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Please login or sign up for a free trial to access the full content. Method 3: Dipyrroketones

DOI: 10.1055/sos-SD-017-01748

Smith, K. M.; Vicente, M. G. H.Science of Synthesis, (2004171096.

The most efficient method for the synthesis of unsymmetrical dipyrroketones (e.g., 68, R1=O) involves a modification of the VilsmeierHaack reaction. Condensation of the phosphoryl chloride complex of a pyrrole N,N-dimethylcarboxamide 67 with a nucleophilic 2-unsubstituted 1H-pyrrole (e.g., 34) followed by hydrolysis of the intermediate imine salt 68 (R1=NMe2+Cl) gives the dipyrroketone 68 (R1=O) in very good yield (Scheme 17).[‌53‌] Alternatively, treatment of a pyrrole acid chloride 69 with a pyrrole Gri­gnard derivative 70 (or with the 2-unsubstituted 1H-pyrrole in the presence of a FriedelCrafts catalyst) gives dipyrroketones 71[‌53‌,‌54‌] (Scheme 17).

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