Unexpected Cascade Reactions of
<i>Ortho</i>
‐Hydroxyenaminones and β,γ‐Unsaturated α‐Ketoesters to Access Hydrogenated Benzoxazolepolycycles and Pyrrole−Phenol Atropisomers
作者:Xuguan Bai、Lele Wang、Ziying Zhang、Kuan Zhang、Zhanwei Bu、Yufeng Wu、Wenjing Zhang、Qilin Wang
DOI:10.1002/adsc.201900950
日期:2019.11.5
BF3 ⋅ OEt2‐catalyzed Michael addition/cyclization/dehydration sequence of ortho‐hydroxyenaminones with aromatic or aliphatic aldehyde‐derived β,γ‐unsaturated α‐ketoesters has been achieved to afford a wide range of fused hydrogenated benzoxazole polycycles in 67–95% yields in a highlydiastereoselective manner. When isatin‐derived β,γ‐unsaturated α‐ketoesters were employed as substrates, completely different reactivities
Chiral NHC-Catalyzed Oxodiene Diels−Alder Reactions with α-Chloroaldehyde Bisulfite Salts
作者:Ming He、Brendan J. Beahm、Jeffrey W. Bode
DOI:10.1021/ol801502h
日期:2008.9.1
hetero-Diels-Alder reactions with various oxodienes under biphasic reaction conditions with high levels of enantioselectivity. This new protocol makes possible enantioselective additions fromcommerciallyavailablechloroacetaldehyde sodium bisulfite and demonstrates that this unique class of catalysts readily tolerates aqueous conditions.
Chiral N-heterocyclic carbene (NHC) catalyzed redox reactions of racemic alpha-chloroaldehydes lead to the generation of chiral enolates suitable for highly enantioselective inverse-electron-demand 1-oxodiene Diels-Alder reactions. Significantly, these reactions proceed under mild, operationally friendly reaction conditions (EtOAc, room temperature, 2-8 h) using less than 1 mol % of a chiral N-mesityl
Direct Synthesis of β,γ-Unsaturated α-Keto Esters from Aldehydes and Pyruvates
作者:John Mansaray、Jiarui Sun、Shisheng Huang、Weijun Yao
DOI:10.1055/s-0037-1612255
日期:2019.4
methods to synthesize β,γ-unsaturated α-keto esters directly from aldehydes and pyruvates promoted by BF3•Et2O in the presence of Ac2O or by Ti(OEt)4 under mild conditions. A variety of aromatic aldehydes was tolerated to afford the desired products in moderate to excellent yield. Moreover, aliphatic aldehydes and Isatin were also employed to give the γ-alkyl β,γ-unsaturated α-keto esters in moderate yield