The reaction of rhenium α-diimine (N-N) tricarbonyl complexes with nitrosonium tetrafluoroborate yields the corresponding dicarbonyl-nitrosyl [Re(CO)2(NO)(N-N)X]+ species (where X = halide). The complexes, accessible in a single step in good yield, are structurally nearly identical higher charge congeners of the tricarbonyl molecules. Substitution chemistry aimed at the realization of equivalent dicationic species (intended for applications as potential antimicrobial agents), revealed that the reactivity of metal ion in [Re(CO)2(NO)(N-N)X]+ is that of a hard Re acid, probably due to the stronger π-acceptor properties of NO+ as compared to those of CO. The metal ion thus shows great affinity for π-basic ligands, which are consequently difficult to replace by, e.g., σ-donor or weak π-acids like pyridine. Attempts of direct nitrosylation of α-diimine fac-[Re(CO)3]+ complexes bearing π-basic OR-type ligands gave the [Re(CO)2(NO)(N-N)(BF4)][BF4] salt as the only product in good yield, featuring a stable Re-FBF3 bond. The solid state crystal structure of nearly all molecules presented could be elucidated. A fundamental consequence of the chemistry of [Re(CO)2(NO)(N-N)X]+ complexes, it that the same can be photo-activated towards CO release and represent an entirely new class of photoCORMs. 相似文献
The sodium siloxide NaOSiMePh2 is accessible from the reaction of Ph2MeSiOH with sodium. The crystal structures of three hexameric double heterocubane compounds containing NaOSiMePh2, one without additional donors and one each supported by THF and [CpFe(CO)2]2 are described. Using an excess of THF results in the formation of tetrameric sodium siloxide NaOSiMePh2. The structures of (NaOSiMePh2)4·(THF)4 (Aba2) and (NaOSiMePh2)4·2[CpFe(CO)2]2 (I41/acd) feature a heterocubane structure. 相似文献
Constructing α‐stereogenic amides and ketones : The highly regioselective and enantioselective conjugate addition of 1,3‐dicarbonyl compounds to 1,4‐dicarbonyl but‐2‐enes has been developed with the chiral bicyclic guanidine as catalyst (ee values up to 97 %; see scheme).
A method to prepare α,α‐acyl amino acid derivatives efficiently by Cu(OTf)2+1,10‐phenanthroline (1,10‐phen)‐catalyzed amination of 1,3‐dicarbonyl compounds with PhI?NSO2Ar is described. The mechanism is thought to initially involve aziridination of the enolic form of the substrate, formed in situ through coordination to the Lewis acidic metal catalyst, by the putative copper–nitrene/imido species generated from the reaction of the metal catalyst with the iminoiodane source. Subsequent ring opening of the resultant aziridinol adduct under the Lewis acidic conditions then provided the α‐aminated product. The utility of this method was exemplified by the enantioselective synthesis of a precursor of 3‐styryl‐2‐benzoyl‐L ‐alanine. 相似文献
A study of the organocatalytic activity of N‐heterocyclic carbenes (NHCs) in the Michael addition of 1,3‐dicarbonyl compounds has allowed us to identify 1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene (IPr) as an excellent catalyst for this transformation (up to 99 % yield with a 2.5 mol % catalyst loading), and the reaction was found to be of broad scope. Two early applications of this unprecedented catalytic activity of NHCs are described, that is, the domino carbocyclization reactions of simple cyclic 1,3‐dicarbonyl and malonic acid derivatives, which allow stereoselective access to bridged bicyclic compounds, and the stereoselective synthesis of cyclohexanols (or cyclohexene). Early mechanistic investigations are also reported. 相似文献
A one‐pot synthesis of Hantzsch pyridines was achieved through NH4I‐promoted condensation of 1,3‐dicarbonyl compounds with DMSO and NH4OAc, in which the C4 of the pyridine rings was derived from DMSO and the nitrogen atom resulted from NH4OAc and NH4I. The target product could be obtained in moderate to excellent yields. 相似文献