Jiajing Tan

Catalytic Asymmetric Claisen Rearrangement of Enolphosphonates: Construction of Vicinal Tertiary and All-Carbon Quaternary Centers†

A Cu-catalyzed enantioselective Claisen rearrangement of easily-accessible enolphosphonates using commercially available (R, R)-PhBOX as the chiral ligand was developed. A wide range of rearrangement products with contiguous tertiary and all carbon quaternary centers were obtained in excellent yields and stereoselectivities. The α-ketophosphonate products could be easily transformed into other functional groups in high efficiency.

The Supersilyl Group as a Carboxylic Acid Protecting Group: Application to Highly Stereoselective Aldol and Mannich Reactions

“Super Power”: The application of the supersilyl” group as carboxylic acid protecting group has been investigated. The unique properties of the “supersilyl” group enabled it to outperform typical carboxyl protecting groups, conferring extraordinary protection upon the carboxyl functionality. “Supersilyl” esters were also utilized for the first time as stable carboxylic acid synthetic equivalents in highly stereoselective aldol and Mannich reactions. The value of this methodology has been further described by the easy photo-deprotection protocol and its applications in rapid synthesis of polyketide subunits.

Ruthenium-Catalyzed Asymmetric Hydrogenation of β‑Ketophosphonates

Significance: The current work represents an efficient protocol for the enantioselective hydrogenation of β-ketophosphonate derivates catalyzed by a ruthenium–(S)-Sunphos complex. Good to excellent enantioselectivity and yield were obtained for a variety of substrates. Comment: Hydroxyphosphonate motifs are known to be mimics of hydroxy carboxylic acids or amino acids. Given their medicinal importance, many synthetic methodologies have been developed. The protocol described herein was even used for the reduction of α-substituted β-ketophosphonates, providing the desired products with good syn diastereoselectivity. R1 O