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1.
Chemoselective and Direct Functionalization of Methyl Benzyl Ethers and Unsymmetrical Dibenzyl Ethers by Using Iron Trichloride 下载免费PDF全文
Dr. Yoshinari Sawama Ryota Goto Saori Nagata Yuko Shishido Dr. Yasunari Monguchi Prof. Dr. Hironao Sajiki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(9):2631-2636
Methyl and benzyl ethers are widely utilized as protected alcohols due to their chemical stability, such as the low reactivity of the methoxy and benzyloxy groups as leaving groups under nucleophilic conditions. We have established the direct azidation of chemically stable methyl and benzyl ethers derived from secondary and tertiary benzyl alcohols. The present azidation chemoselectively proceeds at the secondary or tertiary benzylic positions of methyl benzyl ethers or unsymmetrical dibenzyl ethers and is also applicable to direct allylation, alkynylation, and cyanation reactions, as well as the azidation. The present methodologies provide not only a novel chemoselectivity but also the advantage of shortened synthetic steps, due to the direct process without the deprotection of the methyl and benzyl ethers. 相似文献
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M. Sc. Isabel T. Alt Prof. Dr. Bernd Plietker 《Angewandte Chemie (International ed. in English)》2016,55(4):1519-1522
The nucleophilic iron complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) catalyzes the direct intramolecular C?H amination of α‐azidobiaryls and (azidoaryl)alkenes into the corresponding carbazoles and indoles, respectively, under mild conditions and with low catalyst loadings. These features and the broad functional‐group tolerance render this method a particularly attractive alternative to established noble‐metal‐based procedures. 相似文献
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Tobias Biberger Szabolcs Makai Dr. Zhong Lian Dr. Bill Morandi 《Angewandte Chemie (International ed. in English)》2018,57(23):6940-6944
Among all metathesis reactions known to date in organic chemistry, the metathesis of multiple bonds such as alkenes and alkynes has evolved into one of the most powerful methods to construct molecular complexity. In contrast, metathesis reactions involving single bonds are scarce and far less developed, particularly in the context of synthetically valuable ring‐closing reactions. Herein, we report an iron‐catalyzed ring‐closing metathesis of aliphatic ethers for the synthesis of substituted tetrahydropyrans and tetrahydrofurans, as well as morpholines and polycyclic ethers. This transformation is enabled by a simple iron catalyst and likely proceeds via cyclic oxonium intermediates. 相似文献
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Muhammet Uyanik Naoto Sahara Mayuko Tsukahara Yuhei Hattori Kazuaki Ishihara 《Angewandte Chemie (International ed. in English)》2020,59(39):17110-17117
We report high‐performance I+/H2O2 catalysis for the oxidative or decarboxylative oxidative α‐azidation of carbonyl compounds by using sodium azide under biphasic neutral phase‐transfer conditions. To induce higher reactivity especially for the α‐azidation of 1,3‐dicarbonyl compounds, we designed a structurally compact isoindoline‐derived quaternary ammonium iodide catalyst bearing electron‐withdrawing groups. The nonproductive decomposition pathways of I+/H2O2 catalysis could be suppressed by the use of a catalytic amount of a radical‐trapping agent. This oxidative coupling tolerates a variety of functional groups and could be readily applied to the late‐stage α‐azidation of structurally diverse complex molecules. Moreover, we achieved the enantioselective α‐azidation of 1,3‐dicarbonyl compounds as the first successful example of enantioselective intermolecular oxidative coupling with a chiral hypoiodite catalyst. 相似文献
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Dr. Maialen Espinal‐Viguri Callum R. Woof Dr. Ruth L. Webster 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(33):11605-11608
Iron‐catalyzed hydroboration (HB) of alkenes and alkynes is reported. A simple change in ligand structure leads to an extensive change in catalyst activity. Reactions proceed efficiently over a wide range of challenging substrates including activated, unactivated and sterically encumbered motifs. Conditions are mild and do not require the use of reducing agents or other additives. Large excesses of borating reagent are not required, allowing control of chemo‐ and regioselectivity in the presence of multiple double bonds. Mechanistic insight reveals that the reaction is likely to proceed via a highly reactive iron hydride intermediate. 相似文献
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Didecarboxylative Iron‐Catalyzed Bidirectional Aldolization towards Diversity‐Oriented Ketodiol Synthesis 下载免费PDF全文
Adrien Quintard Jean Rodriguez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14717-14722
1,3‐Acetonedicarboxylic acid was selectively activated by Fe(acac)3, providing a synthetic platform for rapid synthesis of keto‐3,3′‐diols. The bidirectional aldol reaction was efficient for challenging aliphatic aldehydes, providing a rapid route to potentially bioactive complex structures. 相似文献
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Yong‐An Yuan Deng‐Fu Lu Yun‐Rong Chen Prof. Hao Xu 《Angewandte Chemie (International ed. in English)》2016,55(2):534-538
Reported herein is a new iron‐catalyzed diastereoselective olefin diazidation reaction which occurs at room temperature (1–5 mol % of catalysts and d.r. values of up to >20:1). This method tolerates a broad range of both unfunctionalized and highly functionalized olefins, including those that are incompatible with existing methods. It also provides a convenient approach to vicinal primary diamines as well as other synthetically valuable nitrogen‐containing building blocks which are difficult to obtain with alternative methods. Preliminary mechanistic studies suggest that the reaction may proceed through a new mechanistic pathway in which both Lewis acid activation and iron‐enabled redox‐catalysis are crucial for selective azido‐group transfer. 相似文献
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Herein, the iron‐catalyzed reduction of a variety of alkynes with silanes as a reductant has been examined. With a straightforward catalyst system composed of diiron nonacarbonyl and tributyl phosphane, excellent yields and chemoselectivities (>99 %) were obtained for the formation of the corresponding alkenes. After studying the reaction conditions, and the scope and limitations of the reaction, several attempts were undertaken to shed light on the reaction mechanism. 相似文献
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Iridium‐Catalyzed Synthesis of Diaryl Ethers by Means of Chemoselective CF Bond Activation and the Formation of BF Bonds 下载免费PDF全文
Jianping Chen Keyan Zhao Bingyang Ge Chongying Xu Dr. Dawei Wang Prof. Yuqiang Ding 《化学:亚洲杂志》2015,10(2):468-473
Transition‐metal‐catalyzed C? F activation, in comparison with C? H activation, is more difficult to achieve and therefore less fully understood, mainly because carbon–fluorine bonds are the strongest known single bonds to carbon and have been very difficult to cleave. Transition‐metal complexes are often more effective at cleaving stronger bonds, such as C(sp2)? X versus C(sp3)? X. Here, the iridium‐catalyzed C? F activation of fluorarenes was achieved through the use of bis(pinacolato)diboron with the formation of the B? F bond and self‐coupling. This strategy provides a convenient method with which to convert fluoride aromatic compounds into symmetrical diaryl ether compounds. Moreover, the chemoselective products of the C? F bond cleavage were obtained at high yields with the C? Br and C? Cl bonds remaining. 相似文献
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Rhodium‐Catalyzed Dehydrogenative Silylation of Acetophenone Derivatives: Formation of Silyl Enol Ethers versus Silyl Ethers 下载免费PDF全文
Dr. Karin Garcés Dr. Ralte Lalrempuia Dr. Víctor Polo Dr. Francisco J. Fernández‐Alvarez Dr. Pilar García‐Orduña Prof. Fernando J. Lahoz Prof. Jesús J. Pérez‐Torrente Prof. Luis A. Oro 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14717-14729
A series of rhodium–NSiN complexes (NSiN=bis (pyridine‐2‐yloxy)methylsilyl fac‐coordinated) is reported, including the solid‐state structures of [Rh(H)(Cl)(NSiN)(PCy3)] (Cy=cyclohexane) and [Rh(H)(CF3SO3)(NSiN)(coe)] (coe=cis‐cyclooctene). The [Rh(H)(CF3SO3)(NSiN)(coe)]‐catalyzed reaction of acetophenone with silanes performed in an open system was studied. Interestingly, in most of the cases the formation of the corresponding silyl enol ether as major reaction product was observed. However, when the catalytic reactions were performed in closed systems, formation of the corresponding silyl ether was favored. Moreover, theoretical calculations on the reaction of [Rh(H)(CF3SO3)(NSiN)(coe)] with HSiMe3 and acetophenone showed that formation of the silyl enol ether is kinetically favored, while the silyl ether is the thermodynamic product. The dehydrogenative silylation entails heterolytic cleavage of the Si?H bond by a metal–ligand cooperative mechanism as the rate‐determining step. Silyl transfer from a coordinated trimethylsilyltriflate molecule to the acetophenone followed by proton transfer from the activated acetophenone to the hydride ligand results in the formation of H2 and the corresponding silyl enol ether. 相似文献
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Synthesis of All‐Carbon Disubstituted Bicyclo[1.1.1]pentanes by Iron‐Catalyzed Kumada Cross‐Coupling
Jeremy Nugent Bethany R. Shire Dimitri F. J. Caputo Helena D. Pickford Frank Nightingale Ian T. T. Houlsby James J. Mousseau Edward A. Anderson 《Angewandte Chemie (International ed. in English)》2020,59(29):11866-11870
1,3‐Disubstituted bicyclo[1.1.1]pentanes (BCPs) are important motifs in drug design as surrogates for p‐substituted arenes and alkynes. Access to all‐carbon disubstituted BCPs via cross‐coupling has to date been limited to use of the BCP as the organometallic component, which restricts scope due to the harsh conditions typically required for the synthesis of metallated BCPs. Here we report a general method to access 1,3‐C‐disubstituted BCPs from 1‐iodo‐bicyclo[1.1.1]pentanes (iodo‐BCPs) by direct iron‐catalyzed cross‐coupling with aryl and heteroaryl Grignard reagents. This chemistry represents the first general use of iodo‐BCPs as electrophiles in cross‐coupling, and the first Kumada coupling of tertiary iodides. Benefiting from short reaction times, mild conditions, and broad scope of the coupling partners, it enables the synthesis of a wide range of 1,3‐C‐disubstituted BCPs including various drug analogues. 相似文献
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Dr. Yoshinari Sawama Yuko Shishido Takahiro Kawajiri Ryota Goto Dr. Yasunari Monguchi Prof. Dr. Hironao Sajiki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):510-516
Friedel–Crafts benzylations between unactivated arenes and benzyl alcohol derivatives are clean and straightforward processes to construct biologically useful di‐ and tri‐arylmethanes. We have established an efficient iron‐catalyzed Friedel–Crafts benzylation method at room temperature that uses benzyl TMS ethers as substrates, which are poorly reactive under common nucleophilic substitution conditions. The reaction seems to progress through iron‐catalyzed self‐condensation of the benzyl TMS ether to the corresponding dibenzylic ether. The use of excess arene relative to benzyl TMS ether produced mono‐benzylated arene (di‐ and tri‐arylmethane products), whereas the use of excess benzyl TMS ether versus arene provided bis‐benzylated arene (polyarylated products) in high yields and regioselectivities. In previous methods, the latter double Friedel–Crafts benzylations hardly proceed. 相似文献
20.
Conversion of Olefins into Ketones by an Iron‐Catalyzed Wacker‐type Oxidation Using Oxygen as the Sole Oxidant
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Florian Puls Prof. Dr. Hans‐Joachim Knölker 《Angewandte Chemie (International ed. in English)》2018,57(5):1222-1226
We describe a mild and operationally simple procedure for the oxidation of olefins into ketones. The reaction is catalyzed by the hexadecafluorinated iron–phthalocyanine complex FePcF16 with stoichiometric amounts of triethylsilane as an additive under oxygen atmosphere to give ketones in good to high yields with excellent chemoselectivity and functional group tolerance. Ketone formation proceeds in up to 95 % yield and with 100 % regioselectivity while the corresponding alcohols were observed as side products. 相似文献