A general and practical protocol for the tertiary‐amine‐catalysed synthesis of β‐alkoxyacrylates from primary, secondary, and tertiary alcohols is described. Of the currently used catalysts, DABCO proved to be the best one for this process. Three factors seem to influence the outcome of the reaction: (1) the nucleophilic strength of the catalyst, (2) the electrophilicity of the intermediate ammonium acrylate, and (3) the pKa/nucleophilicity of the alcohol/alkoxide nucleophile. Reactivity tuning enables the transformation of a range of tertiary alcohols into the corresponding β‐alkoxyacrylate derivatives. Differences in the reactivity of different types of alcohol allow the selective transformation of diols containing two different hydroxy groups into the corresponding monoprotected derivatives. This protocol will aid other synthetic organic chemists to easily prepare such vinyl ethers under atom‐economic, efficient, and bench‐friendly reaction conditions.
A selective, catalytic and practical method for removing a Boc group from several N,N′-diprotected amino acids and amine derivatives using iron(iii) salts as sustainable catalysts is described.
A highly efficient, diastereoselective, iron(III)-catalyzed intramolecular hydroamination/cyclization reaction involving α-substituted amino alkenes is described. Thus, enantiopure trans-2,5-disubstituted pyrrolidines and trans-5-substituted proline derivatives were synthesized by means of a combination of enantiopure starting materials, easily available from l-α-amino acids, with sustainable metal catalysts such as iron(III) salts. The scope of this methodology is highlighted in an enantiodivergent approach to the synthesis of both (+)- and (-)-pyrrolidine 197B alkaloids from l-glutamic acid. In addition, a computational study was carried out to gain insight into the complete diastereoselectivity of the transformation.
A new, direct, and diastereoselective synthesis of activated 2,3,4,6-tetrasubstituted tetrahydro-2H-pyrans is described. In this reaction, iron(III) catalyzed an S2'-Prins cyclization tandem process leading to the creation of three new stereocenters in one single step. These activated tetrahydro-2H-pyran units are easily derivatizable through CuAAC conjugations in order to generate multifunctionalized complex molecules. DFT calculations support the in situ S2' reaction as a preliminary step in the Prins cyclization.
Catalysis. -Various N,N'-diprotected amino acids and amine derivatives are selectively deprotected from the Boc-group. The general method is clean and doesn't need any purification step. -(LOPEZ-SORIA, J. M.; PEREZ, S. J.; HERNANDEZ, J. N.; RAMIREZ, M. A.; MARTIN*, V. S.; PADRON, J. I.; RSC Adv. 5 (2015) 9, 6647-6651, http://dx.
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