Rutheniun and iridium porphyrin-catalyzed nitrene transfer reactions and synthesis, charaterization and catalysis of iridium porphyrin nonheteroatom-stablized carbene complexes

Abstract

Transition metal porphyrin complexes have been well documented as active catalysts in both nitrene and carbene transfer reactions to respectively form C–N and C–C bonds, which has a wide application in organic synthesis. This thesis describes synthesis, characterization, electrochemistry and catalytic properties of novel metalloporphyrin complexes and/or new types of metalloporphyrin-catalyzed nitrene and carbene transfer reactions, including ruthenium porphyrin-catalyzed acylnitrene transfer reactions and iridium porphyrin-catalyzed nitrene transfer reactions, as well as the synthesis of iridium porphyrin nonheteroatom-stabilized carbene complexes and their structural characterization and catalysis of carbene transfer reactions.

In Chapter 3, using acylazides N3C(O)Ar, under mild conditions, [RuIV(TTP)Cl2] and [RuIV(TDCPP)Cl2] were employed as catalysts for C–N bond formation, including aziridine/oxazoline formation from alkenes, 3-amidoindoles formation from substituted indoles, α-amido ketone formation from silyl enol ethers, amination of C(sp3)–H bonds and functionalization of natural products and sugar compounds. Importantly, the formation of a putative [RuV=NC(O)Ar] intermediate is suggested based on high-resolution ESI-MS spectra. The proposed mechanism of ruthenium(IV) to ruthenium(III) via a one-electron reduction prior to nitrene transfer reaction is consistent with DFT calculations. Furthermore, a time-course experiments of the nitrene transfer reaction between 1-octene and p-nitrobenzoyl azide, catalyzed by ruthenium(IV) /ruthenium(III) species, using UV-vis absorption spectroscopy and kinetic measurements of C(sp3)–H amination were performed to gain mechanistic insights.

In Chapter 4, Iridium(III) porphyrin complexes were found to be active catalysts for the aziridination of alkenes and amination of C(sp3)–H bonds with various azides including phosphoryl azide, tosyl azide, 2,2,2-trichloroethoxycarbonyl azide, alkyl azides and benzoyl azides, as well as with PhI=NTs, in moderate- to- good product yields. It is worth noting that with [Ir(TTP)CH3] as a catalyst and diphenyl phosphoryl azide (DPPA) as nitrene source, the amination of sp3 C–H bonds of hydrocarbons was efficiently accomplished with a broad substrate scope and in up to 99% yields.

In Chapter 5, remarkbly stable iridium porphyrin nonheteroatom-stabilized carbene complexes [Ir(Por)Ad]X (Ad = 2-adamantylidene; X = PF6, ClO4, and Cl)) and their MeIm adducts [Ir(Por)Ad(MeIm)]PF6 were synthesized and characterized by X-ray crystallography, cyclic voltammetry and NMR, ESI-MS and UV-vis spectroscopy. The X-ray crystal structure of [Ir(TMP)Ad(MeIm)]PF6 provides evidence for the presence of a double bond between iridium and carbene (Ad). In addtion, this work describes for the first time (i) the isolation and structural characterization of iridium porphyrin nonheteroatom-stabilized carbene complexes, (ii) iridium porphyrin carbene complexes that can catalyze alkene cyclopropanations with various diazo compounds, (iii) iridium porphyrins capable of carbene transfer to X–H (X = S, N, O, C) bonds in moderate to high yields and (iv) iridium porphyrin carbene complexes capable of intramolecular C(sp3)–H bond insertion with alkyl diazomethanes in high yields and excellent diastereoselectivity.