Spirocyclic Tetramates by Sequential Knoevenagel and [1,5]-Prototropic Shift

Josa-Culleré, Laia; Hirst, Michael G.; Lockett, J.; Thompson, Amber L.; Moloney, Mark G.

doi:10.1021/acs.joc.9b01345

Cited by 8 publications

(3 citation statements)

References 66 publications

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“…benzaldehyde [40] In a plastic flame flask (250 mL), a solution of potassium carbonate (1.2 g, 30.0 mmol) in N, N-dimethylformamide (100 mL), 2-fluorobenzaldehyde (5.6 g, 45.0 mmol), and tetrahydropyrrolidine (4.2 g, 60.0 mmol) were added and stirred at 100 C after added magnetic stirrer. The reaction progress was monitored by TLC (petroleum ether/ethyl acetate volume ratio = 10:1).…”

Section: Synthesis Of 2-(pyrrolidin-1-yl)mentioning

confidence: 99%

Synthesis of 1‐(4‐hydroxybutyl)‐2‐benzoyl indoles from 2‐pyrrolidine benzaldehydes and α‐bromoacetophenones in deep eutectic solvent

Jiang,

Zhang,

Xing

et al. 2024

Journal of Heterocyclic Chem

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A novel and highly efficient method for the synthesis of 1‐(4‐hydroxybutyl)‐2‐benzoyl indoles from 2‐pyrrolidine benzaldehyde and α‐bromoacetophenone in a choline chloride (ChCl)/ZnCl2 eutectic mixture was developed. This method, which does not require any catalyst, additive, or alkali, is useful for realizing tandem cyclization reactions. Several indoles were produced after cyclization and ring opening processes. Not all the compounds obtained are reported in the literature. This synthetic strategy proves that deep eutectic solvents can replace catalysts and organic solvents. Consequently, this is an environmentally friendly strategy that has significant potential in the development of green and sustainable chemistry.

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Section: Synthesis Of 2-(pyrrolidin-1-yl)mentioning

confidence: 99%

Synthesis of 1‐(4‐hydroxybutyl)‐2‐benzoyl indoles from 2‐pyrrolidine benzaldehydes and α‐bromoacetophenones in deep eutectic solvent

Jiang,

Zhang,

Xing

et al. 2024

Journal of Heterocyclic Chem

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“…Inspired by Kamilar’s unprecedented work, a sequential Knoevenagel condensation/[1,5]-prototropic shift of tetramates 167 with aminobenzaldehydes 168 to furnish the functionalized spirocyclic tetramates 170 was reported by Moloney’s group in 2019 ( Scheme 17B ) ( Josa-Cullere et al, 2019 ). The α,β-unsaturated 1,3-dicarbonyl intermediate 169 served as a hydride acceptor and started the sequential reaction under optimized conditions.…”

Section: The Construction Of a Spiro-tetrahydroquinoline Skeleton Con...mentioning

confidence: 99%

The Cascade [1,5]-Hydride Shift/Intramolecular C(sp3)–H Activation: A Powerful Approach to the Construction of Spiro-Tetrahydroquinoline Skeleton

Quan

Xie

et al. 2022

Front. Chem.

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The direct functionalization of inert C–H bonds is regarded as one of the most powerful strategies to form various chemical bonds and construct complex structures. Although significant advancements have been witnessed in the area of transition metal-catalyzed functionalization of inert C–H bonds, several challenges, such as the utilization and removal of expensive transition metal complexes, limited substrate scope and large-scale capacity, and poor atom economy in removing guiding groups coordinated to the transition metal, cannot fully fulfill the high standard of modern green chemistry nowadays. Over the past decades, due to its inherent advantage compared with a transition metal-catalyzed strategy, the hydride shift activation that applies “tert-amino effect” into the direct functionalization of the common and omnipresent C(sp3)–H bonds adjacent to tert-amines has attracted much attention from the chemists. In particular, the intramolecular [1,5]-hydride shift activation, as the most common hydride shift mode, enables the rapid and effective production of multifunctionally complex frameworks, especially the spiro-tetrahydroquinoline derivatives, which are widely found in biologically active natural products and pharmaceuticals. Although great accomplishments have been achieved in this promising field, rarely an updated review has systematically summarized these important progresses despite scattered reports documented in several reviews. Hence, in this review, we will summarize the significant advances in the cascade [1,5]-hydride shift/intramolecular C(sp3)-H functionalization from the perspective of “tert-amino effect” to build a spiro-tetrahydroquinoline skeleton, and the content is categorized by structure type of final spiro-tetrahydroquinoline products containing various pharmaceutical units. Besides, current limitations as well as future directions in this field are also pointed out. We hope our review could provide a quick look into and offer some inspiration for the research on hydride shift strategy in the future.

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“…8 Such reactions are typically high yielding and reliable, and have granted successful creation and introduction of a novel synthetic antibiotic class – spiropyrimidinetriones, 9 and Zoliflodacin drug, in particular. 10 Based on the nature of hydride donor and acceptor fragments, the reaction could be initiated thermally, 11 under the action of catalytic, 12 substoichiometric 13 and stoichiometric amounts 14 of Lewis acid. In the ideal case, when the hydrogen is shifted from the α-position of the amino-substituent to a strong acceptor group such as Meldrum's acid derivatives, the reaction could be initiated at room temperature in hexafluoroisopropanol via hydrogen bond catalysis, 15 while for complicated reactions the required conditions could be as harsh as heating with scandium triflate in mesitylene.…”

mentioning

confidence: 99%