Issue 30, 2022

Highly selective acid-catalyzed olefin isomerization of limonene to terpinolene by kinetic suppression of overreactions in a confined space of porous metal–macrocycle frameworks

Abstract

Natural enzymes control the intrinsic reactivity of chemical reactions in the natural environment, giving only the necessary products. In recent years, challenging research on the reactivity control of terpenes with structural diversity using artificial host compounds that mimic such enzymatic reactions has been actively pursued. A typical example is the acid-catalyzed olefin isomerization of (+)-limonene, which generally gives a complex mixture due to over-isomerization to thermodynamically favored isomers. Herein we report a highly controlled conversion of (+)-limonene by kinetic suppression of over-isomerization in a confined space of a porous metal–macrocycle framework (MMF) equipped with a Brønsted acid catalyst. The terminal double bond of (+)-limonene migrated to one neighbor, preferentially producing terpinolene. This reaction selectivity was in stark contrast to the homogeneous acid-catalyzed reaction in bulk solution and to previously reported catalytic reactions. X-ray structural analysis and examination of the reaction with adsorption inhibitors suggest that the reactive substrates may bind non-covalently to specific positions in the confined space of the MMF, thereby inhibiting the over-isomerization reaction. The nanospaces of the MMF with substrate binding ability are expected to enable highly selective synthesis of a variety of terpene compounds.

Graphical abstract: Highly selective acid-catalyzed olefin isomerization of limonene to terpinolene by kinetic suppression of overreactions in a confined space of porous metal–macrocycle frameworks

Associated articles

Supplementary files

Article information

Article type
Edge Article
Submitted
17 Mar 2022
Accepted
02 Jun 2022
First published
03 Jun 2022
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2022,13, 8752-8758

Highly selective acid-catalyzed olefin isomerization of limonene to terpinolene by kinetic suppression of overreactions in a confined space of porous metal–macrocycle frameworks

W. He, S. Tashiro and M. Shionoya, Chem. Sci., 2022, 13, 8752 DOI: 10.1039/D2SC01561G

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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