Iron catalyzed C-H activation and synthesis of novel ligands

Iron-catalyzed benzylic oxidations, nitrogen transfer reactions such as iminations of sulfides and sulfoxides, aziridinations of olefins and a-aminations of silyl enol ethers were developed. Also, the synthesis of novel nitrogen containing ligands such as 1,4,7-triazacyclononane (TACN) derivatives and dipyridylamine derivatives was undertaken.Iron-catalyzed benzylic oxidation was successfully performed by using a combination of iron(III) chloride (2 mol%) as a catalyst and tert-butyl hydroperoxide (TBHP) as an oxidant. Diarylmethane derivatives gave the corresponding ketones in excellent yields (up to >99%). Also, less reactive substrates bearing one annulated aryl group in a cyclic system, noncyclic compounds bearing one (hetero)aryl group and p-methoxytoluene led to the corresponding ketones or carboxylic acid in good yield. Even diphenylcarbinol was oxidized to afford benzophenone in 86% yield. Interestingly, the oxidation of triphenylmethane afforded tert-butyl triphenylmethyl peroxide in 91% yield instead of triphenylmethanol. Additionally, 1,4-dihydroxynaphthaline underwent oxidation in actonitrile at ambient temperature to afford 1,4-naphthoquinone in high yield (82%). Iron-catalyzed aziridination was achieved by using iron(II) triflate (2.5 mol%), MS 4A (20 mg), 20 equivs. of styrene and 1 equiv. of [N-(p-nitrobenzenesulfonyl)imino]phenyliodinane (PhINNs) affording phenylaziridine in 88% yield. Poorly reactive olefins such as a- or b-methyl styrene were aziridinated. A cyclic olefin such as cis-cyclooctene can be aziridinated efficiently by increasing the catalyst loading up to 20 mol%. These conditions were applied for the asymmetric aziridination of styrene. After ligand screening, an (S,S)-i-Pr-pybox ligand was discovered to be an efficient ligand, affording (R)-phenylaziridine in 83% yield with 40% ee. Also, aziridinations using in situ generated iminophenyliodinanes using 10-20 mol% of iron(II) triflate and a combination of the corresponding sulfonamide and iodobenzene diacetate (2 equivs.) with magnesium oxide (5 equivs.) as a base or iodosylbenzene (PhI=O) led to the corresponding phenylaziridines in high yields (up to 76%). Further investigation of the iron(II) triflate catalyzed aziridination of styrene, has led to the discovery that attempted iron(II) triflate catalyzed aziridinations of silyl enol ethers using the same conditions gave a-amino ketones, or esters. In the synthesis of novel ligands, aryl-TACN derivatives were synthesized by using palladium catalysis. Triple N-arylation of TACN was achieved by use of a catalyst comprised of tris(dibenzyllideneacetone)dipalladium(0) and 2-dicyclohexylphosphino-2’-(N,N-dimethylamino)biphenyl as a phosphine ligand in the presence of 4.2 equivs. of sodium tert-butoxide in toluene at 100 °C. Also, double N-phenylation of mono-tosyl TACN proceeded under the same conditions affording di-phenyl TACN in 70% yield. Furthermore, mono-N-phenylation of di-(Boc), (Cbz) or (Ts) protected TACN was successful by using a mixture of palladium(II) acetate and rac-BINAP affording mono-phenylated TACNs in good yields. Also, a synthesis of dipyridylamine ligands has been developed using palladium catalysis. As a representative example, N-arylation of 2-picolylamine with 2-bromopyridine was achieved by using tris(dibenzyllideneacetone)dipalladium(0) (2 mol%) and rac-BINAP (2 mol%) in the presence of sodium tert-butoxide (2.2 equivs.) in toluene at 100 °C affording 2,2’-N,N-dipyridyl-picolylamine in 80% yield.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2007

Author dc:creator

• Nakanishi, Masafumi

Contributors dc:contributor

• Bolm, Carsten

• info:eu-repo/classification/ddc/540
• Eisen
• Chemie
• Iron
• C-H Activation
• Novel Ligands
• Aziridination
• Oxidation

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123837%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:62259