Dehydrogenation chemistry has long been established as a fundamental aspect of organic synthesis, commonly encountered in carbonyl compounds. Transition metal catalysis revolutionized it, with strategies like transfer-dehydrogenation, single electron transfer and C–H activation. These approaches, extended to multiple dehydrogenations, can lead to aromatization. Dehydrogenative transformations of aliphatic carboxylic acids pose challenges, yet engineered ligands and metal catalysis can initiate dehydrogenation via C–H activation, though outcomes vary based on substrate structures. Herein, we have developed a catalytic system enabling cyclohexane carboxylic acids to undergo multifold C–H activation to furnish olefinated arenes, bypassing lactone formation. This showcases unique reactivity in aliphatic carboxylic acids, involving tandem dehydrogenation-olefination-decarboxylation-aromatization sequences, validated by control experiments and key intermediate isolation. For cyclopentane carboxylic acids, reluctant to aromatization, the catalytic system facilitates controlled dehydrogenation, providing difunctionalized cyclopentenes through tandem dehydrogenation-olefination-decarboxylation-allylic acyloxylation sequences. This transformation expands carboxylic acids into diverse molecular entities with wide applications, underscoring its importance.
A highly practical and step‐economic α,β‐dehydrogenation of carboxylic acids via enediolates is reported through the use of allyl‐palladium catalysis. Dianions underwent smooth dehydrogenation when generated using Zn(TMP)2⋅2 LiCl as a base in the presence of excess ZnCl2, thus avoiding the typical decarboxylation pathway of these substrates. Direct access to 2‐enoic acids allows derivatization by numerous approaches.
more » « less- PAR ID:
- 10040491
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie
- Volume:
- 129
- Issue:
- 42
- ISSN:
- 0044-8249
- Page Range / eLocation ID:
- p. 13302-13305
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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