Enantioselective Synthesis of Dihydrocoumarins <i>via</i> N‐Heterocyclic Carbene‐Catalyzed Cycloaddition of Ketenes and <i>o</i>‐Quinone Methides

Lv, Hui; You, Lin; Ye, Song

doi:10.1002/adsc.200900544

Cited by 156 publications

(38 citation statements)

References 40 publications

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“…The ketene generated in situ from acyl chloride was also proven to undergo the reaction. In addition, a chiral N-heterocyclic carbene-catalyzed cycloaddition of ketenes and o-quinone methides was accomplished for the enantioselective synthesis of dihydrocoumarins (Scheme 79) [178].…”

Section: Nhc (N-heterocyclic Carbene) Catalysismentioning

confidence: 99%

Asymmetric Organocatalysis

Liu

Gong

2011

Asymmetric Catalysis From a Chinese Perspective

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Asymmetric organocatalysis has been receiving considerable attention in the last decade and thereby made tremendous advances. Chinese researchers have also intensified efforts to investigate asymmetric organocatalysis by using diverse types of disciplines, including enamine, iminium, Brønsted acid, carbene, and Lewis base catalysis. As a result, a large number of excellent catalysts and elegant protocols have come out from China. This article summarizes the most representative achievements in enantioselective organocatalysis from Chinese groups.

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Section: Nhc (N-heterocyclic Carbene) Catalysismentioning

confidence: 99%

Asymmetric Organocatalysis

Liu

Gong

2011

Asymmetric Catalysis From a Chinese Perspective

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“…Ketene, in situ generated from acyl halide 143 and base, followed by addition to imine which was generated in situ via basic elimination of a-amido sulfone 144, providing the ketene-imine addition pathway toward the cycloadducts. Ye and his co-workers reported an enantioselective synthesis of 3,3,4-trisubstituted 3,4-dihydrocoumarins 150 via N-heterocyclic carbene-catalyzed cycloaddition of ketenes 148 and o-quinone methides 147, Scheme 3.48 [64]. Noteworthy, it was found that the additive methanol was crucial for the high yields and enantioselectivities.…”

Section: Scheme 345 Bisoxazoline-catalyzed Diels-alder Reactionmentioning

confidence: 92%

Organocatalyzed Cycloadditions

Hong¹

2011

Enantioselective Organocatalyzed Reactions II

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Cycloadditions have been for a long time one of the most useful reactions in organic synthesis. Recently, the ability to promote the reactions by organocatalysts further expands the realm of its synthetic application. This review aims to highlight the recent advances in this area with particular emphasis on the asymmetric cycloaddition promoted by organocatalysts. IntroductionGenerating selectively the maximum number of bonds and stereogenic centers in a one-step (or one-pot) reaction constitute to be of key interest in synthetic chemistry. Among many methodologies for the objective, cycloaddition stand out. While searching for a better and tunable catalyst able to promote a wide spectrum of cycloaddition, organocatalysis was revealed as a powerful tool for efficient operations and many other merits, e.g., high stereoselectivity, moisture and air resistant, environmental benign and user friendly. Surprisingly, organocatalytic synthesis was virtually dominant for few decades until just the turn of this century [1]; nevertheless, it soon become the focal point, and it has occupied an important chapter in the modern synthetic chemistry [2]. In a very short period of time, more than hundred review articles of organocatalytic reactions were reported, and the papers are continuing to appear for summarizing up the thriving and robust subject. Several theoretical studies, including the computational Intramolecular CycloadditionsIn 2005, MacMillan reported an enantioselective organocatalytic intramolecular Diels-Alder reaction (IMDA) of a,b-unsaturated aldehyde and diene, as well as the application in the asymmetric synthesis of solanapyrone D (6), Scheme 3.1 [5]. Later, Danishefsky and Christmann individually reported the total synthesis of UCS1025A (9) by coupling reaction with MacMillan aldehyde (8) [6]. The malimide analogue 10 of the telomerase inhibitor UCS1025A (9) was also prepared by Christmann et al. by modified MacMillan's conditions (10 mol% catalyst loading in nitromethane, affording 74% yield and >99% ee after a sequence of recrystallization and oxidation), Scheme 3.2 [7]. In 2003, an interesting intramolecular organocatalytic [3 + 2] dipolar cycloaddition of an enynoate (19) catalyzed by PBu 3 was developed by Krische and his coworker in the total synthesis of (±)-hirsutene (21), Scheme 3.6 [12]. The intramolecular phosphane-catalyzed [3 + 2] dipolar cycloaddition provides a concise approach to the linear triquinane hirsutene, whereby three contiguous stereogenic centers are created and controlled in a single reaction step.A light-driven enantioselective organocatalysis intramolecular [2 + 2] photocycloaddition of quinolone (24) [4 + 2] cycloadditions. The enantioselectivity was rationalized by the fact that selective formation of the (E)-iminium isomer to avoid nonbonding interactions between the substrate olefin and the geminal methyl substituents and the benzyl group on the catalyst framework which effectively shields the re face of the dienophile, leaving the si face exposed to cycloadditio...

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“…随后叶松等又成功地将此类催化剂分别应用到烯酮与邻亚甲基苯醌 [42] 和与 3-亚甲基吲哚酮 [43] 的环加成反应中, 用来合成二氢香豆素和含有并环二氢吡喃酮结构的吲哚酮(Eqs. 25 和 26).…”

Section: N-杂环卡宾(nhc)催化剂unclassified