A Synthetic Route to α-Substituted Butenolides: Enantioselective Synthesis of (+)-Ancepsenolide
作者:Cynthia Ghobril、Jérémy Kister、Rachid Baati
DOI:10.1002/ejoc.201100491
日期:2011.7
A variety of α-substituted butenolides was efficiently synthesized starting from commercially available tetronic acid and carboxylic acids in four steps. The effectiveness of this approach is illustrated in the short synthesis of one of the first butenolide acetogenins: (+)-ancepsenolide.
Conversion of a hydroxy group in certain alcohols into a fluorosulfonate ester or a trifluoromethylsulfonate ester
申请人:——
公开号:US06395918B1
公开(公告)日:2002-05-28
The present invention provides a method of converting a hydroxy group in alcohols containing an electron withdrawing group into perfluoroalkane sulfonate and fluorosulfonate esters, which are good leaving groups, with inversion of configuration where the hydroxyl-bearing carbon is chiral. The method consists of converting an alcohol to an O—N,N-dialkylsulfamate ester and reacting it with a perfluoroalkansulfonic or fluorosulfonic acid. The method has applications in the synthesis of pharmaceutical and agrochemical compounds.
Bi(OTf)(3)-catalyzed acylation of alcohols with acidanhydride was evaluated in comparison with other acylation methods. The Bi(OTf)(3)/acidanhydride protocol was so powerful that sterically demanding or tertiary alcohols could be acylated smoothly. Less reactive acylation reagents such as benzoic and pivalic anhydride are also activated by this catalysis. In these cases, a new technology was developed
Rh−DuPHOS-Catalyzed Enantioselective Hydrogenation of Enol Esters. Application to the Synthesis of Highly Enantioenriched α-Hydroxy Esters and 1,2-Diols
作者:Mark J. Burk、Christopher S. Kalberg、Antonio Pizzano
DOI:10.1021/ja974278b
日期:1998.5.1
The asymmetric hydrogenation of α-(acetyloxy)- and α-(benzoyloxy)acrylates 4 catalyzed by cationic rhodium−DuPHOS complexes has been examined. A wide range of substrates (4) were prepared via a convenient Horner−Emmons condensation protocol, and subsequently hydrogenated under mild conditions (60 psi of H2) at substrate-to-catalyst ratios (S/C) of 500. Overall, enol ester substrates 4 were reduced
new protocol for the acylation of alcohols with anhydrides in the presence of Zn(ClO4)2·6H2O as the catalyst is reported. The activity of Zn(ClO4)2·6H2O has been proven to be superior to that exerted by dry Mg(ClO4)2 and by metal triflates. Its efficiency allows reactions between poorly reactive substrates, such as sterically hindered tertiary alcohols and aromatic anhydrides. All of the reactions