New strategies for asymmetric photocatalysis: asymmetric organocatalytic/photoredox relay catalysis for efficient synthesis of polycyclic compounds containing vicinal amino alcohols

 Jia-Lu Zhang,†, Wen-Bo He,†, Xiu-Qin Hu, Peng-Fei Xu*

https://doi.org/10.1007/s11426-023-1819-8

Abstract:An asymmetric catalytic strategy in photocatalysis utilizing a chirality-induced approach through an organocatalytic/photoredox relay catalysis strategy is successfully achieved for the rapid construction of polycyclic compounds containing vicinal amino alcohols in a one-pot protocol. This methodology facilitates the efficient synthesis of diverse substituted polycyclic tetrahydroquinoline and benzofuran-derived vicinal amino alcohols, each containing five consecutive chiral centers, with high yields, excellent diastereoselectivities and enantioselectivities (up to 95% yield, >20:1 dr and 98% ee), under mild reaction conditions driven by sequential bifunctional squaramide organocatalyst-catalyzed [4+2] annulation and photocatalyst-catalyzed ketyl radical addition cyclization reaction process. Furthermore, investigations into the stereoselectivity mechanism and high-resolution mass spectrometry (HRMS) experiments on free radical trapping have provided evidence for elucidating the detailed mechanism of chirality-induced processes and chiral intermediate conversions in this procedure.

A novel approach for synthesizing α-amino acids via formate mediated hydrogen transfer using a carbon source

Tian-Tian Zhao,‡  Xu-Gang Zhang,‡  Wen-Bo He and  Peng-Fei Xu *

http://:https://doi.org/10.1039/D3GC02955G

Abstract

Using a formate salt as a promising hydrogen carrier and one-carbon (C1) source, we have developed a novel and practical method for the preparation of α-amino acid derivatives under mild conditions. In this approach, the photoexcited naphthalene thiolate acts simultaneously as a photoexcited single-electron reductant and a hydrogen atom transfer (HAT) catalyst, enabling efficient metal-free radical–radical cross-coupling of formate with ketimines and aldimines.

Synthesis of benzo[f][1,2]thiazepine 1,1-dioxides based on the visible-light-mediated aza Paternò–Büchi reaction of benzo[d]isothiazole 1,1-dioxides with alkenes

Yi-Lin Wang, Peng-Xiang Liu, Huan-Huan Zhang, Peng-Fei Xu and Yong-Chun Luo

https://doi.org/10.1039/D3CC03745B

Abstract

A new two-step, one-pot synthesis of benzo[f][1,2]thiazepine 1,1-dioxides was developed, which contains a visible-light mediated aza Paternò–Büchi reaction of benzo[d]isothiazole 1,1-dioxides with alkenes and a Lewis acid catalyzed ring-expansion of azetidine. In this work, the mechanism of the aza Paternò–Büchi reaction was also investigated.

Sc(OTf)₃ catalyzed intramolecular single-electron transfer of 2-alkyl-1,4-benzoquinones: synthesis of 6-chromanols from donor–acceptor cyclopropanes

Yi-Lin Wang,‡ Xin-Xin Lei,‡ Xin-Chen Jin,  Xin-Yu Zhang,  Peng-Fei Xu*  and  Yong-Chun Luo*

https://doi.org/10.1039/D3CC02988C

Abstract:A Sc(OTf)3 catalyzed intramolecular cyclization reaction of 2-alkyl-1,4-benzoquinone derived from D–A cyclopropane was discovered. This reaction involves single-electron transfer, proton-transfer, an aromatization driven spin center shift, and radical coupling processes, and offers an efficient method for the synthesis of 6-chromanols from D–A cyclopropanes.

Photoredox Catalyzed [3 + 2]-Annulation Reaction of Pyridinium 1,4-Zwitterionic Thiolates with Alkenes: Synthesis of Dihydrothiophenes

Yong-Chun Luo*, Yang Wang#, Run Shi#, Xu-Gang Zhang, Huan-Huan Zhang and Peng-Fei Xu*

https://doi.org/10.1021/acs.orglett.3c02068

Pyridinium 1,4-zwitterionic thiolates are usually used to develop ionic annulation reactions. However, radical reactions were rare. We developed a photoredox catalyzed [3 + 2]-annulation reaction of pyridinium 1,4-zwitterionic thiolates with alkenes, disclosed the new reactivity of pyridinium 1,4-zwitterionic thiolate, and provided a new synthetic method for dihydrothiophene.

Visible-Light-Mediated Intermolecular [2 + 2]-Cycloaddition Reaction of 3-Alkylideneindolin-2-one with Alkenes via Triplet Energy Transfer for the Synthesis of 3-Spirocyclobutyl Oxindoles

Shao-Xian Shi, Huan-Huan Zhang, Yi-Lin Wang, Lin-Hong Jiang, Peng-Fei Xu* and Yong-Chun Luo*

https://doi.org/10.1021/acs.orglett.3c01695

[2 + 2]-Cycloaddition is the most straightforward approach to the construction of cyclobutanes. In this paper, the intermolecular [2 + 2]-cycloaddition reaction of 3-alkylideneindolin-2-ones with alkenes was achieved. This reaction can be used in the synthesis of 3-spirocyclobutyl oxindoles, polycyclic oxindoles, and late stage modification of some drug molecules.

Enantioselective Synthesis of dispirooxindole Derivatives via asymmetric catalytic cascade reactions

Ma, Rui; Zhang, Jia-Lu; Hu, Xiu-Qin*; Xu, Peng-Fei*

https://doi.org/10.1055/a-2017-4738

Abstract 

A series of optically active 3,3′-pyrrolidinyl-dispirooxindole derivatives containing CF3 moiety have been efficiently constructed through asymmetric catalytic cascade reactions catalyzed by cinchona-derived bifunctional squaramide catalyst, bearing four contiguous stereogenic centers and two of which are vicinal spiro-stereocenters. Additionally, a wide range of different substituted products has been achieved with moderate to high yields (up to 99% yield) and excellent stereoselectivities (up to >20:1 dr for all cases and up to 99% ee).

Organic photoredox catalyzed dealkylation/acylation of tertiary amines to access amides

Chen Liu,‡  Han-Nan Chen,‡  Teng-Fei Xiao,   Xiu-Qin Hu,*  Peng-Fei Xu and  Guo-Qiang Xu *

https://doi.org/10.1039/D2CC05842A

Abstract

A mild metal-free C–N bond activation strategy for the direct conversion of inert tertiary amines with acyl chlorides into tertiary amides via organic photoredox catalysis is presented. In this protocol, a novel organic photocatalyst (Cz-NI-Ph) that showed excellent catalytic performance during C–N bond cleavage is developed. Moreover, this reaction features green and mild conditions, broad substrate scope, and readily available raw materials.

Light-Promoted Nickel-Catalyzed C−O/C−N Coupling of Aryl Halides with Carboxylic Acids and Sulfonamides

Tian-Tian Zhao, Hao-Ni Qin, and Peng-Fei Xu*

https://doi.org/10.1021/acs.orglett.2c04210

PCET-Mediated Ring-Opening Alkenylation of Cycloalkanols via Dual Photoredox and Cobalt Catalysis

Zi-Gang Ren, Wan-Lei Yu, Hai-Xue Zheng, and Peng-Fei Xu*

https://doi.org/10.1021/acs.orglett.2c03894