An Improved Method for the Preparation of N-Unsubstituted 1,4,5,6-Tetrahydrocyclopenta[b]pyrroles: Synthesis of an Azaprostacyclin Analogue and Its 7-Cyano Derivative

Preparation of the tricyclic ketopyrrole core of roseophilin by radical macrocyclisation and Paal–Knorr condensation

“…On the basis of these results, pyrroles 29 and 31 were prepared from diketone 4. Whilst the Paal-Knorr condensation to form the N-benzylpyrrole 29 proceeded in reasonable yield under standard conditions, formation of the free pyrrole (30) precursor to 31 required much more forcing conditions, a modification of Gossauer's procedure 19 eventually providing the compound in good yield. N-Benzylpyrrole 29 behaved similarly to the model analogue (26) and an intractable mixture of products was obtained under all oxidation conditions attempted.…”

Formal synthesis of roseophilin

“…ref. 14). Unfortunately we were unable to effect direct aoxidation of either 9a or the N-Boc analogue 9c even though studies on compounds lacking the macrocyclic linking chain gave promising results.…”

Five‐Membered Heterocycles: Pyrrole and Related Systems

“…Modern applications emerge continuously, and allow for instance synthesis of 1-aminopyrrole derivatives by using monoprotected hydrazines [59] or N-aminophthalimide [60] as the amine components. A variant employing amine hydrobromides in refluxing pyridine is available [61], and an efficient synthesis of cyclopenta [b]pyrroles from suitable diketones with hexamethyldisilazane (HMDS) as the ammonia equivalent in the presence of Al 2 O 3 has also been described [62]. Other useful extensions involve montmorillonite KSF clay [63], titanium isopropoxide [64] or iodine [65] as the catalysts.…”