[reaction: see text] Among six different group VIb oxometallic species examined, dioxomolybdenum dichloride and oxomolybdenum tetrachloride were the most efficient catalysts to facilitate nucleophilic acyl substitution (NAS) of anhydrides with a myriad array of alcohols, amines, and thiols in high yields and high chemoselectivity. In contrast to the well-recognized redox chemical behaviors associated with oxomolybdenum(VI) species, the catalytic NAS was unprecedented and tolerates virtually all kinds of functional groups. By using benzoic anhydride as a mediator for in situ generation of an incipient mixed anhydride-MoO(2)Cl(2) adduct with a given functional alkanoic acid, one can achieve oleate, dipeptide, diphenylmethyl, N-Fmoc-alpha-amino, pyruvic, and tert-butylthio ester, N-tert-butylamide, and trityl methacrylate syntheses with appropriate protic nucleophiles. The amphoteric character of the Mo=O unit in oxomolybdenum chlorides was found to be responsible for the catalytic NAS profile as supported by a control NAS reaction of using an authentic adduct-MoOCl(2)(O(2)CBu(t)())(2) between pivalic anhydride and MoO(2)Cl(2) as the catalyst.

A diverse array of oxometallic species were examined as catalysts for a test direct condensation of benzoic acid and 2-phenylethanol in 1:1 stoichiometry. Besides group IVB MOCl2-xH2O and TiOX2-xH2O, group VB VOCl2-xTHF and group IVB TiO(acac)2 were found to be the most efficient and water-tolerant catalysts for the test reaction. The new neutral catalytic protocol with the optimal TiO(acac)2 tolerates many stereo/electronic structural variations in both (di)acid (1 degree -3 degrees alkyl and aryl) and (di)alcohol (1 degree, 2 degrees alkyl, and aryl) components with high chemoselectivity.

A series of chiral vanadyl carboxylates derived from N-salicylidene-L-␣-amino acids and vanadyl sulfate has been developed. These configurationally well defined complexes were examined for the kinetic resolution of double-and mono-activated 2°alcohols. The best chiral templates involve the combination of L-tert-leucine and 3,5-di-t-butyl-, 3,5-diphenyl-, or 3,4-dibromo-salicylaldehyde. The resulting vanadyl(V)-methoxide complexes after recrystallization from air-saturated methanol serve as highly enantioselective catalysts for asymmetric aerobic oxidation of ␣-hydroxyl-esters and amides with a diverse array of ␣-, O-, and N-substituents at ambient temperature in toluene. The asymmetric inductions of the oxidation process are in the range of 10 to >100 in terms of selectivity factors (k rel) in most instances. The previously undescribed aerobic oxidation protocol is also applicable to the kinetic resolution of C-13 taxol side chain with high selectivity factor (k rel ‫؍‬ 35). X-ray crystallographic analysis of an adduct between a given vanadyl complex and N-benzyl-mandelamide allows for probing the stereochemical origin of the nearly exclusive asymmetric control in the oxidation process.alcohol oxidation ͉ ␣-hydroxy acids ͉ asymmetric catalysis ͉ vanadyl(V) methoxides T he oxidation of alcohols normally requires stoichiometric use of DMSO-based reagents or metal oxides of high oxidation state (1). Advances on their aerobic oxidations with catalytic metal oxides [e.g., RuO 2 -H 2 O (2), V 2 O 5 -K 2 CO 3 (3), and OsO 4 -Cu(O 2 CR) 2 (4)], homogeneous metal complexes [e.g., Co(OAc) 2 -N-hydroxyphthalimide (5), Ru(III)NOCl(salen) (6), RuCl 2 (PPh 3 ) 3 -hydroquinone-K 2 CO 3 (7), CuCl-Phen-DBADH 2 (8), RuCl 2 (PPh 3 ) 2 -TEMPO (9)͞CuCl-TEMPO (10), Pd(OAc) 2 -pyridine (11, 12), and Pd 4 Phen 2 (CO)(OAc) 4 (13)], bimetallic complexes [e.g., RuCl 3 -Co(OAc) 2 -aldehyde (14) and MoO 2 (acac) 2 -CuNO 3 ] (14, 15), or heterogeneous metal complexes [e.g., Ru(III) hydroxyapatite (16), polyaniline-supported MoO 2 (acac) 2 (17), and Pd(OAc) 2 -hydrotalcite-pyridine (18)] have been documented. Notably, additives and͞or bases are often needed to increase the catalyst reactivity and͞or to facilitate the turnover process. In addition, the targeted substrates are somewhat limited to primary, benzylic, allylic, and propargylic alcohols. Recently, the asymmetric variants of the aerobic catalytic process have attracted a lot of attention (19,20). So far, Pd(II)-sparteine (21, 22), photoly activated RuNOCl(salen) (23), and Mn(III)(salen)PF 6 (24) have been developed with fair to high enantioselectivity toward kinetic resolutions of 2°benzylic alcohols. In marked contrast, the asymmetric aerobic catalytic process with ␣-hydroxycarboxylic acid derivatives is relatively unexplored (25-31).Optically pure ␣-hydroxycarboxylic acid and mandelic acid derivatives are important precursors toward enantioselective synthesis scopes. Based on our experiences of using vanadyl and oxometallic species in catalyzing C-C and C-X bond forming (47-51), ae...

A new tri‐antennary, galactoside‐capped gallamide dendritic anchor with thiolate focal group is synthesized via click chemistry. The highly hydrophilic dendron was efficiently anchored onto the surface of CdSe/ZnS core/shell nanoparticles in a covalent fashion, as evidenced by 1H NMR spectrum of the resultant nanohybrid with intact core fluorescent property. The water‐soluble nano‐hybrid was found smoothly and selectively uptaken by lung cancer cells enriched with membrane‐bound asialoprotein receptors in 2–3 h, as evidenced by confocal microscopic analysis. Furthermore, cancer cells that are undergoing active mitosis also tend to uptake the nanohybrids efficiently and remain sustainable in serum‐containing medium for several days, which shed light on its application as a photodynamic drug carrier for apoptosis study.

Functionalized N-2-mercaptoethyl-gallamides bearing three or five hydroxyl units that are tethered with diethylene glycol ether(s) allow for transferring hydrophobically pyridine-capped CdSe/ZnS core/shell nanoparticles from an organic to an aqueous layer with intact fluorescent profiles.