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Li D, Rao W, Tay GL, Ayers BJ, Chan PWH. Gold-catalyzed cycloisomerization of 1,6-diyne esters to 1H-cyclopenta[b]naphthalenes, cis-cyclopenten-2-yl δ-diketones, and bicyclo[3.2.0]hepta-1,5-dienes. J Org Chem 2014; 79:11301-15. [PMID: 25263810 DOI: 10.1021/jo5020195] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A synthetic method to chemoselectively prepare 1H-cyclopenta[b]naphthalenes, cis-cyclopenten-2-yl δ-diketones, and bicyclo[3.2.0]hepta-1,5-dienes efficiently by gold-catalyzed cycloisomerization of 1,6-diyne esters is described. These three product classes were accessed divergently by taking advantage of the electronic and steric differences between a phosphine and NHC (NHC = N-heterocyclic carbene) ligand in the respective gold(I) complexes and that of gold(III) complex combined with substrate substitution patterns and optimized reaction conditions. In the presence of [PhCNAuIPr](+)SbF6(-) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidine) as the catalyst, substrates with a pendant aryl group at the acetate alkynyl position were found to undergo preferential 1,3-acyloxy migration/5-exo-dig cyclization/Friedel-Crafts reaction to give 1H-cyclopenta[b]naphthalenes. In contrast, the analogous reactions with PicAuCl2 (Pic =2-picolinate) were found to proceed by selective 1,3-acyloxy migration/5-exo-dig cyclization/1,5-acyl migration to afford cis-cyclopenten-2-yl δ-diketones. Changing the catalyst to [MeCNAu(JohnPhos)](+)SbF6(-) (JohnPhos = (1,1'-biphenyl-2-yl)-di-tert-butylphosphine) and the acetate alkynyl position from an aryl to vinyl substituent in the starting ester led to 1,3-acyloxy migration/5-exo-dig cyclization/Prins-type [2 + 2]-cycloaddition to provide bicyclo[3.2.0]hepta-1,5-dienes.
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Rao W, Sally, Berry SN, Chan PWH. Back Cover: Gold-Catalyzed Cycloisomerization of 1,6,8-Dienyne Carbonates and Esters to cis-Cyclohepta-4,8-diene-Fused Pyrrolidines (Chem. Eur. J. 41/2014). Chemistry 2014. [DOI: 10.1002/chem.201490173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Rao W, Sally, Berry SN, Chan PWH. Gold-catalyzed cycloisomerization of 1,6,8-dienyne carbonates and esters to cis-cyclohepta-4,8-diene-fused pyrrolidines. Chemistry 2014; 20:13174-80. [PMID: 25113644 DOI: 10.1002/chem.201402500] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Indexed: 01/29/2023]
Abstract
A synthetic approach that provides access to cis-cyclohepta-4,8-diene-fused pyrrolidines efficiently through Au(I) -catalyzed cycloisomerization of 1,6,8-dienyne carbonates and esters at a low catalyst loading of 2 mol % is reported. Starting carbonates and esters with a pendant alkyl group on the terminal alkenyl carbon center were found to favor tandem 1,2-acyloxy migration/cyclopropanation followed by Cope rearrangement of the resulting cis-3-azabicyclo[3.1.0]hexane intermediate. On the other hand, substrates containing a terminal diene or starting materials in which the distal alkene moiety bears a phenyl substituent were observed to undergo competitive but reversible 1,3-acyloxy migration prior to the nitrogen-containing bicyclic ring formation. The delineated reaction mechanism also provides experimental evidence for the reversible interconversion between the oft-proposed organogold intermediates obtained in this step of the tandem process.
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Mothe SR, Novianti ML, Ayers BJ, Chan PWH. Silver-Catalyzed Tandem Hydroamination/Hydroarylation of 1-(2-Allylamino)phenyl-4-hydroxy-but-2-yn-1-ones to 1′-Allylspiro[indene-1,2′-indolin]-3′-ones. Org Lett 2014; 16:4110-3. [DOI: 10.1021/ol501809p] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Zhang X, Teo WT, Rao W, Ma DL, Leung CH, Chan PWH. Synthesis of highly substituted indene derivatives by Brønsted acid catalyzed Friedel–Crafts reaction of homoallylic alcohols. Tetrahedron Lett 2014. [DOI: 10.1016/j.tetlet.2014.05.027] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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56
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Zhong HJ, Liu LJ, Chong CM, Lu L, Wang M, Chan DSH, Chan PWH, Lee SMY, Ma DL, Leung CH. Discovery of a natural product-like iNOS inhibitor by molecular docking with potential neuroprotective effects in vivo. PLoS One 2014; 9:e92905. [PMID: 24690920 PMCID: PMC3972188 DOI: 10.1371/journal.pone.0092905] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Accepted: 02/27/2014] [Indexed: 12/11/2022] Open
Abstract
In this study, we applied structure-based virtual screening techniques to identify natural product or natural product-like inhibitors of iNOS. The iNOS inhibitory activity of the hit compounds was characterized using cellular assays and an in vivo zebrafish larvae model. The natural product-like compound 1 inhibited NO production in LPS-stimulated Raw264.7 macrophages, without exerting cytotoxic effects on the cells. Significantly, compound 1 was able to reverse MPTP-induced locomotion deficiency and neurotoxicity in an in vivo zebrafish larval model. Hence, compound 1 could be considered as a scaffold for the further development of iNOS inhibitors for potential anti-inflammatory or anti-neurodegenerative applications.
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Zhong HJ, Liu LJ, Chan DSH, Wang HM, Chan PWH, Ma DL, Leung CH. Structure-based repurposing of FDA-approved drugs as inhibitors of NEDD8-activating enzyme. Biochimie 2014; 102:211-5. [PMID: 24657219 DOI: 10.1016/j.biochi.2014.03.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 03/10/2014] [Indexed: 11/30/2022]
Abstract
We report the discovery of an inhibitor of NEDD8-activating enzyme (NAE) by an integrated virtual screening approach. Piperacillin 1 inhibited NAE activity in cell-free and cell-based systems with high selectivity. Furthermore, piperacillin 1 was able to inhibit the degradation of the NAE downstream protein substrate p27(kip1). Our molecular modeling and kinetic studies suggested that this compound may act as a non-covalent ATP-competitive inhibitor of NAE.
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Teo WT, Rao W, Ng CJH, Koh SWY, Chan PWH. Gold-Catalyzed Benzannulation of 5-Hydroxy-3-oxoalk-6-ynoate Esters to o-Phenolic Esters. Org Lett 2014; 16:1248-51. [DOI: 10.1021/ol5002363] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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59
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Susanti D, Ng LLR, Chan PWH. Silica Gel-Mediated Hydroamination/Semipinacol Rearrangement of 2-Alkylaminophenylprop-1-yn-3-ols: Synthesis of 2-Oxindoles from Alkynes and 1-(2-Aminophenyl) Ketones. Adv Synth Catal 2014. [DOI: 10.1002/adsc.201300911] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Rao W, Chan PWH. Back Cover: Gold-Catalyzed [2+2+1] Cycloaddition of 1,6-Diyne Carbonates and Esters with Aldehydes to 4-(Cyclohexa-1,3-dienyl)-1,3-dioxolanes (Chem. Eur. J. 3/2014). Chemistry 2014. [DOI: 10.1002/chem.201490009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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61
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Lin S, He B, Shiu-Hin Chan D, Hong Chan PW, Leung CH, Ma DL. A G-quadruplex-based platform for the detection of Hg2+ ions using a luminescent iridium(iii) complex. RSC Adv 2014. [DOI: 10.1039/c4ra11240g] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We report herein the synthesis of a series of cyclometalated iridium(iii) complexes as luminescent G-quadruplex-selective probes, which were used to construct an oligonucleotide-based platform for the dual detection and removal of Hg2+ ions.
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Rao W, Chan PWH. Gold-catalyzed [2+2+1] cycloaddition of 1,6-diyne carbonates and esters with aldehydes to 4-(cyclohexa-1,3-dienyl)-1,3-dioxolanes. Chemistry 2013; 20:713-8. [PMID: 24323953 DOI: 10.1002/chem.201303685] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Indexed: 11/10/2022]
Abstract
A synthetic method to stereoselectively prepare 4-(cyclohexa-1,3-dienyl)-1,3-dioxolanes in good to excellent yields by gold(I)-catalyzed [2+2+1] cycloaddition of 1,6-diyne carbonates and esters with aldehydes is described. The cascade process involves 1,2-acyloxy migration followed by cyclopropenation and cycloreversion. This leads to an unprecedented [2+2+1] cycloaddition of the resulting alkenylgold carbenoid species, examples of which are extremely rare, with two aldehyde molecules at catalyst loadings as low as 1 mol %. The usefulness of this cycloisomerization chemistry was further demonstrated by the transformation of one example to the corresponding phenol.
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Kothandaraman P, Lauw SJL, Chan PWH. Metal-free synthesis of 1H-indole-2-carbaldehydes by N-iodosuccinimide-mediated cyclization of 1-(2′-anilinyl)prop-2-yn-1-ols in water. A formal synthesis of (R)-calindol. Tetrahedron 2013. [DOI: 10.1016/j.tet.2013.06.032] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Teo WT, Rao W, Koh MJ, Chan PWH. Gold-Catalyzed Domino Aminocyclization/1,3-Sulfonyl Migration of N-Substituted N-Sulfonyl-aminobut-3-yn-2-ols to 1-Substituted 3-Sulfonyl-1H-pyrroles. J Org Chem 2013; 78:7508-17. [DOI: 10.1021/jo401083m] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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65
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Sze EML, Koh MJ, Tjia YM, Rao W, Chan PWH. Synthesis of (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones by two-step, one-pot gold-catalyzed tandem heterocyclization/Petasis–Ferrier rearrangement of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes. Tetrahedron 2013. [DOI: 10.1016/j.tet.2013.04.069] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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66
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Rao W, Koh MJ, Li D, Hirao H, Chan PWH. Gold-catalyzed cycloisomerization of 1,6-diyne carbonates and esters to 2,4a-dihydro-1H-fluorenes. J Am Chem Soc 2013; 135:7926-32. [PMID: 23627597 DOI: 10.1021/ja4032727] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A synthetic method to prepare 2,4a-dihydro-1H-fluorenes efficiently from gold(I)-catalyzed 1,2-acyloxy migration/cyclopropenation/Nazarov cyclization of 1,6-diyne carbonates and esters is described. The suggested reaction pathway provides rare examples of [2,3]-sigmatropic rearrangement in this class of compounds as well as the involvement of an in situ formed cyclopropene intermediate in gold catalysis. Experimental and ONIOM(QM:QM') [our own n-layered integrated molecular orbital and molecular mechanics(quantum mechanics:quantum mechanics')] computational studies based on the proposed Au carbenoid species provide insight into this unique selectivity.
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Rao W, Sally, Koh MJ, Chan PWH. Gold-catalyzed cycloisomerization of 1,7-enyne esters to structurally diverse cis-1,2,3,6-tetrahydropyridin-4-yl ketones. J Org Chem 2013; 78:3183-95. [PMID: 23458312 DOI: 10.1021/jo400121j] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A synthetic method that relies on gold(I)-catalyzed cycloisomerization of 1,7-enyne esters to prepare highly functionalized cis-1,2,3,6-tetrahydropyridin-4-yl ketone derivatives in good to excellent yields and as a single regio-, diastereo-, and enantiomer is described. By taking advantage of the distinctive differences in the electronic and steric properties between an NHC (NHC = N-heterocyclic carbene) and phosphine ligand in the respective gold(I) complexes, a divergence in product selectivity was observed. In the presence of [PhCNAuIPr](+)SbF6(-) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidine) as the catalyst, tandem 1,3-acyloxy migration/6-exo-trig cyclization/1,5-acyl migration of the substrate was found to selectively occur to give the δ-diketone-substituted 1,2,3,6-tetrahydropyridine adduct. In contrast, reactions with the gold(I) phosphine complex [MeCNAu(JohnPhos)](+)SbF6(-) (JohnPhos = (1,1'-biphenyl-2-yl)-di-tert-butylphosphine) as the catalyst was discovered to result in preferential 1,3-acyloxy migration/6-exo-trig cyclization/hydrolysis of the 1,7-enyne ester and formation of the cis-1,2,3,6-tetrahydropyridin-4-yl ketone derivative. The utility of this piperidine forming strategy as a synthetic tool that makes use of 1,7-enyne esters was exemplified by its application to the synthesis of an enantiopure analogue of the bioactive 2,3,4,4a,5,9b-hexahydroindeno[1,2-c]pyridine family of compounds.
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Kothandaraman P, Koh BQ, Limpanuparb T, Hirao H, Chan PWH. 1-(2′-Anilinyl)prop-2-yn-1-ol Rearrangement for Oxindole Synthesis. Chemistry 2012. [DOI: 10.1002/chem.201202606] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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69
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Susanti D, Koh F, Kusuma JA, Kothandaraman P, Chan PWH. Silver Acetate Catalyzed Hydroamination of 1-(2-(Sulfonylamino)phenyl)prop-2-yn-1-ols to (Z)-2-Methylene-1-sulfonylindolin-3-ols. J Org Chem 2012; 77:7166-75. [DOI: 10.1021/jo301198z] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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70
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Ton TMU, Himawan F, Chang JWW, Chan PWH. Copper(II) triflate catalyzed amination of 1,3-dicarbonyl compounds. Chemistry 2012; 18:12020-7. [PMID: 22890890 DOI: 10.1002/chem.201201219] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Indexed: 11/11/2022]
Abstract
A method to prepare α,α-acyl amino acid derivatives efficiently by Cu(OTf)(2)+1,10-phenanthroline (1,10-phen)-catalyzed amination of 1,3-dicarbonyl compounds with PhI=NSO(2) Ar is described. The mechanism is thought to initially involve aziridination of the enolic form of the substrate, formed in situ through coordination to the Lewis acidic metal catalyst, by the putative copper-nitrene/imido species generated from the reaction of the metal catalyst with the iminoiodane source. Subsequent ring opening of the resultant aziridinol adduct under the Lewis acidic conditions then provided the α-aminated product. The utility of this method was exemplified by the enantioselective synthesis of a precursor of 3-styryl-2-benzoyl-L-alanine.
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Mothe SR, Lauw SJL, Kothandaraman P, Chan PWH. Brønsted Acid-Catalyzed Cycloisomerization of But-2-yne-1,4-diols with or without 1,3-Dicarbonyl Compounds to Tri- and Tetrasubstituted Furans. J Org Chem 2012; 77:6937-47. [DOI: 10.1021/jo301093f] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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72
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Rao W, Koh MJ, Kothandaraman P, Chan PWH. Gold-catalyzed cycloisomerization of 1,7-diyne benzoates to indeno[1,2-c]azepines and azabicyclo[4.2.0]octa-1(8),5-dines. J Am Chem Soc 2012; 134:10811-4. [PMID: 22663059 DOI: 10.1021/ja304964s] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A synthetic method that relies on Au(I)-catalyzed cycloisomerization reactions of 1,7-diyne benzoates to prepare indeno[1,2-c]azepines and azabicyclo[4.2.0]octa-1(8),5-dines is described.
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Mothe SR, Kothandaraman P, Lauw SJL, Chin SMW, Chan PWH. Silver Triflate Catalyzed Tandem Heterocyclization/Alkynylation of 1-((2-Tosylamino)aryl)but-2-yne-1,4-diols to 2-Alkynyl Indoles. Chemistry 2012; 18:6133-7. [DOI: 10.1002/chem.201200578] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Indexed: 11/07/2022]
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Ton TMU, Tejo C, Tiong DLY, Chan PWH. Copper(II) triflate catalyzed amination and aziridination of 2-alkyl substituted 1,3-dicarbonyl compounds. J Am Chem Soc 2012; 134:7344-50. [PMID: 22462638 DOI: 10.1021/ja301415k] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A method to prepare α-acyl-β-amino acid and 2,2-diacyl aziridine derivatives efficiently from Cu(OTf)(2) + 1,10-phenanthroline (1,10-phen)-catalyzed amination and aziridination of 2-alkyl substituted 1,3-dicarbonyl compounds with PhI═NTs is described. By taking advantage of the orthogonal modes of reactivity of the substrate through slight modification of the reaction conditions, a divergence in product selectivity was observed. In the presence of 1.2 equiv of the iminoiodane, amination of the allylic C-H bond of the enolic form of the substrate, formed in situ through coordination to the Lewis acidic metal catalyst, was found to selectively occur and give the β-aminated adduct. On the other hand, increasing the amount of the nitrogen source from 1.2 to 2-3 equiv was discovered to result in preferential formal aziridination of the C-C bond of the 2-alkyl substituent of the starting material and formation of the aziridine product.
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Huang C, Kothandaraman P, Koh BQ, Chan PWH. Study of substrate dependence on the chemoselectivity of the gold-catalysed cycloisomerisation of aryl substituted 1,7-enynes. Org Biomol Chem 2012; 10:9067-78. [DOI: 10.1039/c2ob26458g] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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