Abstract
The reactivity of C-CH3 substituted N-protected aldimines in aza-Henry addition reactions was compared with that of the analogous trifluoromethylated compounds. C-Alkyl aldimines easily reacted with nitro alkanes under solvent-free conditions and in the absence of catalyst, despite being worse electrophiles than C-CF3 aldimines, they gave the aza-Henry addition only when ZrCl4 was added. The presence of a bulky group on the imine carbon deeply influenced the reactivity.
Highlights
IntroductionThe development of stereoselective reactions to create carbon–carbon bonds between compounds bearing a heteroatom functionality can provide valuable building blocks for organic synthesis
The development of stereoselective reactions to create carbon–carbon bonds between compounds bearing a heteroatom functionality can provide valuable building blocks for organic synthesis. Starting from this purpose and considering the importance of the 1,2-diamine structural motif in biologically active natural products, drugs, and more recently as chiral auxiliaries and chiral ligands in asymmetric catalysis, general methods to synthesize this class of compounds are most relevant
C-CF3 substituted aldimines [9,10,11] are reported in the aza-Henry reactions as interesting trifluoromethyl nitrogen-containing starting materials; the reactivity of C-aryl analogues has been well documented in the literature, while very few data are reported on the reactivity of C-alkyl substituted aldimines [2]
Summary
The development of stereoselective reactions to create carbon–carbon bonds between compounds bearing a heteroatom functionality can provide valuable building blocks for organic synthesis. Starting from this purpose and considering the importance of the 1,2-diamine structural motif in biologically active natural products, drugs, and more recently as chiral auxiliaries and chiral ligands in asymmetric catalysis, general methods to synthesize this class of compounds are most relevant. The aza-Henry reaction [1,2,3,4], called nitro-Mannich reaction, involves the nucleophilic addition of nitro alkanes to aldimines and leads to the synthesis of β-nitro amines, valuable compounds containing two vicinal nitrogenated functionalities with different oxidation states.
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