Enantioselective 1,3‐Dipolar Cycloaddition of Nitrones with Ethyl Vinyl Ether: The Difference between Brønsted and Lewis Acid Catalysis

Jiao, Peng; Nakashima, Daisuke; Yamamoto, Hisashi

doi:10.1002/anie.200705314

Cited by 191 publications

(71 citation statements)

References 56 publications

(16 reference statements)

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“…The L-phenylalanine-based 1,1¢-binaphthyl-2,2¢-diamine (BINAM) catalyst 194, with trifluoromethanesulfonic acid as an additive, afforded the optimal results with good endo-diastereoselectivity and enantioselectivity up to 95% ee. [80]. Only 5 mol% of this air-stable catalyst was used, and the reactions were completed within 1 h. The endo-selectivity of this cycloaddition is different to the previously reported exo-selectivity of the aluminum-catalyzed reaction (Lewis acid catalysis).…”

Section: [3 + 2] or 13-dipolar Cycloadditionmentioning

confidence: 64%

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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Section: [3 + 2] or 13-dipolar Cycloadditionmentioning

confidence: 64%

Organocatalyzed Cycloadditions

Hong¹

2011

Enantioselective Organocatalyzed Reactions II

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“…27 We extended the utility of N tri yl oxo phosphoramide to the enantioselective 1,3 dipolar cycloaddition of nitrones with ethyl vinyl ether. 26 It should be noted that in sharp contrast to the exo selectivity of Lewis acid catalyzed cycloaddition of diaryl nitrones with alkyl vinyl ether reported by Jørgensen and co workers, 28 this N tri yl oxo phosphoramide catalyzed cycloaddition reaction gave the desired product with high endo selectivity (Scheme 13). The dramatic difference in diastereoselectivity between the [3 2] cycloaddition catalyzed by the Brønsted acid (up to 97% endo selective) and MeAl BINOL complex (up to 95% exo selective) can be rationalized by transition state structure (Figure 11).…”

Section: Chiral N Tri Yl Oxo Phosphoramidesmentioning

confidence: 93%

“…X ray crystallography analysis revealed that the Brønsted acid has P O bond and P N single bond and the proton is located on the N atom rather than on the O atom as shown in Figure 10. 26 We successfully applied this Brønsted acid to the catalytic asymmetric Diels Alder reaction of ethyl vinyl ketone with siloxydienes, which is the rst example of activation of carbonyl functionality in phosphoric acid catalysis. 25 Introduction of the N tri yl group dramatically increased the reactivity: N tri yl phosphoramide gave the Diels Alder adducts in excellent yields and enantioselectivities, whereas phosphoric acid showed no catalytic activity (Scheme 11 and Table 2).…”

Section: Chiral N Tri Yl Oxo Phosphoramidesmentioning

confidence: 99%

“…The substituents of 3,3 position of BINOL, which have been developed by many researchers, are shown in Table 6. 21,22,26,32,38 In the enantioselective Mukaiyama aldol reaction, the bulky substituent, 9 anthracenyl, at the 4 position of 3,3 aryl substituent of the BINOL improved both diastereoselectivity and enantioselectivity.…”

Section: Chiral N Tri Yl Thio and Seleno Phosphoramidesmentioning

confidence: 99%

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Development of New Chiral Br^|^oslash;nsted Acid Catalysis

Hirashima

Yamamoto

2013

J. Synth. Org. Chem. Jpn.

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“…Our group has made some efforts to increase the acidity of this type of catalysts through modifying chiral phosphoric acid structure to corresponding chiral N-triflyl phosphoramide [67,68] or N-triflyl thio-and seleno-phosphoramide [56,69]. Another interesting approach for enhancing reactivities of chiral phosphoric acid catalysis has appeared recently from two independent studies, in which Lewis acid activation of Brønsted acid (LBA) consideration is the key to success.…”

Section: Lewis Acid/chiral Phosphoric Acid Combinationmentioning

confidence: 99%

Bifunctional Acid Catalysts for Organic Synthesis

Yamamoto

2011

Bifunctional Molecular Catalysis

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The concept of bifunctional acid catalysis is very helpful for inventing new catalytic asymmetric reactions. Compared with single functional acid catalysts, cooperative effect of two acid components has the potential to fine tune the reactivity as well as the selectivity of desired reaction pathways. This chapter focuses on some representative examples on the recent developments of bifunctional acid catalysis, including combined acid catalysis and other cooperative acid catalysis.

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Enantioselective 1,3‐Dipolar Cycloaddition of Nitrones with Ethyl Vinyl Ether: The Difference between Brønsted and Lewis Acid Catalysis

Cited by 191 publications

References 56 publications

Organocatalyzed Cycloadditions

Organocatalyzed Cycloadditions

Development of New Chiral Br^|^oslash;nsted Acid Catalysis

Bifunctional Acid Catalysts for Organic Synthesis

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