A tandem Aldol-Grob reaction of ketones with aromatic aldehydes
作者:George W. Kabalka、David Tejedor、Nan-Sheng Li、Rama R. Malladi、Sarah Trotman
DOI:10.1016/s0040-4020(98)00976-4
日期:1998.12
Aromatic aldehydes react with ketones to produce(E)-1-aryl-1-alkenes via a tandem Aldol-Grob cleavage reaction sequence. The reaction, initiated by boron trifluoride, also produces a carboxylic acid fragment.
Asymmetric copper-catalyzed allylic alkylation between allyl bromides and alkyl Grignard reagents using a P-chiral monophosphorus ligand is described. A range of terminal olefins bearing tertiary or quaternary carbon centers were formed in good branched/linear selectivities and excellent enantioselectivities at copper loadings as low as 0.5 mol %.
The copper complexes of chiral spiro phosphoramidite and phosphite ligands were found to be effective catalysts in the asymmetric allylic alkylations of cinnamyl halides with dialkylzincs. The allylic alkylation products were obtained in high regioselectivities (SN2′/SN2 up to 98:2) and enantiomeric excesses of up to 74% for SN2′ products.
发现手性螺亚磷酰胺和亚磷酸酯配体的铜配合物是肉桂酰卤与二烷基锌的不对称烯丙基烷基化的有效催化剂。烯丙基烷基化产物以高区域选择性(S N 2'/ S N 2高达98:2)获得,对于S N 2'产物,对映体过量高达74%。
Reaction of α,α′ - bis(trimethylsiloxy) sulfides with low valent titanium reagents
作者:T.H. Chan、J.S. Li、T. Aida、David N. Harpp
DOI:10.1016/s0040-4039(00)86962-2
日期:1982.1
We have shown that low valent titanium reagents reductively couple α,α′ -bis-(trimethylsiloxy) sulfidees giving olefins in good yield. With unsymmetrical , mixed olefins are obtained suggesting an intermolecular pathway. Finally, we have demonstrated that -episulfide is quantitatively converted to -stilbene.
Direct Organocatalytic Oxo-Metathesis, a<i>trans-</i>Selective Carbocation-Catalyzed Olefination of Aldehydes
作者:Veluru Ramesh Naidu、Juho Bah、Johan Franzén
DOI:10.1002/ejoc.201403651
日期:2015.3
been developed. The reaction is catalyzed by trityl tetrafluoroborate (TrBF4) and utilizes unactivatedalkenes for the olefination of aromatic aldehydes to give trans -alkylstyrenes in yields of 44-85% with only acetone as the byproduct. The pronounced Lewis acidity of the carbocation results in unusual reactivity that is proposed to catalyze a stepwise [2+2] cycloaddition to give an oxetane intermediate