Recent Advances in C—H Functionalizations Assisted by Removable and/or Modifiable Directing Groups

Abstract

Transition-metal catalyzed chelation-assisted C-H bond functionalization is one of hot topics in current organic chemistry. Recently, using removable and/or modifiable directing groups for C-H bond functionalizations has being received specially attention and developed rapidly. By taking advantage of removable and/or modifiable directing groups, it not only greatly expands the scope of substrates for C-H fuctionalization, but also plays important roles in rapid construction of molecule diversity. Based on the classification according to different hetero-atom (N, O, S, and Si) donors, this review presents the state of the art in design of removable and/or modifiable directing groups for transition-metal catalyzed C-H functionalizations and their application in construction of molecule diversity. Finally, the existing problems and limitations of this field are summarized, and the outlook of the area is also prospected.

Palladium-Catalyzed Aromatic C–H Bond Nitration Using Removable Directing Groups: Regiospecific Synthesis of Substituted o-Nitrophenols from Related Phenols

“…We envision that the introduction of removable and/or modifiable directing groups for the C–H bond nitration could well circumvent the above-mentioned problem (Scheme ). More importantly, by using such directing groups, we can expect that the nitro group could be regiospecifically introduced to the ortho -position of a target functional group even unnecessary to consider the effect of the inherent orientation rules (Scheme )!…”

Pullenvalenes A–D: Nitric Oxide-Mediated Transcriptional Activation (NOMETA) Enables Discovery of Triterpene Aminoglycosides from Australian Termite Nest-Derived Fungi

“…Accounts of fungal natural products featuring a 6-O-methyl-N-acetyl-D-glucosaminyl glycoside residue are rare and to the best of our knowledge limited to twin reports in 2008 of a rice cultivation of Malbranchea f ilamentosa IFM 41300, which yielded the aromatic butenolide glycoside malfilamentosides 5 and triterpene glycoside malbrancheosides 6 (reisolated in 2019 from Auxarthron sp. KCB15F070 7 and in 2022 from Auxarthron umbrinum SCSIO 40432 8 ), and a 2015 report on the triterpene glycoside auxarthonoside from the spongederived fungus Auxarthron reticulatum. 9 Expanding the scope further, reports of fungal natural products featuring an Nacetyl-D-glucosaminyl glycoside residue are also rare and include diterpene isopimaranes from Paraconiothyrium sp.…”

Multiple-cycle photochemical cascade reactions

“…49 As a kind of quite important five-membered heterocycle, the special structure of oxazole enables its derivatives to exhibit many unique properties and bioactivities and thus has a wide range of potential applications in the fields of pharmaceuticals, pesticides, materials, etc. 50 Therefore, the organization of oxazole compounds has been receiving increasing attention. In 2016, Cho and co-workers accomplished a visible-light-induced cascade reaction of readily available α-bromoketones 45 and benzylamines 46, giving multifarious biologically and synthetically useful polysubstituted oxazoles 47 with moderate to good yields (up to 90% yield) (Scheme 12).…”