99
© Springer-Verlag GmbH Germany, part of Springer Nature 2019
A. Lei (ed.), Transition Metal Catalyzed Oxidative Cross-Coupling Reactions,
Lecture Notes in Chemistry 102, https://doi.org/10.1007/978-3-662-58104-9_4
Chapter 4
Oxidative Radical Couplings
Wei Liu
4.1 Introduction
Oxidative radical C-C couplings are constructing C-C bonds involving generation
of radical intermediates, while the strategy of oxidative radical couplings can be
extended to constructing C-X (X = O, S, N, P, etc.) bonds, which provide an efficient and facile method to prepare various important organic motifs. Under
transition- metal-catalysts or transition-metal-free conditions, oxidative radical
cross-couplings can be achieved under oxidation conditions (Scheme 4.1). Based on
the type of C-C bond formation in the cross-coupling reactions, the oxidative radical
C-C couplings can be divided mainly into four types in this text (Scheme 4.2): (1)
coupling of C sp3 -H with C sp -H bonds, (2) coupling of C sp3 -H with C sp2 -H bonds, (3)
coupling of C sp3 -H with C sp3 -H bonds, and (4) coupling of C sp2 -H with C sp2 -H bonds.
4.1.1 Coupling of C sp3 -H with C sp -H Bonds
Alkynylation of benzylic C-H bonds which are not adjacent to a heteroatom is a
possible route for the formation of C sp3 -C sp bonds.
Using CuBr as catalyst and N-bromosuccinimide (NBS) as radical initiator, oxidative coupling of tertiary aliphatic amines with terminal alkynes provides various
C sp3 -H bond functionalized products in good yields (Scheme 4.3). In this transformation, the alkynylation reaction can be selectively performed on the methyl group
of the tertiary amines.
W. Liu (*)
College of Food Science and Technology, Henan University of Technology,
Zhengzhou, Henan Province, People’s Republic of China
© Springer-Verlag GmbH Germany, part of Springer Nature 2019
A. Lei (ed.), Transition Metal Catalyzed Oxidative Cross-Coupling Reactions,
Lecture Notes in Chemistry 102, https://doi.org/10.1007/978-3-662-58104-9_4
Chapter 4
Oxidative Radical Couplings
Wei Liu
4.1 Introduction
Oxidative radical C-C couplings are constructing C-C bonds involving generation
of radical intermediates, while the strategy of oxidative radical couplings can be
extended to constructing C-X (X = O, S, N, P, etc.) bonds, which provide an efficient and facile method to prepare various important organic motifs. Under
transition- metal-catalysts or transition-metal-free conditions, oxidative radical
cross-couplings can be achieved under oxidation conditions (Scheme 4.1). Based on
the type of C-C bond formation in the cross-coupling reactions, the oxidative radical
C-C couplings can be divided mainly into four types in this text (Scheme 4.2): (1)
coupling of C sp3 -H with C sp -H bonds, (2) coupling of C sp3 -H with C sp2 -H bonds, (3)
coupling of C sp3 -H with C sp3 -H bonds, and (4) coupling of C sp2 -H with C sp2 -H bonds.
4.1.1 Coupling of C sp3 -H with C sp -H Bonds
Alkynylation of benzylic C-H bonds which are not adjacent to a heteroatom is a
possible route for the formation of C sp3 -C sp bonds.
Using CuBr as catalyst and N-bromosuccinimide (NBS) as radical initiator, oxidative coupling of tertiary aliphatic amines with terminal alkynes provides various
C sp3 -H bond functionalized products in good yields (Scheme 4.3). In this transformation, the alkynylation reaction can be selectively performed on the methyl group
of the tertiary amines.
W. Liu (*)
College of Food Science and Technology, Henan University of Technology,
Zhengzhou, Henan Province, People’s Republic of China