Pummerer cyclization-cycloaddition

Pummerer reaction conditions was followed by cycUzation to isomilnchnone 292 and hence to cycloadduct 293, which loses water to form a-pyridone 294. Subsequent manipulation involving deoxygenation and debenzylation completed the synthesis. In similar fashion, the azaanthraquinone alkaloid dielsiquinone was synthesized for the first time. Also, the quinolizidine alkaloids ( )-lupinine and ( )-anagyrine, and the ergot alkaloid ( )-costaclavine were synthesized using this Pummerer cyclization-cycloaddition cascade of imidosulfoxides and isomiinch-nones. 

Finally, saturated oxazolo[3,2-tf]pyridine derivatives can also be accessed via a Pummerer cyclization-deprotona-tion-cycloaddition cascade from imidosulfoxides <1999JOC2038> or by a [3+2] cycloaddition of nonstabilized... 

Alternatively, a total synthesis of (-b)-erysotramidine via Pummerer-promoted cyclization-cycloaddition cascade was developed by Padwa (Scheme 21.29). " A similar methodology was also applied in the synthesis of ( )-jamtine by Padwa. 

SCHEME 21.29. Pummerer-promoted cyclization-cycloaddition cascade for the synthesis of (+)-erysotramidine. 

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