Jiang-Lin Liang

Metalloporphyrin-mediated asymmetric nitrogen-atom transfer to hydrocarbons: aziridination of alkenes and amidation of saturated C-H bonds catalyzed by chiral ruthenium and manganese porphyrins.

Chiral metalloporphyrins [Mn(Por*)(OH)(MeOH)] (1) and [Ru(Por*)(CO)(EtOH)] (2) catalyze asymmetric aziridination of aromatic alkenes and asymmetric amidation of benzylic hydrocarbons to give moderate enantiomeric excesses. The mass balance in these nitrogen-atom-transfer processes has been examined. With PhI=NTs as the nitrogen source, the aziridination of styrenes, trans-stilbene, 2-vinylnaphthalene, indene, and 2,2-dimethylchromene catalyzed by complex 1 or 2 resulted in up to 99 % substrate conversions and up to 94 % aziridine selectivities, whereas the amidation of ethylbenzenes, indan, tetralin, 1-, and 2-ethylnaphthalene catalyzed by complex 2 led to substrate conversions of up to 32 % and amide selectivities of up to 91 %. Complex 1 or 2 can also catalyze the asymmetric amidation of 4-methoxyethylbenzene, tetralin, and 2-ethylnaphthalene with PhI(OAc)(2) + NH(2)SO(2)Me, affording the N-substituted methanesulfonamides in up to 56 % ee with substrate conversions of up to 34 % and amide selectivities of up to 92 %. Extension of the complex 1 + PhI=NTs or complex 1 + PhI(OAc)(2) + NH(2)R (R=Ts, Ns) amidation protocol to a steroid resulted in diastereoselective amidation of cholesteryl acetate at the allylic C-H bonds at C-7 with substrate conversions of up to 49 % and amide selectivities of up to 90 % (alpha:beta ratio: up to 4.2:1). An aziridination- and amidation-active chiral bis(tosylimido)ruthenium(VI) porphyrin, [Ru(Por*)(NTs)(2)] (3), and a ruthenium porphyrin aziridine adduct, [Ru(Por*)(CO)(TsAz)] (4, TsAz=N-tosyl-2- (4-chlorophenyl)aziridine), have been isolated from the reaction of 2 with PhI=NTs and N-tosyl-2-(4-chlorophenyl)aziridine, respectively. The imidoruthenium porphyrin 3 could be an active species in the aziridination or amidation catalyzed by complex 2 described above. The second-order rate constants for the reactions of 3 with styrenes, 2-vinylnaphthalene, indene, ethylbenzenes, and 2-ethylnaphthalene range from 3.7-42.5x10(-3) dm(3) mol(-1) s(-1). An X-ray structure determination of complex 4 reveals an O- rather than N-coordination of the aziridine axial ligand. The fact that the N-tosylaziridine in 4 does not adopt an N-coordination mode disfavors a concerted pathway in the aziridination by a tosylimido ruthenium porphyrin active species.

Chiral rhodium(II,II) dimers catalyzed enantioselective intramolecular aziridination of sulfonamides and carbamates

The asymmetric intramolecular aziridination of unsaturated sulfonamides and carbamates catalyzed by chiral dirhodium(II,II) complexes were achieved in good yields (up to 95%) and enantioselectivity (up to 76% e.e.).

Interaction between dioxoruthenium(VI) porphyrins and hydroxylamines: Coordination of N-substituted hydroxylamine to ruthenium and X-ray crystal structures of ruthenium complexes with a unidentate nitrosoarene ligand

The interactions between dioxoruthenium(VI) porphyrins 1 with N-phenylhydroxylamine or unsubstituted hydroxylamine are described. Reaction of complexes 1 with excess PhNHOH leads to isolation of bis(nitrosobenzene)ruthenium(II) porphyrins 3 and mono(nitrosobenzene)ruthenium(II) porphyrins 4. Both the types of ruthenium complexes are characterized by 1H NMR, IR, and UV/Vis spectroscopy, and mass spectrometry. The X-ray structure determinations on [Ru(II)(TPP)(PhNO)2] (3a), [Ru(II)(2,6-Cl-TPP)(PhNO)2] (3e), and [Ru(II)(4-MeO-TPP)(PhNO)(PhNH2)] (4d) (TPP tetraarylporphyrin) disclose a unidentate nitrosoarene coordination in all these complexes, with Ru-N(PhNO) bond lengths of 2.003(3) (3a, average), 1.991(3) (3e, average), and 2.042(2) A (4d). In the case of 4d, the Ru-N(PhNH2) bond length is found to be 2.075(3) A. Mechanistic investigations reveal the formation of intermediates [Ru(II)(Por)(PhNO)(PhNHOH)] (5; Por=porphyrin), a ruthenium complex with N-substituted hydroxylamine ligand, in the 1 + PhNHOH system. The Ru-NH(OH)Ph moiety in 5 undergoes no rapid exchange with free PhNHOH in solution at room temperature, as revealed by 1H NMR spectroscopy. Unlike the interaction between complexes 1 and PhNHOH, reaction of such complexes with NH2OH affords nitrosylruthenium(II) porphyrins [Ru(II)(Por)(NO)(OH)] (6).

1-D polymer containing the [Ru–N–Ru] μ-nitrido moiety: crystal structure and magnetic properties of {[Cu(en)2]3[Ru2N(CN)10]·ClO4}n (en = 1,2-diaminoethane)

A novel (mu-nitrido-diruthenium)-bridged 1-D coordination polymer was formed from reaction of K5[Ru2N(CN)10] with [Cu(en)2](ClO4)2; a similar reaction with [Cu(pn)2][(ClO4)2] (pn = 1,3-diaminopropane) gave ([Cu(pn)2]5[Ru2N(CN)10]2) as a discrete molecular compound; variable temperature susceptibility measurements show that there is a weak ferromagnetic interaction between the Cu(II) ions in 1-D polymer.

Amidation of silyl enol ethers and cholesteryl acetates with chiral ruthenium(II) Schiff-base catalysts: catalytic and enantioselective studies

Chiral ruthenium(II)-salen complexes [RuII(salen)(PPh3)2] catalyse asymmetric aziridination of alkenes with up to 83% ees, asymmetric amidation of silyl enol ethers with up to 97% ees, and allylic amidation of cholesteryl acetates with good regioselectivity.