition Cascade of 2‐Benzylidene‐1‐indanones with Chalcones: Synthesis and Biological Evaluations of Novel Polycyclic Compounds

“…Chalcones and chalcone-like compounds are bioactive molecules and very active compounds synthetically at the same time. [1][2][3][4] The α,β-unsaturated carbonyl system present in its structure allows the synthesis of many new, heterocyclic and polyfunctional compounds. [5][6][7][8] For this reason, chalcones and chalcone-like compounds are highly valuable compounds for organic chemists and they can be used as a key or building block in achieving molecular diversity.…”