Asymmetric Synthesis of Triaryl‐Substituted Chromans with Multiple Stereogenic Centers by [4+2] Cycloaddition Reaction

Zhang, Heng; Li, Guofeng; Guan, Xiangjiu; Gao, Jigang; Qin, Xiangshuo; Jiang, Guofeng; Sun, Dongyang; Zhang, Guangliang; Zhang, Suoqin

doi:10.1002/ejoc.201901286

Cited by 20 publications

(10 citation statements)

References 60 publications

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“…Zhang et al demonstrated the synthesis of trisubstituted chromans 122 with multiple stereocenters (Scheme 42). [ 177 ] This process made use of 1‐styrylnaphthols 120 and ortho‐ hydroxybenzyl alcohols 33 . The most reactive ortho‐ QM intermediates were formed in‐situ from ortho ‐hydroxybenzyl alcohols 33 , which then via a formal [4 + 2] cycloaddition oxa‐Diels–Alder reaction with diene derivatives afforded the cyclic ether products.…”

Section: Resultsmentioning

confidence: 99%

Recent advances on the synthesis of flavans, isoflavans, and neoflavans

Sreenivasulu

Dakoju

Satyanarayana

2020

Journal of Heterocyclic Chem

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Heterocyclic compounds are the omnipresent structural cores comprising many natural and pharmaceutical products of biological significance. Significantly, heterocyclic compounds are widely distributed in nature, and also have applications in agrochemicals, sanitizers, as dyestuff, as copolymers, etc. Among heterocyles, flavonoids are a class of compounds that are highly interesting and constitute many natural products. In general, all flavanoids contains a basic core of C6‐C3‐C6 of phenyl‐benzopyran backbone. The relative placement of the phenyl group on to the benzopyran core makes further classification into flavanoids, isoflavanoids and neoflavanoids. Flavans (2‐aryl chroman) are subclass of anthoxanthanes exhibits a broad spectrum of biological properties such as anti‐inflammatory, anti‐oxidant, and anti‐malarial properties. Some representative naturally occurring products possessing flavan core are apigenin, luteolin, tangeretin, scutellarein, etc. On the other hand, some of the notable isoflavan‐based natural products are glabridin and (S)‐(−)‐equol. Glabridin is isolated from Licorice roots, which regulates paraoxonase (PON2) levels. While the simple isoflavan (S)‐(−)‐equol, is produced from soy isoflavone intake. Also, natural products such as dalbergichromene, centchroman, and (+)‐myristinin A possess neoflavan (4‐aryl‐3,4‐dihydro‐2H‐chromenes) core structure. Owing to their broad biological and pharmacological properties, synthetic chemists are fascinated in developing new routes toward their synthesis. As a result, a decent number of reports have been established in the literature. Thus, for the past 5 years of time frame, many new methodologies have been witnessed, for the synthesis of various flavan systems. This review emphasizes most of the significant methods on accomplishing flavans, isoflavans and neoflavans and also focused on their applications to the synthesis of relevant natural as well as biologically active products.

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Section: Resultsmentioning

confidence: 99%

Recent advances on the synthesis of flavans, isoflavans, and neoflavans

Sreenivasulu

Dakoju

Satyanarayana

2020

Journal of Heterocyclic Chem

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“…Therefore, this reaction system involving o-hydroxynaphthalene needed to continue to optimize the reaction conditions. Subsequently, other groups including Zhang [20] (Scheme 8a), Yuan and You [21] (Scheme 8b), Deng and Shao [22] (Schemes 8c and 8d) independently published beautiful works about the same cycloaddition process of o-hydroxynaphthalene 34 by using different CPA catalysts, again forming a wide range of polysubstituted chromans (35,40) with high level of stereoselectivities. Notably, the lessexplored ortho-alkenyl 1-naphthols were also compatible in this methodology to deliver trans-trans chiral trisubstituted chromans 40.…”

Section: Chiral Phosphoric Acidmentioning

confidence: 99%

Recent Advances in Organocatalytic Asymmetric Cycloaddition Reactions Through Ortho‐Quinone Methide Scaffolds

Yang

et al. 2021

Asian J Org Chem

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This review summarizes the very recent advances in organocatalytic asymmetric cycloaddition reactions involving ortho-quinone methides (o-QMs), a family of versatile species that have proven useful in a broad range of reactions to afford diverse chiral molecules. In the past years, different kinds of organocatalysts have been developed into a privileged class of catalytic systems in asymmetric synthesis.A number of remarkable achievements have been made by many groups around the world. Due to length limitation, this review only summarizes those works published from January 2016 to December 2020. Meanwhile, catalytic systems which combine metal catalysts and organocatalysts will not be discussed in this review.

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“…Diversely substituted chromans are readily available through [4 þ 2] regioselective cycloaddition reactions using various o-quinone methides as starting materials: i) formed from 2-[hydroxy(aryl)methyl]phenols with silver oxide and further reaction with terminal alkenes in ethyl acetate promoted by a thioxanthylium photoredox catalyst under green light LED irradiation (19JOC10669); ii) reaction of salicylaldehydes with terminal alkenes or acetophenones (19JOC13858) or with arylacetaldehyde dimethyl acetals (Scheme 28) (19SL189), TfOH, and trimethyl orthoformate in dry toluene; iii) formed in situ from 2-[hydroxy(aryl)methyl]phenols with 1-styrylnaphth-1-ols in the presence of H 8 -BINOL-type chiral imidodiphosphoric acids as catalyst and molecular sieves in toluene (19EJO7264); iv) formed in situ from 2-[hydroxy(alkyl/aryl)methyl]phenols with methyl (S,E)-3-[dimethyl(phenyl)silyl]hex-4-enoate mediated by anhydrous iron(III) chloride in the presence of 2,6-lutidine in chloroform (19OL32); and v) formed from chemoenzymatic transformation of o-cresols into benzylic alcohols, followed by the loss of water and subsequent reaction with terminal alkenes (19JA20269).…”

Section: Scheme 25mentioning

confidence: 99%