2,4,4,6-Tetrabromo-2,5-cyclohexadienone (TABCO), N-Bromosuccinimide (NBS) and Bromine as Efficient Catalysts for Dithioacetalization and Oxathioacetalization of Carbonyl Compounds and Transdithioacetalization Reactions
作者:Nasser Iranpoor、Habib Firouzabadi、Hamid Reza Shaterian、M. A. Zolfigol
DOI:10.1080/10426500211712
日期:2002.5.1
6-tetrabromo-2,5-cyclohexadienone (TABCO), N-bromosuccinimide (NBS), and bromine as efficient catalysts for conversion of carbonyl compounds to their cyclic and acyclic dithioacetals and 1,3-oxathiolanes under mild reaction conditions are described. These catalysts are also used for efficient transdithioacetalization of acetals, diacetals, ketals, acylals, enamines, hydrazones, and oximes with high
2,4,4,6-Tetrabromo-2,5-cyclohexadienone (TABCO) as a Versatile, Efficient, and Chemoselective Catalyst for the Acetalization and Transacetalization of Carbonyl Compounds, the Preparation of Acetonides from Epoxides and Acylals (1,1-Diacetates) from Aldehydes
The efficient and chemoselective preparation of acetals and ketals from carbonyl compounds, transacetalization reactions, the conversion of epoxides to acetonides, and the preparation of acylals from aldehydes in the presence of catalytic amounts of 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TABCO) are described.
18O-isotope effect in13C nuclear magnetic resonance spectroscopy: 5—Substituent group electronic effects in substituted acetophenones
作者:John M. Risley、Shawn A. DeFrees、Robert L. Van Etten
DOI:10.1002/omr.1270210108
日期:1983.1
AbstractA series of para‐ and meta‐substituted acetophenones were prepared which were highly labeled with 18O at the carbonyl function. The natural abundance 13C NMR spectra of the compounds were recorded and the 18O‐isotope‐induced shifts of the carbonyl carbon were measured in order to determine possible substituent group electronic effects on the 18O‐isotope shift. The isotope shifts were found to be correlated with a number of properties which demonstrate the molecular basis of the isotope shift. Good correlations were obtained for the isotope shift as a function of σp+, the carbonyl stretching frequency, the carbonyl group bond order, the n→π**transition of the carbonyl group and the chemical shift of the ipso carbon. In contrast, no correlation was observed between the magnitude of the 18O‐induced isotope shift and the 13C chemical shift of the carbonyl carbon. These properties are discussed in connection with the theoretical basis of the isotope shift.
Pd(II)-Catalyzed Conversion of Styrene Derivatives to Acetals: Impact of (−)-Sparteine on Regioselectivity
作者:Amy M. Balija、Kara J. Stowers、Mitchell J. Schultz、Matthew S. Sigman
DOI:10.1021/ol053110p
日期:2006.3.1
Pd[(-)-sparteine]Cl-2 catalyzes the formation of dialkyl acetals from styrene derivatives with Markovnikov regioselectivity. The substrate scope of this reaction has been investigated, and initial mechanistic studies indicate that the reaction proceeds through an enol ether intermediate and a Pd-hydride.