Malic Acid as a Green Catalyst for the N-Boc Protection under
Solvent-free Condition

Ashok      Pise; Shripad   M.   Patil; Ajit   P.   Ingale
doi:10.2174/0115701786278928231218113855
Abstract

A protocol for the Chemoselective N-Boc protection of various types of amines has been developed. This includes heteroaryl, aliphatic, and alicyclic amines. The process makes use of malic acid as a catalyst and operates efficiently at ambient temperature without the need for solvents. This technique has been proven to effectively protect a wide range of functionalized amines containing both electron-donating and electron-withdrawing substituents. The benefits of this method include its fast reaction rate, high selectivity, excellent yield, catalyst recyclability, and environmentally friendly conditions.
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[1]
Green, T.; Wuts, P. In protecting group in organic synthesis; John Wiley and Sons: New York, 1999. 
 [http://dx.doi.org/10.1002/0471220574]; 
(b) Kocienski, P.J. In protecting Groups; Georg Thieme: New York, 2000. 

[2]
Sartori, G.; Ballini, R.; Bigi, F.; Bosica, G.; Maggi, R.; Righi, P. Protection (and deprotection) of functional groups in organic synthesis by heterogeneous catalysis. Chem. Rev.,  2004, 104(1), 199-250.
 [http://dx.doi.org/10.1021/cr0200769] [PMID:  14719975]

[3]
Chanda, A.; Fokin, V. Organic Synthesis “On Water. Chem. Rev.,  2000, 58, 2701.
 [PMID:  19209944]

[4]
Lutz, C.; Lutz, V.; Knochel, P. Enantioselective synthesis of 1,2-, 1,3- and 1,4- aminoalcohols by the addition of dialkylzincs to 1,2-, 1,3- and 1,4- aminoaldehydes. Tetrahedron,  1998, 54(23), 6385-6402.
 [http://dx.doi.org/10.1016/S0040-4020(98)00297-X]

[5]
Darnbrough, S.; Mervic, M.; Condon, S.M.; Burns, C.J. An improved synthesis of N-Boc protected aryl amines. Synth. Commun.,  2001, 31(21), 3273-3280.
 [http://dx.doi.org/10.1081/SCC-100106036]

[6]
Upadhyaya, D.J.; Barge, A.; Stefania, R.; Cravotto, G. Efficient, solventless N-Boc protection of amines carried out at room temperature using sulfamic acid as recyclable catalyst. Tetrahedron Lett.,  2007, 48(47), 8318-8322.
 [http://dx.doi.org/10.1016/j.tetlet.2007.09.126]

[7]
Khaksar, S.; Heydari, A.; Tajbakhsh, M.; Vahdat, S.M. Hydrogen bond catalyzed chemoselective N-tert-butoxycarbonylation of amines. Tetrahedron Lett.,  2008, 49(21), 3527-3529.
 [http://dx.doi.org/10.1016/j.tetlet.2008.03.138]

[8]
Kelly, T.A.; McNeil, D.W. A simple method for the protection of aryl amines as their t-butylcarbamoyl (Boc) derivatives. Tetrahedron Lett.,  1994, 35(48), 9003-9006.
 [http://dx.doi.org/10.1016/0040-4039(94)88411-0]

[9]
Chen, J.; Spear, S.; Huddleston, J.; Rogers, R. Polyethylene glycol and solutions of polyethylene glycol as green reaction media. Green Chem.,  2005, 7, 64.
 [http://dx.doi.org/10.1039/b413546f]

[10]
Basel, Y.; Hassner, A. Di-tert-butyl dicarbonate and 4-(dimethylamino)pyridine revisited. Their reactions with amines and alcohols. J. Org. Chem.,  2000, 65(20), 6368-6380.
 [http://dx.doi.org/10.1021/jo000257f] [PMID:  11052078]

[11]
Barceló, G.; Senet, J.P.; Sennyey, G.; Bensoam, J.; Loffet, A. Alkyl 1-chloroalkyl carbonates: Reagents for the synthesis of carbamates and protection of amino groups. Synthesis,  1986, 1986(8), 627-632.
 [http://dx.doi.org/10.1055/s-1986-31724]

[12]
Hardwin, O.; Kim, B.; Margolis, P.; Wang, W.; Wu, C.; Lopez, C.; Blais, J. Preparation of tetra-Boc-protected polymyxin B nonapeptide. Tetrahedron Lett.,  1975, 48, 4393-4394.

[13]
Knölker, H.J.; Braxmeier, T.; Schlechtingen, G. Isocyanates, Part 2.7 Synthesis of Symmetrical and Unsymmetrical Ureas by DMAP-Catalyzed Reaction of Alkyl- and Arylamines with Di-tert-butyldicarbonate. Synlett,  1996, 1996(6), 502-504.
 [http://dx.doi.org/10.1055/s-1996-5472]

[14]
Sharma, G.V.M.; Janardhan Reddy, J.; Sree Lakshmi, P.; Radha Krishna, P. Rapid and facile Lewis acid catalysed Boc protection of amines. Tetrahedron Lett.,  2004, 45(37), 6963-6965.
 [http://dx.doi.org/10.1016/j.tetlet.2004.07.072]

[15]
Heydari, A.; Hosseini, S.E. Lithium Perchlorate‐Catalyzed Boc Protection of Amines and Amine Derivatives. Adv. Synth. Catal.,  2005, 347(15), 1929-1932.
 [http://dx.doi.org/10.1002/adsc.200505218]

[16]
Chakraborti, A.K.; Chankeshwara, S.V. HClO 4 –SiO 2 as a new, highly efficient, inexpensive and reusable catalyst for N-tert-butoxycarbonylation of amines. Org. Biomol. Chem.,  2006, 4(14), 2769-2771.
 [http://dx.doi.org/10.1039/B605074C] [PMID:  16826301]

[17]
Chankeshwara, S.V.; Chakraborti, A.K. Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for N-tert-butoxycarbonylation of amines under solvent-free conditions at room temperature. Tetrahedron Lett.,  2006, 47(7), 1087-1091.
 [http://dx.doi.org/10.1016/j.tetlet.2005.12.044]

[18]
Bartoli, G.; Sambri, L.; Bosco, M.; Locatelli, M.; Marcantoni, E.; Massaccesi, M.; Melchiorre, P. A Lewis Acid-Mediated Protocol for the Protection of Aryl Amines as their Boc-Derivatives. Synlett,  2004, 10(10), 1794-1798.
 [http://dx.doi.org/10.1055/s-2004-829059]

[19]
Suryakiran, N.; Prabhakar, P.; Reddy, T.S.; Rajesh, K.; Venkateswarlu, Y. Facile N-tert-butoxycarbonylation of amines using La(NO3)3·6H2O as a mild and efficient catalyst under solvent-free conditions. Tetrahedron Lett.,  2006, 47(46), 8039-8042.
 [http://dx.doi.org/10.1016/j.tetlet.2006.09.081]

[20]
Tasneem; Rajanna, K.C. Ferric Chloride–Promoted Efficient and Facile BOC Protection of Amines. Synth. Commun.,  2011, 41(5), 715-719.
 [http://dx.doi.org/10.1080/00397911003642641]

[21]
Suryakiran, N.; Prabhakar, P.; Reddy, T.S.; Srinivasulu, M.; Swamy, N.R.; Venkateswarlu, Y. Rapid N-tert-butoxycarbonylation of amines using Bi(NO3)3·5H2O as a mild and highly efficient catalyst under solvent-free conditions. J. Mol. Catal. Chem.,  2007, 264(1-2), 40-43.
 [http://dx.doi.org/10.1016/j.molcata.2006.09.005]

[22]
Chankeshwara, S.; Chakraborti, A. Indium(III) Halides as New and Highly Efficient Catalysts for N-tert-Butoxycarbonylation of Amines. Synthesis,  2006, 16, 2784.

[23]
Inahashi, N.; Matsumiya, A.; Sato, T. Efficient N-tert-Butoxycarbonylation of Indoles with Di-tert-butyl Dicarbonate Catalyzed by Cesium Fluoride. Synlett,  2008, 02, 294.

[24]
Varala, R.; Nuvula, S.; Adapa, S.R. Molecular iodine-catalyzed facile procedure for N-Boc protection of amines. J. Org. Chem.,  2006, 71(21), 8283-8286.
 [http://dx.doi.org/10.1021/jo0612473] [PMID:  17025327]

[25]
Shailaja, M.; Manjula, A.; Rao, B.V. (Bromodimethyl)sulfonium Bromide Mediated Rapid and Facile Protection of Amines. Synth. Commun.,  2011, 41(14), 2073-2080.
 [http://dx.doi.org/10.1080/00397911.2010.497592]

[26]
Heydari, A.; Khaksar, S.; Tajbakhsh, M. 1,1,1,3,3,3-Hexafluoroisopropanol: A Recyclable Organocatalyst for N -Boc Protection of Amines. Synthesis,  2008, 2008(19), 3126-3130.
 [http://dx.doi.org/10.1055/s-2008-1067272]

[27]
Khaksar, S.; Vahdat, S.M.; Tajbakhsh, M.; Jahani, F.; Heydari, A. Thioglycoluril as a highly efficient, recyclable and novel organocatalyst for N-Boc protection of amines. Tetrahedron Lett.,  2010, 51(49), 6388-6391.
 [http://dx.doi.org/10.1016/j.tetlet.2010.09.096]

[28]
Jahani, F.; Tajbakhsh, M.; Golchoubian, H.; Khaksar, S. Guanidine hydrochloride as an organocatalyst for N-Boc protection of amino groups. Tetrahedron Lett.,  2011, 52(12), 1260-1264.
 [http://dx.doi.org/10.1016/j.tetlet.2011.01.023]

[29]
Shirini, F.; Zolfigol, M.A.; Abedini, M. Saccharin sulfonic acid catalyzed N-Boc protection of amines and formation of tert-butyl ethers from alcohols. J. Indian Chem. Soc.,  2010, 7(3), 603-607.
 [http://dx.doi.org/10.1007/BF03246047]

[30]
Shirini, F.; Khaligh, N.G. Succinimide sulfonic acid (SuSA): An efficient and recyclable catalyst for the chemoselective N-Boc protection of amines. Monatsh. Chem.,  2012, 143(4), 631-635.
 [http://dx.doi.org/10.1007/s00706-011-0612-5]

[31]
Durvasula, V.V.; Khanna, B. Molecular sieves as a new, highly efficient, inexpensive and reusable catalyst for n-ter-butoxycarbonylation of amines. Organic Chem Curr. Res.,  2015, S5, 3.

[32]
(a) Kumar, K.S.; Iqbal, J.; Pal, M. Amberlyst-15: A mild, efficient and reusable heterogeneous catalyst for N-tert-butoxycarbonylation of amines. Tetrahedron Lett.,  2009, 50(46), 6244-6246.
 [http://dx.doi.org/10.1016/j.tetlet.2009.09.018]; 
(b) Das, B.; Venkateswarlu, K.; Krishnaiah, M.; Holla, H. A highly chemoselective Boc protection of amines using sulfonic-acid-functionalized silica as an efficient heterogeneous recyclable catalyst. Tetrahedron Lett.,  2006, 47(43), 7551-7556.
 [http://dx.doi.org/10.1016/j.tetlet.2006.08.093]; 
(c) Atghia, S.V.; Sarvi Beigbaghlou, S. Nanocrystalline titania-based sulfonic acid (TiO2-Pr-SO3H) as a new, highly efficient and recyclable solid acid catalyst for the N-Boc protection of amines at room temperature. J. Organomet. Chem.,  2013, 745-746, 42-49.
 [http://dx.doi.org/10.1016/j.jorganchem.2013.07.033]; 
(d) Shirini, F.; Mamaghani, M.; Atghia, S.V. Sulfonic acid-functionalized ordered nanoporous Na+-montmorillonite (SANM): A novel, efficient and recyclable catalyst for the chemoselective N-Boc protection of amines in solventless media. Catal. Commun.,  2011, 12(12), 1088-1094.
 [http://dx.doi.org/10.1016/j.catcom.2011.03.030]; 
(e) Heydari, A.; Shiroodi, R.K.; Hamadi, H.; Esfandyari, M.; Pourayoubi, M. N-tert-Butoxycarbonylation of amines using H3PW12O40 as an efficient heterogeneous and recyclable catalyst. Tetrahedron Lett.,  2007, 48(33), 5865-5868.
 [http://dx.doi.org/10.1016/j.tetlet.2007.06.064]; 
(f) Chankeshwara, S.V.; Chakraborti, A.K. Montmorillonite K 10 and montmorillonite KSF as new and reusable catalysts for conversion of amines to N-tert-butylcarbamates. J. Mol. Catal. Chem.,  2006, 253(1-2), 198-202.
 [http://dx.doi.org/10.1016/j.molcata.2006.03.042]; 
(g) Veisi, H.; Sedrpoushan, A.; Ghazizadeh, H.; Hemmati, S. Efficient N-Boc protection of amines by a reusable heterogeneous solid acid nanocatalyst at room temperature. Res. Chem. Intermed.,  2016, 42(2), 1451-1461.
 [http://dx.doi.org/10.1007/s11164-015-2096-0]; 
(h) Karmakar, B.; Banerji, J. An expeditious, efficient green methodology for the Boc protection of amines and silyl protection of alcohols over tungstophosphoric acid-doped mesoporous silica. Tetrahedron Lett.,  2010, 51(29), 3855-3858.
 [http://dx.doi.org/10.1016/j.tetlet.2010.05.080]; 
(i) Khaligh, N.G.; Hazarkhani, H. The chemoselective N-Boc protection
of amines in the presence of solid-supported perchloric acid
as an efficient and reusable solid acid. Monatsh. Chem,  2014, 145(12), 1975-1980.
 [http://dx.doi.org/10.1007/s00706-014-1274-x]; 
(j) Shirini, F.; Atghia, S.V.; Jirdehi, M.G. Nanocrystalline TiO2–HClO4: A novel, efficient and recyclable catalyst for the chemoselective N-Boc protection of amines under solvent-free conditions. Chin. Chem. Lett.,  2013, 24(1), 34-36.
 [http://dx.doi.org/10.1016/j.cclet.2012.12.005]; 
(k) Zolfigol, M.A.; Moosavi-Zare, A.R.; Moosavi, P.; Khakyzadeh,
V.; Zare, A. Nano-ferrous ferric oxide (nano-Fe3O4): Powerful, reusable,
and stable catalyst for N-Boc protection of amines C. R.
Chim,  2013, 16(11), 962-966.
 [http://dx.doi.org/10.1016/j.crci.2013.05.010]; 
(l) Chaskar, A.; Yewale, S.; Langi, B.; Deokar, H. Indion 190
amine catalyzed rasin N-Boc protection of practical. Journal of the
Korean Chemical Society,  2009, 53, 4.

[33]
(a) Sunitha, S.; Kanjilal, S.; Reddy, P.S.; Prasad, R.B.N. An efficient and chemoselective Brønsted acidic ionic liquid-catalyzed N-Boc protection of amines. Tetrahedron Lett.,  2008, 49(16), 2527-2532.
 [http://dx.doi.org/10.1016/j.tetlet.2008.02.126]; 
(b) Akbari, J.; Heydari, A.; Ma’mani, L.; Hassan Hosseini, S. Protic ionic liquid [TMG][Ac] as an efficient, homogeneous and recyclable catalyst for Boc protection of amines. C. R. Chim.,  2010, 13(5), 544-547.
 [http://dx.doi.org/10.1016/j.crci.2009.10.003]; 
(c) Karimian, S.; Tajik, H. N-Protection of amines using pyridinium 2,2,2-trifluoroacetate ionic liquid as an efficient and reusable catalyst. Chin. Chem. Lett.,  2014, 25(2), 218-220.
 [http://dx.doi.org/10.1016/j.cclet.2013.11.052]; 
(d) Shirini, F.; Jolodar, O.G.; Seddighi, M.; Borujeni, H.T. Preparation, characterization and application of succinimidinium hydrogensulfate ([H-Suc]HSO 4) as an efficient ionic liquid catalyst for the N-Boc protection of amines. RSC Advances,  2015, 5(26), 19790-19798.
 [http://dx.doi.org/10.1039/C4RA14130J]; 
(e) Sarkar, A.; Roy, S.R.; Parikh, N.; Chakraborti, A.K. Nonsolvent application of ionic liquids: Organo-catalysis by 1-alkyl-3-methylimidazolium cation based room-temperature ionic liquids for chemoselective N-tert-butyloxycarbonylation of amines and the influence of the C-2 hydrogen on catalytic efficiency. J. Org. Chem.,  2011, 76(17), 7132-7140.
 [http://dx.doi.org/10.1021/jo201102q] [PMID: 21774556]; 
(f) Shirini, F.; Khaligh, N. 1, 3-Disulfonic acid imidazolium hydrogen sulfate as an efficient and reusable ionic liquid catalyst for the N-Boc protection of amines J. Mol. Liq. 177, 386; h) Majumdar S, De J, Chakraborty A and Maiti D, 2014 General solvent-free highly selective N-tert-butyloxycarbonylation strategy using protic ionic liquid as an efficient catalyst. RSC Advances,  2013, 04, 24544.

[34]
Reddy, M.; Narender, M.; Nageswar, Y.; Rao, K. N-Boc Protection of Amines with Di-tert-butyldicarbonate in Water under Neutral Conditions in the Presence of β-Cyclodextrin. Synlett,  2006, 07, 1110.

[35]
Chankeshwara, S.V.; Chakraborti, A.K. Catalyst-free chemoselective N-tert-butyloxycarbonylation of amines in water. Org. Lett.,  2006, 8(15), 3259-3262.
 [http://dx.doi.org/10.1021/ol0611191] [PMID:  16836380]

[36]
Vilaivan, T. A rate enhancement of tert-butoxycarbonylation of aromatic amines with Boc2O in alcoholic solvents. Tetrahedron Lett.,  2006, 47(38), 6739-6742.
 [http://dx.doi.org/10.1016/j.tetlet.2006.07.097]

[37]
Siddaiah, V.; Basha, G.M.; Rao, G.P.; Prasad, U.V.; Rao, R.S. PEG-mediated Facile Protocol for N -Boc Protection of Amines. Chem. Lett.,  2010, 39(11), 1127-1129.
 [http://dx.doi.org/10.1246/cl.2010.1127]

[38]
Ingale, A.P.; More, V.K.; Gangarde, U.S.; Shinde, S.V. Chemoselective N-tert -butyloxycarbonylation of amines in glycerol. New J. Chem.,  2018, 42(12), 10142-10147.
 [http://dx.doi.org/10.1039/C8NJ01585F]

[39]
a) Jia, X; Huang, Q; Li, J; Li, S Yang, Q Environmentally Benign N Boc Protection under Solvent and Catalyst-Free Conditions. Synlett 2007, (5), 0806-0808.; 
b) Dighe, S.N.; Jadhav, H.R. Microwave assisted mild, rapid, solvent-less, and catalyst-free chemoselective N-tert-butyloxycarbonylation of amines. Tetrahedron Lett.,  2012, 53(43), 5803-5806.
 [http://dx.doi.org/10.1016/j.tetlet.2012.08.089]; 
(c) Nardi, M.; Cano, N.H.; Costanzo, P.; Oliverio, M.; Sindona, G.; Procopio, A. Aqueous MW eco-friendly protocol for amino group protection. RSC Advances,  2015, 5(24), 18751-18760.
 [http://dx.doi.org/10.1039/C4RA16683C]

[40]
(a) Anastas, P.; Warner, J. Theory and Practice, Oxford University Press; Green Chemistry: New York, 1998. ; 
(b) Roopan, S.; Nawaz Khan, F. ZnO nanoparticles in the synthesis of AB ring core of camptothecin. Chem. Pap.,  2010, 64(6), 812.
 [http://dx.doi.org/10.2478/s11696-010-0058-y]; 
(c) Song, J.; Han, B. Green chemistry: A tool for the sustainable development of the chemical industry. Natl. Sci. Rev.,  2015, 2(3), 255-256.
 [http://dx.doi.org/10.1093/nsr/nwu076]

[41]
(a) Guo, R.Y.; An, Z.M.; Mo, L.P.; Wang, R.Z.; Liu, H.X.; Wang, S.X.; Zhang, Z.H. Meglumine: A novel and efficient catalyst for one-pot, three-component combinatorial synthesis of functionalized 2-amino-4H-pyrans. ACS Comb. Sci.,  2013, 15(11), 557-563.
 [http://dx.doi.org/10.1021/co400107j] [PMID: 24138196]; 
(b) Cue, B.W.; Zhang, J. Green process chemistry in the pharmaceutical industry. Green Chem. Lett. Rev.,  2009, 2(4), 193-211.
 [http://dx.doi.org/10.1080/17518250903258150]; 
(c) Varma, R.S. “Greener” chemical syntheses using mechanochemical mixing or microwave and ultrasound irradiation. Green Chem. Lett. Rev.,  2007, 1(1), 37-45.
 [http://dx.doi.org/10.1080/17518250701756991]

[42]
(a) Werpy, T.; Petersen, G. Top value-added chemicals from biomass volume i: Results of screening for potential candidates from sugars and synthesis gas, national renewable energy lab, United States 2004. Available From: https://www.osti.gov/biblio/15008859; 
(b) de Jong, E.; Higson, A.; Walsh, P.; Wellisch, M. Bio-based Chemicals: Value Added Products from Biorefineries; , 2012.  Available From: [https://www.ieabioenergy.com/blog/publications/bio-based-chemicals-value-added-products-from-biorefineries/]

[43]
Kumar, A.; Rai, P.; Vijay, B.; Sagir, H.; Siddiqui, I. Malic Acid as Bio-organocatalyst. Sustainable, One-pot and Multicomponent Synthesis Current Organocatalysis,  2018, 05, 3.

[44]
Ingale, A.P.; Garad, D.N.; Ukale, D.; Thorat, N.M.; Shinde, S.V. Thiamine hydrochloride as a recyclable organocatalyst for the efficient and chemoselective N-tert -butyloxycarbonylation of amines. Synth. Commun.,  2021, 51(24), 3791-3804.
 [http://dx.doi.org/10.1080/00397911.2021.1994998]

[45]
Patil, S.; Tandon, R.; Tandon, N. A Current Research on Silica Coated Ferrite Nanoparticle and their application: [Review]. Curr. Res. Green Sustain. Chem.,  2021, 4, 100063.

[46]
Tandon, R.; Patil, S.; Tandon, N.; Kumar, P. Magnetically recyclable silica-coated magnetite-molybdate nanocatalyst and its applications in N-formulation reactions under solvent-free conditions. Lett. Org. Chem.,  2022, 19(8), 616-626.
 [http://dx.doi.org/10.2174/1570178619666220112112901]

[47]
Ingale, A.P.; Patil, S.M.; Shinde, S.V. Catalyst-free, efficient and one pot protocol for synthesis of nitriles from aldehydes using glycerol as green solvent. Tetrahedron Lett.,  2017, 58(52), 4845-4848.
 [http://dx.doi.org/10.1016/j.tetlet.2017.11.032]

[48]
Tandon, N.; Patil, S.M.; Tandon, R.; Kumar, P. Magnetically recyclable silica-coated ferrite magnetite-K 10 montmorillonite nanocatalyst and its applications in O, N, and S-acylation reaction under solvent-free conditions. RSC Advances,  2021, 11(35), 21291-21300.
 [http://dx.doi.org/10.1039/D1RA02222A] [PMID:  35478786]

[49]
Tandon, R.; Tandon, N.; Patil, S.M. Overview on magnetically recyclable ferrite nanoparticles: Synthesis and their applications in coupling and multicomponent reactions. RSC Advances,  2021, 11(47), 29333-29353.
 [http://dx.doi.org/10.1039/D1RA03874E] [PMID:  35479579]

[50]
Patil, S.M.; Tandon, R.; Tandon, N. Magnetically Recoverable Silica-Decorated Ferromagnetic-Nanoceria Nanocatalysts and Their Use with O - and N -Butyloxycarbonylation Reaction via Solvent-Free Condition. ACS Omega,  2022, 7(28), 24190-24201.
 [http://dx.doi.org/10.1021/acsomega.2c01107] [PMID:  35874196]

[51]
Patil, S.M.; Tandon, R.; Tandon, N. Recent developments in silver nanoparticles utilized for cancer treatment and diagnosis: A patent review. Pharm. Pat. Anal.,  2022, 11(6), 175-186.
 [http://dx.doi.org/10.4155/ppa-2022-0010] [PMID:  36475455]

[52]
Patil, S; Ingale, A; Pise, A Bhondave, R Novel Cobalt‐Supported Silica‐Coated Ferrite Nanoparticles Applicable for Acylation of Amine, Phenol, and Thiols Derivatives under Solvent‐Free Condition. Chem Select,  2022, 7(26)

[53]
Patil, S.M.; Tandon, R.; Tandon, N. Synthesis and characterization of Fe3O4 @SiO2 @K10 NPs applicable for N-ter-butyloxycarbonylation using solvent-free conditions. J. Phys. Conf. Ser.,  2022, 2267(1), 012107.
 [http://dx.doi.org/10.1088/1742-6596/2267/1/012107]

[54]
Patil, S. A comprehensive review on biological activities of oxazole derivatives. BMC Chem.,  2019, 13(16)

[55]
(a) Patil, S.M.; Tandon, R.; Tandon, N.; Singh, I.; Bedre, A.; Gade,
V. Magnetite-supported montmorillonite (K 10 ) (nanocat-Fe-Si-
K10): An efficient green catalyst for multicomponent synthesis of
amidoalkyl naphthol. RSC Advances,  2023, 13(25), 17051-17061.
 [http://dx.doi.org/10.1039/D3RA01522J]; 
(b) Patil, S.M.; Bedre, A.V.; Gade, V.B.; Jopale, M.K. Metal-free,
an effective and one-pot protocol for the reductive amination of aldehydes
using glycerol as a green solvent. J. Chem. Sci.,  2023, 135(2), 50.
 [http://dx.doi.org/10.1007/s12039-023-02172-3]; 
(c) Patil, S.; Bedre, A.; Gade, V.; Jopale, M.; Bhagat, R.; Pise, A.
One-pot protocol for the reductive amination of aldehydes using
thiamine hydrochloride as a green catalyst under solvent-free condition. Synth. Commun.,  2023, 53(18), 1545-1558.
 [http://dx.doi.org/10.1080/00397911.2023.2236258]; 
(d) Rajesh, M.K.; Vilas, G.B.; Dhananjay, G.N. [EMIm][BH3CN]
Ionic Liquid as an Efficient Catalyst for the Microwave- Assisted
One-Pot Synthesis of Triaryl Imidazole Derivatives Lett. Organ.
Chem,  2023, 12(10), 967-975.; 
(e) Pise, AS; Ingale, AP; Patil, SM An efficient synthesis of 1, 3-
oxazine derivatives catalyzed under ceric ammonium nitrate in an
aqueous medium at ambient temperature. Polycyclic Aromat.
Comp.,  2023, 2023
 [http://dx.doi.org/10.1080/10406638.2023.2259569]
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DOI https://dx.doi.org/10.2174/0115701786278928231218113855	Print ISSN 1570-1786
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Letters in Organic Chemistry

Malic Acid as a Green Catalyst for the N-Boc Protection under Solvent-free Condition

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