Direct catalytic alkynylation of N-unprotected trifluoromethyl ketimines allowed an unprecedented direct access to N-unprotected α-tetrasubstituted primary amines without additional deprotection steps.
Enantioselective Synthesis of 2‐Substituted Indoles Bearing Trifluoromethyl Moiety by the Friedel‐Crafts Alkylation Reaction of 4,7‐Dihydroindole with
<i>N</i>
−H Trifluoromethyl Ketimines
The Friedel‐Crafts alkylation reaction of 4,7‐dihydroindole with N‐unprotected trifluoromethyl ketimines by means of chiral phosphoric acid and the subsequent oxidation with DDQ afforded chiral 2‐indolylmethylamines bearing a trifluoromethyl moiety in good to high yields with excellent enantioselectivities under one‐pot conditions. The adduct was transformed without loss of enantioselectivity and the
enantioselective Friedel–Crafts alkylation reaction of pyrroles and indoles with N‐unprotected trifluoromethyl ketimines by use of chiral phosphoric acid provided α‐trifluoromethylated primary amines bearing chiral tetrasubstituted carbon centers in high yields and with high to excellent enantioselectivities. The present reaction is unique to N‐unprotected trifluoromethyl ketimines. No reaction took place
Direct Access to N-Unprotected α- and/or β-Tetrasubstituted Amino Acid Esters via Direct Catalytic Mannich-Type Reactions Using N-Unprotected Trifluoromethyl Ketimines
bond‐forming reactions using Mannich‐type reactions as a model case. We demonstrate that Lewis acid catalysis was effective for promoting reactions with various N‐unprotected trifluoromethyl ketimines, and thiourea organocatalysis was effective for promoting highly enantioselective reactions with various carbonyl nucleophiles, providing direct access to various N‐unprotected α‐ and/or β‐tetrasubstituted
The first enantioselective hydrophosphonylation of ketimines with phosphine oxides was developed. The reaction of unprotected ketimines with phosphine oxides using a bis(imidazoline)-phosphoric acid catalyst gave chiral α-quaternary aminophosphorous compounds having a primary amino group in excellent yields and enantioselectivities. Based on experimental results and DFT calculation, transition states