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Catalytic Asymmetric Synthesis of Five- and Six-Membered Heterocycles via Cascade Reactions of Nitroalkenes
Published in Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera, Catalytic Asymmetric Reactions of Conjugated Nitroalkenes, 2020
Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera
The Xiao group reported L2-Zn(OTf)2-catalyzed enantioselective Michael addition/cyclization cascade reaction of 3-nitro-2H-chromenes 1m with 3-isothiocyanato oxindoles 75 to deliver highly functionalized spirooxindoles 76 in high yields and excellent enantioselectivities (Scheme 12.29).25 In this reaction, the zinc complex acts as Lewis acid and activates the olefin via coordination between Zn and a nitro group (TS-18, Scheme 12.29). At the same time, the nitrogen of oxindole –NH group acts as a Lewis base and directs the incoming nucleophile to attack from the Re-face through H-bonding.
Reactions With Disinfectants
Published in Richard A. Larson, Eric J. Weber, Reaction Mechanisms in Environmental Organic Chemistry, 2018
Richard A. Larson, Eric J. Weber
Chlorination of glutamic acid at pH 7.2 gave a high yield of the cyano acid 52 (Equation 5.26). Proline reacted to give the dichlorodiacid 53 (De Leer et al., 1987), which represents one of the major structural types found in humic acid chlorination products (vide supra). Tryptophan reacted with HOCl under acidic conditions to give an oxindole and a C-chlorinated oxindole (Equation 5.27) (Burleson et al.,
Palladium(II)-assisted ortho alkylation of C(sp2)-H bonds in substituted azobenzenes with simple alkyl halides
Published in Journal of Coordination Chemistry, 2018
Mainak Mitra, Debojyoti Mukherjee, Ujjwal Mandal, Albert A. Shteinman
Azobenzenes are important class of compounds widely used in many fields, such as organic dyes and pigments, food additives, photoluminophores and photoconductors, liquid crystals, etc. [7]. Organometallic Pd(II) complexes incorporating azo group(s) are active towards Suzuki and Heck and other coupling reactions [8(a–c)] and alkene epoxidation [8(c)]. Synthesis of newly substituted azobenzenes via directed C-H activation represents an active area of chemical research. Metal-center promoted functionalization of azobenzenes including halogenations, alkylation, arylation, acylation, alkoxylation, amination, etc. using azo directing groups has gained considerable attention [9–11]. Han et al. have recently described the remarkable one-pot syntheses of oxindoles via selective C-H alkylation of azobenzenes with internal olefins, such as maleimides, maleates, and fumarates, followed by reductive intramolecular cyclization [12]. The formation of an oxindole scaffold could be a valuable contribution to the development of bioactive compounds with medical applications [13]. However, selective introduction of substituents into unsymmetrical azobenzenes still represents a formidable challenge [14].