Unexpected Isomerization of Oxetane-Carboxylic Acids – substrate design.
Having established a viable model for the unexpected isomerism of oxetane carboxylic acids to lactones[cite]10.1021/acs.orglett.2c01402[/cite], and taken a look at a variation in the proton transfer catalyst needed to accomplish the transformation, I now investigate the substrate itself.
R’ is set to have three values, R’=H (the original substituent), R’= CH3 and R’= CF3 (FAIR data DOI: 10.14469/hpc/10820)
R’
ΔG‡, kcal/mol
H
27.0
CH3
29.1
CF3
39.6
The inference is clear-cut; to inhibit the isomerisation to a lactone, CF3 groups substituted onto the methylene groups of the oxetane will effectively do this, with CH3 itself having a much weaker effect.
DOI: 10.14469/hpc/10861 and 10.14469/hpc/10862
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