Iron-catalyzed aerobic oxidative cross-coupling amidation of N,N-dimethylanilines

An efficient iron-catalyzed dehydrogenative cross-coupling amidation/imidation reaction between N,N-dimethylanilines and amides/imides is reported. The protocol uses an inexpensive and readily available Fe(NO₃)₃·9H₂O/O₂ catalytic system in the absence of additional ligands at room temperature.     

Mechanistic Insight into Peptidyl-Cysteine Oxidation by the Copper-Dependent Formylglycine-Generating Enzyme

The copper-dependent formylglycine-generating enzyme (FGE) catalyzes the oxygen-dependent oxidation of specific peptidyl-cysteine residues to formylglycine. Our QM/MM calculations provide a very likely mechanism for this transformation. The reaction starts with dioxygen binding to the tris-thiolate Cu^I center to form a triplet Cu^II-superoxide complex. The rate-determining hydrogen atom abstraction involves a triplet-singlet crossing to form a Cu^II−OOH species that couples with the substrate radical, leading to a Cu^I-alkylperoxo intermediate. This is accompanied by proton transfer from the hydroperoxide to the S atom of the substrate via a nearby water molecule. The subsequent O−O bond cleavage is coupled with the C−S bond breaking that generates the formylglycine and a Cu^II-oxyl complex. Moreover, our results suggest that the aldehyde oxygen of the final product originates from O₂, which will be useful for future experimental work.     

过氧化氢生产与利用的新进展

过氧化氢既可用作环境友好的绿色氧化剂,也可用作燃料电池中的太阳能燃料,因而受到越来越多的关注.本文综述了太阳能驱动分子氧氧化水制备过氧化氢及其作为绿色氧化剂和燃料的研究进展.利用太阳能将水的e^-和4e^-氧化与分子氧的e^-还原相结合,使光催化生产过氧化氢成为可能;本文讨论了与e^-和4e^-水氧化选择性及e^-和4e^-氧还原选择性相关的催化反应控制.由于光催化e^-氧化水和e^-还原分子氧的过程都产生过氧化氢,因此该组合的催化效率较高.太阳能光驱动水氧化及分子氧还原生产过氧化氢与过氧化氢催化氧化底物相结合,在该过程中分子氧用作最环保的氧化剂.     

Cobalt-catalyzed aerobic oxidation of (E)- and (Z)-bishomoallylic alcohols

Stereoselectivity for (5-phenyltetrahydrofur-2-yl)alkan-1-ol formation (cis:trans < 1:99) from 5-methyl- and 5-phenyl-substituted 1-phenylpent-4-en-1-ols via cobalt-catalyzed aerobic oxidation was independent of the olefinic π-bond configuration of the substrates.     

Remarkable enhancement of aerobic epoxidation reactivity for olefins catalyzed by μ-oxo-bisiron(III) porphyrins under ambient conditions

With μ-oxo dimeric iron(III) porphyrins [(Fe^IIITPP)₂O] as catalyst, isobutylaldehyde as co-reductant, and dioxygen as oxidant, an efficient model system for epoxidation of olefins has been developed. Compared with mono-metalloporphyrins as catalyst, a remarkable enhancement of reactivity was obtained for the present olefin epoxidation system, in which the turnover number (TON) of the catalyst has doubled from about 700 million to 1400 million. Moreover, a plausible mechanism involving both binuclear and mononuclear intermediate has been proposed.     

钴（Ⅱ）Schiff碱螯合物及其氧加合物的合成与表征

合成了一种新的四齿Schiff碱配体N,N-亚乙基-双(1-乙酰萘酚-2(L~2),两种新的钴(Ⅱ)螯合物CoL~2和CoL~3·H_2O(L~3=N,N-亚苯基(1-苯基-3-甲基-4-苯甲酰基吡唑啉酮-5)及两种新的1:1氧加合物CoL~1·Py·O_2·2H_2O(L~1=N,N-亚乙基-双(1-苯基-3-甲基-4-苯甲酰基吡唑啉酮-5)和CoL~2·Py·O_2·2H_2O。用元素分析、IR、UV、ESR、~1H NMR、MS、TGA、磁矩和电导测定进行了表征。     

Efficient oxidative dimerization of 1-naphthols to 2,2-binaphthyls with dioxygen mediated by semiconductors

A novel and efficient oxidative dimerization of 1-naphthols 1 with dioxygen in the presence of several semiconductors including SnO₂, ZrO₂, and activated charcoal as catalytic mediators took place selectively to give the corresponding 2,2^′-binaphthols 2 or 2,2^′-binaphthyl-1,1^′-quinones 3 in excellent yields without light irradiation. Among these semiconductors, the catalytic activity of SnO₂ could be fully restored by appropriate reactivation treatment after oxidation. The products 2 and 3 should be useful as synthetic intermediates for natural binaphthyls.     

Development of an efficient method for preparation of 1,3,5-trihydroxyisocyanuric acid (THICA) and its use as aerobic oxidation catalyst

1,3,5-Trihydroxyisocyanuric acid (THICA), which serves as an efficient radical-producing catalyst from hydrocarbons, was successfully prepared by two methods. The reaction of O-benzylhydroxyamine with phenyl chloroformate gave formbenzyloxycarbamic acid phenyl ester of which subsequent treatment with dimethylaminopyridine (DMAP) produced 1,3,5-tribenzyloxyisocyanurate leading to THICA by hydrogenation with H₂ on Pd/C. The other method involved the direct synthesis of 1,3,5-tribenzyloxyisocyanurate from O-benzylhydroxyamine and diphenyl carbonate. The aerobic oxidation of p-methylanisole catalyzed using THICA as a key catalyst afforded p-anisic acid in almost quantitative yield (>99%).     

New morpholine- and piperazine-functionalized triphenylantimony(V) catecholates: The spectroscopic and electrochemical studies

Novel functionalized triphenylantimony(V) catecholates - Ph₃Sb[4-O(CH₂CH₂)₂N-3,6-DBCat] (1), Ph₃Sb[4-PhN(CH₂CH₂)₂N-3,6-DBCat] (2), Ph₃Sb[4-Ph₂CHN(CH₂CH₂)₂N-3,6-DBCat] (3), Ph₃Sb[4,5-Piperaz-3,6-DBCat] (4) and binuclear bis-catecholate Ph₃Sb[3,6-DBCat-4-N(CH₂CH₂)₂N-4-3,6-DBCat]SbPh₃ (5) were synthesized by the oxidative addition reaction of corresponding o-quinones with triphenylantimony. The [4-O(CH₂CH₂)₂N-3,6-DBCat]²⁻, [4-PhN(CH₂CH₂)₂N-3,6-DBCat]²⁻, [4-Ph₂CHN(CH₂CH₂)₂N-3,6-DBCat]²⁻ and [4,5-Piperaz-3,6-DBCat]²⁻ are 4-(morpholin-1-yl)-, 4-(4-phenyl-piperazin-1-yl)-, 4-(4-dephenylmethyl-piperazin-1-yl)-, and 4,5-(piperazin-1,4-diyl)-3,6-di-tert-butyl-catecholate dianionic ligands, correspondingly. Complexes 1-5 were characterized in details by IR-, ¹H and ¹³C NMR spectroscopy and cyclic voltammometry. Molecular structure of 4·CH₃OH was determined by X-ray crystallography to be a distorted tetragonal-pyramidal. The NMR spectroscopic and electrochemical investigations of complexes in the presence of air reveal the reactions of complexes with dioxygen leading to the formation of spiroendoperoxides of 1,2,4,3-trioxastibolane type in a NMR yield of 25-37%.     

Synthesis of α-hydroxy-γ-butyrolactones from acrylates and 1,3-dioxolanes using N-hydroxyphthalimide (NHPI) as a key catalyst

A new route to α-hydroxy-γ-butyrolactones through three-component radical coupling of 1,3-dioxoranes, acrylates, and molecular oxygen using N-hydroxyphthalimide (NHPI) as a key catalyst has been developed. For example, the addition of 1,3-dioxarane to methyl acrylate under dioxygen by NHPI followed by catalytic hydrogenation of the resulting adduct on Pd/C afforded α-hydroxy-γ-butyrolactone in good yield. This method provides a facile approach to α-hydroxy-γ-butyrolactones, which are difficult to synthesize by conventional methods.