Cyclopropanation with Fischer acyloxycarbene complexes: preparation of cyclopropane and cycloheptane-fused gamma-lactones

Toward Efficient and Stereoselective Aromatic and Dearomative Cope Rearrangements: Experimental and Theoretical Investigations of α-Allyl-α'-Aromatic γ-Lactone Derivatives

The aromatic Cope rearrangement is an elusive transformation that has been the subject of a limited number of investigations compared to those seemingly close analogues, namely the Cope and aromatic Claisen rearrangement. Herein we report our investigations inspired by moderate success observed in the course of pioneering works. By careful experimental and theoretical investigations, we demonstrate that key substitutions on 1,5-hexadiene scaffold allow fruitful transformations. Especially, efficient functionalisation of the heteroaromatic rings results from the aromatic Cope rearrangement, while highly stereoselective interrupted aromatic Cope rearrangements highlight the formation of chiral compounds through a dearomative process.

Cope Rearrangement of 1-Acyl-2-vinylcyclopropanes to Cyclohept-4-Enones

Cycloheptenones are widespread in natural products and bioactive molecules. An efficient and convenient NaH-mediated Cope Rearrangement of doubly activated vinylcyclopropanes is reported for the synthesis of cyclohepten-4-ones. These flexible intramolecular reactions were applicable to a wide range of substrates and could be performed on gram scale. The derivatization of the product leads to short and highly efficient synthesis of some useful functional molecules.

Aromatic Cope rearrangements

Reviewed herein is the aromatic Cope rearrangement, a Cope rearrangement where one (or both) of the alkenes of the 1,5-diene are part of a greater aromatic system. While the Cope rearrangement of 1,5-dienes has seen wide utility, variation, and application in chemical synthesis, the aromatic Cope rearrangement, comparatively, has not. This review summarizes the ∼40 papers dating back to 1956 on this topic and is divided into the following sections: (1) introduction, including kinetic and thermodynamic challenges of the aromatic Cope rearrangement, and (2) key substrate features, of which there are four general types: (i) α-allyl-α-aryl malonates (and related substrates), (ii) 1-aryl-2-vinylcyclopropanes, and (iii) anion-accelerated aromatic oxy-Cope substrates, and (iv) the concept of synchronized aromaticity. Ultimately, we hope this review will draw attention to a potentially valuable transformation for arene functionalization that warrants further studies and development.

Synthesis of fused tricyclic systems by thermal Cope rearrangement of furan-substituted vinyl cyclopropanes

A novel method for the construction of hexahydroazuleno[4,5-b]furans has been developed in which 1-furanyl-2-alkenylcyclopropanes undergo highly stereoselective thermal Cope rearrangement.

New Benzenoid Derivatives and Other Constituents from Lawsonia inermis with Inhibitory Activity against NO Production

Three new benzenoid derivatives, lawsoinermone (1), inermidioic acid (2), and inermic acid (3) have been isolated from the aerial part of Lawsonia inermis, together with 11 known compounds (4-14). The structures of three new compounds were determined through spectroscopic and MS analyses. Compounds 1, 4-6, 13 and 14 were evaluated for inhibition of nitric oxide production in LPS-stimulated product of nitrite in RAW 264.7 cells with IC₅₀ values of 6.12, 16.43, 18.98, 9.30, 9.30 and 14.90 μg/mL, respectively.

Iridium-catalysed asymmetric allylic alkylation of benzofuran γ-lactones followed by heteroaromatic Cope rearrangement: study of an unusual reaction sequence

The iridium-catalysed asymmetric allylic alkylation of benzofuran γ-lactones produces 1,5-hexadienes that were found to be excellent substrates for an unusual heteroaromatic Cope rearrangement.

Ligating properties of anionic Fischer-type carbene complexes, [(CO)(5)M[double bond, length as m-dash]C(X)Y](-)

With the simplest of anionic Fischer-type carbene complexes acting as ligands, Cp(2)Zr(Cl){OCMe}M(CO)(5) compounds (M = Cr or W) promote alpha-olefin oligomerization and polymerization in the presence of MAO. Attaching an N-heterocyclic ring to the carbene carbon atom in similar precursors, allows a variety of hard metal ions and fragments to be captured by external bidentate coordination. The outcome of the attachment of a phosphorus or sulfur functionality to an alpha-carbon of an O-anionic carbene is formation of a bidentate ligand and then internal four-membered carbene-heteroatom chelate formation. alpha-Deprotonated carbene complexes are also precursors for remote, one-N, six-membered carbene complexes of various metals whereas alpha-C-, alpha-N- or alpha-O-deprotonated as well as beta-deprotonated Fischer-type carbene complexes display unique synthon properties towards Ph(3)PAu(+) and partake in unusual ensuing coordination of liberated group 6 metal carbonyl moieties to form dinuclear products.

Dearomatization reactions of aryl-substituted silaaziridines

Silaaziridines with an aryl group on either the carbon or the nitrogen atom undergo dearomatization reactions upon treatment with benzaldehyde. The reactions form new bonds ortho to the nitrogen substituents with high diastereoselectivity. These dearomatization processes likely are driven by relief of the considerable ring strain of the silaaziridine.