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Open sesame: A direct synthesis of functionalised and stereodefined dienes, relying on a domino allylic alkylation/electrocyclic ring-opening sequence, is reported. This method allows concise access to doubly vinylogous esters. A further systematic study of ring-opening rates of carbon-substituted cyclobutenes allowed the design of substrates amenable to sequential pericyclic reactions (see scheme)., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The development of a direct ylide transfer to carbonyl derivatives and of a sulfoxide-mediated arylation is presented from a unified perspective. Mechanistic studies (including density functional calculations) support a common reaction pathway and showcase how subtle changes in reactant properties can lead to disparate and seemingly unrelated reaction outcomes.

An unusual cleavage of the non-ylidic carbon-sulfur bond of a sulfonium ylide is reported. The reaction can be catalysed by a variety of palladium(II) complexes under mild conditions. Preliminary results show that coordination of the ylide to the metal center results in significant structural changes.

Catalytic asymmetric allylation of lactone 1 with allyl boronates leads to functionalized cyclobutenes in high regio- and stereoselectivity.

Rearranging its feathers: The transformation of simple linear amides into a diverse range of branched, functionalized products by conversion to iminium esters is followed by sequential treatment with nucleophiles and electrophiles (see scheme). The method takes advantage of a novel Claisen rearrangement and the use of aromatic substrates greatly facilitates the formation of the intermediate iminium ether., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Diastereomers made to order: In an unprecedented ligand-controlled process a racemic mixture of four stereoisomers can be converted with high selectivity into each one of the diastereomers of the product, at will (see scheme). The mechanism of this deracemization of epimers, that is, a de-epimerization, was also studied., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new protocol for the direct two-electron oxidative Umpolung of alkali halide salts is reported. This procedure, relying on the use of a commercially available sulfoxide as the oxidant, allows the electrophilic halogenation of carbonyl compounds as well as halolactonisation reactions to proceed from the corresponding sodium salts, at room temperature and under mild conditions.

Your wish is my command: Deracemization is a powerful strategy wherein a racemate is converted into a 100 % yield of a single enantiopure product. A new concept in catalytic deracemization is presented, in which a racemate with n stereogenic elements can be selectively converted into each one of 2(m) (m = number of chiral centers of the product) different enantiopure products, by simple tuning of the reaction conditions., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Keteniminium salts are powerful electrophilic heterocumulene reagents well-known for their selectivity and stereocontrol in [2+2] cycloadditions to olefins and carbonyl derivatives. Furthermore, they are readily accessible from stable and simple precursors under a variety of different conditions. Herein, we present the chemistry of keteniminium salts with the hindsight of time, describe preparation methods, recent [2+2] chemistry, mechanistic studies, and assorted applications that significantly extend the scope of utility of these unique electrophilic heterocumulenes., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A novel sulfoxide-mediated α-arylation of carbonyl compounds is reported. This reaction proceeds under very mild conditions at room temperature and does not require any transition-metal promoter or catalyst.

The development of a modular synthesis of 3-substituted-2-pyrones is described. The attainment of this strategy hinges on a new electrophilic pyrone derivative which can be readily prepared on a multigram scale and which performs very competently in metal-catalyzed cross-coupling reactions with a variety of nucleophiles.

A novel catalytic alkyne cross-coupling reaction is reported which connects tertiary propargyl alcohols with omega-alkynylnitriles with perfect atom economy. This remarkable process generates highly functionalized, stereodefined dienones that are formal aldol products in a single step. Moreover, the specificity of the cyano substituent for this reaction demonstrates the unique and somewhat underappreciated properties of that functional group.

A novel, dual-pathway ring expansion of alkynylcyclopropanols is described. On treatment with a ruthenium catalyst, these compounds undergo highly selective enlargement to either (Z)-alkylidene cyclobutanones or beta-substituted cyclopentenones. The unique ability to access the least selective double bond isomers of alkylidene cyclobutanones and the dramatic shift of reactivity observed further illustrate the particular intricacies of ruthenium catalysis when compared to other alkynophilic transition metals.

The first condensations between bis(trimethylsilyloxy)cyclobutene derivatives and functionalized orthoesters are reported. The resulting adducts are readily converted into spirocycloethers, which undergo a variety of -CH2- and -O- insertions with excellent regioselectivity.

The development of a novel, chemoselective, and catalytic deprotection methodology that proceeds under mild and neutral conditions is described, and its mechanism of action is analyzed in some detail. The scope, limitations, and advantages of this protocol are discussed. Selected applications in synthesis are also highlighted.

[reaction: see text] The use of 2-(trimethylsilyloxy)furan derivatives as dianion equivalents leads to a general and connective spiroannulation protocol for the efficient preparation of spirocyclic butenolides.

The skeletal rearrangement of bicyclo[2.2.2]lactones, involving a mild and chemoselective palladium-catalysed translocation key-step, provides an efficient and diastereoselective access to synthetically useful bicyclo[3.3.0]lactones.

An efficient two-step annelation of functionalized orthoesters with trimethylsilyloxyfuran derivatives, which delivers suitably decorated bicyclo[3.n.0]lactones in high overall yields and with complete diastereocontrol of up to three contiguous stereocenters, is reported.