64666-40-6Relevant academic research and scientific papers
The Influence of Remote Heteroatom Substituents on the Stereoselectivity of Cyclopentene Ozonolysis
Bunnelle, William H.,Isbell, Terry A.
, p. 729 - 740 (2007/10/02)
The stereoselectivity for ozonide formation from cyclopentenes with allylic heteroatom substituents has been examined.Silyl ethers give high selectivity in favor of the exo-substituted ozonide, while esters of 2-cyclopentenol form ozonide mixtures with little stereoselection.Trapping experiments establish that fragmentation of the primary ozonides is highly regioselective to give only one of the isomeric ω-oxo carbonyl oxide intermediates and that the variation in final ozonide stereochemistry results from differing interactions between the remote substituent groupsand the carbonyl oxide system during cyclization of this intermediate.The effect of substituent and solvent on ozonide stereochemistry suggests a dominant role for electrostatic repulsion between carbonyl oxide and the heteroatom substituent during intramolecular cycloaddition.A chair-like transition state is proposed for this process and is in accord with the increase in exo selectivity for derivatives of 2-methyl-2-cyclopentenol.
Stereochemical Studies on Porphyrin a: Assignment of the Absolute Configuration of a Model Porphyrin by Degradation
Battersby, Alan R.,Cardwell, Kevin S.,Leeper, Finian J.
, p. 1565 - 1580 (2007/10/02)
The synthesis is described of a porphyrin alcohol (22) which has a structure very similar to that of porphyrin a (2).The model porphyrin was resolved by separation of its camphanate esters.Ozonolysis of the 2-nitrobenzoate of each enantiomer in tritiated form gave a derivative of 2-hydroxypentadioic acid whose configuration was determined by dilution analysis.It is demonstrated that correlation of the stereochemistry of porphyrin a with that of the model (22) will be possible by means of the (1)H and (19)F n.m.r. spectra of the corresponding esters with (-)-3,3,3-trifluoro-2-methoxy-2-phenylpropanoic acid.
