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1.
Elizabeth Tyrrell Julien Millet Kibur Hunie Tesfa Neil Williams Alastair Mann Caroline Tillett Christophe Muller 《Tetrahedron》2007,63(51):12769-12778
Three systematic approaches have been employed to investigate asymmetric Nicholas reactions. We found that the use of a chiral N-enoyl derivative provided acceptable levels of selectivity for an intermolecular Nicholas reaction, however, we were unable to identify an auxiliary that could be utilized in an asymmetric conjugate addition and a tandem inter/intramolecular series of Nicholas reactions. The use of chiral pool non-racemic propargyl alcohols, derived from citronellal, provided enhanced levels of selectivity. As a result of these studies we developed a series of Nicholas cyclisations derived from chiral non-racemic salicylaldehyde derivatives. These underwent an extremely rapid and highly efficient cyclisation, under Nicholas conditions, to afford a range of benzopyrans. The adjacent stereogenic centres appear to be formed with high levels of stereocontrol. 相似文献
2.
《Tetrahedron: Asymmetry》1999,10(10):1873-1875
A facile route to chiral functionalised tetramic acids through C-acylation–cyclisation reactions of active methylene compounds with N-hydroxysuccinimide esters of N-acetyl-l-amino acids is described. Enantiomeric excesses and physical characteristics of all compounds are reported. 相似文献
3.
Energy profiles for alternative intramolecular cyclisations of 4-(aminoalkyl)-ortho-quinones have been calculated using the AM1 method and ab initio energies of the transition states are determined. In all the cases cyclisation at position 5 occurs via a significantly lower energy transition state than cyclisation at position 3. This is consistent with experimental observations. Optimal trajectories for attack have been determined from a study of the reactions of methylamine with 4-methyl-ortho-quinone. For cyclisation of aminoalkyl derivatives deviation from the optimal direction is less for reaction at position 5 but constraint on angle of attack only partially accounts for the regioselectivity. Intrinsic differences in the electronic energies of the alternative transition states are the main contributor to regioselectivity. The relative energies of transition states can be modified by variation of the substituent at position 4. The calculations suggest that seven-membered ring formation may occur via a boat transition state and steric hindrance in the seven-membered transition states may account for the experimentally observed influence of N-substituents on the mode of reaction. 相似文献
4.
Six-membered ring cyclisation of N-ethylbenzazepinone, prepared from the condensation of benzazepinone with phenethyl iodide under basic conditions, smoothly provided the corresponding product, isoquino[1,2-b][3]benzazepinone, under acid-mediated conditions. On the other hand, the attempted direct five-membered ring cyclisation using the acid-mediated conditions failed to give the 7,5 fused ring isoindolinobenzazepinone from N-benzylbenzazepinone, but the 7,6 fused ring product was instead obtained. However, five-membered ring cyclisation of N-benzylbenzazepinone could be effected efficiently by employing the Heck reaction followed by catalytic hydrogenation to furnish the desired isoindolinobenzazepinone. 相似文献
5.
Guillaume Pousse Vincent Dalla Marie-Claire Lasne Jérôme Blanchet 《Tetrahedron》2009,65(51):10617-1548
Original phosphorodithioic acid diesters were prepared according to an improved synthesis of 3,3′-disubstituted H8-BINOL derivatives. In preliminary experiments, these new Brønsted acids were tested as organocatalysts in three reactions. They promoted the Nazarov cyclisation with mixed selectivities, the Mannich reaction with good enantioselectivity and they catalyzed efficiently the alkylation of N-acyliminium with enol silyl ether. 相似文献
6.
《Tetrahedron》2019,75(38):130513
The synthesis of large numbers of diverse molecular scaffolds with controlled molecular properties is a significant challenge in synthetic organic chemistry. A modular unified synthesis was developed, and was exploited in the synthesis of sixteen diverse three-dimensional scaffolds. The approach exploited two cyclisation precursors to be converted, using a toolkit of cyclisation reactions, into spirocyclic and fused-ring scaffolds. Remarkably, Pd-catalysed aminoarylation of substituted N-Boc-hex-5-enylamine cyclisation precursors to yield N-Boc piperidine-containing scaffolds was successful which was ascribed to a significant Thorpe−Ingold effect. Computational property analysis showed that the decorated scaffolds are shape-diverse, and enable diverse lead-like chemical space to be targeted. 相似文献
7.
The development of a preparative route to a series of novel 4-(1H-indol-6-yl)-1H-indazole compounds as potential PDK1 inhibitors is described. The synthetic strategy centres on the late-stage Suzuki cross-coupling of N-unprotected indazole and indole fragments. The use of a monoligated palladium catalyst system was found to be highly beneficial in the cross-coupling reaction. The indazole and indole fragments were constructed by diazotisation/cyclisation and SNAr/reductive cyclisation sequences, respectively. 相似文献
8.
Christiane Albrecht Henning Böckemeier Mark Dennis Matthew D. Fletcher Vera Leitmann Richard Rowles Richard A. Stephenson Michael B. Hursthouse 《Tetrahedron letters》2008,49(1):185-188
The cyclisation of N-allyl- and N-homoallylguanidines using DMDO or I2/K2CO2 leading to novel heterocycles is reported. 相似文献
9.
Polyphosphoric acid-catalysed cyclisation of derivatives of crotonophenone and chalcone is shown to be a general reaction which occurs without migration of aryl substituents evident with other Friedel-Crafts catalysts. Two other reactions, however, may intervene: hydrogenation and α-carbonyl cleavage. Thus 4-bromochalcone gives 3 - (p - bromophenyl) -1 - phenylpropan -1 - one, 3 - (p - bromophenyl)indan -1 - one and some benzole acid. A mechanism for the cyclisation is discussed in comparison with those reported for cyclisations of α,β-unsaturated esters and divinyl ketones. The formation of intermediate Wheland complexes is predicted to be conrotatory. 相似文献
10.
Alan M. Jones 《Tetrahedron》2009,65(2):563-5718
A practical strategy for the synthesis of diazabenz[e]aceanthrylene-based heterocycles is reported. The key step in this approach is a microwave-assisted condensation and cyclisation reaction between an anthranilic acid derivative and a 2′-carbomethoxy substituted N-aryl lactam. The scope of the reaction has been explored as a function of both the nature and position of substituents in both components and variations in lactam ring size. Interesting structural and spectroscopic variations observed across the compound collection are described and explored using NMR, X-ray crystallography and computational techniques. 相似文献
11.
Thermally promoted reactions of a range of alkynes with the orthomanganated acetophenone (η2-2-acetylphenyl)Mn(CO)4 generally give 1H-inden-1-ols in good yield; effects of substituents and solvent on these reactions are reported, along with the crystal structure of 1-methyl-2,3-diphenyl-1H-inden-1-ol. The corresponding orthomanganated benzophenone similarly gives the indenol with diphenylacetylene but by exception, orthomanganated 3-acetylthiophene with phenylacetylene reacts via triple alkyne insertion and cyclisation, shown by crystal structure determination of the π-complex product [(1,2,3,4,5-η)-2-(3-acetylthien-2-yl)-1,3,5-triphenylcyclohexadienyl]tricarbonylmanganese. Corresponding orthomanganated derivatives of N,N-dimethylbenzamide, methyl 3,4,5-trimethoxybenzoate and 4-dimethylaminobenzaldehyde all give indenones with diphenylacetylene, but with (excess) acetylene only the aldehyde gives an indenone, the amide and ester giving instead [(1,2,3,4,5-η)-6-arylcyclohexadienyl]Mn(CO)3 complexes. 1H NMR analysis of these complexes shows H at C6 to be on the same face of the cyclohexadienyl ring as Mn(CO)3 (endo-6-H; exo 6-aryl) as expected from three successive syn additions of alkyne at metallated carbon followed by intramolecular syn addition of alkene in the final cyclisation stage. 相似文献
12.
Investigation of the intramolecular Diels-Alder reactions of 6-fumaryl 1,3,8-nonatrienes, substituted at the C5 by a vinyl group, to afford the B-ring of FR182877 are reported. The synthesis of the required 1,3,8-nonatriene was achieved quickly and in high yield. 6-Fumaryl 1,3,8-nonatrienes substituted at the C5 by a vinyl group were found to undergo competing tandem sigmatropic rearrangement/Diels-Alder cyclisation when heated under standard Diels-Alder cyclisation conditions. This rearrangement became the exclusive pathway when the reaction was performed in the presence of a Lewis acid. As expected from modeling studies, the major intramolecular Diels-Alder cyclisation product was the desired exo-trans adduct, which was required for the synthesis of FR182877. Intrigued by the rearrangements, a number of alterations were made to the 1,3,8-nonatriene. Replacement of the fumaryl group by an acetyl group resulted in the diminished reactivity of the 1,3,8-nonatriene with neither rearrangements nor cycloadditions observed. Variation of the C5 substituent was found to be very important in determining the π-diastereoselectivity of the Diels-Alder cyclisation. 相似文献
13.
Annelation reactions between pentafluorobenzonitrile and N,N-dimethylethylene diamine and 3-methyl picoline gave [6,6]-bicyclic and [6,5,6]-tricyclic ring-fused systems, respectively. Reaction of 4-morpholino tetrafluorobenzonitrile with hydrazine and phenyl hydrazine gave [5,6] ring-fused systems arising from a tandem SNAr and cyclisation process involving annelation onto the pendant cyano group providing an indication of the synthetic possibilities for heterocycle formation using the pentafluorobenzonitrile scaffold. 相似文献
14.
Colin L. Gibson Alan R. Kennedy Raghavendar R. Morthala John A. Parkinson Colin J. Suckling 《Tetrahedron》2008,64(32):7619-7625
Reactions of N-protected derivatives of Weinreb amides of alanine with strong base unexpectedly gave tetramic acid derivatives or an imidazolidinone. The tetramic acid derivatives were obtained by unusual cyclisation of N-acyl N-methoxy derivatives of alanine Weinreb amide upon treatment with potassium hexamethyldisilazide and benzyl bromide. In contrast, treatment of a bromobenzylidine alanine Weinreb amide with potassium hexamethyldisilazide gave rise to cyclisation to form an imidazolidinone. 相似文献
15.
A protocol for the synthesis of quinolines substituted on both pyridine and benzo-fused rings is reported. The method is based on the formylation of a substituted N-(tert-butoxycarbonyl)aniline followed by direct cyclisation and aromatisation of the intermediate product obtained by condensation of the formed N-Boc o-aminobenzaldehyde with an enolisable carbonyl compound. Yields up to 88% have been obtained. 相似文献
16.
The synthesis of the marine alkaloid sebastianine A and of a regioisomer has been accomplished via hetero-Diels-Alder reaction of indole-4,7-dione or N-tosylindole-4,7-dione with trifluoroacetamidocinnamaldehyde dimethylhydrazone, and subsequent cyclisation in alkaline conditions. 相似文献
17.
Prof. Dr. A. Stephen K. Hashmi Prof. Dr. Douglas W. Stephan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(36):11928-11938
A series of propargyl amides were prepared and their reactions with the Lewis acidic compound B(C6F5)3 were investigated. These reactions were shown to afford novel heterocycles under mild conditions. The reaction of a variety of N‐substituted propargyl amides with B(C6F5)3 led to an intramolecular oxo‐boration cyclisation reaction, which afforded the 5‐alkylidene‐4,5‐dihydrooxazolium borate species. Secondary propargyl amides gave oxazoles in B(C6F5)3 mediated (catalytic) cyclisation reactions. In the special case of disubstitution adjacent to the nitrogen atom, 1,1‐carboboration is favoured as a result of the increased steric hindrance (1,3‐allylic strain) in the 5‐alkylidene‐4,5‐dihydrooxazolium borate species. 相似文献
18.
Nicolas Fleury-Brégeot 《Tetrahedron》2007,63(48):11920-11927
The use of chiral, binaphthyl-based phosphepines as catalysts improves previous results for the enantioselective [3+2] cyclisation reactions between allenic esters and N-tosylimines, both in terms of conversion rate and enantioselectivity. Pyrrolines bearing 1-naphthyl, phenyl, o-tolyl and p-MeO-phenyl substituents on the stereogenic alpha-carbon have been obtained with enantiomeric excesses up to 64-80%. 相似文献
19.
A potentially versatile route to 2-(2-aminoaryl)indoles is described based on a palladium-mediated cyclisation of N-substituted indoles, together with free radical cyclisation of their N-benzyliodoacetamide derivatives to the 7,12-dihydro-indolo[3,2-d][1]benzazepin-6(5H)-one system. 相似文献
20.
Olena O. Shyshkina Tetyana M. TkachukTetiana A. Volovnenko Yulian M. VolovenkoRoman I. Zubatyuk Volodymyr V. MedviedievOleg V. Shishkin 《Tetrahedron letters》2012,53(33):4296-4299
A convenient synthesis of isothiochromen-4-one 2,2-dioxide was carried out via cyclisation of o-cyanobenzyl thioacetate by a Thorpe reaction. The reactions of isothiochromen-4-one 2,2-dioxide with nitrogen-containing nucleophilic reagents have been investigated. 相似文献