Meldrum's acid, 2'5-diphenyl-1'3-dioxane-4'6-dione, was produced by [2+2] cycloadditions of the (chlorocarbony1)phenylketene with benzaldehyde. Acid hydrolysis of the meldrum's acid regenerated benzaldehyde and also yielded phenylacetic acid as the final product

While the fundamental series of [2+2]cycloadditions and retro[2+2]cycloadditions that make up the pathways of ruthenium-catalysed metathesis reactions is well-established, the exploration of mechanistic aspects of alkene metathesis continues. In this Feature Article, modern mechanistic studies of the alkene metathesis reaction, catalysed by well-defined ruthenium complexes, are discussed. Broad...

The hetero Diels–Alder (HDA) reactions of 1-diethoxyphosphonyl-1,3-butadiene with various nitroso dienophiles have been studied at the B3LYP/6-31G** level. Structural, energetic and electronic properties are discussed. These cycloadditions with nitroso dienophiles are characterized by a total proximal regioselectivity and an endo selectivity. The influence of the nitroso substitution on the act...

Allenes are important 2π building blocks in organic synthesis and engage as 2-carbon components in many metal-catalyzed reactions. Wender and co-workers discovered that methyl substituents on the terminal allene double bond counterintuitively change the reactivities of allenes in [Rh(CO)2Cl]2-catalyzed intermolecular (5 + 2) cycloadditions with vinylcyclopropanes (VCPs). More sterically encumbe...

Hydroxyallyl cation and lithium and sodium oxyallyl cations are predicted to react with 1,3-butadiene both in a stepwise fashion and via concerted [4‡ 3] cycloaddition with so-called extended stereochemistry. With hydroxyallyl cation, the stepwise process is preferred and subsequent second bond closures generate products equivalent to those that would arise from concerted [4‡ 3] or [3‡ 2] cyclo...

The frontispiece shows the transformation of Fischer Carbene Complexes in a wide variety compounds through Higher-order Cycloadditions. flask, containing carbene, pour on paper different products synthesized last 20 years. In background, blackboard draws traces important contributions area, such as orbital correlation diagrams for Cycloadditions and representation molecular orbitals made by Woo...

Intramolecular cycloadditions of photogenerated azaxylylenes provide access to unprecedented polyheterocyclic scaffolds, suitable for subsequent postphotochemical modifications to further grow molecular complexity. Here we explore approaches to rapid "assembly" of novel photoprecursors with nitrogen/oxygen-rich tethers capable of producing potential pharmacophores and also compatible with subse...

The synthesis of polysubstituted hexahydroindoles through trienamine-organocatalyzed cycloadditions of pyrrolidinyl dienals, prepared by palladium-catalyzed cycloisomerization, is reported. The cycloadditions of this novel class of dienals proceed with excellent levels of enantio- and diastereoselectivity, with the regioselectivity of cycloaddition with respect to the tethering ring readily tun...

In this article the utility of phosphoramidite ligands in enantioselective Au(I) catalysis was explored in the development of highly diastereo- and enantioselective Au(I)-catalyzed cycloadditions of allenenes. A Au(I)-catalyzed synthesis of 3,4-disubstituted pyrrolidines and γ-lactams is described. This reaction proceeds through the enantioselective Au(I)-catalyzed cyclization of allenenes to f...

Strain-promoted cycloadditions of cyclic nitrones with biaryl-aza-cyclooctynone (BARAC) proceed with rate constants up to 47.3 M(-1) s(-1), this corresponds to a 47-fold rate enhancement relative to reaction of BARAC with benzyl azide and a 14-fold enhancement over previously reported strain promoted alkyne-nitrone cycloadditions (SPANC). Studies of the SPANC reaction using the linear free ener...