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Why do thioureas and squaramides slow down the Ireland-Claisen rearrangement?

ABSTRACT: A range of chiral hydrogen-bond-donating organocatalysts was tested in the Ireland-Claisen rearrangement of silyl ketene acetals. None of these organocatalysts was able to impart any enantioselectivity on the rearrangements. Furthermore, these organocatalysts slowed down the Ireland-Claisen rearrangement in comparison to an uncatalyzed reaction. The catalyst-free reaction proceeded well in green solvents or without any solvent. DFT calculations showed that the activation barriers are higher for reactions involving hydrogen-donating organocatalysts and kinetic experiments suggest that the catalysts bind stronger to the starting silyl ketene acetals than to transition structures thus leading to inefficient rearrangement reactions.

SUBMITTER: Kristofikova D

PROVIDER: S-EPMC6941421 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Why do thioureas and squaramides slow down the Ireland-Claisen rearrangement?

Krištofíková Dominika D Filo Juraj J Mečiarová Mária M Šebesta Radovan R

Beilstein journal of organic chemistry 20191210

A range of chiral hydrogen-bond-donating organocatalysts was tested in the Ireland-Claisen rearrangement of silyl ketene acetals. None of these organocatalysts was able to impart any enantioselectivity on the rearrangements. Furthermore, these organocatalysts slowed down the Ireland-Claisen rearrangement in comparison to an uncatalyzed reaction. The catalyst-free reaction proceeded well in green solvents or without any solvent. DFT calculations showed that the activation barriers are higher for ...[more]

PMID: 31921366

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