Recent Advances in Nickel‐Catalyzed Synthesis of Allenes: New Insights and Perspectives

Abstract

Allenes are one of the most important functional groups in organic chemistry, featuring unique physical and chemical properties. They are not only the key scaffolds widely present in natural products, pharmaceutical molecules, and advanced functional materials, but also the valuable and versatile building blocks for the construction of various complex and bioactive molecules in organic synthesis. Accordingly, benefiting from the rapid development of transition metal catalysis, numerous remarkable and efficient approaches for the synthesis of allenes from readily available chemicals have been established in the past decades. In this brief review, we focus on the recent advancements in nickel‐catalyzed synthesis of allenes. These transformations are divided into two categories according to the types of reactions and sorted further by starting materials. Moreover, a concise discussion of the limitations and potential areas of improvement in this field is also provided, which would give an inspiration for future study on allene synthesis.

Recent advances in nickel-catalyzed propargylic substitution

“…Additionally, some allene products will also be included. 14 The review will elucidate the underlying mechanisms and provide valuable insights into the versatility and applicability of these reactions. Meanwhile, this review outlines the challenges and identifies potential areas for improvement in this field, intending to act as a source of inspiration for future research endeavors.…”

Hydride-free reduction of propargyl electrophiles: a nickel-catalyzed photoredox strategy for allene synthesis

“…In this context, we present a novel nickel-catalyzed photoredox reduction strategy for a selective, sustainable and robust access to diversely substituted allenes under mild reaction conditions from propargyl electrophiles. 6 Unlike traditional methods, our approach eliminates the requirement for hydride nucleophiles, instead relying on protodemetalation of an allenylmetal intermediate. Notably, we demonstrate that a trialkylamine plays the roles of both a redox mediator, as a reductive quencher of the photocatalytic cycle, and a proton source, via proton transfer from its photochemically generated amine radical cation (Fig.…”

Nickel-Catalyzed Deaminative Alkyl–Alkyl Cross-Coupling of Katritzky Salts with Cyclopropanols: Merging C–N and C–C Bond Activation

“…With our continuing interest in nickel-catalyzed cross-coupling reactions, and the conversions of Katritzky type pyridinium salts, ,, we envisioned if cyclopropanolsan important class of ketone homoenolate precursors in organic synthesiscould be employed as reactive partners to fulfill the desired transformation via C–C bond cleavage. However, despite their widespread use in the preparation of β-functionalized carbonyl compounds, the application of unmasked cyclopropanols in nickel catalysis, especially in coupling with unactivated alkyl electrophiles, remains scarce and challenging .…”