Recent Advances in the Cascade Cyclization Reactions of 1,7‐Enynes

Abstract

Elaborated molecular architectures, especially carbocyclic, heterocyclic, endocyclic, and polycyclic molecular structures, serve as an important class of organic complexes because they are frequently occurring core structural units in a variety of biologically and pharmacologically relevant natural products, drug molecules, agrochemicals, and functional materials. A main challenge of current synthetic approaches is the development of strategically efficient and selective formation of these compounds from easy‐to‐handle starting materials. The cascade cyclizations of 1,7‐enynes have afforded an indispensable method for accessing molecular complexity and diversity, thus highlighting their potential significance in both academic and industrial communities. In the last decades, tremendous efforts have been devoted to discovering convenient routes to access sophisticated annulation derivatives, and a wide range of powerful and straightforward synthetic strategies have been reported. In this review, the latest achievements in the cascade cyclization reactions of 1,7‐enynes are summarized, which could be separated into three categories: (1) Visible‐light‐induced reactions of 1,7‐enynes; (2) Metal‐free catalyzed reactions of 1,7‐enynes; (3) Transition‐metal‐catalyzed reactions of 1,7‐enynes.

Stereoselective Three-Component Carbocyclization of 1,7-Enynes with Sulfoxonium Ylides and Water under Photoredox Catalysis

“…We suspect that a proton-coupled electron transfer process probably occurred in the initial step of sulfoxonium ylide activation. Based on the above experimental results and prior studies, 2,13,14 quinoline molecule 3a with excellent chemoselectivities and stereoselectivities.…”

“…Based on the above experimental results and prior studies, ,, a possible mechanism for three-component carbocyclization reaction was proposed (Scheme d). Initially, irradiation of the iridium photocatalyst [Ir III ] with blue-light-emitting diodes (LEDs) generates the excited-state complex [Ir III ]*.…”

“…As a paradigm, cyclopentane[ c ]quinoline molecules are the critically important structural core of heterocycles due to their wide prevalence in myriad biologically active molecules and pharmaceutical agents, which have therefore attracted considerable attention from the synthetic community and related domains in the past decades. A particularly promising avenue lies in the realm of carbon-radical-mediated cascade cyclizations of 1,7-enynes, which, compared to other traditional methods such as aza -Bergman cyclization, Friedel–Crafts-type reaction, imino Diels–Alder reaction, and Baylis–Hillman adducts, , facilitates a rapid and efficient buildup of cyclopentane[ c ]quinolines utilizing readily available starting materials (Scheme a). In this field, the groups of Jiang and Li have made pioneering achievements in the design and synthesis of a range of C(sp 3 )–H hydrocarbon substrates, realizing oxidative radical carboannulation of 1,7-enynes to efficiently construct functionalized cyclopentane[ c ]quinoline compounds in the performance of oxidants.…”