Lisa Candish

• Monash University (Australia)

Donor-acceptor cyclopropanes are known to serve as dipole precursors capable of engaging in (3+2) annulations with electron-deficient π-systems. In 2013, the reaction of donor-acceptor cyclopropanes with α,β-unsaturated acyl fluorides in an all-carbon (3+2) annulation was discovered. The reaction proceeds in good yields using the IMes NHC to provid...

This account describes studies on the application of N-heterocyclic carbene (NHC) catalysis to the synthesis of the iridoid natural product (-)-7-deoxyloganin. The synthesis has been completed in 17 steps, while an improved formal synthesis can be achieved in 10 steps. Pivotal to both approaches is the application of NHC catalysis with ester oxidat...

An enantioselective N-heterocyclic carbene (NHC)-catalyzed diene regenerative (4 + 2) annulation has been achieved through the use of highly nucleophilic morpholinone-derived catalysts. The reaction proceeds with good to excellent yields, high enantioselectivity (most >92% ee), and good diastereoselectivity (most >7:1). The generality of the reacti...

A limited array of reactive intermediates have enabled a wealth of discoveries in N-heterocyclic carbene organocatalysis. In this study, the viability of α,β-unsaturated sulfonyl azoliums as double electrophiles in new reactions is examined. Specifically, the (3+3) annulation of such species with the trimethylsilyl enol ethers of various 1,3-dicarb...

A limited array of reactive intermediates have enabled a wealth of discoveries in N-heterocyclic carbene organocatalysis. In this study, the viability of α,β-unsaturated sulfonyl azoliums as double electrophiles in new reactions is examined. Specifically, the (3+3) annulation of such species with the trimethylsilyl enol ethers of various 1,3-dicarb...

An NHC-catalyzed conversion of trienyl esters such as (I) to benzaldehydes (II) via a cascade coupled with a rare redox isomerization is described.

N-Heterocyclic carbene catalysed redox isomerisation with reduction about the carbonyl has been developed in the transformation of trienyl esters to tetrasubstituted benzaldehydes. The reaction proceeds in good to excellent yield, and in cases that provide 2,2′-biaryls, enantioselectivity is observed. Mechanistic studies demonstrate the intermediac...

Lewis base catalysis by lone pair donation into anti-bonding π orbitals (n–π*) is a growing field with a range of Lewis bases capable of this type of catalysis. In this review, catalysis of the Morita–Baylis–Hillman reaction, the Steglich rearrangement, and the annulation of α,β-unsaturated acyl Lewis adducts are discussed, using N-heterocyclic car...

The enantioselective vinylogous Michael/aldol cascade is an underdeveloped approach to cyclohexenes. Herein we describe a highly enantio- (most ≥98:2 er) and diastereoselective (all ≥15:1 dr) N heterocyclic carbene catalyzed cycloisomerization of acyclic ester dienolates to cyclohexyl β-lactones. Derivatizations avail various cyclohexenes bearing 4...

But(yl) not futile: A range of N-tert-butyl-substituted triazolylidene N-heterocyclic carbenes have been prepared. Of these, the morpholinone-derived catalyst (1) proved best suited to the enantioselective synthesis of cyclopentanes from donor-acceptor cyclopropanes and α,β-unsaturated acyl fluorides. The performance of this catalyst has been corre...

NHC-Katalysator: Eine Reihe von N-tert-Butyl-substituierten N-heterocyclischen Triazolylidencarbenen wurde hergestellt. Darunter erwies sich der von Morpholinon abgeleitete Katalysator 1 als am besten geeignet für enantioselektive Synthesen von Cyclopropanen ausgehend von Donor-Akzeptor-Cyclopropanen und α,β-ungesättigten Acylfluoriden. Die Aktivit...

Reaction discovery using N-heterocyclic carbene organocatalysis has been dominated by the chemistry of acyl anion equivalents. Recent studies demonstrate that NHCs are far more diverse catalysts, with a variety of reactions discovered that proceed without acyl anion equivalent formation. In this tutorial review selected examples of acyl anion free...

The NHC-catalyzed Claisen rearrangement of hybrid Ireland Coates structures has been achieved allowing (3 + 2) annulation between donor-acceptor cyclopropanes and α,β-unsaturated acyl fluorides. The reaction proceeds with high diastereoselectivity (>20:1) affording a diverse range of β-lactone fused cyclopentanes. Mechanistic studies are detailed.

The first example of Brønsted/Lewis base cascade catalysis using an N-heterocyclic carbene has been realised through the rearrangement of cyclopropylesters to dihydropyranones. The scope and mechanism of this transformation has been examined implicating a novel NHC-mediated electrocyclic cyclopropanerearrangement followed by an anionic oxy Claisen-...

NHC catalysed rearrangement of α,β-unsaturated enol esters derived from formyl acetates and cyclopentyl annulated α,β-unsaturated acids provides the cyclopentapyranone core of (-)-7-deoxyloganin (1) with diastereo- and chemoselectivity in 6 steps starting from (-)-citronellal. The elaboration to the natural product has been investigated using two n...

NHCs activate a diverse range of materials and thereby play a central role in modern reaction discovery. Our studies have focused on the application of NHCs as Lewis base catalysts. We recently developed an all-carbon [4+2] cycloaddition-decarboxylation that typifies this type of catalysis. Herein, the discovery of this methodology, its context and...

The synthesis of 1-acyl-2-alkylcycloalkenes from a variety of cycloalkanones has been achieved via either β-keto enol phosphates or β-bromoenones. Both methods exploit simple and readily scalable transformations allowing the preparation of the desired compounds to be achieved in three, or four steps, respectively. The utility of these strategies ha...

Herein we report the first all-carbon N-heterocyclic carbene-catalyzed (4 + 2) cycloaddition. The reaction proceeds with α,β-unsaturated acid fluorides and silyl dienol ethers and produces 1,3-cyclohexadienes with complete diastereocontrol (dr >20:1) while demonstrating a new type of reaction cascade exploiting α,β-unsaturated acyl azoliums.

The diastereoselective N-heterocyclic carbene (NHC) catalyzed rearrangement of α,β-unsaturated enol ester (S)-2b has been used to assemble dihydropyranone (S)-3b, a material embodying the bicyclic core of the iridoid family of natural products. Elaboration of this intermediate, by chemoselective reduction followed by stereoselective β-glycosylation...

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(Chemical Equation Presented) Catalytic generation of α,β- unsaturated acyl imidazolium cations and enolates has been achieved, and their involvement in a Michael addition acylation sequence exploited, to provide a range of dihydropyranones. α,β-Unsaturated enol esters, or α,β-unsaturated acid fluorides in association with TMS enol ethers, serve as...