Asymmetric Organocatalytic Cyclization and Cycloaddition Reactions

Pyrrolidine-Mediated Direct Preparation of (E)-Monoarylidene Derivatives of Homo- and Heterocyclic Ketones with Various Aldehydes

“…The use of such a ketone for the production of new α,β-unsaturated ketones of biological interest is not very extensive. Recently, chiral secondary amines were used as organocatalysts in the direct aldol reaction with great success [34][35][36][37]. The mechanism suggesting that ketones and amines facilicate the formation of the intermediate enamine, encouraged us to study the direct aldol-dehydration reaction for producing the title compounds.…”

Investigation of the Pathway for Intramolecular Electron Transfer in Anodic [2 + 2] Cycloaddition Reactions

“…1 H and 13 C NMR spectra were taken on a 600 MHz JNM-ECA spectrophotometer. High resolution mass spectrometry was performed on AccuTOF time-of-flight mass spectrometer.…”

Enantioselective Organocatalytic Cyclopropanation of Enals Using Benzyl Chlorides

“…Finally, we tested the reaction of substrates bearing other aromatic substituents and it was found that the cyclopropanation reaction requires two strong EWGs on the aromatic ring of the benzylic chloride in order to enhance the acidity and nucleophilicity of the benzylic position. 4-Trifluoromethyl-2-nitrobenzyl chloride reacted with enals to give the corresponding chiral cyclopropanes in moderate yields and diastereoselectivities and good enantioselectivities ( Table 2, entries [15][16]. However, this reaction requires higher reaction temperatures (60 o C), which could be responsible for the lower stereoselectivities obtained as compared with those observed for dinitrobenzyl derivatives.…”

“…(4)]. The in-situ generation of a carbanion at the α-position of the benzyl halide could initiate the organocascade reaction, [16] in which the α,β-unsaturated aldehyde, activated by an aminocatalyst, would act as electrophilic counterpart; the following irreversible intramolecular alkylation would give the benzylic cyclopropanated products by iminium and enamine activation. Surprisingly, diphenyl prolinol IV and MacMillan's second-generation imidazolidinone catalyst V, which has been previously used by Lattanzi and co-workers in similar MIRC reactions with excellent results, did not catalyze the reaction to any significant extent, yielding only a trace amount of product (Table 1, entries [10][11].…”