Asymmetric Catalysis on the Intramolecular Cyclopropanation of α-Diazo-β-keto Sulfones

Honma, Masahiro; Sawada, Takashi; Fujisawa, Yuri; Utsugi, Masayuki; Watanabe, Hideaki; Umino, Akinori; Matsumura, Takehiko; Hagihara, Takayuki; Takano, Masashi; Nakada, Masahisa

doi:10.1021/ja029534l

Cited by 136 publications

(70 citation statements)

References 7 publications

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“…and 2,2-bis[(4S)-4-isopropyloxazolin-2-yl]-1,3-diphenylpropane, [38] as well as (4S)-2-bromo-4-benzyloxazoline, [39] (4R,5S)-2-bromo-4,5-indanediyloxazoline, [39] (4R)-2-bromo-4-phenyloxazoline [39] were synthesised according to literature procedures. 2,2-Bis[(4S)-4-isopropyloxazolin-2-yl]-4,4-dimethylpentan-3-one, 2,2-bis[(4S)-4-isopropyloxazolin-2-yl]-1-phenylpropan-1-one, 2,2-bis[(4S)-4-isopropyloxazolin-2-yl]-1,3-di(naphth-2-yl)propane and 2,2-bis[(4S)-4-isopropyloxazolin-2-yl]-1,3-di(pyrin-2-yl)propane were obtained according to previously published protocols.…”

Section: Resultsmentioning

confidence: 99%

Using a Tripod as a Chiral Chelating Ligand: Chemical Exchange Between Equivalent Molecular Structures in Palladium Catalysis with 1,1,1‐Tris(oxazolinyl)ethane (“Trisox”)

Foltz

Enders

Bellemin‐Laponnaz

et al. 2007

Chemistry A European J

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Threefold symmetrical chiral podands may simplify the stereochemistry of key catalytic intermediates for cases in which they only act as bidentate ligands. This applies to systems in which chemical exchange between the different kappa2-coordinated forms takes place and in which the non-coordinated sidearm may play a direct or indirect role at some earlier or later stage in the catalytic cycle. Palladium(II)-catalysed allylic substitutions provide appropriate test reactions along these lines. A series of neutral dichloropalladium(II) complexes, [PdCl2(iPr-trisox)] (1a), [PdCl2(Ph-trisox)] (1b), [PdCl2(Bn-trisox)] (1c) and [PdCl2(Ind-trisox)] (1d) (trisox=1,1,1-tris(oxazolinyl)ethane) were synthesised by reaction of the respective trisox derivative with [PdCl2(PhCN)2] and characterised inter alia by 15N NMR spectroscopy. Direct detection of the heteronuclei without isotope enrichment and with "normal" sample concentrations was achieved with the aid of a cryogenically cooled NMR probe on a 600 MHz NMR spectrometer. Whereas the 15N nuclei of the coordinated oxazoline rings resonate at delta=160-167 ppm and appear as two singlets due to their diastereotopicity, the signal assigned to the dangling oxazoline "arm" is observed at delta=238-240 ppm. Variable-temperature NMR studies along with a systematic series of magnetisation transfer experiments established exchange between ligating and non-ligating oxazoline rings. Reaction of [Pd(allyl)(cod)]BF4 (cod=cyclooctadiene) with Ph-trisox in CH(2)Cl(2) gave the corresponding allyl complex 2, for which fast exchange between the three oxazoline heterocycles as well as between the exo and endo diastereomers was observed along with a very slow eta3-eta1-eta3 process of the allyl fragment (magnetisation transfer). Palladium(0) complexes were prepared by reaction of trisox derivatives or sidearm-functionalised BOX (BOX=bis(oxazolinyl)dimethylmethane) ligands with [Pd(nbd)(alkene)] (nbd=norbornadiene, alkene=maleic anhydride or tetracyanoethylene). X-ray diffraction studies of the iPr-trisox and Ph-trisox complexes (3a and 3b) established Y-shaped trigonal planar coordination geometries with the trisox ligand coordinated in a bidentate fashion, whilst the pi-coordinated maleic anhydride ligand adopts one of the two possible diastereotopic orientations. As the catalytic test reaction, the allylic alkylation of 1,3-diphenylprop-2-enyl acetate substrate with dimethyl malonate as nucleophile (in the presence of N,O-bis(trimethylsilyl)acetamide) was investigated for the trisox derivatives, their BOX analogues, and a series of less symmetric "sidearm" functionalised bisoxazolines. The trisoxazoline-based catalysts generally induce a better enantioselectivity compared to their bisoxazoline analogues and display significant reduction of the induction period as well as rate enhancement.

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Section: Resultsmentioning

confidence: 99%

Using a Tripod as a Chiral Chelating Ligand: Chemical Exchange Between Equivalent Molecular Structures in Palladium Catalysis with 1,1,1‐Tris(oxazolinyl)ethane (“Trisox”)

Foltz

Enders

Bellemin‐Laponnaz

et al. 2007

Chemistry A European J

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“…To our knowledge, the only report of such an enantioselective cycloaddition (98% ee) is a Cu(I)-catalyzed intramolecular cyclopropanation of a-diazo-b-keto sulfones (Scheme 1). [3] Müller has also reported an enantioselective intramolecular cyclopropanation of a malonate derivative, however, the optimized conditions led to a product having 83% ee in only 24% yield (Scheme 1).…”

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Rhodium‐Catalyzed Asymmetric Intramolecular Cyclopropanation of Substituted Allylic Cyanodiazoacetates

Lin

Charette

2005

Adv Synth Catal

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A chiral rhodium catalyst, Rh 2 [4S-(4')-FBNAZ] 4 , was synthesized and was shown to catalyze the intramolecular cyclopropanation of substituted allylic cyanodiazoacetates. Alkenes bearing an electron-deficient substituent including carbonyl and halogens are converted into the corresponding cyclopropanes in high yields with both chiral and achiral rhodium catalysts. The cyclopropane derivatives were generated with an enantioselectivity of up to 91% ee. For the asymmetric intramolecular cyclopropanation, cis-halogen-substituted substrates afforded cyclopropanes with higher enantioselectivities than the corresponding trans diastereomers. However, only moderate enantioselectivities were observed with alkenes bearing electron-donating groups such as alkyls. The cyclopropanation of 3-substituted 2-propenyl cyanodiazoacetates was strongly influenced by steric and electronic factors arising from substituents on the alkenes. For the first time, we demonstrated that the intramolecular reaction of gem-dihaloallylic cyanodiazoacetate afforded highly functionalized gem-dihalocyclopropanes. This reaction is an appealing alternative to the addition of dihalocarbenes to alkenes for the formation of gem-dihalocyclopropanes.

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“…Therefore, we began to investigate asymmetric catalysis for the intramolecular cyclopropanation of a-diazo-b-keto sulfones because (a) the sulfonyl group is apparently sterically different from the keto group, implying that good enantioselectivity would emerge; (b) the sulfonyl group is a better surrogate for the ester group because of its utility; and (c) a-diazo-b-keto sulfones are easily prepared and stable, fulfilling the requirements for natural product synthesis. Only one example had been reported for the CAIMCP of a-diazo-b-keto sulfones prior to our report, 5,7,8 and the enantiomeric excess observed for 4a (see Table 1) was low at about 12% ee. 9 Therefore, we first examined the reaction of the simple substrate 3a in the presence of the easily accessible ligand 2a ( Table 1, entry 1).…”

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confidence: 52%

Development of Catalytic Asymmetric Intramolecular Cyclopropanation of α-Diazo-β-Keto Sulfones and Applications to Natural Product Synthesis

Honma¹,

Takeda²,

Takano³

et al. 2009

Synlett

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The catalytic asymmetric intramolecular cyclopropanation (CAIMCP) of a-diazo-b-keto sulfones developed in our laboratory and applications to the total synthesis of natural products are described. CAIMCP features (a) a wide applicability, not only to the preparation of bicyclo[n.1.0]alkanes and tricyclo[4.n.0.0]alkenes, but also to the enantioselective total synthesis of natural products, (b) the formation of highly crystalline products, which facilitate the production of enantiomerically pure synthetic intermediates, and (c) the generation of products with a variety of functionalities, such as cyclopropane, ketone, and sulfone, beneficial to the total synthesis of natural products.

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Asymmetric Catalysis on the Intramolecular Cyclopropanation of α-Diazo-β-keto Sulfones

Cited by 136 publications

References 7 publications

Using a Tripod as a Chiral Chelating Ligand: Chemical Exchange Between Equivalent Molecular Structures in Palladium Catalysis with 1,1,1‐Tris(oxazolinyl)ethane (“Trisox”)

Using a Tripod as a Chiral Chelating Ligand: Chemical Exchange Between Equivalent Molecular Structures in Palladium Catalysis with 1,1,1‐Tris(oxazolinyl)ethane (“Trisox”)

Rhodium‐Catalyzed Asymmetric Intramolecular Cyclopropanation of Substituted Allylic Cyanodiazoacetates

Development of Catalytic Asymmetric Intramolecular Cyclopropanation of α-Diazo-β-Keto Sulfones and Applications to Natural Product Synthesis

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