1-Propanephosphonic Acid Cyclic Anhydride (T3P) as an Efficient Promoter for the Lossen Rearrangement: Application to the Synthesis of Urea and Carbamate Derivatives
The synthesis of hydroxamic acids starting from carboxylic acids employing 1-propanephosphonic acid cyclic anhydride (T3P) activation is described. Application of ultrasonication accelerates this conversion. Further, the T3P has also been employed to activate the hydroxamates, leading to isocyanates via the Lossenrearrangement. The isocyanates were trapped with suitable nucleophiles to afford the
protocol for the synthesis of peptide hydroxamicacids directly from carboxylic/amino acids by ethyl 2-(tert-butoxycarbonyloxyimino)-2-cyanoacetate in the presence of DIPEA/DMAP at room temperature is described. The compatibility of this method with Fmoc based solidphase peptide synthesis (SPPS) is also demonstrated by synthesizing three relatively large N-terminal peptide hydroxamicacids on resin. Also
Divergent Synthesis of Tunable Cyclopentadienyl Ligands and Their Application in Rh-Catalyzed Enantioselective Synthesis of Isoindolinone
作者:Wen-Jun Cui、Zhi-Jie Wu、Qing Gu、Shu-Li You
DOI:10.1021/jacs.0c02813
日期:2020.4.22
unprecedented enantioselective [4+1] annulation reaction of benzamides and alkenes was achieved with a broad substrate scope under mild reaction conditions, providing a variety of isoindolinones with excellent regio- and enantioselectivity (up to 94% yield, 97:3 er). Preliminary mechanistic studies suggest that the reaction involves an oxidative Heck reaction and an intramolecular enantioselective alkene
Product Control using Substrate Design: Ruthenium-Catalysed Oxidative C−H Olefinations of Cyclic Weinreb Amides
作者:Riki Das、Manmohan Kapur
DOI:10.1002/chem.201603126
日期:2016.11.14
A new class of Weinreb amides has been developed as directing groups for the ruthenium‐catalysed regioselective oxidative C−H olefination. The new Weinreb amides successfully inhibit the N−O bond reductive cleavage usually associated with the cationic ruthenium system, thereby keeping intact the synthetic utility of Weinreb amides. Mechanistic studies reveal interesting aspects of the directing group
precursors in reactions with thioethers under the catalysis of a commercially available Ru(II) complex, from which a variety of sulfimides were synthesized efficiently and mildly. If an allyl group is contained in the thioether precursor, the [2,3]-sigmatropic rearrangement of the sulfimide occurs simultaneously and the N-allyl-N-(thio)amides were obtained as the final products. Preliminary mechanistic studies