Highly Regio- and Diastereoselective Synthesis of 6,7-Dihydro-4H-furo[3,4-c]pyran Derivatives through Pd-Catalyzed Formal (3 + 3) Allylic Cycloaddition of 2-Butene-1,4-diols with 2-(1-Alkynyl)-2-alken-1-ones

A highly efficient synthesis of 7-vinyl-6,7-dihydro-4H-furo[3,4-c]pyran derivatives from 2-butene-1,4-diols and 2-(1-alkynyl)-2-alken-1-ones has been achieved with high regio- and diastereoselectivity (dr > 20:1) by Pd-catalyzed tandem heterocyclization/cross-coupling. The π-allyl palladium species Int II generated from 2-butene-1,4-diol by direct cleavage of the C-OH bond is the key to the success in this formal (3 + 3) cycloaddition reaction.

Divergent Gold Catalysis: Unlocking Molecular Diversity through Catalyst Control

The catalyst-directed divergent synthesis, commonly termed as "divergent catalysis", has emerged as a promising technique as it allows chartering of structurally distinct products from common substrates simply by modulating the catalyst system. In this regard, gold complexes emerged as powerful catalysts as they offer unique reactivity profiles as compared to various other transition metal catalysts, primarily due to their salient electronic and geometrical features. Owing to the tunable soft π-acidic nature, gold catalysts not only evolved as superior contenders for catalyzing the reactions of alkynes, alkenes, and allenes but also, more intriguingly, have been found to provide divergent reaction pathways over other π-acid catalysts such as Ag, Pt, Pd, Rh, Cu, In, Sc, Hg, Zn, etc. The recent past has witnessed a renaissance in such examples wherein, by choosing gold catalysts over other transition metal catalysts or by fine-tuning the ligands, counteranions or oxidation states of the gold catalyst itself, a complete reactivity switch was observed. However, reviews documenting such examples are sporadic; as a result, most of the reports of this kind remained scattered in the literature, thereby hampering further development of this burgeoning field. By conceptualizing the idea of "Divergent Gold Catalysis (DGC)", this review aims to consolidate all such reports and provide a unified approach necessary to pave the way for further advancement of this exciting area. Based on the factors governing the divergence in product formation, an explicit classification of DGC has been provided. To gain a fundamental understanding of the divergence in observed reactivities and selectivities, the review is accompanied by mechanistic insights at appropriate places.

Consecutive reactions to construct tricarbonyl compounds and synthetic applications thereof

A cascade process to construct synthetically valuable β-keto-β′-acylcycloalkanecarboxylic acid esters and their transformation into bicyclic and tricyclic systems through intramolecular condensation reactions.

Gold Catalysis and Furans: A Powerful Match for Synthetic Connections

This review summarizes the advances made on the synthesis and functionalization of furans via gold catalysis during the period between 2016 and 2020. A separate section is dedicated to the tandem gold-catalyzed synthesis and functionalization of furans.

1 Introduction

2 Gold-Catalyzed Synthesis of Furans

2.1 Cycloisomerizations of Alkynyl and Cumulenyl Alcohols

2.2 Cycloisomerizations of Alkynyl and Allenyl Ketones

2.3 Reactions with External Oxidants

2.4 Miscellaneous

3 Gold-Catalyzed Functionalization of Furans

3.1 Cycloadditions

3.2 Furan Ring Decorations

3.3 Reactions Involving Furan Ring Opening

4 Gold-Catalyzed Tandem Synthesis and Functionalization of Furans­

4.1 Cycloisomerizations Followed by Gold-Catalyzed Cycloaddition

4.2 Cycloisomerizations to a Gold 1,3- or 1,4-Dipole and Intermolecular Annulation

4.3 Cycloisomerizations to a Gold Carbene and Intermolecular Trapping

5 Conclusion

Selectivity-switchable construction of benzo-fused polycyclic compounds through a gold-catalyzed reaction of enyne-lactone

A gold-catalyzed selectivity-switchable reaction of enyne-lactone is reported. The choice of the gold complex is the key for the chemoselectivity.