Selective activation of organocatalysts by specific signals

Abstract

Activation of the responsive organocatalyst proline by three different signals allows temporal control over chemical reaction kinetics.

On the use of catalysis to bias reaction pathways in out-of-equilibrium systems

“…Here, to illustrate how a simple feedback loop can be incorporated in this generic fuel-driven CRN, we add an additional reaction step (Scheme 2reaction in maroon colour). Instead of having both catalysts C1 and C2 from the beginning in the reaction mixture, we introduce an inactive procatalyst [37][38][39] for C2, which can be converted into the active catalyst C2 and a waste product (W3). This activation is catalysed by product P itself.…”

On the Use of Catalysis to Bias Reaction Pathways in out Of-Equilibrium Systems

“…Here, to illustrate how a simple feedback loop can be incorporated in this generic fuel-driven CRN, we add an additional reaction step (Scheme 2 -reaction in maroon colour). Instead of having both catalysts C1 and C2 from the beginning in the reaction mixture, we introduce an inactive procatalyst 37,38,39 for C2, which can be converted into the active catalyst C2 and a waste product (W3). This activation is catalysed by product P itself.…”

Visible Light‐Gated Organocatalysis Using a RuII‐Photocage

“…It is widely recognized that the possibility to externally photocontrol processes with high spatial and temporal precision is very attractive for transducing an optical signal into an amplified and focused response of chemical transformation or other action [31] . Despite these notions and the abundant exploitation of photocaged compounds in the most varied contexts, [36, 37] the observation of light‐gated organocatalysis has been limited to very few literature examples [10–14] . One of them is the UV‐light activation of an adduct of 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) with tetraphenylboric acid.…”

“…The released TBD was used to catalyze a ring‐opening polymerization [10] . In other examples, photocages were activated by UV light to release 1,6‐hexanediamine, [11] nornicotine, [13] or proline [14] to catalyze classical organic transformations such as Michael additions, aldol condensations or Mannich reactions. However, the use of high‐energy UV light constitutes a severe drawback, because secondary photoreactions could interfere with the organocatalytic process.…”

“…This has been mainly triggered by the renaissance of photoredox catalysis with organometallic complexes (e.g., Ru II or Ir III complexes) [4–6] or purely organic photosensitizers [7–9] . However, light may be used as well (a) to release photocaged catalysts, [10–14] (b) to create an active site in a metal complex via ligand dissociation [15–22] or (c) for the reversible photoswitching of the catalyst state [23–30] . In these strategies (see Figure 1) photons are not directly implicated in the catalytic cycle, but used to activate the catalyst in a light‐gated manner [31]…”