Iron cyclopentadienone complexes have recently received particular attention in organic chemistry. This is due to their easy synthesis from simple and cheap materials, air-water stability, and most importantly for their unique catalytic features arising from the presence of a non-innocent ligand, triggering powerful redox properties. Herein we discuss the properties of such complexes from synthetic and mechanistic points of view, and their applications in original redox-neutral transformations in both racemic and enantioselective series.

Three is a lucky number: An enantioselective transformation of allylic alcohols into β-chiral saturated alcohols has been developed by combining two distinct metal- and organocatalyzed catalytic cycles. This waste-free triple cascade process merges an iron-catalyzed borrowing-hydrogen step with an aminocatalyzed nucleophilic addition reaction.

An unprecedented and simple direct vinylogous addition of deconjugated butenolide to enals has been developed in excellent stereoselectivities (>95% ee), with Aminal-PYrrolidine (APY) catalyst. This methodology allows for the efficient preparation of complex γ-butenolide from readily available renewable resources. Furthermore, preliminary mechanistic investigations have allowed for the better understanding of the origin of both stereoselectivities and of the observed high reactivities.

By controlling the kinetics of alkynylation over aldolisation (by slowing adding the acceptor), the challenging asymmetric catalytic alkynylation of acetaldehyde has been realized. This protocol yields the corresponding attractive synthons in good to excellent enantiocontrol and shows broad tolerance and applicability. This was highlighted by its application to the synthesis of several natural products such as the rapid construction of the macrocyclic diolide (+)-tetrahydropyrenophorol.

Independent workers with team spirit: A catalytic sequence that exploits the compatibility of (chiral) cationic iridium catalysts for the isomerization of primary allylic alcohols to aldehydes with organocatalysts has been developed for the highly enantioselective α functionalization of aldehydes (see scheme: up to 66 % yield, d.r. 49:1, 99 % ee). The reaction displayed useful generality with respect to both the nucleophile and the electrophile

The recent discovery of temporally controlled gels opens broad perspectives to the field of smart functional materials. However, to obtain fully operative systems, the design of simple and robust gels displaying complex functions is desirable. Herein, we fuel dissipative gelating materials through iterative additions of trichloroacetic acid (TCA). This simple fuel enables to switch over time an acid/base-dependent commercially available amino acid gelator/DBU combination between three distinct states (anionic, cationic, and neutral), while liberating volatile CO 2 and CHCl 3 upon fuel consumption. Of interest, the anionic resting state of the system is obtained through trapping of 1 equiv of CO 2 through the formation of a carbamate. The system is tunable, robust, and resilient over time with over 25 consecutive sol−gel−sol cycles possible without significant loss of properties. Most importantly, because of the chiral nature of the amino acid gelator, the system features chiroptical switching properties moving reversibly between three distinct states as observed by ECD. The described system considerably enhances the potential of smart molecular devices for logic gates or data storage by adding a time dimension based on three states to the gelating materials. It is particularly simple in terms of chemical components involved, but it enables sophisticated functions.

The 1,2-sulfone rearrangement resulting from nucleophilic addition to bis activated vinyl-sulfones has been studied in more detail. Various nucleophiles activated by different types of catalysts (enamine, Brönsted base, thiourea) are able to promote such rearrangement in excellent yields and moderate to excellent enantioselectivities (up to 94% ee). Mechanistic studies have led to a better understanding of the mechanism and allowed its application to other electrophiles such as vinyl-sulfone acrylates.

Living on borrowed hydrogen: Recent developments in iron- and cobalt-catalyzed borrowing hydrogen have shown that economically reliable catalysts can be used in this type of waste-free reactions. By using well-defined inexpensive catalysts, known reactions can now be run efficiently without the necessary use of noble metals; however, in addition new types of reactivity can also be discovered.