The iso-Nazarov reaction

Abstract

The construction of five-membered rings is essential in organic chemistry. In this context, pentannulation reactions that provide a straightforward access to cyclopentenones are of particular interest, as these structures are not only embedded in important molecules such as some prostaglandins, but also serve as versatile building blocks in organic synthesis. This review documents the acid-promoted cycloisomerization of conjugated dienals and linearly-conjugated dienones for the construction of cyclopentenones, a transformation that has been largely eclipsed by the well-known Nazarov reaction, i.e. the acid-promoted cycloisomerization of cross-conjugated ketones.

A Fused Hexacyclic Ring System: Diastereoselective Polycyclization of 2,4‐Dienals through an Interrupted iso‐Nazarov Reaction

“…Its structure was determined by 2D NMR and confirmed by X-ray structures of few analogues. [10] Thef ormation of the fused benzo- [4,5]pentaleno [1,6-bc]indeno[2,1-e]piperidine polycylic core of 6ahas not been anticipated and exceeded our expectations. It arises from the formation of three new cycles,f our new bonds,and four contiguous stereocenters in one reaction from achiral starting materials with high levels of chemo and stereoselectivity and an impressive increase in structural complexity.H aving established the optimal reaction conditions for the polycyclization sequence,wethen examined the scope and limitations of this transformation.…”

“…Beyond that, diversity-oriented synthesis [2] (DOS) based on readily available and versatile starting materials is one of the most attractive strategies to achieve skeletal diversity.T hus, merging domino polycyclizations with DOS approach could lead to intricate small-molecule libraries. [3] In this context, our current interest in designing new methods to afford functionalized polycyclic scaffolds from simple unsaturated aldehydes [4] prompted us to investigate domino reactions initiated by an iso-Nazarov [5] reaction (Scheme 1).…”

A Fused Hexacyclic Ring System: Diastereoselective Polycyclization of 2,4‐Dienals through an Interrupted iso‐Nazarov Reaction

“…Thus, merging domino polycyclizations with DOS approach could lead to intricate small‐molecule libraries . In this context, our current interest in designing new methods to afford functionalized polycyclic scaffolds from simple unsaturated aldehydes prompted us to investigate domino reactions initiated by an iso‐Nazarov reaction (Scheme ).…”

Recent Advances in the Interrupted Nazarov Reaction

“…The subsequent trapping of the cyclopentenyl cation by nucleophiles can occur both at the α‐carbon atom giving compound 116a and at the γ‐carbon atom furnishing cyclopentenol 116b . Our current knowledge on the iso ‐Nazarov reaction was summarized in a recent review article, so only the most recent works on this topic have been included in the present review.…”