17017-59-3Relevant academic research and scientific papers
Palladium-catalysed dehydrogenative generation of imines from amines. A nature-inspired route to indoles via cross-couplings of amines with arylhydrazines
Taddei, Maurizio,Mura, Manuel G.,Rajam?ki, Suvi,De Luca, Lidia,Porcheddu, Andrea
, p. 3002 - 3013 (2014/03/21)
H-substituted imines are elusive compounds formed when aldehydes or ketones are mixed with ammonia. However, this class of molecules can be prepared through selective removal of a hydrogen molecule from a primary amine using a transition metal catalyst. This biomimetic transformation, previously employed for the N-alkylation of anilines, is applied here to a domino preparation of differently substituted indoles from aliphatic primary amines and arylhydrazines. Several different linear and branched aliphatic primary amines are oxidized with reusable palladium on charcoal to the corresponding primary imines entrapped as arylhydrazones that can be isolated as such. Arylhydrazones can be further converted into N-alkylindole derivatives via an acid-mediated indolisation reaction. The one-pot domino hydrogen transfer Fischer indole synthesis under heterogeneous catalysis is also possible, giving access to diverse substituted indoles, including NH indoles obtained after deprotection of the corresponding benzyl compounds. The truly heterogeneous nature of the catalyst was demonstrated by recycling the catalyst in the same reaction, and in other palladium-catalysed transformations.
29. Synthesis of Indole Derivatives by [2 + 2] Photocycloaddition of Indoline-2-thiones with Alkenes and Photodesulfurization of Indoline-2-thiones
Nishio, Takehiko,Oka, Mitsuru
, p. 388 - 397 (2007/10/03)
The photochemical synthesis of indole derivatives starting from the indoline-2-thiones 1 is described. Irradiation of indoline-2-thiones 1 in the presence of alkenes 3 gave 2-alkyl-3H-indoles 4-7 or 2-alkylindoles 8-22 through the ring cleavage of the intermediates, spirocyclic amino-thietanes, initially derived by [2 + 2] cycloaddition of the C=S bond of 1 and the C=C bond of 3. Irradiation of 1 in the presence of trialkylamines 26 gave desulfurization products 27-32 and unexpected 3-alkylindoles 33-40. N-Acylindoline-2-thiones 1l-p yielded the deacylated products, indoline-2-thiones 1a-b, and ethyl esters 43 through γ-H abstraction by the excited thioamide S-atom when irradiated in CDCl3/EtOH or benzene/EtOH. Oxygen analogues 2a-d also underwent intramolecular H abstraction to give the indolin-2-ones 2e-f and ethyl esters 43 in a similar way.
An Expeditious Synthesis of 3-Alkyl-, Aryl- and Heteroaryl-indoles by way of an Intramolecular Horner-Wittig Reaction
Couture, Axel,Deniau, Eric,Gimbert, Yves,Grandclaudon, Pierre
, p. 2463 - 2466 (2007/10/02)
A variety of 3-alkyl-, aryl- and heteroaryl-indoles have been efficiently prepared by base-induced intramolecular cyclization of suitable aromatic o-acyl substituted Horner-Wittig reagents.
