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1.
Modular Access to the Stereoisomers of Fused Bicyclic Azepines: Rhodium‐Catalyzed Intramolecular Stereospecific Hetero‐[5+2] Cycloaddition of Vinyl Aziridines and Alkenes
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Dr. Jian‐Jun Feng Tao‐Yan Lin Prof. Dr. Hai‐Hong Wu Prof. Dr. Junliang Zhang 《Angewandte Chemie (International ed. in English)》2015,54(52):15854-15858
The first rhodium‐catalyzed intramolecular hetero‐[5+2] cycloaddition reaction of vinyl aziridines and alkenes was realized, wherein both internal and terminal alkenes were applicable. With this method, a variety of unique substituted chiral fused bicyclic azepines, bearing multiple contiguous stereogenic centers, were facilely accessed in a straightforward, high‐yielding, and highly stereoselective manner under mild reaction conditions. Notably, the E/Z geometry of the C?C bonds in the vinyl aziridine‐alkene substrates impact the cis/trans stereochemistry of the cycloadducts and up to six stereoisomers could be delivered. 相似文献
2.
Synthesis of Cyclobutenes and Allenes by Cobalt‐Catalyzed Cross‐Dimerization of Simple Alkenes with 1,3‐Enynes
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Akira Nishimura Eri Tamai Dr. Masato Ohashi Prof. Dr. Sensuke Ogoshi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(22):6613-6617
Cobalt‐catalyzed cross‐dimerization of simple alkenes with 1,3‐enynes is reported. A [2+2] cycloaddition reaction occurred, with alkenes bearing no allylic hydrogen, by reductive elimination of a η3‐butadienyl cobaltacycle. On the other hand, aliphatic alkenes underwent 1,4‐hydroallylation by means of exo‐cyclic β‐H elimination. These reactions can provide cyclobutenes and allenes that were previously difficult to access, from simple substrates in a highly chemo‐ and regioselective manner. 相似文献
3.
Haifeng Zheng Yan Wang Chaoran Xu Qian Xiong Lili Lin Xiaoming Feng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(16):5381-5385
We report the combination of transition‐metal‐catalyzed diversified cycloisomerization of 1,6‐enynes with chiral Lewis acid promoted asymmetric Diels–Alder reaction to realize asymmetric cycloisomerization/Diels–Alder relay reactions of 1,6‐enynes with electron‐deficient alkenes. A broad spectrum of chiral [5,6]‐bicyclic products could be acquired in high yields (up to 99 %) with excellent diastereoselectivy (>19:1 dr) and enantioselectivity (up to 99 % ee). 相似文献
4.
Cobalt‐Catalyzed Allylation of Heterobicyclic Alkenes: Ligand‐Induced Divergent Reactivities
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Yuan Huang Chao Ma Yi Xin Lee Rui‐Zhi Huang Prof. Yu Zhao 《Angewandte Chemie (International ed. in English)》2015,54(46):13696-13700
The allylation of heterobicyclic alkenes is presented for the first time. By using an inexpensive cobalt salt as the catalyst and easy‐to‐handle potassium allyltrifluoroborate as the reagent, an unprecedented formal hydroallylation of the bicyclic alkenes is realized in high efficiency. When a chiral cobalt/bis(phosphine) complex is used instead, the alternative ring‐opening products can be obtained in high yield and excellent enantioselectivity. 相似文献
5.
Stereoselective Synthesis of Trisubstituted Alkenes through Sequential Iron‐Catalyzed Reductive anti‐Carbozincation of Terminal Alkynes and Base‐Metal‐Catalyzed Negishi Cross‐Coupling
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Dr. Chi Wai Cheung Prof. Dr. Xile Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18439-18444
The stereoselective synthesis of trisubstituted alkenes is challenging. Here, we show that an iron‐catalyzed anti‐selective carbozincation of terminal alkynes can be combined with a base‐metal‐catalyzed cross‐coupling to prepare trisubstituted alkenes in a one‐pot reaction and with high regio‐ and stereocontrol. Cu‐, Ni‐, and Co‐based catalytic systems are developed for the coupling of sp‐, sp2‐, and sp3‐hybridized carbon electrophiles, respectively. The method encompasses a large substrate scope, as various alkynyl, aryl, alkenyl, acyl, and alkyl halides are suitable coupling partners. Compared with conventional carbometalation reactions of alkynes, the current method avoids pre‐made organometallic reagents and has a distinct stereoselectivity. 相似文献
6.
Theoretical prediction on the synthesis of 2,3‐dihydropyridines through Co(III)‐catalysed reaction of unsaturated oximes with alkenes
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Xiang‐Biao Zhang Bin‐Bin Yu Sheng‐Meng Si Song Wang 《International journal of quantum chemistry》2017,117(8)
Cobalt‐based catalysts can replace the homologous group‐9 rhodium‐based ones. Herein, we used density functional theory (DFT) calculations to predict the synthesis of 2,3‐dihydropyridines using α,β‐unsaturated oxime pivalates and alkenes catalysed by [Cp*CoOAc]+ instead of [Cp*RhOAc]+. The catalytic cycle involves reversible acetate‐assisted metalation‐deprotonation, migratory insertion of alkenes, and reductive elimination/N‐O cleavage. The migratory insertion of alkenes was determined to be the rate‐determining step, and the reaction is irreversible due to the strongly exergonic reductive elimination/N? O cleavage. When using the CF3‐substituted Cp*Co(III) catalyst, the apparent activation energy indicates that the title reaction can proceed at higher temperatures. Electron‐withdrawing substituent groups on Cp* facilitate the reaction. In contrast, substituting phenyl with the electron‐deficient p‐CF3‐phenyl at the 2‐position of α,β‐unsaturated oxime pivalate hinders the reaction, and so does the use of polarized alkenes with electron‐withdrawing substituent groups 相似文献
7.
Construction of Quaternary Stereogenic Carbon Centers through Copper‐Catalyzed Enantioselective Allylic Cross‐Coupling with Alkylboranes
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Kentaro Hojoh Yoshinori Shido Prof. Dr. Hirohisa Ohmiya Prof. Dr. Masaya Sawamura 《Angewandte Chemie (International ed. in English)》2014,53(19):4954-4958
A combination of an in situ generated chiral CuI/DTBM‐MeO‐BIPHEP catalyst system and EtOK enabled the enantioselective SN2′‐type allylic cross‐coupling between alkylborane reagents and γ,γ‐disubstituted primary allyl chlorides with enantiocontrol at a useful level. The reaction generates a stereogenic quaternary carbon center having three sp3‐alkyl groups and a vinyl group. This protocol allowed the use of terminal alkenes as nucleophile precursors, thus representing a formal reductive allylic cross‐coupling of terminal alkenes. A reaction pathway involving addition/elimination of a neutral alkylcopper(I) species with the allyl chloride substrate is proposed. 相似文献
8.
Balzs Budai Alexandre Leclair Qian Wang Jieping Zhu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(30):10411-10415
Reported here is a copper‐catalyzed 1,2‐methoxy methoxycarbonylation of alkenes by an unprecedented use of methyl formate as a source of both the methoxy and the methoxycarbonyl groups. This reaction transforms styrene and its derivatives into value‐added β‐methoxy alkanoates and cinnamates, as well as medicinally important five‐membered heterocycles, such as functionalized tetrahydrofurans, γ‐lactones, and pyrrolidines. A ternary β‐diketiminato‐CuI‐styrene complex, fully characterized by NMR spectroscopy and X‐ray crystallographic analysis, is capable of catalyzing the same transformation. These findings suggest that pre‐coordination of electron‐rich alkenes to copper might play an important role in accelerating the addition of nucleophilic radicals to electron‐rich alkenes, and could have general implications in the design of novel radical‐based transformations. 相似文献
9.
The intramolecular bromo‐amidation and the dibromination‐cyclisation of the N‐acylcyclohex‐3‐en‐1‐amines 4, 8, 9, 11, 13, 14 , and 16 was studied in view of the synthesis of bicyclic amines that are of interest as building blocks and potential glycosidase inhibitors. The trifluoroacetamides 4, 9 , and 14 reacted with N‐bromosuccinimide (NBS) in AcOH to give dihydro‐1,3‐oxazines in good yields. The stereoselectivity of the dibromination of the alkenes 8 and 9 depends on the nature of the protecting group, the reagent, and the reaction conditions. Br2 in CH2Cl2 transformed the alkenes 8 and 9 predominantly into diaxial trans,trans‐dibromides. Bromination of 9 with PhMe3NBr3 or with Br2 in the presence of Et4NBr gave predominantly the diequatorial trans,cis‐ 27 besides some trans,trans‐ 28 . A similar bromination of the C(5)‐substituted N‐acyl‐4‐aminocyclohexenes 11, 13, 14 , and 16 with PhMe3NBr3 was accompanied by intramolecular side reactions that were suppressed by the addition of excess Et4NBr. Under these conditions, 11 gave diastereoselectively trans‐dibromides, while its reaction with Br2 gave trans‐dibromides along with the dihydrooxazinone 31 . Also the carbamate 13 reacted with PhMe3NBr3/Et4NBr selectively to the trans‐dibromide 32 and with Br2 to the trans‐dibromides 32 and 33 , the dihydrooxazinone 34 , and the bicyclic ether 35 . Similarly, the trifluoroacetamide 14 provided the dibromide 36 (89%), while its reaction with Br2 led to the dihydrooxazine 22 , and the dibromides 36 and 37 . The N‐benzyl‐N‐Boc derivative 16 did not yield any dibromide; it reacted with PhMe3NBr3/Et4NBr to the dihydrooxazinone 38 , and with Br2 to the oxazinone 38 and the bicyclic ether 39 . The high stereoselectivity of the bromination with PhMe3NBr3/Et4NBr suggests an anchimeric assistance of the NHR substituent. Deprotection, cyclisation, and carbamoylation transformed the dibromides 27, 29 , and 32 into the 7‐azanorbornanes 42, 49 , and 53 . The diols 45 and 57 were obtained from 42 and 53 via HBr elimination and stereoselective dihydroxylation; they proved weak inhibitors of several glycosidases. In no case could the formation of a bicyclic azetidine (6‐azabicyclo[3.1.1]heptane) from the dibromides 26 and 30 be observed. 相似文献
10.
Darius Vrubliauskas Christopher D. Vanderwal 《Angewandte Chemie (International ed. in English)》2020,59(15):6115-6121
A novel CoII‐catalyzed polyene cyclization was developed that is uniquely effective when performed in hexafluoroisopropanol as the solvent. The process is presumably initiated by metal‐catalyzed hydrogen‐atom transfer (MHAT) to 1,1‐disubstituted or monosubstituted alkenes, and the reaction is remarkable for its tolerance of internal alkenes bearing either electron‐rich methyl or electron‐deficient nitrile substituents. Electron‐rich aromatic terminators are required in both cases. Terpenoid scaffolds with different substitution patterns are obtained with excellent diastereoselectivities, and the bioactive C20‐oxidized abietane diterpenoid carnosaldehyde was made to showcase the utility of the nitrile‐bearing products. Also provided are the results of several mechanistic experiments that suggest the process features an MHAT‐induced radical bicyclization with late‐stage oxidation to regenerate the aromatic terminator. 相似文献
11.
Hydroarylations of Heterobicyclic Alkenes through Rhodium‐Catalyzed Directed CH Functionalizations of S‐Aryl Sulfoximines
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Dr. Wanrong Dong Dr. Kanniyappan Parthasarathy Ying Cheng Dr. Fangfang Pan Prof. Dr. Carsten Bolm 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(48):15732-15736
Rhodium‐catalyzed directed CH‐functionalizations have been used in hydroarylations of heterobicyclic alkenes with NH‐sulfoximines. Unexpectedly, the bicyclic framework is retained, resulting in the formation of addition products being attractive intermediates for functionalized molecules that are difficult to prepare by other means. 相似文献
12.
Diastereoselective [3+2] Annulation of Aromatic/Vinylic Amides with Bicyclic Alkenes through Cobalt‐Catalyzed C−H Activation and Intramolecular Nucleophilic Addition
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Dr. Parthasarathy Gandeepan Dr. Pachaiyappan Rajamalli Prof. Dr. Chien‐Hong Cheng 《Angewandte Chemie (International ed. in English)》2016,55(13):4308-4311
A highly diastereoselective method for the synthesis of dihydroepoxybenzofluorenone derivatives from aromatic/vinylic amides and bicyclic alkenes is described. This new transformation proceeds through cobalt‐catalyzed C?H activation and intramolecular nucleophilic addition to the amide functional group. Transition‐metal‐catalyzed C?H activation reactions of secondary amides with alkenes usually lead to [4+2] or [4+1] annulation; to the best of our knowledge, this is the first time that a [3+2] cycloaddition is described in this context. The reaction proceeds under mild conditions and tolerates a wide range of functional groups. Mechanistic studies imply that the C?H bond cleavage may be the rate‐limiting step. 相似文献
13.
Nucleosides that have ambivalent tautomeric properties have value in a variety of nucleic‐acid hybridisation applications and as mutagenic agents. We describe here synthetic studies directed to stable derivatives based on N4‐aminocytosine. Treatment of the 5‐(chloroethyl)‐4‐(triazol‐1‐yl)pyrimidine‐nucleoside derivative 1 with benzylhydrazine leads to the formation of the 6,6‐bicyclic pyrimido‐pyridazin‐7‐one 6 , in addition to the 5,6‐bicyclic derivative 7 . The 6,6‐bicyclic benzyl derivative 6 was converted to its 5′‐triphosphate for studies with DNA polymerases. Reaction of the triazole 1 with hydrazine, followed by acetylation, led to the desired acetylated 6,6‐bicyclic derivative 12 . However, the latter compound undergoes acyl migration followed by ring contraction to the 5,6‐bicyclic compound 13 on treatment with base. 相似文献
14.
Synthesis of Pyrrolidine Derivatives by a Platinum/Brønsted Acid Relay Catalytic Cascade Reaction
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Alicia Galván Dr. Jonás Calleja Prof. Dr. Francisco J. Fañanás Prof. Félix Rodríguez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(8):3409-3414
A new catalytic reaction for the synthesis of pyrrolidine derivatives is presented. The method implies the coupling of N‐Boc‐protected alkynamine derivatives and appropriate alkenes or alkynes in a process catalysed by a platinum/triflic acid catalytic binary system. This reaction is believed to proceed through a cascade process implying an initial platinum‐catalysed cycloisomerization of the alkynamine derivative followed by a triflic acid promoted nucleophilic addition of the alkene or alkyne and trapping of the cationic species formed by the Boc group. Not only simple alkenes and alkynes were used in this reaction but also allyltrimethylsilane and propargyltrimethylsilane. Particularly, when allyltrimethylsilane is used as the alkene counterpart interesting bicyclic compounds containing a trimethylsilane group are obtained. However, when propargyltrimethylsilane is used in the presence of water we observed the formation of a related bicyclic compound lacking the trimethylsilane group and containing an exocyclic carbon?carbon bond. 相似文献
15.
Guangzhu Wang Xinyi Liang Lili Chen Qian Gao Jian‐Guo Wang Panke Zhang Qian Peng Senmiao Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(24):8271-8275
The regioselective hydroboration of aliphatic internal alkenes remains a great challenge. Reported herein is an iridium‐catalyzed hydroboration of aliphatic internal alkenes, providing distal‐borylated products in good to excellent yields with high regioselectivity (up to 99:1). We also demonstrate that the C?B bond of the distal‐borylated product can be readily converted into other functional groups. DFT calculations indicate that the reaction proceeds through an unexpected IrIII/IrV cycle. 相似文献
16.
PdII‐Catalyzed Oxidative Tandem aza‐Wacker/Heck Cyclization for the Construction of Fused 5,6‐Bicyclic N,O‐Heterocycles
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Chenghao Ye Xuezhen Kou Jingzhao Xia Dr. Guoqiang Yang Li Kong Quhao Wei Prof. Dr. Wanbin Zhang 《化学:亚洲杂志》2018,13(15):1897-1901
A PdII‐catalyzed oxidative tandem cyclization was developed for the construction of fused 5,6‐bicyclic N, O‐heterocycles. This reaction was enabled by the combined use of a 3‐methylpyridine ligand and pentafluorobenzoic acid additive. A range of heterocyclic products with different substituents could be prepared in moderate to good yields via this methodology. Several transformations, including a scaled‐up preparation of product 2 a , were also carried out showing the good applicability of our methodology. 相似文献
17.
Sulfonylation of alkenes through photoredox‐catalyzed functionalization of alkenes with thiourea dioxide under visible‐light irradiation is achieved. The reaction of alkenes, thiourea dioxide and electrophiles provides a green and efficient access to alkyl sulfones and sulfonamides. A broad reaction scope is presented with good functional group compatibility and excellent regioselectivity. A plausible mechanism involving a radical addition process with sulfur dioxide radical anion (SO2‐) derived from the oxidation of sulfur dioxide anion (SO22–) is proposed, which is supported by fluorescence quenching experiments. 相似文献
18.
Palladium‐Catalyzed Oxidative Difunctionalization of Alkenes with α‐Carbonyl Alkyl Bromides Initiated through a Heck‐type Insertion: A Route to Indolin‐2‐ones
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Jian‐Hong Fan Wen‐Ting Wei Ming‐Bo Zhou Dr. Ren‐Jie Song Prof. Dr. Jin‐Heng Li 《Angewandte Chemie (International ed. in English)》2014,53(26):6650-6654
The oxidative interception of various σ‐alkyl palladium(II) intermediates with additional reagents for the difunctionalization of alkenes is an important research area. A new palladium‐catalyzed oxidative difunctionalization reaction of alkenes with α‐carbonyl alkyl bromides is described, in which the σ‐alkyl palladium(II) intermediate is generated through a Heck insertion and trapped using an aryl C(sp2)? H bond. This method can be applied to various α‐carbonyl alkyl bromides, including primary, secondary, and tertiary α‐bromoalkyl esters, ketones, and amides. 相似文献
19.
Ken Motokura Dr. Satoka Tanaka Dr. Mizuki Tada Dr. Yasuhiro Iwasawa Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(41):10871-10879
We report the first tunable bifunctional surface of silica–alumina‐supported tertiary amines (SA–NEt2) active for catalytic 1,4‐addition reactions of nitroalkanes and thiols to electron‐deficient alkenes. The 1,4‐addition reaction of nitroalkanes to electron‐deficient alkenes is one of the most useful carbon–carbon bond‐forming reactions and applicable toward a wide range of organic syntheses. The reaction between nitroethane and methyl vinyl ketone scarcely proceeded with either SA or homogeneous amines, and a mixture of SA and amines showed very low catalytic activity. In addition, undesirable side reactions occurred in the case of a strong base like sodium ethoxide employed as a catalytic reagent. Only the present SA‐supported amine (SA–NEt2) catalyst enabled selective formation of a double‐alkylated product without promotions of side reactions such as an intramolecular cyclization reaction. The heterogeneous SA–NEt2 catalyst was easily recovered from the reaction mixture by simple filtration and reusable with retention of its catalytic activity and selectivity. Furthermore, the SA–NEt2 catalyst system was applicable to the addition reaction of other nitroalkanes and thiols to various electron‐deficient alkenes. The solid‐state magic‐angle spinning (MAS) NMR spectroscopic analyses, including variable‐contact‐time 13C cross‐polarization (CP)/MAS NMR spectroscopy, revealed that acid–base interactions between surface acid sites and immobilized amines can be controlled by pretreatment of SA at different temperatures. The catalytic activities for these addition reactions were strongly affected by the surface acid–base interactions. 相似文献
20.
《Journal of heterocyclic chemistry》2017,54(5):2605-2613
A series of novel isoxazole, dihydropyrazolone, and tetrahydropyridine derivatives were synthesized by the reaction of corresponding ethyl 1‐substituted aryl‐2‐methyl‐4‐oxo‐1,4,5,6‐tetrahydropyridine‐3‐carboxylates with different hydrazines and hydroxylamine. Reaction of tetrahydropyridone with N ,N‐dimethylformamide dimethyl acetal provided 1‐(5‐chloro‐2‐methylphenyl)‐2‐[2‐(dimethylamino)ethenyl]‐4‐oxo‐1,4,5,6‐tetrahydropyridine‐3‐carboxylate, which was cyclized into a bicyclic compound on treatment with ammonium acetate. The structures of all synthesized compounds were confirmed by IR, 1H NMR, and 13C NMR spectroscopy data. The structure of 5‐(5‐chloro‐2‐methylphenyl)‐4‐methyl‐2‐phenyl‐2,5,6,7‐tetrahydro‐3H‐pyrazolo[4,3‐c]pyridin‐3‐one was unambiguously assigned by means of X‐ray analysis data. 相似文献