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Iron(III)‐Catalyzed Cycloisomerizations of Acetal–Vinylidenecyclopropanes: An Efficient Synthetic Route to 1,2‐Disubstituted Cyclobutenes 下载免费PDF全文
Song Yang Wei Yuan Dr. Qin Xu Prof. Dr. Min Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):15964-15969
A novel iron(III)‐catalyzed intramolecular cycloisomerization of acetal–vinylidenecyclopropanes to afford a series of halogenated 1,2‐disubstituted cyclobutenes tethered with a tetrahydropyrrole has been developed. The reaction is thought to proceed through a formal iron‐catalyzed Prins cyclization followed by a ring‐enlarging rearrangement of the methylenecyclopropane carbocation. The present protocol provides an alternative route to functionalized disubstituted cyclobutenes and the corresponding products could be successfully transformed into eight‐membered oxacyclic products. 相似文献
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Atropisomeric [(diphosphine)Au2Cl2] Complexes and their Catalytic Activity Towards Asymmetric Cycloisomerisation of 1,6‐Enynes 下载免费PDF全文
Dr. Elena M. Barreiro Dr. Ekaterina V. Boltukhina Dr. Andrew J. P. White Dr. King Kuok Hii 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2686-2690
X‐ray crystal structures of two [(diphosphine)Au2Cl2] complexes (in which diphosphine=P‐Phos and xylyl‐P‐Phos; P‐Phos=[2,2′,6,6′‐Tetramethoxy‐4,4′‐bis(diphenylphosphino)‐3,3′‐bipyridine]) were determined and compared to the reported structures of similar atropisomeric gold complexes. Correlations between the Au???Au distances and torsional angles for the biaryl series of ligands (MeOBIPHEP, SEGPhos, and P‐Phos; BIPHEP=2,2′‐bis(diphenylphosphino)‐1,1′‐biphenyl, SEGPhos=[(4,4′‐bi‐1,3‐benzodioxole)‐5,5′‐diyl]bis[diphenylphosphine]) can be made; these measurements appear to be very dependent upon the phosphorous substituent. Conversely, the same effect was not observed for ligands based on the binaphthyl (BINAP) series. The catalytic activity of these complexes was subsequently assessed in the enantioselective cycloisomerisation of 1,6‐enynes and revealed an over‐riding electronic effect: more‐electron‐rich phosphines promote greater enantioselectivity. The possibility of silver acting as a (co‐)catalyst was ruled out in these reactions. 相似文献
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Andrew Whyte Jonathan Bajohr Alexa Torelli Mark Lautens 《Angewandte Chemie (International ed. in English)》2020,59(38):16409-16413
We report a cobalt‐catalyzed hydroacylation of 1,6‐enynes with exogenous aldehydes in a domino sequence to construct enantioenriched ketones. The products were obtained in good yields with excellent regio‐, diastereo‐, and enantioselectivity. Furthermore, the chiral products served as valuable precursors to access complex spirocyclic scaffolds with three contiguous stereocenters. The asymmetric hydroacylation process exhibited no C?H crossover and no KIE, thus indicating that the C?H bond cleavage was not involved in the turnover‐limiting step. 相似文献
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Dr. Xu Deng Shao‐Fei Ni Zheng‐Yu Han Yu‐Qing Guan Prof. Dr. Hui Lv Prof. Dr. Li Dang Prof. Dr. Xu‐Mu Zhang 《Angewandte Chemie (International ed. in English)》2016,55(21):6295-6299
An enantioselective rhodium(I)‐catalyzed cycloisomerization reaction of challenging (E)‐1,6‐enynes is reported. This novel process enables (E)‐1,6‐enynes with a wide range of functionalities, including nitrogen‐, oxygen‐, and carbon‐tethered (E)‐1,6‐enynes, to undergo cycloisomerization with excellent enantioselectivity, in a high‐yielding and operationally simple manner. Moreover, this RhI‐diphosphane catalytic system also exhibited superior reactivity and enantioselectivity for (Z)‐1,6‐enynes. A rationale for the striking reactivity difference between (E)‐ and (Z)‐1,6‐enynes using RhI‐BINAP and RhI‐TangPhos is outlined using DFT studies to provide the necessary insight for the design of new catalyst systems and the application to synthesis. 相似文献
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Rhodium(II)‐Catalyzed Intramolecular Cycloisomerizations of Methylenecyclopropanes with N‐Sulfonyl 1,2,3‐Triazoles 下载免费PDF全文
Kai Chen Zi‐Zhong Zhu Yong‐Sheng Zhang Dr. Xiang‐Ying Tang Prof. Min Shi 《Angewandte Chemie (International ed. in English)》2014,53(26):6645-6649
A novel rhodium(II)‐catalyzed tandem cycloisomerization of methylenecyclopropanes (MCPs) with N‐sulfonyl 1,2,3‐triazoles is disclosed. The reaction produces a series of highly functionalized polycyclic N heterocycles via a rhodium imino carbene intermediate. A distinct feature of this divergent synthesis is that different types of substrates control the reaction pathways. Moreover, several interesting transformations of these products to construct diazabicyclo[3.2.1]octane derivatives are also reported. 相似文献
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Liang‐Feng Yao Min Shi Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(15):3875-3881
Cascade reactions : Lewis acid catalyzed cascade reactions of 1,6‐diynes and 1,6‐enynes with arylvinylidenecyclopropanes produce polycyclic compounds and isopropylidene‐3,3‐diarylcyclobut‐1‐enylmethyl derivatives (see scheme) in good to high yields along with a PtCl2‐catalyzed cyclization and a Cu(OAc)2 ? H2O‐catalyzed Eglinton coupling reaction.
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Ana Escribano‐Cuesta Verónica López‐Carrillo Dominic Janssen Dr. Antonio M. Echavarren Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(23):5646-5650
Gold and rings : The gold(I)‐catalyzed addition of aldehydes to 1,6‐enynes gives 1,3‐dienes, by a cycloaddition/fragmentation process. 1,5‐Enynes react with aldehydes and ketones by the 5‐endo‐dig pathway to give the corresponding cycloadducts.
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《化学:亚洲杂志》2017,12(17):2245-2257
The [2+2+2] intermolecular carbocyclization reactions between 1,6‐enynes and alkynes catalyzed by [RuCl(cod)(Cp*)] (cod=1,5‐cyclooctadiene, Cp*=pentamethylcyclopentadienyl) are reported to provide bicyclohexa‐1,3‐dienes. The presented reaction conditions are compatible with internal and terminal alkynes and the chemo‐ and regioselectivity issues are controlled by the presence of substituents at the propargyl carbon center of the alkyne(s) partner(s). 相似文献
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Catalytic Enantioselective Quick Route to Aldol‐Tethered 1,6‐ and 1,7‐Enynes from ω‐Unsaturated Aldehydes 下载免费PDF全文
Prof. Dr. Jesús M. García Dr. José M. Odriozola Dr. Jesús Razkin Irati Lapuerta Amaiur Odriozola Iñaki Urruzuno Dr. Silvia Vera Prof. Dr. Mikel Oiarbide Prof. Dr. Claudio Palomo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15543-15554
An effective asymmetric route to functionalized 1,6‐ and 1,7‐enynes has been developed based on a direct cross‐aldol reaction between ω‐unsaturated aldehydes and propargylic aldehydes (α,β‐ynals) promoted by combined α,α‐dialkylprolinol ether/Brønsted acid catalysis. This synergistic activation strategy is key to accessing the corresponding aldol adducts with high stereoselectivity, both enantio‐ and diastereoselectivity. The aldol reaction also proceeds well with propargylic ketones (α,β‐ynones) thus enabling a stereocontrolled access to the corresponding tertiary alcohols. The utility of these adducts, which are difficult to prepare through standard methodology, is demonstrated by their transformation into trisubstituted bicyclic enones using standard Pauson–Khand conditions. 相似文献
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Qingxi Meng Ming Li Jinsheng Zhang Wei Shen 《International journal of quantum chemistry》2006,106(7):1569-1579
The PtCl2‐catalyzed asymmetric cycloisomerization reaction of hydroxylated enynes was studied using density functional theory (DFT). All structures have been optimized completely at the B3LYP/6‐311G(d,p) level. As shown, the cycloisomerization reaction is exothermic. The cycloisomerization reaction mainly undergoes the formation of catalyst‐hydroxylated enzyme coordination, the asymmetric cyclopropyl platinum carbene, catalyst–cyclopropyl enol coordination, and catalyst–cyclopropyl ketone coordination. The chirality‐limiting step for the asymmetric cycloisomerization reaction is the formation of the asymmetric cyclopropyl platinum carbene, and the rate‐determining step for this reaction is the formation of the catalyst–cyclopropyl ketone coordination. The dominant products predicted theoretically are (R,S) ‐syn_5a, in agreement with the experiment. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献
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Xiao‐Lin Lu Dr. Mao‐Yun Lyu Prof. Dr. Xiao‐Shui Peng Prof. Dr. Henry N. C. Wong 《Angewandte Chemie (International ed. in English)》2018,57(35):11365-11368
A novel gold‐catalyzed tandem protocol, initiated by hydride transfer in the presence of catalytic (C6F5)3PAuCl/AgSbF6, for the formation of fused polycyclic ring systems has been achieved. This tandem reaction provides rapid access to various fused polycyclic species in a single chemical operation, leading to stereospecific formation of two carbon–carbon bonds and three rings. 相似文献
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