Simple preparation of chiral 1,3-dimethyl-2-iminoimidazolidines (monocyclic guanidines) and applications to asymmetric alkylative esterification

Isobe, Toshio; Fukuda, Keiko; Ishikawa, Tsutomu

doi:10.1016/s0957-4166(98)00152-9

Cited by 57 publications

(33 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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). The salts 5 may react with activated unsaturated substrates (CϭD) to give addition products such as in the Michael reaction, trimethylsilyl (TMS) cyanation, or nucleophilic epoxidation, in which guanidines should act as catalysts (route A in Chart 2).…”

Section: Modified Guanidines As Chiral Auxiliaries (Functionality As mentioning

confidence: 99%

Guanidine Chemistry

Ishikawa

2010

Chem. Pharm. Bull.

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Modified Guanidines As Chiral Auxiliaries (Functionality As mentioning

confidence: 99%

Guanidine Chemistry

Ishikawa

2010

Chem. Pharm. Bull.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Compound 8 a (X = Cl): [53] Representative procedure for the formation of hexafluorophosphate salts-Compound 7 b (X = PF 6 ): AgPF 6 (147 mg, 0.58 mmol) was added to a solution of chloride salt 7 a (X = Cl, 210 mg, 0.58 mmol) in CH 2 Cl 2 (4 mL) and the resulting suspension was stirred for 1 h at ambient temperature under argon. The mixture was filtered and the solvent was evaporated to give the corresponding hexafluorophosphate salt 7 b in analytically pure form (219 mg, 79 %).…”

Section: Compound 6 a (X =mentioning

confidence: 99%

Diaminocarbene‐ and Fischer‐Carbene Complexes of Palladium and Nickel by Oxidative Insertion: Preparation, Structure, and Catalytic Activity

Kremzow

Seidel

Lehmann

et al. 2005

Chemistry A European J

218

113

View full text Add to dashboard Cite

Oxidative insertion of [Pd(PPh3)4] or [Ni(cod)2]/PPh3 into the C-Cl bond of various 2-chloroimidazolinium- and other -amidinium salts affords metal-diaminocarbene complexes in good to excellent yields. This procedure is complementary to existing methodology in which the central metal does not change its oxidation state, and therefore allows to incorporate carbene fragments that are difficult to access otherwise. The preparation of a variety of achiral as well as enantiomerically pure, chiral metal-NHC complexes (NHC = N-heterocyclic carbene) and metal complexes with acyclic diaminocarbene ligands illustrates this aspect. Furthermore it is shown that oxidative insertion also paves a way to prototype Fischer carbenes of Pd(II). Since the required starting materials are readily available from urea- or thiourea derivatives, this novel approach allows for substantial structural variations of the ligand backbone. The catalytic performance of the resulting library of nickel- and palladium-carbene complexes has been evaluated by applications to prototype Suzuki-, Heck-, and Kumada-Corriu cross-coupling reactions as well as Buchwald-Hartwig aminations. It was found that even Fischer carbenes show appreciable catalytic activity. Moreover, representative examples of all types of neutral and cationic metal-carbene complexes formed in this study have been characterized by X-ray crystallography.

show abstract

“…The residue obtained after conventional work-up was subjected to column chromatography (hexane:ethyl acetate 5.22 (1H,dd,J ¼ 8.6,4.7 Hz,5.23 (1H,d,J ¼ 4.7 Hz,m,ArH),7.95 (1H,br s,NH); À 4.79, 13.83, 18.12, 25.83, 61.91, 63.14, 70.25, 73.94, 125.88, 126.12, 126.99, 127.12, 127.14, 127.20, 127.52, 127.58, 128.51, 128.52, 128.65, 138.43, 141.60, 142.58, 144.59, 152.78, 153.18 4.73,4.83 (each 1H,d,J ¼ 4.4 Hz,CH),5.15 (1H,d,J ¼ 3.8 Hz,5.52 (1H,dd,J ¼ 7.5,3.8 Hz,m,ArH),7.80 (1H, br s, NH); 13 C NMR: d ¼ 13. 74,62.20,63.15,70.47,73.58,78.40,125.90,126.13,127.29,127.46,127.50,127.56,127.66,127.72,128.26,128.74,138.28,139.82,142.13,143.77,153.25,154.34;IR (KBr) 23,62.78,64.33,69.65,72.94,...…”

Section: Experimental Section Generalmentioning

confidence: 99%

“…[5] We have explored the possibility of readily available modified guanidines [6] as re-useable chiral superbases in asymmetric synthesis. [7] The reaction of carbonyl compounds with TMSCN in the presence of a modified guanidine was examined in the course of our studies on guanidine chemistry and reasonable asymmetric induction was observed when a newly prepared C 2 -symmetrical bicyclic guanidine, (2S,3S,7S,8S)-tetraphenyl-1, 4,8-triaza[2.2.0]bicyclooct-4-ene, was used as a catalyst. In this paper we present the guanidine-catalyzed asymmetric trimethylsilylcyanation (TMS-cyanation) of carbonyl compounds.…”

Section: Introductionmentioning

confidence: 99%