Unusual Diastereoselectivity in Intramolecular Diels-Alder Reactions of Substituted 3,5-Hexadienyl Acrylates. Preference for a Boatlike Structure of the Six-Atom Tether Due to Ester Overlap

Tandem cross enyne metathesis (CEYM)-intramolecular Diels-Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds

A new tandem cross enyne metathesis (CEYM)-intramolecular Diels-Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM-IMDAR protocols.

Ethyl (4aR*,7S*,8S*,8aS*)-1-oxo-7-phenyl-3,4,4a,7,8,8a-hexa-hydro-1H-isochromene-8-carboxyl-ate

In the title compound, C₁₈H₂₀O₄, both the tetra­hydro­pyran­one ring and the cyclo­hexene ring adopt envelope conformations. The crystal packing is stabilized by weak inter­molecular C—H⋯O hydrogen bonding.

Development of efficient Lewis acid catalysts for intramolecular cycloaddition reactions of ester-tethered substrates

We have developed novel bidentate Lewis acids that efficiently promote the intramolecular cycloaddition reactions of ester-tethered substrates. Bis-aluminated triflic amide derivatives [TfN(AlR(1)R(2))2], which are generated by simply mixing triflic amide and 2 equiv of methyl aluminum or aluminum hydride, catalyzed intramolecular Diels-Alder (DA) reactions of ester-tethered 1,7,9-trienes and intermolecular DA reactions of alpha,beta-unsaturated lactones. We also found that bimetallic Lewis acid derived from 1,1'-biphenyl-2,2'-di(triflyl)amide and dimethylaluminum chloride promoted the intramolecular [3 + 2] cycloaddition reaction of acrylate derivatives having an allylsilane part.

Cationic Rh(I) Catalyst in Fluorinated Alcohol: Mild Intramolecular Cycloaddition Reactions of Ester-Tethered Unsaturated Compounds

In fluorinated alcohols, the cationic Rh(I) species, which is derived from [Rh(COD)Cl]2 and AgSbF6, efficiently catalyzed intramolecular [4+2] cycloaddition reactions of ester-tethered 1,3-diene-8-yne derivatives. The catalytic system was also effective in intramolecular [5+2] cycloaddition reactions of ester-tethered omega-alkynyl vinylcyclopropane compounds.

Tandem Diels-Alder/fragmentation approach to the synthesis of eleutherobin

[reaction: see text] A synthesis of 28, the carbon framework of the eleutherobin aglycone, is reported in a 15-step sequence from readily available starting materials. The tandem Diels-Alder reaction of 6 and 7 to produce 18, in which three new rings and six new stereocenters are formed, is a key step in the reaction sequence.

On the endo/exo stereoselectivity of intramolecular Diels-Alder reactions of hexadienylacrylates: an interesting failure of density functional theory

[formula: see text] A combined experimental and computational study of endo/exo stereoselectivity in a series of IMDA reactions of hexadienylacrylates has found that DFT makes erroneous predictions when the endo and exo transition states possess differing degrees of conjugation. These problems are overcome by carrying out calculations at the MP2 level of theory, which gives remarkably accurate Boltzmann distributions of products. These findings are used to predict ways to obtain either endo- or exo-cycloadducts exclusively.

Conformational study of the intramolecular diels-alder reaction of a pentadienyl acrylate. Theoretical evaluation of kinetic and thermodynamic control

Acrylate 4, prepared from diacetylrhamnal, underwent intramolecular Diels-Alder cycloaddition to give the thermodynamically disfavored trans-fused gamma-lactone 15 as the major product, along with two stereoisomeric cycloadducts. A computational analysis of each of the four transition states arising from 4 and the corresponding cycloadducts permits an understanding of the contrasting requirements for kinetic versus thermodynamic control of the reaction.