- Restricted Rotation Involving the Tetrahedron Carbon. XLIII. Buttressing Effect on Rotational Barriers in Bromine-substituted 9-(2-Methoxy-4,6-dimethylphenyl)fluorenes
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9-(2-Methoxy-4,6-dimethylphenyl)fluorenes carrying one or two bromo groups on the phenyl ring were prepared and the buttressing effect on the rotational barrier about the C9-Cph bond were investigated.The free energies of activation
- Aoki, Masahiro,Nakamura, Mikio,Oki, Michinori
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- Electrophilic aryl-halogenation using N-halosuccinimides under ball-milling
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We report here a methodology of chemo- and regio-selective aryl bromination and iodination using respective N-halosuccinimides at room temperature in the absence of any solvents, catalyst/additives under ball-milling condition. However, for chlorination ceric ammonium nitrate was used as additive. The coupled product succinimide, produced from the reactions, was recycled via regeneration of NBS. This methodology works with the electron-donor substituted or unsubstituted arenes.
- Bose, Anima,Mal, Prasenjit
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supporting information
p. 2154 - 2156
(2015/03/18)
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- Electrophilic aryl-halogenation using N-halosuccinimides under ball-milling
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We report here a methodology of chemo- and regio-selective aryl bromination and iodination using respective N-halosuccinimides at room temperature in the absence of any solvents, catalyst/additives under ball-milling condition. However, for chlorination ceric ammonium nitrate was used as additive. The coupled product succinimide, produced from the reactions, was recycled via regeneration of NBS. This methodology works with the electron-donor substituted or unsubstituted arenes.
- Bose, Anima,Mal, Prasenjit
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supporting information
p. 2154 - 2156
(2014/04/03)
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- Synthesis of deuterated benzopyran derivatives as selective COX-2 inhibitors with improved pharmacokinetic properties
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We designed a series of specifically deuterated benzopyran analogues as new COX-2 inhibitors with the aim of improving their pharmacokinetic properties. As expected, the deuterated compounds retained potency and selectivity for COX-2. The new molecules possess improved pharmacokinetic profiles in rats compared to their nondeuterated congeners. Most importantly, the new compounds showed pharmacodynamic efficacy in several murine models of inflammation and pain. The benzopyran derivatives were separated into their enantiomers, and the activity was found to reside with the S-isomers. To streamline the synthesis of the desired S-isomers, an organocatalytic asymmetric domino oxa-Michael/aldol condensation reaction was developed for their preparation.
- Zhang, Yanmei,Tortorella, Micky D.,Wang, Yican,Liu, Jianqi,Tu, Zhengchao,Liu, Xiaorong,Bai, Yang,Wen, Dingsheng,Lu, Xin,Lu, Yongzhi,Talley, John J.
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p. 1162 - 1166
(2014/12/10)
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- Hindered organoboron groups in organic chemistry. 27. Preparations and some properties of alkylbis(2,6-dimethyl-4-methoxyphenyl)boranes ((DMP)2BR)
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Akylbis(2,6-dimethyl-4-methoxyphenyl)boranes ((DMP)2BR) have been synthesized in an attempt to overcome the limitations of the steric hindrance approach to the production of boron stabilised carbanions. Anion production from (DMP)2BR, followed by alkylations and condensations with aldehydes are reported. Reduction of (DMP)2F with potassium hydride yields the corresponding hydroborate. Attempts to isolate (DMP)2BH were unsuccessful but the borane was readily trapped with alkynes, yielding alkenylboranes. The allyl derivative, (DMP)2BAllyl, was made and some of its reactions were investigated.
- Pelter, Andrew,Drake, Robert
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p. 13775 - 13800
(2007/10/02)
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- Reductive cleavage of the carbon-phosphorus bond with alkali metals. I. Cleavage of functionalised triphenylphosphines; formation of secondary and primary phosphines
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The reductive cleavage reaction of functionalised triphenylphosphines 1-34 with Na/NH3 and Li/THF depends strongly on the nature of the functionality and on the reducing agent. No reduction occurs with 11, 24, 30, 31 and 32 in Na/NH3.Compounds 3, 4, 5, 10, 12, 13, 15, 19, 23, 25, 26 and 27 cleave to give the secondary phosphide in high yield with Na/NH3, whereas 2, 7 and 9 give a high yield with Li/THF.Reduction occurs but cleavage is poor with 6, 7, 14, 29 and 34 and Na/NH3, or with 11 and Li/THF.Primary ortho-functionalised phenyl phosphines are obtained by a double cleavage reduction from 2, 5, 12, 25, 26 and 27 with Na/NH3.This unprecedented reaction proceeds via the secondary phosphine, which is formed by protonation of the corresponding phosphide with NH3.It occurs when the aryl group contains a strongly electron-donating substituent.Multiple cleavage of aryl groups with extended ? systems occurs with 7 and 34 when they are made to react with Li/THF.Halogens are cleaved from the phenyl group (16, 17, 18, 28 and 33, with Na/NH3), whereas SCH3 groups are converted to the corresponding mercapto group (20, 21 and 22).Birch reduction (2 and 10) can take place in NH3 but not in the aprotic solvent THF; it occurs only when other reactions are slow.Sodium amide is obtained via reaction of 8 in Na/NH3.Restricted Hartree-Fock calculations were carried out for a number of substituted phenylphosphines.From the correlation between the energies and coefficients of the LUMO (always an aryl ?* orbital) and the experimental cleavage data, it was concluded that there are three requirements for successful cleavage.The LUMO energy should be neither too high (no reduction) nor too low (radical anion too stable) and, further, the coefficient of the LUMO on the carbon attached to phosphorus must be large.
- Budzelaar, Peter H. M.,Doorn, Johannes A. van,Meijboom, Nico
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p. 420 - 432
(2007/10/02)
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- Bromination of 2,6-Dimethyl-4-methoxybenzyl Alcohol Derivatives
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The reaction of 2,6-dimethyl-4-methoxybenzyl alcohols, ethyl ethers, and acetates, possessing electrondonating and -withdrawing groups at the benzylic position, with bromine water was studied at different temperatures.The reaction was strongly affected by the electronegativity of a benzyl substituent to afford bromination products of aromatic nuclei and 2,4-dibromo-3,5-dimethylmethoxybenzene along with 2,4,6-tribromo derivatives formed by the cleavage of C-C bond.
- Nakatani, Munehiro,Takahashi, Kimi,Watanabe, Sumie,Shintoku, Atsuko,Hase, Tsunao
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p. 1510 - 1514
(2007/10/02)
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