Structure reassignment of the major isomer from the Diels-Alder reaction of acryloyl chloride and 4,5,6,6a-tetrahydropentalene

Article Abstract:

The two adducts formed from the Diels-Alder reaction of 4,5,6,6a-tetrahydropentalene acryloyl chloride and were originally assigned 7-exo- and 7-endo-carboxylic acid structures after hydrolysis and hydrogenation.Unexpected results came from using these acids as starting materials for a superacid carbocation study, so assignments were reinvestigated. It appears, based on extensive investigation using 2D NMR, that one structure is correct, but that the other isomer is the 9-endo carboxylic acid. Formation of the two isomers can be explained. An X-ray study of one structure was performed for final proof of the structure.

Canada, Isomerization, Aromatic compounds, Diels-Alder reaction

---

1,3-Diphenylsulphonylcyclobutane: an unprecedented case of a higher stability of the trans isomer of 1,3-disubstituted cyclobutane

Article Abstract:

Equilibration of 1,3-diphenylsulfonylcyclobutane in t-BuOK/t-BuOH shows that the cis isomer is less stable than the cis isomer, an enthalpic effect. The difference is 2,1 kcal/mol. This represents an unprecedented situation for the trans isomer of 1,3-disubstituted cyclobutane. Cyclobutane rings are almost planar, which may explain the greater stability of the trans isomer. Why the system would avoid steric interaction in that way, not adopting the puckered conformation, is not clear. If the puckered conformation were adopted, the two bulky substituents would be at equatorial positions.

Chemical equilibrium, Stereoisomers, Butane, Enthalpy

---

Reaction of carbanions generated from arylmethylphosphonates with cyclic enones: regio- and steroselectivity of addition

Article Abstract:

XC6H4CH(Li)PO3Et2, alpha-lithiated benzylphosphonate esters, add to cyclohex-2-enone at the carbonyl group regioselectively. Increased reaction temperatures bring on reversal to starting materials rather than to the 1,4 addition. Configuration of the C(1) and C-sub-alpha centers relative to one another in the 1,2-adducts was found using the 13D NMR spectra. Regioselectivity of the addition is decreased for 2-methylcyclohex-2-enone.

Models, Molecules, Esters, Stereochemistry, Phosphonates, Carbonyl compounds

Similar abstracts:

• Abstracts: Structure, synthesis, and chemical reactions of fluorinated cyclopropanes and cyclopropenes. Carbon-carbon bond forming reactions mediated by silicon Lewis acid
• Abstracts: Structure, synthesis, and chemical reactions of fluorinated cyclopropanes and cyclopropenes. part 2 Catalytic enantioselective Strecker reactions and analogous syntheses
• Abstracts: Structural insight into the aromatic amino acid hydroxylases and their disease-related mutant forms. Partially modified retro-inverso peptides: development, synthesis, and conformational behavior
• Abstracts: Mechanism of the benzidine disproportionation of (arylhydrazo)pyridines: the reactions of 4-(4-chlorophenylazo)pyridine and (-hydrazo)pyridine in acid media
• Abstracts: Correlation of the rates of solvolysis of arylmethyl p-toluenesulfonates: application of the aromatic ring parameter and a discussion of similarity models

This website is not affiliated with document authors or copyright owners. This page is provided for informational purposes only. Unintentional errors are possible.