Recent advances in photo-promoted generalized C3-H alkylation of quinoxalin-2(1H)-ones
Youpeng Zuo1, Xiufang Bai2, Cong Wang1
1School of Chemistry and Chemical Engineering, Suzhou University, Suzhou, Anhui, 234000, People's Republic of China. 812901107@qq.com.
Abstract:
With the continuous advancement of organic synthetic chemistry, photocatalysis has gradually emerged as one of the effective methods for constructing complex compounds. Given the significant role played by quinoxalin-2(1H)-ones in various fields, it is imperative to urgently develop methodologies for their efficient synthesis, transformation, and modification. Similarly, the generalized C3-alkylation reaction of quinoxalin-2(1H)-ones is a more direct method for constructing diverse heterocyclic skeletons. The currently known alkylating agents mainly include simple hydrocarbons, halogenated hydrocarbons, carboxylic acids, aldehydes, ketones, amines, and their derivatives. In addition to the most common two-component reactions, multi-component reactions are included. This review covers the literature reports published from 2019 to early 2025. A bright outlook is provided at the end of the review.
![Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60786.jpg&w=3840&q=50)
![[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59739.jpg&w=3840&q=50)
Related Concept Videos
01:26Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
02:38Electrophilic Addition to Alkynes: Halogenation
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
02:27Preparation of Alkynes: Alkylation Reaction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
00:51Base-Promoted α-Halogenation of Aldehydes and Ketones