共查询到20条相似文献,搜索用时 15 毫秒
1.
Catalyst-controlled asymmetric ring opening of a racemic oxabicyclic alkene leads to two readily separable regioisomeric products both in excellent ee. A cationic Rh catalyst, with added NH(4)BF(4) to modulate reactivity, was required to obtain synthetically useful yields. The utility of each substituted aminotetralin product has been demonstrated by their conversion to different biologically relevant molecules in a highly efficient and practical manner. 相似文献
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Selective 1,2-iodine, bromine, and chlorine migration in haloallenyl ketones in the presence of Au catalyst has been demonstrated. It was found that, depending on the nature of the Au catalyst used, either selective bromine migration or hydrogen shift occurs, leading to the formation of 3- or 2-bromofurans, respectively. Halirenium intermediate was proposed for the unusual 1,2-halogen migration. This cascade transformation allows for mild and efficient synthesis of various types of 3-halofurans. 相似文献
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-Aminopyrroles are used in a new, versatile and high yield substituted benzene ring synthesis. 相似文献
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The reaction of a racemic perhydroisoquinolene derivative 9 with the homochiral lithium amide basse 3 in the presence of Me3SiCl in an regiodivergent fashion to give the two non-racemic regioisomeric enol silanes 10 and 11. Conversion of 10 into enone 15, an intermediate useful in the synthesis of the alkaloid (+)-yohimbine, was also possible. 相似文献
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《中国化学快报》2023,34(6):107914
A regiodivergent hydrophosphorylation of enynes with phosphites has been developed using earth-abundant nickel catalyst. The manipulation of regioselectivity can be achieved by regulating the insertion order of alkyne bonds with (RO)2P(O)–Ni–H or R2P(O)O–Ni–H species, respectively. Under the Ni/Xantphos catalysis, 4,1-hydrophosphorylation is selectively obtained while the adding of acid can promote reactions towards 1,2-addition. By employing an additional Pd–H catalysis, 2,1-hydrophosphorylation is also an accessible task in one-pot reaction. Mechanistic studies and analysis have also been performed to interpret the origin of the regioselective regulation. This work highlights the arts in accessing different regioisomers by diverting common elementary reaction steps. 相似文献
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A new route to obtain the polyalkylated indole (+/-)-trans-trikentrin A was developed. The synthesis of this natural alkaloid features a thallium(III)-mediated ring contraction reaction to obtain the trans-1,3-disubstituted five-membered ring in a diastereoselective manner. Thallium(III) is chemoselective in this rearrangement, reacting with the olefin without oxidation of the indole moiety. Other key transformations are the Bartoli's reaction to construct the heterocyclic ring and a Heck coupling to add the carbons atom that will originate the nonaromatic cycle. 相似文献
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Michelangelo Gruttadauria Renato Noto Serena Riela 《Journal of heterocyclic chemistry》1998,35(4):865-869
The stereoselective synthesis of a 2-substituted tetrahydropyran with adjacent alkoxy-bearing stereogenic centre is described. The key steps of this synthesis were the stereoselective epoxidation of an allylic alcohol and the regioselective epoxide ring opening by lithium aluminum hydride. The regio and stereoselective synthesis of a trihydroxyselenide and a trihydroxysulfide is also described. The latter compounds are not suitable for cyclization to tetrahydrofuran ring. 相似文献
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A new approach toward the synthesis of 1H-isochromenes based on the recyclization of the furan ring in the corresponding ortho-hydroxymethylbenzylfurans is described. 相似文献
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A concise synthesis of the oxygen substituted ring A compound 2 found in Taxol®1a and Taxotere®1b starting from 2,2-dimethylcyclohexane-1,3-dione and proceeding via the key intermediates 8 and 11, is described. The absolute configuration of 2 was established from an X-ray crystal structure determination of a 4-bromophenylbenzoate derivative, viz. 15. 相似文献
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This paper demonstrates that the secondary hydroxyl can be functionalized in preference to the primary hydroxyl of a 1,2-diol. The site selectivity is achieved by using an enantioselective organic catalyst that is able to bond to the diol reversibly and covalently. The reaction has been parlayed into a divergent kinetic resolution on a racemic mixture, providing access to highly enantioenriched secondary-protected 1,2-diols in a single synthetic step. 相似文献
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Won Keun Chung Jin Hyun Chung Kyoichi A. Watanabe 《Journal of heterocyclic chemistry》1983,20(2):457-457
A very simple method for the preparation of 5-fluorouracil ( 1 ) from 1,3-dimethyl-5-azauracil ( 2 ) by a novel ring transformation reaction is reported. 相似文献
15.
Herdemann M Al-Mourabit A Martin MT Marazano C 《The Journal of organic chemistry》2002,67(6):1890-1897
On the basis of a biogenetic proposal for explaining the biogenesis of manzamine A, the cycloaddition of dihydropyridinium salt 26 with diene derivative 5 leads to adducts 27. These adducts, as well as their related and previously described analogues 9, are now shown to be precursors of diene derivatives such as 10, 13, and 28. Treatment of diene 32 with sodium azide resulted in a one-step formation of the tricyclic imino derivative 34. This key intermediate was further transformed into tricyclic derivative 40, which possesses the essential features of the ABC ring of manzamine A. 相似文献
16.
Zhi Chen Yu-Fan Li Shun-Zhong Tan Qin Ouyang Zhi-Chao Chen Wei Du Ying-Chun Chen 《Chemical science》2022,13(42):12433
Although nucleophilic benzylation-type reaction to introduce various aromatic systems into molecules has been widely explored, the related pyrrolylmethylation version remains to be disclosed. Reported herein is a palladium-catalysed multiple auto-tandem reaction between N-Ts propargylamines, allyl carbonates and aldimines in the presence of an acid, proceeding through sequential allylic amination, cycloisomerisation, vinylogous addition and aromatisation steps. A diversity of formal pyrrolylmethylated amine products were finally furnished efficiently. In addition, switchable regiodivergent 3-pyrrolylmethylation and 4-pyrrolylmethylation were realised by tuning catalytic conditions. Moreover, remote chirality transfer with readily available enantioenriched starting materials was well achieved with an achiral ligand, relying on diastereoselective generation of η2-Pd(0) complexes between Pd(0) and chiral 1,3-diene intermediates in the key vinylogous addition step. A few control experiments were conducted to elucidate the palladium-involved tandem reaction and regiodivergent synthesis.A formal nucleophilic pyrrolylmethylation reaction was disclosed via a palladium-catalysed tandem reaction between propargyl amines, allyl carbonates and aldimines. Switchable regiodivergent synthesis and chirality transfer could be well achieved. 相似文献
17.
A short and efficient RCM route is reported for the construction of the key nine-membered B ring of eleutherobin starting from the readily available 1,2,5,6-diisopropylidene-d-glucose. 相似文献
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《Tetrahedron letters》1988,29(37):4743-4746
Oxetanocin has been synthesized starting from cis-2-buten-1,4-diol through α- or β-D-oxetanosyl acetate as an important intermediate which has an α-(methyl oxalyloxy)methyl group at C2-position. 相似文献
20.
Kenichi Harada 《Tetrahedron letters》2005,46(43):7407-7410
An efficient route to the AB ring motif of merrilactone A has been established by remarkable regioselective reduction of cyclic anhydrides 3 and 8 to the γ-lactone moiety, followed by the successive Stille and Heck reactions of 1,1-dibromo-1-alkene. 相似文献