Enantioselective [2 + 2] Cycloaddition of Unactivated Alkenes with α-Acyloxyacroleins Catalyzed by Chiral Organoammonium Salts

Ishihara, Kazuaki; Nakano, Kazuhiko

doi:10.1021/ja073435w

Cited by 125 publications

(39 citation statements)

References 13 publications

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“…Considering that 24 •2C 6 F 5 SO 3 H is much less active than 24 •2.75C 6 F 5 SO 3 H as a catalyst for the Diels–Alder reaction of dienes with 35 as well as α-(acyloxy)acroleins, 59),66) we assume that 24 •3C 6 F 5 SO 3 H may be a real active catalyst, which activates 35b as aldiminium salt ( 46 ) with 24 •3C 6 F 5 SO 3 H. In our previous papers, 30),52) it was assumed that ( Z )-aldiminium salt derived from 24 •2HX and 25 would be a key intermediate. However, an aldiminium salt derived from 26 •3HX and 25 may be more favorable.…”

Section: Chiral Ammonium Salt Catalysts For the Enantioselective Dielmentioning

confidence: 98%

“…52) To the best of our knowledge, there are only three previous examples of catalytic enantioselective [2+2] cycloaddition reactions for the synthesis of optically active cyclobutanes or cyclobutenes. 53)–57) The previous methods are limited to the [2+2] cycloaddition of highly nucleophilic alkenyl or alkynyl sulfides 53)–56) and sterically demanding alkenes such as norbornene derivatives.…”

Section: Chiral Ammonium Salt Catalysts For the Enantioselective [2+2mentioning

confidence: 99%

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Rational design of dynamic ammonium salt catalysts towards more flexible and selective function

Ishihara

2009

Proceedings of the Japan Academy. Ser. B: Physical and Biologic

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This review focuses on the development of dynamic ammonium salt catalysis for selective organic transformations conducted in our laboratory since 2002. Several important concepts in designing of catalysts are described with some examples. In particular, the practial synthesis of chiral 1,1′-binaphthyl-2,2′-disulfonic acid (BINSA) and its application in chiral ammonium salt catalysis for the enantioselective direct Mannich-type reaction are described.

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Section: Chiral Ammonium Salt Catalysts For the Enantioselective Dielmentioning

confidence: 98%

Section: Chiral Ammonium Salt Catalysts For the Enantioselective [2+2mentioning

confidence: 99%

Rational design of dynamic ammonium salt catalysts towards more flexible and selective function

Ishihara

2009

Proceedings of the Japan Academy. Ser. B: Physical and Biologic

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“…[21] These intermediates were found to undergo facile acid-catalyzed rearrangement to give interesting polycyclics caffolds (38). In the second example, synthetically useful cyclobutanes (40)(41)(42)(43)w ere accessed by cycloaddition of 4-pyridones (e.g., 39). [22] Thecyclobutane 43 was used to access the natural product (+ +)-lupinine (44)i n only six steps.…”

Section: Direct Absorptionmentioning

confidence: 99%

“…(Scheme 18). [43] It is notable that this method allowed for the cycloaddition of relatively unactivated alkenes and that the products contain vicinal quaternary centers.Amodel (127) that rationalizes the stereochemical outcome is illustrated in Scheme 18.…”

Section: Amine-catalyzed Reactionsmentioning

confidence: 99%

Cyclobutane and Cyclobutene Synthesis: Catalytic Enantioselective [2+2] Cycloadditions

2015

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Cyclobutanes and cyclobutenes are important structural motifs found in numerous biologically significant molecules, and they are useful intermediates for chemical synthesis. Consequently, [2+2] cycloadditions to access cyclobutanes and cyclobutenes have been established to be particularly useful transformations. Within the last 10 years, an increase in the frequency of publications for catalytic enantioselective [2+2] cycloadditions has occurred. These reactions provide access to a wide array of enantiomerically enriched chemical diversity that was not previously attainable. Described in this review are the advances made in catalytic enantioselective [2+2] cycloadditions to access cyclobutanes and cyclobutenes.

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“…Ishihara, K. et al reported an enantioselective [2 + 2] cycloaddition of unactivated alkenes (e.g., 161) with a-acyloxyacroleins 162, catalyzed by chiral organoammonium salts, catalyst 163, Scheme 3.52 [68]. A possible stepwise mechanism was proposed by authors to account for the stereoselectivity, which includes initial Michael addition of alkene to (Z)-iminium enal intermediate and intramolecular cyclization to afford the cycloadducts.…”

Section: [2 + 2] Cycloadditionsmentioning

confidence: 99%

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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Enantioselective [2 + 2] Cycloaddition of Unactivated Alkenes with α-Acyloxyacroleins Catalyzed by Chiral Organoammonium Salts

Cited by 125 publications

References 13 publications

Rational design of dynamic ammonium salt catalysts towards more flexible and selective function

Rational design of dynamic ammonium salt catalysts towards more flexible and selective function

Cyclobutane and Cyclobutene Synthesis: Catalytic Enantioselective [2+2] Cycloadditions

Organocatalyzed Cycloadditions

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