80819-62-1Relevant academic research and scientific papers
Solvent/oxidant-switchable synthesis of multisubstituted quinazolines and benzimidazoles via metal-free selective oxidative annulation of arylamidines
Lin, Jian-Ping,Zhang, Feng-Hua,Long, Ya-Qiu
supporting information, p. 2822 - 2825 (2014/06/23)
A fast and simple divergent synthesis of multisubstituted quinazolines and benzimidazoles was developed from readily available amidines, via iodine(III)-promoted oxidative C(sp3)-C(sp2) and C(sp 2)-N bond formation in nonpolar and polar solvents, respectively. Further selective synthesis of quinazolines in polar solvent was realized by TEMPO-catalyzed sp3C-H/sp2C-H direct coupling of the amidine with K2S2O8 as the oxidant. No metal, base, or other additives were needed.
N-arylbenzonitrilium ions. Photochemical generation and effect of substituents in the phenyl rings on lifetimes in water and reactivity with azide ion
Ruane, Patrick H.,Ahmed, Abid R.,McClelland, Robert A.
, p. 312 - 317 (2007/10/03)
Nitrilium ions Ar-C≡N+-Ar′ have been studied by laser flash photolysis in aqueous solutions containing 20% acetonitrile. The cations were generated by photoheterolysis of benzimidate esters Ar-CZ=N-Ar′ (Z = -OC6H4-4-CN) with 4-cyanophenoxide as the photochemical leaving group. Rate constants for the reaction with water (kw), azide ion (kaz) and hydroxide (kOH) were measured. The cation Ph-C≡N+-Ph is only 50-fold shorter lived in water compared to Ph-C≡N+-iPr (2); thus the effect of replacing an N-alkyl group with N-phenyl is modest. These two cations are also shown to have similar lifetimes to iminium analogs, e.g. Ph-CH=N+ (Me)-Ph. Thus, addition of water to analogous sp and sp2 hybridized systems occurs at a similar rate, and the increased steric access to the nitrilium plays at most a modest role. For the series where substituents in Ar′ were varied with Ar equal to phenyl, the Hammett plot for log kw correlated with σ, with ρ = - 1.4. For the series where Ar was varied, the data correlated much better with σ+, although ρ+ was only -0.6. This remarkably small effect of substituents in Ar constrasts with the effects seen in benzylic carbocations, but is consistent with the nitrilium structure, with most of the positive charge located on the nitrogen. Rate constant ratios kaz:kw, including the N-alkylnitrilium ion 2, are constant at ～104, with values of kaz well below the diffusion limit, even for the most reactive nitrilium ions. This is very different behaviour from that of carbocations and arylnitrenium ions of similar lifetimes in water. For these cations the rate constants kaz would be at or at least approaching the diffusion limit.
Asymmetric aza-Claisen rearrangement of allyl imidates catalyzed by homochiral cationic palladium(II) complexes
Uozumi, Yasuhiro,Kato, Kazuhiko,Hayashi, Tamio
, p. 1065 - 1072 (2007/10/03)
The asymmetric aza-Claisen rearrangement of (E)-3-alkyl-2-propenyl N- [4-trifluoromethyl)phenyl]benzimidates was catalyzed by a homochiral cationic palladium(II) complex generated from PdCl2{(S)-2-(2- diphenylphosphino)phenyl-4-benzyloxazoline}
First Enantioselective Catalyst for the Rearrangement of Allylic Imidates to Allylic Amides
Calter, Michael,Hollis, T. Keith,Overman, Larry E.,Ziller, Joseph,Zipp, G. Greg
, p. 1449 - 1456 (2007/10/03)
A series of Pd(II) complexes containing chiral diamine ligands were investigated as asymmetric catalysts for the rearrangement of allylic imidates to allyl amides. The best catalysts were cations obtained by dechlorination of dichloro[ (S)-2-(isoindolinylmethyl)-N-methylpyrrolidine]palladium-(II) (17) with silver salts in CH2Cl2. Catalyst 18 was studied thoroughly and shown by 1H NMR and X-ray crystallography analysis to be a C1 symmetric dimer (Figure 1). A series of related catalysts 22-27 having various counterions and anionic ligands were also prepared and studied as asymmetric catalysts for the rearrangement of allylic AT-(4-trifluorophenyl)benzimidate 29 to allylic benzamide 30 (eq 4). Rearrangement of 29 in CH2Cl2 (48 h at 40°C) in the presence of 5 mol % of 18 affords (-)-30 in 69% yield and 55% ee. Enantioselection is increased to 60% when an isomerically pure sample of 18 is employed. Chemical correlation of allylic benzamide 30 with (R)-norvaline established that (-)-30 has the R absolute configuration (Scheme 3). A cyclization-induced rearrangement mechanism (Scheme 1) requires that in the major pathway the imidate nitrogen attacks the re face of the olefin with Pd coordinated to the si face. These studies constitute the first report of asymmetric catalysis of the rearrangement of allylic imidates to allylic amides. However, significant hurdles remain to be overcome before the enantioselective rearrangement of allylic imidates becomes a practical route to enantioenriched nitrogen compounds.
