Base-promoted aerobic oxidation of N-alkyl iminium salts derived from isoquinolines and related heterocycles

Abstract

A green access to azine-derived unsaturated lactams is developed via potassium tert-butoxide-promoted aerobic oxidation of N-alkyl iminium salts.

Concise Synthesis of Isocoumarins through Rh-Catalyzed Direct Vinylene Annulation: Scope and Mechanistic Insight

“…A coupling product 3f was treated with tryptamine under microwave irradiation to afford the corresponding isoquinolinone 9 . Sequential Lewis acid mediated cyclization and oxidation by CeCl 3 delivered a pentacyclic product, 2-bromonorketoyobyrine ( 10 ), in 42% yield over two steps . Installation of functional groups onto the inherently less reactive ring over the pyrrol moiety is challenging for the manipulation of indole alkaloids, and cumbersome multistep synthesis is usually inevitable.…”

“…Sequential Lewis acid mediated cyclization and oxidation by CeCl 3 delivered a pentacyclic product, 2-bromonorketoyobyrine (10), in 42% yield over two steps. 11 Installation of functional groups onto the inherently less reactive ring over the pyrrol moiety is challenging for the manipulation of indole alkaloids, 12 and cumbersome multistep synthesis is usually inevitable. As shown in this particular example, the present method may provide synthetically useful building blocks for various multicyclic compounds.…”

Synthesis of 3‐Methyleneisoindolin‐1‐ones and Isoquinolinium Salts via Exo and Endo Selective Cyclization of 2‐(1‐Alkynyl)benzaldimines

“…With these isoquinolinium salts of 5 in hand, we next studied their reactivities towards several interesting transformations, which had been previously studied by using isoquinolinium salts with less bulky N ‐alkyl group as substrates. We first investigated the transformation of isoquinolinium salts into isoquinolinones through a modified reported procedure, in which air was used as an abundant, inexpensive, clean, and atom‐economical oxidant [2f] . Thus, N ‐aryl isoquinolinium salts of 5 a ∼ 5 e were converted into isoquinolinone products of 8 a ∼ 8 e in the presence of KO t Bu in THF under air with moderate to good yields of 49–83 %, respectively (Scheme 8).…”

Iodination/Amidation of the N-Alkyl (Iso)quinolinium Salts

“… In addition, many derivatives of N -alkyl quinolinones were shown to exhibit anticancer, antitumor, antibacterial, and anti-HIV activities properties. Accordingly, many synthetic methods of quinolinones and isoquinolinones have been developed during the past decades . Among them, the iodine-functionalized (iso)­quinolinones as valuable synthetic intermediates have aroused great interest among the chemists in recent years because the weak carbon–iodine bond is easy to be further functionalized through a series of coupling reactions, thus constructing a diversity of bioactive molecules and drug candidates .…”