SN1-Type Reaction Promoted by Chiral Thioureas

The presence of a primary amino group in a catalyst was shown to be necessary for catalysis in the present case where the enamine of the branched aldehyde was involved. The thiourea also plays an essential role in promoting the reactivity by 

SnI-Typc Organocatalytic Reaction of Iminium, Oxonium, and Aziridinium Intermediates 

The reactivity discovered by Jacobsen with chiral thiourea is fully consistent with S(jl-type chemistry. Besides the formation of reactive N-acyliminium species. 

Another elegant example was demonstrated by the same authors in the enantioselective total synthesis of (-i-)-minfiensine, through an iminiiun activation that allows a Diels-Alder cyclization step to generate the tetracycHc stracture with 

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