61797-99-7Relevant articles and documents
Ligand-Promoted, Boron-Mediated Chemoselective Carboxylic Acid Aldol Reaction
Nagai, Hideoki,Morita, Yuya,Shimizu, Yohei,Kanai, Motomu
, p. 2276 - 2279 (2016)
The first carboxylic acid selective aldol reaction mediated by boron compounds and a mild organic base (DBU) was developed. Inclusion of electron-withdrawing groups in the amino acid derivative ligands reacted with BH3·SMe2 forms a boron promoter with increased Lewis acidity at the boron atom and facilitated the carboxylic acid selective enolate formation, even in the presence of other carbonyl groups such as amides, esters, ketones, or aliphatic aldehydes. The remarkable ligand effect led to the broad substrate scope including biologically relevant compounds.
Cyclization-cycloaddition cascade of rhodium carbenoids using different carbonyl groups. Highlighting the position of interaction
Padwa, Albert,Zhang, Zhijia J.,Zhi, Lin
, p. 5223 - 5232 (2007/10/03)
A series of 3-diazoalkanediones, when treated with a catalytic quantity of a rhodium(II) carboxylate, were found to afford oxabicyclic dipolar cycloadducts derived by the trapping of a carbonyl ylide intermediate. The reaction involves generation of the 1,3-dipole by intramolecular cyclization of the keto carbenoid onto the oxygen atom of the neighboring keto group. Both five- and six-ring carbonyl ylides are formed with the same efficiency. A study of the tandem cyclization-cycloaddition cascade of several α-diazo ketoesters was also carried out, and the cascade sequence proceeded in high yield. When the interacting keto carbonyl group was replaced by an imido group, the rhodium(II)-catalyzed reaction proceeded uneventfully. In contrast, α-diazo amidoesters do not undergo nitrogen extrusion on treatment with a Rh(II) catalyst. Instead, the diazo portion of the molecule undergoes 1,3-dipolar cycloaddition with various dipolarophiles to give substituted pyrazoles as the final products.
