- Asymmetric Aza-Wacker-Type Cyclization of N-Ts Hydrazine-Tethered Tetrasubstituted Olefins: Synthesis of Pyrazolines Bearing One Quaternary or Two Vicinal Stereocenters
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We have developed an asymmetric aza-Wacker-type cyclization of N-Ts hydrazine-tethered tetrasubstituted olefins, affording optically active pyrazolines bearing chiral tetrasubstituted carbon stereocenters. This reaction is tolerant to a broad range of substrates under mild reaction conditions, giving the desired chiral products with high enantioselectivities. Generation of two vicinal stereocenters on the C=C double bonds was also achieved with high selectivities, a process which has been rarely studied for Wacker-type reactions. A mechanistic study revealed that this aza-Wacker-type cyclization undergoes a syn-aminopalladation process. It was also found that for substrates bearing two linear alkyl substituents on the outer carbon atom of the olefin, both of which are larger than a methyl group, the alkyl substituent that is cis to the intranucleophilic group participates more readily in β-hydride elimination. When one of the two alkyl substituents on the outer carbon atom of the olefin is a methyl group, β-hydride elimination proceeds selectively at the methylene side, thus both diastereomers can be prepared via switching the configuration of the olefin. Furthermore, the product can be converted to a pharmaceutical compound in high yields over three steps.
- Kou, Xuezhen,Shao, Qihang,Ye, Chenghao,Yang, Guoqiang,Zhang, Wanbin
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supporting information
p. 7587 - 7597
(2018/06/04)
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- 2-AMINO-1,3,4-THIADIAZINE AND 2-AMINO-1,3,4-OXADIAZINE BASED ANTIFUNGAL AGENTS
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The invention provides a compound which is a diazine of formula (I) or a tautomer thereof, or a pharmaceutically acceptable salt thereof, for use as an antifungal agent: (I) wherein X, N', C', A and E are as defined herein. The invention also provides a compound of Formula (I) as defined herein.
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Page/Page column 55
(2017/02/09)
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- Nano-K2CO3: Preparation, characterization and evaluation of reactive activities
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A novel base, nano-K2CO3, was easily prepared by ultrafine wet milling. The surface properties and the reactive activities of nano-K2CO3 were characterized. It was found that such a base showed higher basicity than normal K2CO3 and could replace sodium (or potassium) alkoxide to carry out monoalkylation and oximation of active methylene compounds. The nano-K2CO3 could be regenarated and reused 10 times without loss of its reactive activity.
- Li, Jun-Zhang,Fan, Shi-Ming,Sun, Xuan-Fei,Liu, Shouxin
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p. 1865 - 1869
(2016/01/20)
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- Synthesis of Potential Bioactive Novel 7-[2-Hydroxy-3-(1,2,3-triazol-1-yl) propyloxy]-3-alkyl-4-methylcoumarins
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A series of 50 novel 7-[2-hydroxy-3-(1,2,3-triazol-1-yl)propyloxy]-3-alkyl-4-methylcoumarins had been designed and synthesized in good to excellent yields via Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction "click chemistry" of 7-(3-azido-2-hydroxypropyloxy)-3-alkyl-4-methylcoumarins with variety of acetylene derivatives. In turn, the precursor compound, that is, 7-(3-azido-2-hydroxypropyloxy)-3-alkyl-4-methylcoumarin, was synthesized by condensation of epichlorohydrin with 7-hydroxy-3-alkyl-4-methylcoumarins followed by opening of the epoxide ring in the resulted 7-epoxymethoxy-3-alkyl-4-methylcoumarins with sodium azide. All the synthesized compounds were unambiguously identified on the basis of their spectral data analyses (IR, 1H-NMR, 13C-NMR spectra, and HRMS).
- Arya, Anu,Kumar, Vinod,Mathur, Divya,Singh, Sukhdev,Brahma, Raju,Singh, Rajpal,Singh, Seema,Sharma,Parmar, Virinder S.,Prasad, Ashok K.
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- Manganese(III)-promoted tandem oxidation and cyclization of β-keto ester derivatives of terpenoids
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A new type of terpenoid cyclization directed by a β-keto ester moiety has been developed, which proceeded by manganese(III)-initiated oxidation of the β-keto ester, followed by an intramolecular hetero Diels-Alder reaction with the terpenoid chain. This reaction produces polycyclic dihydropyrans in high yields and stereoselectivities under mild conditions. Copyright
- Li, Zhilong,Jung, Heejung,Park, Mira,Lah, Myoung Soo,Koo, Sangho
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supporting information; experimental part
p. 1913 - 1917
(2011/10/08)
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- Specificities of Calreticulin Transacetylase to acetoxy derivatives of 3-alkyl-4-methylcoumarins: Effect on the activation of nitric oxide synthase
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Calreticulin Transacetylase (CRTAase) catalyzes the transfer of acetyl groups from polyphenolic acetates (PAs) to the receptor proteins and modulates their biological activities. CRTAase was conveniently assayed by the irreversible inhibition of cytosolic glutathione S-transferase (GST) by the model acetoxycoumarin, 7,8-diacetoxy-4-methylcoumarin (DAMC). We have studied earlier, the influence of acetoxy groups on the benzenoid ring, the effect of reduction of double bond at C-3 and C-4 position, the effect of methyl/phenyl group at C-4, and the influence of position of carbonyl group with respect to oxygen heteroatom in the benzopyran nucleus, for the catalytic activity of CRTAase. In this communication, we have extended our previous work; wherein we studied the influence of an alkyl group (ethyl, hexyl and decyl) at the C-3 position of the acetoxy coumarins on the CRTAase activity. The substitution at C-3 position of coumarin nucleus resulted in the reduction of CRTAase activity and related effects. Accordingly the formation of NO in platelets by C-3 alkyl substituted acetoxy coumarins was found to be much less compared to the unsubstituted analogs. In addition the alkyl substitution at C-3 position exhibited the tendency to form radicals other than NO.
- Kathuria, Abha,Gupta, Anjali,Priya, Nivedita,Singh, Prabhjot,Raj, Hanumantharao G.,Prasad, Ashok K.,Parmar, Virinder S.,Sharma, Sunil K.
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experimental part
p. 1550 - 1556
(2009/08/07)
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- Asymmetric synthesis of 2-substituted butane-1,4-diols by hydrogenation of homochiral fumaramide derivatives
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Diastereoselective hydrogenation of homochiral fumaramides 1 derived from (2R)-Oppolzer's sultam was observed by analysis of the 1H NMR spectra of the succinamide mixtures with de's of 77-88%. Reduction of these succinamides using LiAlH4 gave the corresponding (2S)-butane-1,4- diols and established that addition of hydrogen takes place selectively on the re-face of fumaramides 1. The stereoselectivity was confirmed by estimating the ee's from the 19F NMR spectra of the Mosher's diesters of the diols. This methodology was applied to the synthesis of selected pyrrolidine natural products in homochiral form.
- Jawaid, Samaila,Farrugia, Louis J.,Robins, David J.
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p. 3979 - 3988
(2007/10/03)
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- Beta-ketoester compounds
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The beta-ketoesters of formula I are useful as precursors for organoleptic compounds, especially for flavors, fragrances and masking agents and antimicrobial compounds.
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Page column 13
(2010/11/30)
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- Beta-ketoester compounds
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The beta-ketoesters of formula I are useful as precursors for organoleptic compounds, especially for flavors, fragrances and masking agents and antimicrobial compounds.
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- Reactions of N-Substituted Pyridinium Cations with Carbanions: 5,6,8,9-Tetrahydro-7-phenylbisbenzoacridine, a Superior Leaving Group
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N-Substituents are transferred from pyridinium cations to malonate, cyanoacetate , and acetoacetate carbanions: for alkyl substituents the pentacyclic derivatives (4) attain the required activity.
- Katritzky, Alan R.,Thind, Sukhpal S.
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p. 661 - 663
(2007/10/02)
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