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1.
A convenient new method was developed to prepare two types of vinyl cyclopropane derivatives through gold-catalyzed cyclization of 1-alkynyl cyclopropyl tert-butyl carbonates 2. Different from the previous reported 5-exo-dig route, the 6-endo-dig addition is the preferred pathway to provide six-membered cyclized carbonates. Two factors, including stereoelectronic effect and steric effect might affect the regioselectivity. Therefore, low steric aliphatic substrates afforded only six-membered isomers. The synthetic utility of compound 3 was also explored to afford a series of β-carbonyl cyclopropanol derivatives. 相似文献
2.
An easy synthesis of (Z)-1-alkylidene-1,3-dihydroisobenzofurans and 1H-isochromenes by palladium-catalyzed cycloisomerization of readily available 2-alkynylbenzyl alcohols under neutral conditions is reported. Reactions were carried out at 70-100°C in the presence of catalytic amounts (1-2%) of PdI2 in conjunction with 2 equiv. of KI for 1.5-24 h. The preference towards the 5-exo-dig cyclization mode (leading to 1,3-dihydroisobenzofurans) or the 6-endo-dig cyclization mode (leading to isochromenes) turned out to be dependent on the substitution pattern of the substrate as well as reaction conditions. In several cases, by properly adjusting the reaction conditions, the same substrate could be selectively converted into either the dihydroisobenzofuran or the 1H-isochromene derivative. 相似文献
3.
Steffen Maier Robin Heckershoff Nikolai Hippchen Kerstin Brödner Dr. Frank Rominger Dr. Jan Freudenberg Prof. A. Stephen K. Hashmi Prof. Uwe H. F. Bunz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(64):e202201842
Brominated pentannulated dihydrotetraazapentacenes were prepared by gold- or palladium-catalyzed 5-endo-dig cyclization of TIPS-ethynylated dihydrotetraazaacenes (TIPS = triisopropylsilyl). Post-functionalization was demonstrated by Sonogashira alkynylation and Rosenmund-von Braun cyanation. Calculations predict these species to act as n-type semiconductors, which was verified for two derivates through characterization in organic field-effect transistors. 相似文献
4.
Genesis Infante Assoc. Prof. Sara Eisler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(65):16121-16126
Sequential anionic intramolecular cyclizations and modelling were used for the first time to access unusual fused heterocyclic frameworks in excellent yields. 5-Exo-dig cyclizations yielded isoindolinone motifs and a subsequent 6-exo- and 7-endo-dig cyclization was directed to provide either fused isoquinoline or azepine frameworks. Regioselectivities were controlled by exploiting stereoelectronic effects via nC−→π*(Ph) interactions, and modelling studies provided reaction scope. 相似文献
5.
Ariadna Fuente‐Hernàndez Philippe Costes Philippe Kalck Ulises Jáuregui‐Haza Odile Dechy‐Cabaret Martine Urrutigoïty 《应用有机金属化学》2011,25(11):815-819
The CO‐bubbling effect in cycloisomerization reactions of enynes derived from monoterpenes has been studied using PtCl2, [Rh2Cl2(CO)4] and AuCl3 as catalytic systems. All the precursors are efficient catalysts for the cycloisomerization of O‐tethered enynes. The reaction proceeds through exo‐dig and endo‐dig pathways, which are consistent with the exclusive coordination of the alkyne triple bond to the metal center. The CO ligand not only increases the reaction rates but also induces significant variations in the two reaction pathways. Notably, this effect is also strongly dependent on the nature of the starting enyne. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
6.
Dr. Rosana Álvarez Claudio Martínez Youssef Madich J. Gabriel Denis Dr. José M. Aurrecoechea Prof. Dr. Ángel R. de Lera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(42):12746-12753
Structurally diverse C3‐alkenylbenzofurans, C3‐alkenylindoles, and C4‐alkenylisoquinolones are efficiently prepared by using consecutive Sonogashira and cascade Pd‐catalyzed heterocyclization/oxidative Heck couplings from readily available ortho‐iodosubstituted phenol, aniline, and benzamide substrates, alkynes, and functionalized olefins. The cyclization of O‐ and N‐heteronucleophiles follows regioselective 5‐endo‐dig‐ or 6‐endo‐dig‐cyclization modes, whereas the subsequent Heck‐type coupling with both mono‐ and disubstituted olefins takes place stereoselectively with exclusive formation of the E isomers in most cases. 相似文献
7.
4-exo-dig and 5-exo-dig Cyclocarbopalladations: an expeditious solution toward molecular complexity?
Christophe Bour 《Tetrahedron》2006,62(45):10567-10581
The 4-exo-dig and 5-exo-dig cyclocarbopalladations have been efficiently used to produce molecular complexity in a straightforward manner. Strained 1,2-cyclobutanediols are rapidly obtained under microwave irradiation in high yields. In many cases, the cyclocarbopalladation cascade reaction is associated with a 6 or 8π electrocyclic reaction. During the process of the 5-exo-dig cyclocarbopalladation on benzosuberone derivatives, an aromatic C-H activation leads to vinylic substituted aromatics. Polycyclic skeletons of natural products of the family of Ophiobolin and Aleurodiscal can be prepared in few steps from simple starting material. 相似文献
8.
Haruki Sashida Mamoru Kaname Akemi Nakayama Hirokazu Suzuki Mao Minoura 《Tetrahedron》2010,66(27-28):5149-5157
The intramolecular cyclizations of four types of dibenzyl chalcogenols, which contained one or two ethynyl groups, were carried out. Either the double 5-exo or 6-endo-dig mode ring closure reaction regio- and stereoselectively proceeded to give the corresponding symmetrical bis(benzo[c]chalcogenophene) or bis(isochromene) derivatives from the dibenzyl chalcogenols having a diyne moiety. In contrast, the regioselective tandem 5-exo-dig mode intramolecular ring closure reactions of dibenzyl thiol and selenol having a mono-yne into a triple bond gave the trans-biisobenzothiophene and selenophene as the sole product. However, the similar cyclization of dibenzyl tellurol proceeded in both tandem 5-exo and 6-endo-dig modes to afford the trans-biisobenzotellurophene and ditellurachrysene in good yields with the ratio of 1:1. The X-ray structural analysis of these novel compounds is also presented. 相似文献
9.
Diversity Oriented Synthesis of Indoloazepinobenzimidazole and Benzimidazotriazolobenzodiazepine from N1‐Alkyne‐1,2‐diamines 下载免费PDF全文
Ravi Kumar Rajesh K. Arigela Srinivas Samala Dr. Bijoy Kundu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18828-18833
A one‐pot protocol for the diversity oriented synthesis of two N‐polyheterocycles indoloazepinobenzimidazole and benzimidazotriazolobenzodiazepine from a common N1‐alkyne‐1,2‐diamine building block is described. The approach involves sequential formation of benzimidazole through cyclocondensation and oxidation, which is followed by the formation of either an azepine ring (through alkyne activation and 6‐endo‐dig cyclization, 1,2‐migration with ring expansion, and re‐aromatization), or diazepine and triazole rings through 1,3‐dipolar cycloaddition. 相似文献
10.
A facile synthesis of a series of 1-alkoxyisoquinolines and (2H)-isoquinolones by an intramolecular 6-endo-dig cyclization of ortho-alkynylbenzonitriles in the presence of a catalytic amount of hydrido(dimethylphosphinous acid-κP)[hydrogen bis(dimethylphosphinito-κP)]platinum(II) in various alcohols at 65-90 °C is described for the first time. 相似文献
11.
Gold-catalyzed reactions of 3-silyloxy-1,5-enynes in the presence of sterically demanding alcohols afford 4-acylcyclopentenes. The cascade process most likely proceeds through a 6-endo-dig carbocyclization and subsequent pinacol-type rearrangement. Studies that define scope and limitations of the cyclization-migration strategy are also described. An alternative cascade yields highly substituted aryls through an unprecedented cyclization-fragmentation pathway. 相似文献
12.
Metal‐Catalyzed Cyclization Reactions of 2,3,4‐Trien‐1‐ols: A Joint Experimental–Computational Study 下载免费PDF全文
Prof. Dr. Benito Alcaide Prof. Dr. Pedro Almendros Sara Cembellín Dr. Israel Fernández Dr. Teresa Martínez del Campo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(33):11667-11676
Controlled preparation of tri‐ and tetrasubstituted furans, as well as carbazoles has been achieved through chemo‐ and regioselective metal‐catalyzed cyclization reactions of cumulenic alcohols. The gold‐ and palladium‐catalyzed cycloisomerization reactions of cumulenols, including indole‐tethered 2,3,4‐trien‐1‐ols, to trisubstituted furans was effective, due to a 5‐endo‐dig oxycyclization by attack of the hydroxy group onto the central cumulene double bond. In contrast, palladium‐catalyzed heterocyclization/coupling reactions with 3‐bromoprop‐1‐enes furnished tetrasubstituted furans. Also studied was the palladium‐catalyzed cyclization/coupling sequence involving protected indole‐tethered 2,3,4‐trien‐1‐ols and 3‐bromoprop‐1‐enes that exclusively generated trisubstituted carbazole derivatives. These results could be explained through a selective 6‐endo‐dig cumulenic hydroarylation, followed by aromatization. DFT calculations were carried out to understand this difference in reactivity. 相似文献
13.
Chandrasekaran Praveen 《Tetrahedron letters》2010,51(36):4767-238
An efficient, regioselective Cu(OTf)2-catalyzed 5-exo-dig intramolecular hydroalkoxylation of 2-(ethynyl)benzyl alcohol, which provides a concise access to functionalized phthalan in high yields has been developed. A wide range of substrates possessing terminal, internal, and heteroaromatic alkynes can be efficiently transformed into the targeted phthalans. Substrates with primary, secondary, and tertiary benzyl alcohols also proceed well to produce the corresponding phthalans in good yields. Irrespective of the nature of the substrates, the cyclization follows highly selective 5-exo-dig regiochemistry when regioselectivity is an issue. 相似文献
14.
N. V. Zyk E. K. Beloglazkina V. S. Tyurin Yu. K. Grishin 《Russian Chemical Bulletin》1998,47(11):2220-2225
Bromochlorination of norbornene whose chemo- and regio-selectivity is determined by the type of the halogenating reagent used
was studied. Three isomeric bromochloronorbornanes (2-endo-bromo-3-exo-chloro-, 2-exo-bromo-3-endo-chloro-, and 2-exo-bromo-7-syn-chlorobicyclo[2.2.1.]heptanes), 2-exo-7-syn- and 2-exo-7-anti-dibromo- and-dichloronorbornanes, and 2-bromonortricyclane were isolated and characterized by1H and13C NMR spectra. The spectral and structural characteristics of the resulting compounds are discussed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2290–2295, November, 1998. 相似文献
15.
Hung-Chin Shen 《Tetrahedron letters》2004,45(50):9245-9247
Treatment of 3-en-1-ynyl imines with TpRuPPh3(CH3CN)2PF6 catalyst (1 mol %) in DCE (50 °C, 6 h) effected catalytic cyclization with suitable nucleophiles and gave functionalized pyrroles in good yields. The reaction mechanism is proposed to proceed via (2-pyrrolyl)carbenoid intermediates derived from 5-exo-dig cyclization. This catalytic reaction works well with various nucleophiles, including water, alcohols and anilines. 相似文献
16.
《Comptes Rendus de l''Academie des Sciences Series IIB Mechanics Physics Astronomy》2001,4(6):423-426
This communication describes our preliminary results on the radical cyclization of homopropargylic bromomethyldimethylsilyl ethers, an unknown reaction. With precursor 5a, only the very rare 7-endo-dig process was observed. The reduction of the resulting vinyl radical is not stereoselective and gives a cis/trans, 1.35:1 mixture of silaoxepan derivatives, as determined after a methyllithium treatment yielding olefins 11 and 12. This represents a new example of formation of a trans heterocyclic cycloheptene. With disubstituted precursor 5b, the system is less reactive and still no 6-exo-dig radical cyclization has been observed. 相似文献
17.
Sanjay S. Palimkar 《Tetrahedron》2007,63(51):12786-12790
An efficient synthesis of the potent KDR kinase inhibitor 3-[5-[[4-(methylsulfonyl)-1-piperazinyl]methyl]-1H-indol-2-yl]quinoline-2-(1H)-one using a Sonogashira coupling-5-endo-dig-cyclization strategy is described. 相似文献
18.
《Tetrahedron: Asymmetry》1998,9(13):2207-2210
The enantiomerically pure 1,2-diacylferrocenes (+)-(R)-10–12 (ee>99%) were synthesized from (N,N-dimethylaminomethyl)ferrocene via enantiomerically pure 2-acyl-1-formylferrocene (+)-(R)-4–6. A novel methodology was performed using the chemo- and diastereoselective addition of diethylzinc to the formyl function through an intramolecular autoactivation. 相似文献
19.
Jiayue Fu Bingbing Li Xiugui Wang Qida Liang Xiaoshi Peng Lu Yang Tao Wan Xinxiu Wang Bin Lin Maosheng Cheng Yongxiang Liu 《中国化学》2022,40(1):46-52
A gold(I)-catalyzed 6-endo-dig cyclization of aromatic 1,5-enynes was developed to synthesize 2-(naphthalen-2-yl)anilines. The functional group tolerance of this cyclization was examined systematically and a possible mechanism was proposed. The derivatization of 2-(naphthalen-2-yl)aniline was carried out to facile access to benzo[α]carbazole, benzo[c,h]cinnoline and dibenzo[i]phenanthridine derivatives in a divergent way. 相似文献
20.
Ynamides are tested as new partners in radical and organometallic transformations. A radical cascade involving a 5-exo-dig cyclization followed by a 6-endo-trig radical trapping transforms ynamides into hetero-polycyclic compounds such as isoindoles, isoindolinones and pyrido-isoindolones. Various ene-tosylynamides react with platinum(II) chloride and lead to bicyclic nitrogenated heterocycles. This unprecedented and easily operated process can be coupled with a hydrolysis of the intermediate cyclic tosylenamides in a one-pot transformation, which provides cyclobutanones. 相似文献