- Enantioselective Kinetic Resolution/Desymmetrization of Para-Quinols: A Case Study in Boronic-Acid-Directed Phosphoric Acid Catalysis
-
A chiral phosphoric acid-catalyzed kinetic resolution and desymmetrization of para-quinols operating via oxa-Michael addition was developed and subsequently subjected to mechanistic study. Good to excellent s-factors/enantioselectivities were obtained over a broad range of substrates. Kinetic studies were performed, and DFT studies favor a hydrogen bonding activation mode. The mechanistic studies provide insights to previously reported chiral anion phase transfer reactions involving chiral phosphate catalysts in combination with boronic acids. (Figure presented.).
- Huang, Banruo,He, Ying,Levin, Mark D.,Coelho, Jaime A. S.,Bergman, Robert G.,Toste, F. Dean
-
supporting information
p. 295 - 301
(2019/11/03)
-
- Heterogeneous phase alkylation of phenols making use of phase transfer catalysis and microwave irradiation
-
The benzylation of cresol was studied under liquid-liquid and solid-liquid phase transfer catalytic conditions. Microwave irradiation was useful only in the solid-liquid phase benzylations. Using acetonitrile as the solvent, the benzylations were fully O-selective, but complete conversions were obtained only in the presence of Cs2CO3. There was no need to use an onium salt. In the absence of solvent, an O-selectivity of ca. 90% could be obtained in the presence of an alkali carbonate and an onium salt. The optimum set of conditions was extended to the reaction of other phenol derivatives and alkylating agents.
- Keglevich, Gyoergy,Balint, Erika,Karsai, Eva,Varga, Judit,Gruen, Alajos,Balint, Maria,Greiner, Istvan
-
experimental part
p. 535 - 539
(2010/04/23)
-
- Zirconia-modified superacid UDCaT-5: An efficient and versatile catalyst for alkylation reactions under solvent-free conditions
-
UDCaT-5, a modified version of zirconia, efficiently catalyzes alkylation of phenols with alcohols under environmentally safe, heterogeneous reaction conditions with high selectivity and in excellent yields. The high content present in UDCaT-5 with preservation of tetragonal phase of zirconia was responsible for the superactivity. Several phenolic compounds carrying either electron-sulfer releasing or electron-withdrawing substituents in the ortho, meta, and para positions afforded high yields of the products. Copyright Taylor & Francis Group, LLC.
- Yadav, Ganapati D.,Pathre, Ganesh S.
-
p. 2684 - 2691
(2008/12/22)
-
- The structure and synthesis of tsitsikammafuran: A new furanosesquiterpene from a south african Dysidea sponge
-
Three furanosesquiterpenes, the new tsitsikammafuran (1) and the known nakafurans-8 (2) and -9 (3) were isolated from a South African Dysidea sponge. The structure of tsitsikammafuran, initially proposed as 3-[(furan-3-yl)methyl]-p-cymene, from a combination of biosynthetic arguments and the available spectroscopic data, was unequivocally confirmed by the synthesis of 1 from thymol. The synthesis of two regioisomers of tsitsikammafuran, 4-[(furan-3-yl)methyl]-m-cymene (4) and 2-[(furan-3-yl)methyl]-p-cymene (22), from p-cresol and 2-bromo-2-nitrocamphane respectively, further supported the structural assignment of 1. (C) 2000 Elsevier Science Ltd.
- McPhail, Kerry L.,Rivett, Douglas E.A.,Lack, David E.,Davies-Coleman, Michael T.
-
p. 9391 - 9396
(2007/10/03)
-
- Lewis Acids Catalysed Fries Rearrangement of Isopropylcresol Esters
-
In the course of the Fries rearrangement, aluminium chloride frequently induces migration or elimination of alkyl groups.The results obtained with titanium tetrachloride for the synthesis of vicinal o-hydroxyketones are compared with those obtained with aluminium chloride for some aliphatic and aromatic esters of isopropylcresols.In order to understand the migration and elimination processes occurring, the stabilities of the o-hydroxyketones are studied in the presence of aluminium chloride at different temperatures.Furthermore, all-vicinal o-hydroxyketones were prepared by the Fries rearrangement of 6-tert-butyl-p-thymol with titanium tetrachloride.
- Martin, Robert,Demerseman, Pierre
-
p. 227 - 236
(2007/10/02)
-
- Arylazoarylazo-substituted azo, azomethine 1:2 chromium complex dyes
-
1:2 Chromium complex dyes of the formula STR1 wherein A is the radical of a diazo component of the benzene or naphthalene class which carries the complex forming group X in ortho-position to the azo group, B is the radical of a coupling component which couples in ortho-position to the oxy group, D is the radical of an amine of the benzene or naphthalene class which carries the complex-forming group in ortho-position to the azo group, X is an oxygen atom or a --CO--O-- group, Ar is an aromatic carbocyclic radical. Ar' and A" are aromatic carbocyclic or heterocyclic radicals, q is an integer from 0 to 5, n is an integer from 1 to 3, m is an integer from 0 to 2 and p is 0 or 1, but the sum of n+m may be at most 3, and wherein the benzene ring can carry a further fused benzene ring or can be substituted by halogen, nitro, alkyl or alkoxy, and K+ is a cation. The water-insoluble dyes are useful in dyeing polyamide textile material and for coloring leather, oil vanishes, and paper as well as viscose, polyamide, cellulose ether and cellulose ester spinning compositions, and the water-soluble dyes are useful in dyeing leather, wool, silk, casein, polyamide and polyurethane fibers and furs; and the dyes possess good covering power and fastness properties.
- -
-
-
- Isothymol: Synthesis and Biogenesis
-
Isothymol (I), the C10-analogue of elvirol (II), has been synthesized from 2-hydroxy-5-methylacetophenone, and synthetic (I) is shown to be identical with natural isothymol.A probable biogenesis of I has been suggested.
- Dinge, A. S.,Kirtany, J. K.,Paknikar, S. K.
-
p. 245 - 246
(2007/10/02)
-
- Chromium complex dye, including azo and azo methine dye compounds
-
1:2 Chromium complex dyes of an azo compound of the formula STR1 and an azomethine compound of the formula STR2 COMPLEXED TO A CHROMIUM ATOM, WHEREIN A is an ortho-phenylene or -- naphthylene diazo component radical; B is an ortho-phenylene or -- naphthylene coupling component radical; X is --O-- or --CO--O--; X' is --O--, --NH--, --N(lower alkyl)--, --N(aralkyl)-- or --N(aryl)--; R is an aliphatic radical; the benzene ring "a" is unsubstituted or substituted by a fused benzene ring, halo, nitro alkyl or alkoxy; the molecule containing 0-5 water solubilizing groups and optionally a group of the formula --N=N--Ar--N=N--Ar' and/or -N=N--Ar" wherein Ar, Ar' and Ar" represent an aromatic or carbocyclic radical.
- -
-
-