- Pendant Alkoxy Groups on N-Aryl Substitutions Drive the Efficiency of Imidazolylidene Catalysts for Homoenolate Annulation from Enal and Aldehyde
-
Hydrogen-transfer in the tetrahedral intermediate generated from an imidazolylidene catalyst and α,β-unsaturated aldehyde forms a conjugated Breslow intermediate. This is a critical step affecting the efficiency of the NHC-catalyzed γ-butyrolactone formation via homoenolate addition to aryl aldehydes. A novel type of imidazolylidene catalyst with pendant alkoxy groups on the ortho-N-aryl groups is described. Catalyst of this sort facilitates the formation of the conjugated Breslow intermediate. Studies of the rate constants for homoenolate annulation affording γ-butyrolactones, reveal that introduction of the oxygen atoms in the appropriate position of the N-aryl substituents can increase the efficiency of imidazolylidene catalysts. Structural and mechanistic studies revealed that pendant alkoxy groups can be located close to the proton of the tetrahedral intermediate, thereby facilitating the proton transfer.
- Kyan, Ryuji,Mase, Nobuyuki,Narumi, Tetsuo,Sato, Kohei
-
supporting information
p. 19031 - 19036
(2020/08/25)
-
- Expeditious synthesis of benzopyrans via lewis acid-catalyzed C-H functionalization: Remarkable enhancement of reactivity by an ortho substituent
-
An expeditious construction of a benzopyran skeleton via Lewis acid-catalyzed C-H functionalization was achieved. In this process, a [1,5] hydride shift and 6-endo cyclization successively occurred to give benzopyrans. The presence of substituents ortho to the alkoxy group significantly enhanced the reactivity, affording the desired compounds in excellent chemical yields with short reaction times.
- Mori, Keiji,Kawasaki, Taro,Sueoka, Shosaku,Akiyama, Takahiko
-
supporting information; experimental part
p. 1732 - 1735
(2010/09/05)
-
- Carbamic acid 2-trimethylsilylethyl ester as a new ammonia equivalent for palladium-catalyzed amination of aryl halides
-
Carbamic acid 2-trimethylsilylethyl ester (Teoc-NH2) serves as an ammonia equivalent in the palladium-catalyzed amination of aryl bromides and aryl chlorides. Anilines with sensitive functional groups can be readily prepared using these amine derivatives.
- Mullick, Dibakar,Anjanappa, Prakash,Selvakumar, Kumaravel,Ruckmani, Kandasamy,Sivakumar, Manickam
-
supporting information; experimental part
p. 5984 - 5987
(2010/11/21)
-
- Synthesis and structure-activity relationships of a series of benzazepine derivatives as 5-HT2C receptor agonists
-
To identify potent and selective 5-HT2C receptor agonists, a series of novel benzazepine derivatives were synthesized, and their structure-activity relationships examined. The compounds were evaluated for their 5-HT2C, 5-HT2A/s
- Shimada, Itsuro,Maeno, Kyoichi,Kondoh, Yutaka,Kaku, Hidetaka,Sugasawa, Keizo,Kimura, Yasuharu,Hatanaka, Ken-ichi,Naitou, Yuki,Wanibuchi, Fumikazu,Sakamoto, Shuichi,Tsukamoto, Shin-ichi
-
p. 3309 - 3320
(2008/09/20)
-
- New staves for old barrels: Regioisomeric (12,2 2,33,42,53,62,7 3,82)-p-octiphenyl rods with an NMR tag
-
The usefulness of rigid-rod p-octiphenyls with the novel 1 2,22,33,42,53,6 2,73,82-motif as staves in rigid-rod β-barrel pores is evaluated. Comparison with the known
- Ronan, Dawn,Jeannerat, Damien,Pinto, Andre,Sakai, Naomi,Matile, Stefan
-
p. 168 - 176
(2007/10/03)
-
- HIV INHIBITING 1,2,4-TRIAZIN-6-ONE DERIVATIVES
-
The present invention relates to HIV replication inhibitors of formula (I) a N-oxide, a pharmaceutically acceptable addition salt, a quaternary amine or a stereochemically isomeric form thereof, wherein ring A and ring B represent phenyl, pyridyl, pyridaz
- -
-
Page/Page column 54-55
(2008/06/13)
-
- Synthesis of the spirocyclic cyclohexadienone ring system of the schiarisanrins.
-
[structure: see text] Studies on the synthesis of the spirocyclic cyclohexadienone ring system 2 of the schiarisanrin family of natural products 1 are described and were based on the Lewis acid-promoted C-alkylation of the corresponding phenolic precursor.
- Coleman,Guernon,Roland
-
p. 277 - 280
(2007/10/03)
-
- Collisionally induced dissociation in the study of A-ring hydroxylated vitamin D type compounds
-
Colllslonally Induced dissociation (CID) is often used to determine the structure of ions based on comparison with the CID spectra of known ions. The latter are generated from Judiciously selected compounds taking into account basic principles of Ion chemistry. We report here on the use of this approach toward determination of the site of A-ring hydroxylation of vitamin D. Although not Intrinsically an aromatic compound, vitamin D gives rise in its mass spectrum to an aromatic methytstyryl cation at mlz 118. A-ring hydroxylated metabolites of vitamin D would thus Incorporate the extra OH group on the ion at mlz 118, shifting it to mlz 134. The position of substitution of the extra OH group on a metabolite could then be ascertained by comparing the CID spectrum of its mlz 134 fragment to those of the four possible (hydroxymethyl)styryl cations generated from synthesized authentic compounds. Because of their propensity to polymerize, these cations were generated in situ via the McLafferty rearrangement of the corresponding (hydroxyphenyl)ethanols. For optimum differentiation of Isomeric Ions, preparation of permethylated derivatives of vitamin D was necessary. The validity of the hypothesis was verified using 1,25-dihydroxy-vitamin D3 as a test compound. This method provides a viable approach for the characterization of A-ring hydroxylated metabolites of vitamin D as well as for related aromatic compounds.
- Young, David C.,Vouros, Paul,Holick, Michael F.,Higuchi, Tetsuo
-
p. 837 - 842
(2007/10/02)
-