Deciphering the Chameleonic Chemistry of Allenols: Breaking the Taboo of a Onetime Esoteric Functionality

Abstract

The allene functionality has participated in one of the most exciting voyages in organic chemistry, from chemical curiosities to a recurring building block in modern organic chemistry. In the last decades, a special kind of allene, namely, allenol, has emerged. Allenols, formed by an allene moiety and a hydroxyl functional group with diverse connectivity, have become common building blocks for the synthesis of a wide range of structures and frequent motif in naturally occurring systems. The synergistic effect of the allene and hydroxyl functional groups enables allenols to be considered as a unique and sole functionality exhibiting a special reactivity. This Review summarizes the most significant contributions to the chemistry of allenols that appeared during the past decade, with emphasis on their synthesis, reactivity, and occurrence in natural products.

Iron‐Catalyzed Cross‐Coupling of Propargyl Ethers with Grignard Reagents for the Synthesis of Functionalized Allenes and Allenols

“…Allenes constitute an interesting class of compounds and have attracted considerable attention in synthetic organic chemistry in recent years. [1] Functionalized allenes are frequently used as building blocks in organic synthesis and they occur in a range of natural products and pharmaceuticals. [2] An interesting feature with functionalized allenes is that they can possess axial chirality.…”

Rh(iii)-Catalyzed [5 + 1] annulation of 2-alkenylanilides and 2-alkenylphenols with allenyl acetates

“…Controlling regio- and chemoselectivity are the major challenging factors that impede the use of allenes in transition metal catalyzed C–H functionalizations in comparison to other π-systems like alkenes and alkynes. 1 At the same time, deciphering the versatile reactivity of allenes in C–H annulations has great potential to generate molecular complexity rapidly. 2 Addressing these inherent selectivity issues, recent years have witnessed significant advancements in unravelling the unique reactivities of allenes in C–H activation reactions with a variety of transition metals.…”

Rh(I)‐Catalyzed Decarboxylative Arylation of Alkynyl Cyclic Carbonates: Divergent Access to Substituted α‐Allenols and 1,3‐Butadienes

“…1). Among the different classes of allenes, 2,3‐allenols are particularly considered as an eminent subcategory as they can be efficiently transformed into a wide range of valuable heterocyclic derivatives such as dihydrofurans, furanones and other biologically relevant motifs [6] . After the pioneering report by Fürstner and Méndez [7a] in 2003 on iron‐catalyzed alkylation of propargyl oxiranes via S N 2′‐type nucleophilic substitution with Grignard reagents, various methods have been devised to achieve straightforward access to di‐, tri‐ or tetra‐substituted α ‐allenols with a variety of transition‐metal catalysts like Cu, Pd, Fe and Rh (Scheme 1a, eq.…”