Catalytic and Asymmetric Vinylogous Mukaiyama Reactions on Aliphatic Ketones: Formal Asymmetric Synthesis of Taurospongin A

Phosphine-Catalyzed Intramolecular Vinylogous Aldol Reaction of α-Substituted Enones

We demonstrate the first phosphine-catalyzed intramolecular vinylogous aldol reaction (IVAR) of α-substituted enones. This strategy provides access to various pentannulated (hetero)arenes and dibenzocycloheptanones incorporated with two contiguous stereocenters, one of which is an all-carbon quaternary center. The scope of this work is further broadened through elaborations of the IVAR adducts to (i) benzannulated nine-membered carbocyclic systems, (ii) interesting classes of 1,3-dienes, 1,3,5-trienes, and 1-yn-3,5-dienes, and (iii) the analogs of echinolactone D and russujaponol F.

Total Synthesis of (R)-Argentilactone and (R)-Goniothalamin Using a Free-Radical Photoredox Approach to α,β-Unsaturated δ-Lactones

α,β-Unsaturated δ-lactones are structural motifs found in diverse pharmacologically active natural products. In fact, the unsaturated lactone is often responsible for the biological activity. Herein, we report a new approach for the syntheses of (R)-argentilactone and (R)-goniothalamin based on a photoredox intermolecular iodolactonization mediated by a photoredox process. This new approach, already employed in our research group, stands as a new methodology to achieve several natural products containing α,β-unsaturated δ-lactones.

Intertwined Analytical, Experimental and Theoretical Studies on the Formation and Structure of a Copper Dienolate

The reaction of a silyl dienolate, a Cu(II) salt and TBAT yielding the corresponding copper dienolate is addressed. A combined NMR and cyclic voltammetry analysis first highlight the role of TBAT in the Cu(II) to Cu(I) reduction and the structure of the precatalytic species. From these first results a second set of NMR and theoretical studies enable the determination of the structure and the mechanism of formation of the copper dienolate catalytic species. Finally, we showed that that the copper catalyst promote the E/Z s-cis/s-trans equilibration of the silyl dienolate precursor through a copper dienolate intermediate. All of these results unveil some peculiarities of the catalytic and asymmetric vinylogous Mukaiyama reaction.

Activation of allylic esters in an intramolecular vinylogous kinetic resolution reaction with synergistic magnesium catalysts

Kinetic resolution (KR) of racemic starting materials is a powerful and practical alternative to prepare valuable enantiomerically enriched compounds. A magnesium-catalyzed kinetic resolution based on a designed intramolecular vinylogous Michael reaction is disclosed. Here we show a synergistic catalytic strategy based on the development of chiral ligands. Substrates containing linear allylic ester structures are designed and synthesized to construct key [6.6.5]-tricyclic chiral skeletons via this kinetic resolution process. Detailed mechanistic studies reveal a rational mechanism for the current intramolecular vinylogous KR reaction. The desired direct intramolecular asymmetric vinylogous Michael reaction of linear allylic esters is realized in high efficiency and enantioselectivity with the synergistic catalytic system.

Kinetic resolution allows to obtain enantioenriched compounds from racemic mixtures. Here, the authors report a synergistic magnesium catalyst promoting kinetic resolution of an intramolecular vinylogous Michael reaction to access [6.6.5]-tricyclic chiral skeletons.

Triflimide: An Overlooked High-Performance Catalyst of the Mukaiyama Aldol Reaction of Silyl Ketene Acetals with Ketones

The Mukaiyama aldol reaction is a widely applied carbon-carbon bond forming reaction. However, despite numerous well-established methods using aldehydes as acceptors, only few examples exist with ketones. Here we report a highly practical catalytic approach to this transformation, namely, the triflimide catalyzed Mukaiyama aldol reaction of silyl ketene acetals with ketones. This method exhibits a broad substrate scope, is very rapid, tolerates functionalized substrates, and requires only parts-per-million catalyst loadings with preparative scale reactions up to hundreds of grams in excellent purity (>99 %).

Direct catalytic enantio- and diastereoselective ketone aldol reactions of isocyanoacetates

A catalytic asymmetric aldol addition/cyclization reaction of unactivated ketones with isocyanoacetate pronucleophiles has been developed. A quinine-derived aminophosphine precatalyst and silver oxide were found to be an effective binary catalyst system and promoted the reaction to afford chiral oxazolines possessing a fully substituted stereocenter with good diastereoselectivities and excellent enantioselectivities.

Chiral N,N′-dioxide–In(OTf)3-catalyzed asymmetric vinylogous Mukaiyama aldol reactions

The chiralN,N′-dioxide–In(OTf)₃catalyst system has been successfully developed to catalyze the vinylogous Mukaiyama aldol reaction of silyl dienol ester with aldehydes. Furthermore, (R,E)-methyl 5-hydroxydec-2-enoate can be easily converted into (R)-δ-decalactone, (3R,5R)-valerolactone and (4R,6R,10R,12R)-verbalactone.