Abstract
Background: Enamines and their variant enamides as powerful and versatile synthons have attracted great attention in synthetic chemistry. Enamides display unique stability and reduce enaminic reactivity in view of the electron-withdrawing effect of N-acyl group. A great deal of satisfactory achievements in the synthesis and application of enamides has been made in recent years. Especially, tertiary enamides without N-H bond regarded as low reactivity of compounds in the past can act as excellent nucleophiles to react with electrophiles for the construction of various nitrous molecules.
Objective: This review focuses on recent advances on tertiary enamides in the synthetic strategies and applications including addition, coupling reaction, functionalization and electro- or photo-chemical reaction.
Conclusion: Tertiary enamides as electron-deficient nucleophiles display a satisfactory balance between stability and reactivity to offer multiple opportunities for the construction of various functionalized nitrogencontaining compounds. Further exploration of the reactive mechanisms involved tertiary enamides and the development of novel and efficient transformations to generate ever more complex building blocks starting from tertiary enamides are particularly worth pursuing.
Keywords: Tertiary enamide, nucleophilic reaction, addition, coupling reaction, functionalization, electro- or photochemical reaction.
Graphical Abstract
[2]
Stork, G.; Landesman, H. A new alkylation of carbonyl compounds. J. Am. Chem. Soc., 1956, 78, 5128-5129.
[3]
Stork, G.; Brizzolara, A.; Szmuszkovicz, J.; Terrell, R. The enamine alkylation and acylation of carbonyl compounds. J. Am. Chem. Soc., 1963, 85, 207-222.
[6]
Mukherjee, S.; Yang, J.W.; Hoffmann, S.; List, B. Asymmetric enamine catalysis. Chem. Rev., 2007, 107, 5471-5569.
[7]
Matsubara, R.; Kobayashi, S. Enamides and enecarbamates as nucleophiles in stereoselective C-C and C-N bond-forming reactions. Acc. Chem. Res., 2008, 41, 292-301.
[8]
Nugent, T.C.; El-Shazly, M. Chiral amine synthesis recent developments and trends for enamide reduction, reductive amination, and imine reduction. Adv. Synth. Catal., 2010, 352, 753-819.
[10]
Gopalaiah, K.; Kagan, H.B. Use of nonfunctionalized enamides and enecarbamates in asymmetric synthesis. Chem. Rev., 2011, 111, 4599-4657.
[11]
Bernadat, Q.; Masson, G. Enamide derivatives: Versatile building blocks for highly functionalized α,β-substituted amines. Synlett, 2014, 25, 2842-2867.
[12]
Dagousset, G.; Courant, T.; Masson, G. Enamide derivatives: Versatile buil-ding blocks for total synthesis. Synthesis, 2015, 47, 1799-1826.
[13]
Yang, L.; Deng, G.; Wang, D-X.; Huang, Z-T.; Zhu, J.; Wang, M-X. Highly efficient and stereoselective N-vinylation of oxiranecarboxamides and unprecedented 8-endo-epoxy-arene cyclization: Expedient and biomi-metic synthesis of some clausena alkaloids. Org. Lett., 2007, 9, 1387-1390.
[14]
Yang, L.; Zheng, Q-Y.; Wang, D-X.; Huang, Z-T.; Wang, M-X. Reversal of nucleophilicity of enamides in water: Control of cyclization pathways by reaction media for the orthogonal synthesis of dihydropyridinone and pyrrolidinone clausena alkaloids. Org. Lett., 2008, 10, 2461-2464.
[15]
Yang, L.; Wang, D-X.; Pan, J.; Zheng, Q-Y.; Huang, Z-T.; Wang, M-X. Highly efficient and concise synthesis of both antipodes of SB204900, clausenamide, neoclausenamide, homoclausenamide and ζ-clausenamide. Implication of biosynthetic pathways of clausena alkaloids. Org. Biomol. Chem., 2009, 7, 2628-2634.
[16]
Yang, L.; Tong, S.; Wang, D-X.; Huang, Z-T.; Zhu, J.; Wang, M-X. Synthesis of hydroxylated 3,4-dihydropyridine-2-ones from intramolecular nucleophilic addition reaction of oxirane-containing tertiary enamides. Synlett, 2011, 2011, 927-930.
[17]
Yang, L.; Lei, C-H.; Wang, D-X.; Huang, Z-T.; Wang, M-X. Highly efficient and expedient synthesis of 5-hydroxy-1H-pyrrol-2-(5H)-ones from FeCl3-catalyzed tandem intramolecular enaminic addition of tertiary enamides to ketones and 1,3-hydroxy rearrangement. Org. Lett., 2010, 12, 3918-3921.
[18]
Tong, S.; Wang, D-X.; Zhang, L.; Zhu, J.; Wang, M-X. Enantioselective synthesis of 4-hydroxytetrahydropyridine derivatives by intramolecular addition of tertiary enamides to aldehydes. Angew. Chem. Int. Ed., 2012, 51, 4417-4420.
[19]
Tong, S.; Xu, Y.; Wang, D-X.; Zhao, L.; Zhu, J.; Wang, M-X. Synthesis of 4-amino-1,2,3,4-tetrahydropyridine derivatives by intramolecular nucleophilic addition of tertiary enamides to in-situ generated imines. Tetrahedron, 2012, 68, 6492-6497.
[20]
Lei, C-H.; Wang, D-X.; Zhao, L.; Zhu, J.; Wang, M-X. Synthesis of substituted pyridines from cascade [1+5] cycloaddition of isonitriles to N-formylmethyl-substituted enamides, aerobic oxidative aromatization, and acyl transfer reaction. J. Am. Chem. Soc., 2013, 135, 4708-4711.
[21]
Lei, C-H.; Wang, D-X.; Zhao, L.; Zhu, J.; Wang, M-X. Synthesis of multifunctionalized 1,2,3,4-tetrahydropyridines, 2,3-dihydropyridin-4(1H)-ones, and pyridines from tandem reactions initiated by [5+1] cycloaddition of N-formylmethyl-subsittuted enamides to isocyanides: Mechanistic insight and synthetic application. Chem. Eur. J., 2013, 19, 16981-16987.
[22]
Wang, M-X. Exploring tertiary enamides as versatile synthons in organic synthesis. Chem. Commun., 2015, 51, 6039-6049.
[23]
Liang, H.; Ren, Z-H.; Wang, Y-Y.; Guan, Z-H. Copper-catalyzed direct synthesis of iodoenamides from ketoximes. Chem. Eur. J., 2013, 19, 9789-9794.
[24]
Ran, L.; Liang, H.; Guan, Z-H. Progress in transition metal-catalyzed reactions of oximes and their derivatives. Chin. J. Org. Chem, 2013, 33, 66-75.
[25]
Zhao, M-N.; Du, W.; Ren, Z-H.; Wang, Y-Y.; Guan, Z-H. FeCl3-catalyzed self-condensation of enamides for the synthesis of enamido substituted nitrogen-containing quaternary carbon centers. Eur. J. Org. Chem., 2013, 7989-7995.
[26]
Boeckman, R.K.; Goldstein, S.W.; Walters, M.A. Synthetic studies of the cyclopropyl iminium ion rearrangement. 3. Application of the cyclopropyl acyliminium ion rearrangement to a concise and highly convergent synthesis of (+-)-lycorine. J. Am. Chem. Soc., 1988, 110, 8250.
[27]
Couture, A.; Deniau, E.; Grandclaudon, P. A convenient synthesis of enamides and dienamides by Horner-Wittig and Wadsworth-Emmons reactions. Tetrahedron Lett., 1993, 34, 1479-1482.
[28]
Kondo, T.; Tanaka, A.; Kotachi, S.; Watanabe, Y. Ruthenium complex-catalysed addition of N-aryl substituted amides to alkynes: Novel synthesis of enamides. J. Chem. Soc. Chem. Commun., 1995, 413-414.
[29]
Kuramochi, K.; Watanabe, H.; Kitahara, T. Synthetic study on oximidines: A concise synthesis of (Z)-enamides. Synlett, 2000, 2000, 397-399.
[30]
Fürstner, A.; Brehm, C.; Cancho-Grande, Y. Stereoselective synthesis of enamides by a Peterson reaction manifold. Org. Lett., 2001, 3, 3955-3957.
[31]
Weiner, B.; Szymaóski, W.; Janssen, D.B.; Minnaard, A.J.; Feringa, B.L. Recent advances in the catalytic asymmetric synthesis of β-amino acids. Chem. Soc. Rev., 2010, 39, 1656-1691.
[32]
Kuranaga, T.; Sesoko, Y.; Inoue, M. Cu-mediated enamide formation in the total synthesis of complex peptide natural products. Nat. Prod. Rep., 2014, 31, 514-532.
[33]
Yet, L. Chemistry and biology of salicylihalamide A and related compounds. Chem. Rev., 2003, 103, 4283-4306.
[34]
Delforge, A.; Georgiou, I.; Kremer, A.; Wouters, J., and ; Bonifazi, D. Synthesis of tertiary enamides by Ag2CO3-promoted Pd-catalyzed alkenylation of acyclic secondary amides. Org. Lett., 2016, 18, 4844-4847.
[35]
Dehli, J.R.; Legros, J.; Bolm, C. Synthesis of enamines, enol ethers and related compounds by cross-coupling reactions. Chem. Commun., 2005, 2005, 973-986.
[36]
Han, C.; Shen, R.; Su, S.; Porco, J.A. Copper-mediated synthesis of N-Acyl vinylogous carbamic acids and derivatives: Synthesis of the antibiotic CJ-15, 801. Org. Lett., 2004, 6, 27-30.
[37]
Pan, X.; Cai, Q.; Ma, D. CuI/N,N-Dimethylglycine-catalyzed coupling of vinyl halides with amides or carbamates. Org. Lett., 2004, 6, 1809-1812.
[38]
Jiang, L.; Job, G.E.; Klapars, A.; Buchwald, S.L. Copper-catalyzed coupling of amides and carbamates with vinyl halides. Org. Lett., 2003, 5, 3667-3669.
[39]
Genovino, J.; Lagu, B.; Wang, Y.; Touré, B.B. Synthesis of sterically hindered enamides a Ti-mediated condensation of amides with aldehydes and ketones. Chem. Commun., 2012, 48, 6735-6737.
[40]
Panda, N.; Jena, A.K.; Raghavender, M. Stereoselective synthesis of enamides by palladium catalyzed coupling of amides with electron deficient olefins. ACS Catal., 2012, 2, 539-543.
[41]
Panda, N.; Mothkuri, R. Stereoselective synthesis of enamides by Pd-catalyzed hydroamidation of electron deficient terminal alkynes. J. Org. Chem., 2012, 77, 9407-9412.
[42]
Herrero, M.T.; Sarralde, J.D.; SanMartin, R.; Bravo, L.; Domíngueza, E. Cesium carbonate-promoted hydroamidation of alkynes: Enamides, indoles and the effect of iron chloride. Adv. Synth. Catal., 2012, 354, 3054-3064.
[43]
Gigant, N.; Habib, S.; Medoc, M.; Goekjian, P.G.; Gueyrard, D.; Gillaizeau, I. Synthesis of exo-enamides from protected lactams using a modified julia olefination reaction: Application to the synthesis of spiroaminal fragments. Eur. J. Org. Chem., 2014, 2014, 6501-6506.
[44]
Yan, Z.H.; Xu, Y.; Tian, W.S. A new and concise way to enamides by fluoroalkanosulfonyl fluoride-mediated Beckmann rearrangement of α,β-unsaturated ketoximes. Tetrahedron Lett., 2014, 55, 7186-7189.
[45]
Raushel, J.; Fokin, V.V. Efficient synthesis of 1-sulfonyl-1,2,3-triazoles. Org. Lett., 2010, 12, 4952-4955.
[46]
Liu, Y.; Wang, X.; Xu, J.; Zhang, Q.; Zhao, Y.; Hu, Y. Highly controlling selectivity of copper(I)-catalyzed azide/alkyne cycloaddition (CuAAC) between sulfonyl azids and normal alkynes. Tetrahedron, 2011, 67, 6294-6299.
[47]
Miura, T.; Fujimoto, Y.; Funakoshi, Y.; Murakami, M. A reaction of triazoles with thioesters to produce β-sulfanyl enamides by insertion of an inamine moiety into the sulfur–carbonyl bond. Angew. Chem. Int. Ed., 2015, 54, 9967-9970.
[48]
Maity, P.; Kundu, D.; Ranu, B.C. Nickel-copper-catalyzed C(sp2)-N cross-coupling of cyclic and bridged amides: An access to cyclic enamides and alkenyl vince lactams. Adv. Synth. Catal., 2015, 357, 3617-3626.
[49]
Philkhana, S.C.; Seetharamsingh, B.; Dangat, Y. Vanka, B.K.; Reddy, D.S. Synthesis of palmyrolide A and its cis-isomer and mechanistic insight into trans–cis isomerisation of the enamide macrocycle. Chem. Commun., 2013, 49, 3342-3344.
[50]
Wadsworth, A.D.; Furkert, D.P.; Brimble, M.A. Total synthesis of the macrocyclic N-methyl enamides palmyrolide A and 2S-sanctolide A. J. Org. Chem., 2014, 79, 11179-11193.
[51]
Yadav, J.S.; Suresh, B.; Srihari, P. Expedient synthesis of large-ring trans-enamide macrolides by CuI-mediated intramolecular coupling of vinyl iodide with amide: Total synthesis of palmyrolide A. Eur. J. Org. Chem., 2016, 2016, 2509-2531.
[52]
Borra, S.; Amrutapu, S.K.; Pabbaraja, S.; Singh, Y.J. Stereoselective total synthesis of palmyrolide A intramolecular trans N-methyl enamide formation. Tetrahedron Lett., 2016, 57, 4456-4459.
[53]
Reddy, A.S.; Swamy, K.C.K. Ethanol as a hydrogenating agent: palladium-catalyzed stereoselective hydrogenation of ynamides to give enamides. Angew. Chem. Int. Ed., 2017, 56, 6984-6988.
[54]
Lingua, H.; Vibert, F.; Mouysset, D.; Siri, D.; Bertrand, M.P.; Feray, L. Iron(II)/copper(I)-mediated stereoselective carbozincation of ynamides. One-pot synthesis of α-allyl-tetrasubstituted-enamides. Tetrahedron, 2017, 73, 3415-3422.
[55]
Kozak, J.A.; Patrick, B.O., and ; Dake, G.R. Gold(I)-catalyzed intramolecular tandem addition/friedel-crafts reactions between acyclic enamides and 1-arylalkynes. J. Org. Chem., 2010, 75, 8585-8590.
[56]
Brizgys, G.J.; Jung, H.H.; Floreancig, P.E. Stereoselective piperidine synthesis through oxidative carbon–hydrogen bond functionalizations of enamides. Chem. Sci. , 2012, 3, 438-442.
[57]
Zhu, W.J. Zhao, L.; Wang, M.-X. Synthesis of 2,3-dihydro-1H-azepine and 1H-azepin-2(3H)-one derivatives from intramolecular condensation between stable tertiary enamides and aldehydes. J. Org. Chem., 2015, 80, 12047-12057.
[58]
Zhang, X.Y.; Xu, X.M.; Zhao, L.; You, J.S.; Zhu, J.P.; Wang, M-X. Synthesis of diverse di- to penta-substituted 1,2-dihydropyridine derivatives from gold (I)-catalyzed intramolecular addition of tertiary enamides to alkynes. Tetrahedron Lett., 2015, 56, 3898-3901.
[59]
Xu, X-M.; Zhao, L.; Zhu, J.; Wang, M-X. Catalytic asymmetric tandem reaction of tertiary enamides: Expeditious synthesis of pyrrolo[2,1-α]isoquinoline alkaloid derivatives. Angew. Chem. Int. Ed., 2016, 55, 3799-3803.
[60]
Zhang, H-J.; Bolm, C. Highly regioselective intermolecular hydroacylations of enamides with salicylaldehydes. Org. Lett., 2011, 13, 3900-3903.
[61]
Ma, Z-X.; Feltenberger, J.B.; Hsung, R.P. Total syntheses of chelidonine and norchelidonine an enamide-benzyne-[2+2] cycloaddition cascade. Org. Lett., 2012, 14, 2742-2745.
[62]
He, L.; Zhao, L.; Wang, D-X.; Wang, M-X. Catalytic asymmetric difunctionalization of stable tertiary enamides with salicylaldehydes: Highly efficient, enantioselective, and diastereoselective synthesis of diverse 4-chromanol derivatives. Org. Lett., 2014, 16, 5972-5975.
[63]
Nocquet-Thibault, S.; Minard, C.; Retailleau, P.; Cariou, K.; Dodd, R.H. Iodine (III)- mediated ethoxychlorination of enamides with iron(III) chloride. Tetrahedron, 2014, 70, 6769-6775.
[64]
Nocquet-Thibault, S.; Rayar, A.; Retailleau, P.; Cariou, K.; Dodd, R.H. Iodine(III)-mediated diazidation and azido-oxyamination of enamides. Chem. Eur. J., 2015, 21, 14205-14212.
[65]
He, L.; Liu, H-B.; Zhao, L.; Wang, D-X.; Wang, M-X. Lewis acid-catalyzed reaction between tertiary enamides and imines of salicylaldehydes: expedient synthesis of novel 4-chromanamine derivatives. Tetrahedron, 2015, 71, 523-531.
[66]
Li, H.H.; Li, X.X.; Zhao, Z.G.; Ma, T.; Sun, C.Y.; Yang, B.W. Intermolecular iodofunctionalization of allenamides with indoles, pyrroles, and furans: synthesis of iodine-substituted Z-enamides. Chem. Commun., 2016, 52, 10167-10170.
[67]
Jiang, R.; Wu, X-J.; Zhu, X.; Xu, X-P., and; Ji, S-J. Ferric(III) nitrate: An efficient catalyst for the regioselective Friedel–Crafts reactions of indoles and tert-enamides in water. Eur. J. Org. Chem., 2010, 2010, 5946-5950.
[68]
Jiang, R.; Xu, H-Y.; Xu, X-P.; Chu, X-Q., and; Ji, S-J. Direct alkylation of indoles and amines by tert-enamides: facile access to pharmaceutically active 2-oxo-1-pyrrolidine analogues. Org. Biomol. Chem., 2011, 9, 5659-5669.
[69]
Zhang, Y.; Jiang, J.; Chu, X-Q.; Jiang, R.; Xu, X-P.; Li, D-H.; Ji, S-J. Friedel–Crafts alkylation of indoles by tert-enamides in acetic acid. Synlett, 2012, 23, 751-754.
[70]
Chu, X-Q.; Wang, S-Y., and; Ji, S-J. Recyclable NaHSO4 catalyzed alkylation of tertenamides with indoles or amines in water: facile construction of pharmaceutically analogous bis-alkaloid scaffolds. RSC Adv, 2013, 3, 8380-8387.
[71]
Xu, H-Y.; Zi, Y.; Xu, X-P.; Wang, S-Y.; Ji, S-J. TFA-catalyzed C-N bond activation of enamides with indoles: efficient synthesis of 3,3-bisindolylpropanoates and other bisindolylalkanes. Tetrahedron, 2013, 69, 1600-1605.
[72]
Huo, C.D.; Kang, L.S. Xu, X.L.; Jia, X.D.; Wang, X.C.; Xie, H.S.; Yuan, Y. Triarylaminium salt facilitated Friedel-Crafts reaction of indoles with enamides and vinyl ethers. Tetrahedron Lett., 2014, 55, 954-958.
[73]
Huo, C.D.; Kang, L.S.; Xu, X.L. Jia, X.D.; Wang, X.C.; Yuan, Y.; Xie, H.S. Friedele-Crafts alkylation of 2-naphthols with enamides and enethers induced by catalytic amount of triarylaminium salt. Tetrahedron, 2014, 70, 1055-1059.
[74]
Jha, A.; Chou, T-Y.; Aljaroudi, Z.; Bobby, D.E., and; Cameron, T.S. Aza-Diels–Alder reaction between N-aryl-1-oxo-1H-isoindolium ions and tert-enamides: Steric effects on reaction outcome. Beilstein J. Org. Chem., 2014, 10, 848-857.
[75]
Liu, H-M.; Lu, W.; Luo, C-P.; Yang, L. Pd-catalyzed chemo- and regioselective cross-coupling of two enamides. Tetrahedron Lett., 2016, 57, 4243-4245.
[76]
Liu, Y.; Li, D.; Park, C-M. Stereoselective synthesis of highly substituted enamides by an oxidative Heck reaction. Angew. Chem. Int. Ed., 2011, 50, 7333-7336.
[77]
Gigant, N.; Chausset-Boissarie, L.; Belhomme, M.C.; Poisson, T.; Pannecoucke, X.; Gillaizeau, I. Copper-catalyzed direct arylation of cyclic enamides using diaryliodonium salts. Org. Lett., 2013, 15, 2278-2281.
[78]
Alamsetti, S.K.A.; Persson, K.A.; Jiang, T.; Báckvall, J-E. Scalable synthesis of oxazolones from propargylic alcohols through multistep palladium(II) catalysis: β-Selective oxidative Heck coupling of cyclic sulfonyl enamides and aryl boroxines. Angew. Chem. Int. Ed., 2013, 52, 13745-13750.
[79]
Lone, A.M.; Bhat, B.A. Metal free stereoselective synthesis of functionalized enamides. Org. Biomol. Chem., 2014, 12, 242-246.
[80]
He, L.; Gu, M.; Wang, D.; Wang, M. Tandem Heck reaction of tertiary enamides: A novel access to trans-2,5-disubstituted-3-pyrroline derivatives. Acta Chim. Sinica., 2015, 73, 1018-1024.
[81]
Beng, T.K.; Sincavage, K.; Silaire, A.W.V.; Alwali, A.; Bassler, D.P.; Spence, L.E.; Beale, O. Direct access to functionalized benzotropones, azepanes, and piperidines by reductive crosscoupling of α-bromo enones with α-bromoenamides. Org. Biomol. Chem., 2015, 13, 5349-5353.
[82]
Sato, S.; Takeda, N.; Ueda, M.; Miyata, O. Sequential [3,3]-sigmatropic rearrangement/ nucleophilic arylation of N-(benzoyloxy)enamides towards the preparation of cyclic β-aryl-β-amino alcohols. Synthesis, 2016, 48, 882-892.
[83]
Rey-Rodriguez, R.; Retailleau, P.; Bonnet, P.; Gillaizeau, I. Iron-catalyzed trifluoromethylation of enamide. Chem. Eur. J., 2015, 21, 3572-3575.
[84]
Gu, J-W.; Min, Q-Q.; Yu, L-C.; Zhang, X.G. Tandem difluoroalkylation-arylation of enamides catalyzed by nickel. Angew. Chem. Int. Ed., 2016, 55, 12270-12274.
[85]
Caillot, G.; Dufour, J.; Belhomme, M-C.; Poisson, T. Grimaud, L.; Pannecoucke, X.; Gillaizeau, I.C. Copper-catalyzed olefinic C-H difluoroacetylation of enamides. Chem. Commun., 2014, 50, 5887-5890.
[86]
Li, L-J.; Jiang, Y-Y.; Jiang, C.; Lam, M.; Zeng, C-C. Hu, L.-M.; Little, R.D. Aromatic C−H bond functionalization induced by electrochemically in situ generated tris(p-bromophenyl)aminium radical cation: cationic chain reactions of electron-rich aromatics with enamides. J. Org. Chem., 2015, 80, 11021-11030.
[87]
Jiang, H.; Huang, C.M. Guo, J.J.; Zeng, C.Q.; Zhang, Y.; Yu, S.Y. Direct C-H functionalization of enamides and enecarbamates by using visible-light photoredox catalysis. Chem. Eur. J., 2012, 18, 15158-15166.
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