10.1016/j.tetlet.2010.09.149
The study explores the use of o-benzenedisulfonimide as a reusable Br?nsted acid catalyst in the Pictet–Spengler reaction to synthesize tetrahydroisoquinolines and tetrahydro-β-carbolines. These compounds possess various biological activities and are found in numerous natural and synthetic organic compounds. The reaction involves 2-arylethylamine derivatives and aldehydes, with o-benzenedisulfonimide facilitating the cyclization of iminium ions formed from the dehydration reaction of these reactants. The study demonstrates that the catalyst can be easily recovered and reused, offering economic and ecological benefits. The reactions are carried out under mild and green conditions, yielding good target product yields.
10.1021/acs.joc.8b00235
The research presents a novel protocol for synthesizing N,N- and N,O-aminals via direct azidation of sp3 C–H bonds in substrates with an α-nitrogen or α-oxygen atom. The study utilized various chemicals, including substrates such as tetrahydroisoquinolines (THIQs), tetrahydro-β-carbolines (THβCs), and cyclic benzyl ethers. The key reagents employed in the azidation process were 2,2,6,6-tetramethylpiperidine-1-oxoammonium (T+BF4–) as the oxidant and trimethylsilylazide as the azide source. The reactions were typically carried out in acetonitrile (CH3CN) solvent under mild conditions at room temperature. The protocol enabled high yields of aminal products without the need for prefunctionalization or expensive metal catalysts. Additionally, the resulting aminals could be readily transformed into more complex molecules through azide chemistry, demonstrating the versatility and practicality of this method for the synthesis of bioactive molecules and functional materials.
10.1021/acs.orglett.6b00151
The research presents a novel intramolecular redox-Mannich process for synthesizing benzo[a]quinolizine-2-one derivatives using 1,2,3,4-tetrahydroisoquinoline (THIQ) and documented β-ketoaldehydes. The reactions are promoted by acetic acid and involve azomethine ylides as reactive intermediates. The study explores the scope of this reaction with various β-ketoaldehydes, including nonenolizable and enolizable ones, and demonstrates its applicability to different cyclic amines such as tryptoline. The optimal reaction conditions involve using 10 equivalents of acetic acid, and the method moderate provides to good yields of the desired tricyclic products. The research also highlights the stability of the products under reaction conditions and their relevance to natural products and bioactive compounds.
10.1021/acs.orglett.8b02377
The study presents a biomimetic oxidative coupling cyclization strategy for the functionalization of tetrahydrocarbolines (THCs) to rapidly construct complex isochromanoindolenine scaffolds. The reaction involves using iron(II) phthalocyanine (FePc) as a catalyst and 2,3-bishydroxybenzoic acid as a coupling partner, with tert-butyl hydroperoxide (TBHP) as the oxidant. Acetic acid and methanesulfonic acid (MsOH) are also used to enhance the reaction efficiency. The FePc catalyst is crucial for the conversion, facilitating the formation of a tert-butyloxy radical from TBHP, which abstracts a hydrogen atom from the THC substrate. The resulting radical species then reacts with an unstable ortho-quinone intermediate formed from the oxidation of 2,3-bishydroxybenzoic acid, ultimately yielding the desired isochromanoindolenine product through acid-mediated transformation. This method is scalable, operationally simple, and compatible with a wide range of functional groups, including electron-donating and electron-withdrawing groups, and can be applied to various THCs, such as tetrahydro-β-carbolines (THβCs) and tetrahydro-γ-carbolines (THγCs), to produce the corresponding products in moderate to excellent yields.
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