2‐Pyrrolidones have aroused enormous interest as a useful structural moiety in drug discovery; however, not only does their syntheses suffer from low selectivity and yield, but also it requires high catalyst loadings. The radical cyclization of 1,n‐enynes and 1,n‐dienes has demonstrated to be an attractive method for the synthesis of 2‐pyrrolidones due to its mild reaction conditions, fewer steps, higher atom economy, excellent functional group compatibility, and high regioselectivity. Furthermore, radical receptors with unsaturated bonds (i. e. 1,n‐enynes and 1,n‐dienes) play a crucial role in realizing radical cyclization because of the ability to selectively introduce one or more radical sources. In this review, we discuss representative examples of methods involving the radical cyclization of 1,n‐enynes and 1,n‐dienes published in the last five years and discuss each prominent reaction design and mechanism, providing favorable tools for the synthesis of valuable 2‐pyrrolidone for a variety of applications.
Copper-catalyzed cyclization of alkynes has played a significant role in modern catalytic chemistry. However, the selective cyclization in this transformation is extremely limited by the uncontrolled reactivity of the vinyl-CuII...
A novel polychloromethylation/acyloxylation of 1,6-enynes with chloroalkanes and diacyl peroxides through dual roles designs to prepare 2-pyrrolidinone derivatives with polychloromethyl units has been developed by the use of inexpensive copper...
A new, efficient, and practical radical cyclization of olefinic amides with ketones through α-C(sp3)–H functionalization in the presence of tert-butyl peroxybenzoate (TBPB) is described for the first time. This protocol assembles a wide range of pivotal and useful benzoxazines in good to excellent yields under mild, catalyst-free, ligand-free, and base-free conditions with wide functional group tolerance. Moreover, the mechanistic study indicates that the α-carbonyl radical is involved in this transformation.
A novel method for assembling pyrrolidine-2,4-diones from 1,5-enenitriles and acetone/acetonitrile via a cyclization/hydrolysis has been established under metal catalyst- and base-free conditions, with Oxone as a green oxidant and H2O as an additive at 90-110 ℃. This strategy is highlighted by cyclization/hydrolysis of alkyl cyanides, achieving direct C(sp3)–H oxidative functionalization, and giving full conversion of the substrates with excellent functional group compatibility.
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