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1012-72-2 Bond Fixation in Annulenes. 14. Synthesis of and Bond Shifting Equilibrium between 1,4- and 1,6-Di-tert-butylcyclooctatetraenes

https://www.lookchem.com/CASDataBase_1012-72-2.htm Photolysis of the Diels-Alder adduct of 3,6-di-tert-butyl-o-benzoquinone and cyclobutadiene at ice-bath temperatures afforded the bicyclooctatriene 12.During warming to room temperature, this hydrocarbon underwent kinetically first-order valence isomerization to provide 5 and its bond shift isomer 4.This finding adumbrated the facility with which 4 and 5 are interconverted.Reaction of this cyclooctatetraene mixture with N-methyltriazolinedione gave urazoles 16 and 17 as chromatographically separable entities.Like 13, the related cycloadduct of 12 wherein both bridgehead tert-butyl groups exhibit restricted rotation , the angular tert-butyl substituent in 17 is sterically perturbed.Hydrolysis-oxidation of either 16 or 17 returned only mixtures of 4 and 5 because of their rapid bond shifting rates.When the equilibrium constant between these two isomers was determined by 1H NMR spectroscopy, it was found that 5, the apparently more conges...
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732-26-3 Chemistry of Sulfenic Acids. 3. Studies of Sterically Hindered Sulfenic Acids Using Flash Vacuum Pyrolysis

https://www.lookchem.com/CASDataBase_732-26-3.htm Flash vacuum pyrolysis (FVP) of sulfoxides containing β-hydrogen atoms affords sulfenic acids (RSOH) in good concentration under conditions where they are stable.The application of this technique to the synthesis and study of sterically hindered sulfenic acids 12a-e is described.The principal or primary reaction of simple sulfenic acids prepared in this manner is dehydration to thiosulfinates 13 (eq 1).Steric inhibition to dehydration (eq 1) appears to only be of importance for 2-methyl-2-propanesulfenic acid (12a) which was trapped in good yield with methyl propiolate to afford 16a. 2,4,6-Tri-tert-butylbenzenesulfenic acid (12e) appears to be destabilized as a consequence of interaction between the SOH and adjacent tert-butyl groups.In the pyrolysis section of the apparatus, 12e decomposes to phenol 21 and aryl radical 22, which reacts further.Thermolysis of sulfoxides generates the sulfenic acids 12a-e in very low concentration at any...
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1020-31-1 SEMI-HINDERED PHENOLS. 1. SYNTHESIS OF 3,5-DI-TERT-BUTYLSALICYLIC ALDEHYDE

 https://www.lookchem.com/CASDataBase_1020-31-1.htm Some differences were observed in the solid- and liquid-phase benzylic oxidation of 2-(hydroxy- or dialkylamino)methyl-4,6-di-tert-butylphenols.Oxidation of these semi-hindered phenols with lead tetraacetate gave a new compound: 3,5-di-tert-butyl-ortho-benzoquinone diacylal.Keywords: semi-hindered phenols, synthesis, aldehyde, benzylic alcohol, oxidation, liquid phase, solid phase.
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10326-41-7

 https://www.lookchem.com/CASDataBase_10326-41-7.htm Rac-α-bromo acids, rac-4, have been converted into(R)- or(S)-α-hydroxy acids, (R)- or (S)-9 by DCC-induced esterification with the chiral auxiliaries (R)or (S)-1, followed by reaction with sodium p-methoxyphenoxide in the presence of tetra-n-hexylammonium iodide, conditions of dynamic kinetic resolution, to give quite diastereoselectively the (αR,3S)- or (αS,3R)-α-(p-methoxyphenoxy) esters, 7, which were then oxidized with eerie ammonium nitrate and hydrolyzed under controlled acid conditions. 
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75-90-1 Hemiaminals of trifluoroacetaldehyde, as trifluoromethylating agents

https://www.lookchem.com/CASDataBase_75-90-1.htm Hemiaminals of trifluoroacetaldehyde are new trifluoromethylating agents. These reagents are synthesised from amines and gaseous trifluoroacetaldehyde. tBuONa is able to deprotonate the hemiaminals to form trifluoromethyl anion equivalents CF 3 CH(O - )NMe 2 . The trifluoromethyl anion has been transferred from such intermediates to benzaldehyde yielding phenyl (trifluoromethyl) methanol.
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7440-38-2 Etching AlAs with HF for epitaxial lift-off applications

https://www.lookchem.com/CASDataBase_7440-38-2.htm The epitaxial lift-off process allows the separation of a thin layer of III/V material from the substrate by selective etching of an intermediate AlAs layer with HF In a theory proposed for this process, it was assumed that for every mole of AIAs dissolved three moles of H 2  gas are formed. In order to verify this assumption the reaction mechanism and stoichiometry were investigated in the present work. The solid, solution and gaseous reaction products of the etch process have been examined by a number of techniques, It was found that aluminum fluoride is formed, both in the solid form as well as in solution. Furthermore, instead of H 2  arsine (AsH 3 ) is formed in the etch process. Some oxygen-related arsenic compounds like AsO, AsOH, and AsO 2  have also been detected with gas chromatography/mass spectroscopy. The presence of oxygen in the etching environment accelerates the etching process, while a total absence of o...
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17480-69-2 Prolinol as a Chiral Auxiliary in Organophosphorus Chemistry

https://www.lookchem.com/CASDataBase_17480-69-2.htm Several strategies for the development of the synthesis of P-chiral organophosphorus compounds with (L)-prolinol as a source of chirality have been examined. A reaction of L-prolinol with a set of different alkyl/arylphosphonous acid diamides led in most of the cases to the quantitative formation of the appropriate bicyclic oxazaphospholidines with complete diastereo and enantioselectivity. The latter were reacted with BH 3  complex and the formed borane analogues were submitted to structural modifications leading to tertiary phosphine-boranes. Additionally, the effectiveness of oxazaphospholidines as ligands in transition metal asymmetric catalysis has been tested in hydrogenation of dehydroaminoacid esters and imine. 
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