A facile and mild synthesis of enamides using a gold-catalyzed nucleophilic addition to allenamides

A mild and facile synthesis of enamides has been developed, based on nucleophilic addition of electron-rich aromatic and heteroaromatics to an allenamide unit catalyzed by a gold salt. Yields for the transformation were 29-98%

Synthesis and solid state structure of pyridyl diboroxines linked by a chiral spacer analogous to Troger's base

Pyridyl-assisted templating of phenyl boronic acid has been utilised to link two remote boroxines via a chiral spacer. The chiral spacer is a carbocyclic analogue of Tröger's base and contains a unique chiral cavity, and the flanking boroxine units have been shown, by single crystal X-ray analysis, to extend the size and shape of this cavity

Cycloaddition chemistry of allenamides

Allenamides are electron deficient allenamine equivalents that can participate in a range of cycloaddition events giving rise to novel heterocycles and diverse molecular architectures contained within natural products. This review summarizes some of the recent research in this area, with particular reference to predicting the stereochemical outcomes of such transformations and highlighting recent applications of allenamides in cycloaddition transformations which showcase the utility of this under-utilized synthon

The regioselective outcome of ring rearrangement metathesis transformations performed on bicyclo[2.2.2]oct-2-ene derivatives

Treatment of bicyclo[2.2.2]oct-2-en-7-one with organometallic reagents gives the addition products in good yield and moderate diastereoselectivities in favour of the syn-products. Subsequent exposure of these addition products to ruthenium catalysed ring rearrangement metathesis (RRM) conditions reveals significant product divergence as a consequence of the newly acquired stereocentre

Organocatalysis [review article]

Reactions carried out with substoichiometric quantities of organic molecules as catalysts have received much attention over the past decade. This review highlights progress in 2011 towards highly enantioselective organocatalytic systems and the natural product/biologically active compounds that can be prepared using these types of processes

A biosynthetically inspired route to substituted furans using the Appel reaction: total synthesis of the furan fatty acid F₅

Appel reaction conditions have been harnessed to affect a mild biosynthetically inspired dehydration of endoperoxides to deliver multi-substituted electron rich furans. Unlike traditional dehydrative procedures, this method is metal and acid free, and can be achieved under redox neutral conditions. It is general for a range of aryl and alkyl substituted endoperoxides, and is functional group tolerant. Furthermore, this procedure has been used to deliver an effective total synthesis of the furan fatty acid (FFA) F5

An asymmetric synthesis of trans-fused butyrolactones from endoperoxides

The intermolecular addition of 1,3-dicarbonyl equivalents to endoperoxides in the presence of an organocatalyst yields trans-fused butyrolactones in high yield and enantioselectivities. This methodology expands the synthetic utility of endoperoxides and further underlines their potential as sources of oxygen functionality for natural and non-natural product target synthesis

Indium-mediated 2-oxonia cope rearrangement of 1,4-dienols to 1,3-dienols

An indium-mediated isomerization of 1,4-dienols to 1,3-dienols is described. This procedure consists of the addition of pentadienylindium, in a protic solvent, to aldehydes giving the kinetic γ-allylation product in high yields. The subsequent conversion of this γ-allylation product to its thermodynamic 1,3-dienol α-isomer can be achieved by its exposure to indium triflate in the presence of a substoichiometric amount of aldehyde at room temperature. This transformation exhibited moderate to good substrate scope and has been shown to proceed by a 2-oxonia Cope rearrangement

Total synthesis of the marine-derived cyclic depsipeptide alternaramide

The first synthesis of the marine fungus derived natural product alternaramide is described using solution phase coupling protocols and via a macrolactonization and macrolactamization route. The structure of alternaramide was confirmed and was supported by single crystal X-ray analysis which exhibited three similar molecules in the asymmetric unit, each with transannular hydrogen bonds

Photoredox approach to N-Acyl-N'-aryl-N,N'-aminals using enamides and their conversion to γ-lactams

A photoredox catalytic approach to synthetically valuable N-acyl-N'-aryl-N,N'-aminals is described. This method uses the addition of a radical precursor to enamides, with subsequent interception of the cationic iminium intermediate with an arylamine. The reaction has been shown to be compatible with electron-rich and electron-deficient arylamines, and moderate to good levels of diastereoselectivity can be attained using a chiral enamide. Furthermore, the N-acyl-N'-aryl-N,N'-aminal reaction products can be readily cyclized, providing a novel synthetic route to valuable γ-lactams