Guanidine‐Catalyzed Asymmetric Synthesis of 2,2‐Disubstituted Chromane Skeletons by Intramolecular Oxa‐Michael Addition

Saito, Noriko; Ryoda, Akemi; Nakanishi, Waka; Kumamoto, Takuya; Ishikawa, Tsutomu

doi:10.1002/ejoc.200800089

Cited by 72 publications

(38 citation statements)

References 35 publications

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“…It is theoretically possible to introduce five chiral centers in the guanidine system. We found that modified guanidines prepared using our original methods [4][5][6] were effective not only in catalytic [7][8][9][10][11][12][13] but also in stoichiometric asymmetric syntheses. 14,15) The concept of modified guanidines as chiral auxiliaries in asymmetric synthesis is illustrated in Chart 2, [16][17][18] in which reactive, but resonance-stabilized, guanidinium salts 5 could be produced from guanidines 4 by quarternarization with a reagent (A-B).…”

Section: Modified Guanidines As Chiral Auxiliaries (Functionality As mentioning

confidence: 99%

Guanidine Chemistry

Ishikawa

2010

Chem. Pharm. Bull.

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Guanidines are categorized as strong organobases; however, their catalytic utility in organic synthesis has not been discussed thoroughly. The author's group has extensively and systematically studied their potential ability focusing on: 1) modified guanidines as chiral auxiliaries; 2) guanidinium ylides for aziridine formation; 3) the affinity of bisguanidine for proton and metal salts; and 4) the potential chirality of bisguanidine. Under the first topic, a variety of chiral guanidines was designed by the introduction of chirality on the three guanidinyl nitrogens, and the modified guanidines prepared using our original methods were found to be effective not only in catalytic but also in stoichiometric asymmetric syntheses. Under the second topic, the reaction of guanidinium salts carrying a glycinate function with aromatic or unsaturated aldehydes under basic conditions unexpectedly afforded aziridine-2-carboxylates, which were available as useful building blocks in organic synthesis due to their convertibility to functionalized amino acid derivatives in the ring-opening reaction, together with urea compounds recyclable to the starting guanidinium salts. The introduction of a chiral template to the guanidinium salt allowed us to expand the cyclic aziridination reaction to an asymmetric version. Under the third topic, effective complexabilty of bisguanidines with either proton or metal ions in water was observed, suggesting their possible application to the removal of toxic substances from polluted water and recovery of rare elements as material sources. Under the final topic, monomethylation or monoethylation of bisguanidine afforded a chiral product via asymmetric crystallization, indicating that bisguanidines have a potential chiral character due to the plane asymmetry.

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Section: Modified Guanidines As Chiral Auxiliaries (Functionality As mentioning

confidence: 99%

Guanidine Chemistry

Ishikawa

2010

Chem. Pharm. Bull.

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“…In addition, the current method could be applied to the AIOM addition of the ester congeners 25a-d to provide the corresponding dihydrobenzofurans 26a-d with higher enantioselectivities (86-89% ee) as compared to literature precedents [52][53][54][55][56]. It is worthy to note that the construction of a chiral tetrasubstituted carbon center was also successful, and the corresponding O-heterocycle 26d was obtained in 75% yield with 86% ee.…”

Section: The Intramolecular Oxa-michael Addition Of Phenolsmentioning

confidence: 90%

“…4 prevail in natural products and pharmaceuticals, the AIOM reaction of α,β-unsaturated amides and esters bearing phenolic OH groups would be useful and practical from the viewpoint of atom economy. So far, there have been only a few reports on the same reaction of α,β-unsaturated esters [52][53][54][55][56], and no reports with regard to α,β-unsaturated amides have yet been described. Recently we discovered that benzothiadiazine catalyst 3a effectively promoted the AIOM addition to α,β-unsaturated amides 23a-i (Table 11) [11].…”

Section: The Intramolecular Oxa-michael Addition Of Phenolsmentioning

confidence: 99%

“…Moreover, in the oxa-Michael adducts of a thioester or imide, there is the risk of racemization via retro-Michael/Michael addition during these transformations. Therefore, the direct AIOM addition to unactivated α,β-unsaturated esters [52][53][54][55][56] or amides [11] would be more desirable from the perspective of substrate availability and tolerance to racemization of products. However, such a reaction has received much less attention, likely because of the poor reactivity of both the Michael acceptor and the O-nucleophiles employed.…”

Section: The Intramolecular Oxa-michael Addition To αβ-Unsaturated Amentioning

confidence: 99%

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Bifunctional Guanidines as Hydrogen-Bond-Donating Catalysts

Kobayashi

Takemoto

2015

Topics in Heterocyclic Chemistry

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Bicyclic guanidines, bearing 2-aminoquinazolin-4-one and 3-aminobenzothiadiazine-1,1-dioxide core structures, work as bifunctional amine catalysts, due to a double hydrogen-bond-donating ability of two guanidine N-H protons, which are capable of activating both nucleophile and electrophile simultaneously. In fact, these guanidine catalysts revealed to promote several asymmetric reactions such as hydrazination of active methylene compounds with azodicarboxylate and 1,3-proton migration of alkynoates to allenoates as well as the oxa-Michael addition and epoxidation of α,β-unsaturated amides and esters with better chemical yields and higher enantioselectivities than the corresponding thioureas. The catalytic mechanisms of these asymmetric reactions and their synthetic applications for biologically active molecules are also discussed in this chapter.

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“…9 Various catalysts have been reported for intermolecular oxa-Michael additions, such as pro-azaphosphatranes of ionic liquid as solvent for toluenesulfonic acid-catalyzed oxa-Michael addition has also been reported. 22 For intramolecular oxa-Michael addition, cinchona alkaloids, 23 thiourea derivatives, 24 quinine, 25 guanidine, 26 30,31 have been utilized as the catalysts. It was reported that the intramolecular oxa-Michael addition of (E)-1-aryl-4-hydroxy-4-methylpent-1-en-3-ones in the presence of TsOH should be carried out by refluxing in dichloroethane for 24 h, while the products were hard to purify due to the impurities.…”

Section: Introductionmentioning

confidence: 99%

Acid-catalyzed intramolecular oxa-Michael addition reactions under solvent-free and microwave irradiation conditions

Hong¹,

Shen²,

Hu³

et al. 2010

Arkivoc

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The acid-catalyzed intramolecular oxa-Michael addition of (E)-1-aryl-4-hydroxy-4-methyl--pent-1-en-3-ones under solvent-free and microwave irradiation conditions has been investigated. The results showed that Bronsted acids are more efficient than Lewis acids in this reaction. Up to 90% conversion and 81% yield were obtained using trifluoromethanesulfonic acid (triflic acid) as the catalyst, with short reaction times and an environmentally benign procedure.

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Guanidine‐Catalyzed Asymmetric Synthesis of 2,2‐Disubstituted Chromane Skeletons by Intramolecular Oxa‐Michael Addition

Cited by 72 publications

References 35 publications

Guanidine Chemistry

Guanidine Chemistry

Bifunctional Guanidines as Hydrogen-Bond-Donating Catalysts

Acid-catalyzed intramolecular oxa-Michael addition reactions under solvent-free and microwave irradiation conditions

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