Enantioselective Synthesis of a Furan Lignan (+)-Sylvone

Computational insight into the mechanism and stereoselectivity of cycloaddition between donor-acceptor spirocyclopropane and aldehyde catalyzed by Brønsted acid TsOH

The mechanism and diastereoselectivity of the cycloaddition reaction between D-A spirocyclopropane and aldehydes, catalyzed by para-toluenesulfonic acid (TsOH) in dichloromethane to produce 2,5-disubstituted tetrahydrofuran-type lignans, have been investigated by density functional theory (DFT) at the M06-2X/6-311+G(d,p)//B3LYP-D3/6-31G(d,p) level combined with the solvation SMD model. Our calculations show that the entire reaction process includes three stages: the activation of the D-A cyclopropane by Brønsted acid, TsOH, the nucleophilic attack of the aldehyde on the spirocyclopropane, and the formation of the final product, 2,5-disubstituted tetrahydrofuran. It was concluded from the conceptual density functional theory (CDFT) reactivity index analysis that aldehydes with electron-rich substituents are more nucleophilic and more favorable for the reaction to proceed. Furthermore, based on the analyses of energetics as well as the noncovalent interaction (NCI) and reduced density gradient (RDG) in the key transition states, the origin of stereoselectivity was revealed to be determined thermodynamically rather than kinetically. The present work explains the experimental phenomenon well, and provides useful theoretical information for the future design of similar reactions.

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.

Lewis acid-catalyzed enantiospecific [3 + 2] annulations of γ-butyrolactone fused cyclopropanes with aromatic aldehydes: synthesis of chiral furanolignans

An enantiospecific [3 + 2] annulation of γ-butyrolactone fused cyclopropanes with aromatic aldehydes was realized to construct chiral furanolignans.

Chirality transfer in metal-catalysed intermolecular addition reactions involving allenes

This review covers chirality transfer in metal-catalysed intermolecular addition reactions involving allenes, including axial-to-central chirality transfer, asymmetric catalysis and racemization.