A Calix[4]pyrrole Organocatalyst

Significance

The authors introduce calix[4]pyrrole 1 as a new catalyst motif for the hetero-Diels-Alder reaction of Danishefsky’s diene and 4-nitro­benzaldehyde. Using two equivalents of the aldehyde, the authors obtained a mixture of products 2 and 3. At high concentration ketone 2 is the major product and at low concentration aldol 3 is the major product. Diels-Alder adduct 4 was obtained when five equivalents of the aldehyde were used.