Nucleophilic substitutions Tandem Michael additions

Increasing importance has to be attributed to modem tandem (or cascade ) techniques—reaction sequences that can be performed as a one-pot procedure because the first reaction step creates the arrangement of functional groups needed for the second to occur. Schemes 5-7 present some in situ preparations for iminium species, which can then react further with appropriate nucleophiles that are already present (preferably in the same molecule). Most elegantly, in situ generation of iminium ions for tandem processes was performed by a 3,3-sigmatropic (aza-Cope-type) rearrangement (Scheme 5), but also by initial Michael-type addition reactions to vinyl-substituted Atio... 

Lithium enolate 329 and a nitrile-furnished enamino ester 330, which on condensation with isocyanates/isothiocyanates gave N-3 substituted 331 (X = O, S) through a tandem nucleophilic addition-intramolecular aza-Michael reaction (Scheme 126) (09JFC1145). 

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