Metal-Free Allene-Based Synthesis of Enantiopure Fused Polycyclic Sultones

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

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.

Progress in the synthesis of δ-sultones

Abstract

Sultones, the cyclic esters of hydroxyl sulfonic acids, are a fascinating class of heterocycles and the recent years have witnessed an increasing interest in these molecules, especially in six-ring δ-sultones. The importance of these compounds is either because of their biological properties themselves or due to their versatility as intermediates in more complex target syntheses. Accordingly, the development of new synthesis methods to access δ-sultones is an important and rewarding task which we wish to highlight in this review.

Graphical abstract

[3,3]-Sigmatropic rearrangement of allenic alcohols: stereoselective synthesis of 1,3-diene-2-ol sulfonates

An efficient synthetic pathway to 1,3-diene-2-ol sulfonates involving the [3,3]-sigmatropic rearrangement of allenic alcohols with sulfonic acids under mild reaction conditions is described. These products can easily undergo reduction or transition-metal catalyzed cross-coupling reactions to yield a series of stereodefined multisubstituted 1,3-dienes.