- Stereocontrolled substitution of benzylic ethers complexed to tricarbonylchromium(0)
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The nitrogen nucleophile HN(OH)C(O)OBu(t) reacts with non-racemic chiral tricarbonylchromium(0) complexes of benzylic ethers with retention of configuration to provide a novel approach to non-racemic N-hydroxycarbamates and amines.
- Albanese, Domenico,Gibson, Susan E.,Rahimian, Ellian
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Read Online
- Thiamine hydrochloride as a recyclable organocatalyst for the efficient and chemoselective N-tert-butyloxycarbonylation of amines
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Thiamin hydrochloride promoted highly efficient and ecofriendly approach has been described for the chemoselective N-tert-butyloxycarbonylation of amines under solvent-free conditions at ambient temperature. The demonstrated approach has been applicable for the N-Boc protection of variety of aliphatic, aryl, heteroaryl amines. The chemoselective protection of amino group occurs in chiral amines and amino alcohol without racemization in high yield. Thiamin hydrochloride is stable, economical, easy to handle and environmentally friendly.
- Ingale, Ajit P.,Garad, Dnyaneshwar N.,Ukale, Dattatraya,Thorat, Nitin M.,Shinde, Sandeep V.
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supporting information
p. 3791 - 3804
(2021/11/04)
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- Ultrasound promoted environmentally benign, highly efficient, and chemoselective N-tert-butyloxycarbonylation of amines by reusable sulfated polyborate
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The sulfated polyborate catalyzed an efficient and chemoselective N-tert-butyloxycarbonylation of amines under ultrasonic irradiation is developed. A broad substrate scope has been demonstrated for N-Boc protection of various primary/secondary amines. It allows converting several aliphatic/aryl/heteroaryl amines, amino alcohol, aminoester, and chiral amines to their N-Boc-protected derivatives under solvent-free conditions with excellent yields. The protocol has several advantages such as easy catalyst, and product isolation, short reaction time, excellent yields, outstanding chemoselectivity, and catalyst recyclability, among others. This makes the process practicable, economical, and environmentally benign.
- Pise, Ashok S.,Ingale, Ajit P.,Dalvi, Navnath R.
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supporting information
p. 3768 - 3780
(2021/10/26)
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- Sulfated tungstate: A highly efficient, recyclable and ecofriendly catalyst for chemoselective N-tert butyloxycarbonylation of amines under the solvent-free conditions
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Sulfated tungstate catalyzed an efficient and ecofriendly protocol has been described for the chemoselective N-tert-butyloxycarbonylation of amines under the solvent-free conditions at room temperature. The variety of functionalized aliphatic, aromatic and heteroaromatic amines efficiently undergoes the N-tert-butyloxycarbonylation under the developed protocol. The aminoalcohol, aminophenol, aminoester as well as various chiral amines underwent the chemoselective N-Boc protection under the optimized reaction condition. The rapid reaction rate, mild conditions, very good functional group tolerance, excellent yield, solvent-free, easy recovery products and excellent catalyst recyclability are the advantages of this protocol. This makes the protocol feasible, economical and environmentally benign.
- Ingale, Ajit P.,Shinde, Sandeep V.,Thorat, Nitin M.
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supporting information
p. 2528 - 2543
(2021/07/02)
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- Nanoceria as an efficient and green catalyst for the chemoselective N-tert-butyloxycarbonylation of amines under the solvent-free conditions
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Nanocerium oxide mediated an efficient and green protocol has been described for the chemoselective N-tert-butyloxycarbonylation of amines under the solvent-free conditions at ambient temperature. Various aliphatic, aromatic and heteroaromatic amines were protected using developed protocol and several functional groups such as alcohol, phenol and ester were well tolerated under these conditions. The rapid reaction rate, mild conditions, very good functional group tolerance, excellent yield, solvent-free, easy recovery products and excellent catalyst recyclability are the advantages of this protocol. This makes the protocol feasible, economical and environmentally benign.
- Garad, Dnyaneshwar N.,Ingale, Ajit P.,Shinde, Sandeep V.,Ukale, Dattatraya
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supporting information
p. 1656 - 1668
(2021/04/05)
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- A One-Pot Iodo-Cyclization/Transition Metal-Catalyzed Cross-Coupling Sequence: Synthesis of Substituted Oxazolidin-2-ones from N-Boc-allylamines
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A one-pot iodo-cyclization/transition metal-catalyzed cross-coupling sequence is reported to access various C5-functionalized oxazolidin-2-ones from unsaturated N-Boc-allylamines. Depending on the Grignard reagents used for the cross-coupling, e.g., aryl- or cyclopropylmagnesium bromide, a cobalt or copper catalyst has to be used to obtain the functionalized oxazolidin-2-ones in good yields.
- Chaumont-Olive, Pauline,Cossy, Janine
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supporting information
(2020/05/14)
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- Novel Chiral Alfa-Amino Tertiary Boronic Esters
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The present disclosure relates to a novel, highly efficient and enantiospecific borylation method to synthesize a wide range of enantiopure alfa-amino tertiary boronic esters, and novel alfa-amino tertiary boronic acids and esters prepared by the method. More specifically, highly enantiospecific borylation of configurationally stable α-N-Boc substituted tertiary organolithium species and HBpin has been developed to synthesize various alfa-amino tertiary boronic esters through the formation of a new C—B bond with excellent enantiopurities.
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Paragraph 0084; 0092
(2020/04/09)
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- Asymmetric Stepwise Reductive Amination of Sulfonamides, Sulfamates, and a Phosphinamide by Nickel Catalysis
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Asymmetric reductive amination of poorly nucleophilic sulfonamides was realized in the presence of nickel catalysts and titanium alkoxide. A wide range of ketones, including enolizable ketones and some biaryl ones, were converted into sulfonamides in excellent enantiomeric excess. The cyclization of sulfamates and intermolecular reductive amination of a diarylphosphinamide were also successful. Formic acid was used as a safe and economic surrogate of high-pressure hydrogen gas.
- Zhao, Xiaohu,Xu, Haiyan,Huang, Xiaolei,Zhou, Jianrong Steve
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p. 292 - 296
(2018/12/13)
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- Chemoselective: N-tert -butyloxycarbonylation of amines in glycerol
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A catalyst-free, efficient and green protocol has been developed for the chemoselective N-Boc protection of amines by using glycerol as a solvent at room temperature. A variety of functionalized amines, such as aliphatic, aromatic as well as heteroaromatic were protected using the developed protocol. N-tert-Butyloxycarbonylation derivatives were formed without the formation of isocyanate, urea, N,N-di-t-Boc, or oxazolidinone as side products. The operational simplicity, cleaner reaction, rapid reaction convergence, functional group tolerance, excellent yield, high selectivity, catalyst-free feature and solvent recyclability are the distinct advantages of this protocol. Owing to these merits, this protocol is feasible, economical and environmentally benign.
- Ingale, Ajit P.,More, Vishal K.,Gangarde, Uddhav S.,Shinde, Sandeep V.
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supporting information
p. 10142 - 10147
(2018/06/18)
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- Highly Enantiospecific Borylation for Chiral α-Amino Tertiary Boronic Esters
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Herein we report a highly efficient and enantiospecific borylation method to synthesize a wide range of enantiopure (>99 % ee) α-amino tertiary boronic esters. The configurationally stable α-N-Boc substituted tertiary organolithium species and pinacolborane (HBpin) underwent enantiospecific borylation at ?78 °C with the formation of a new stereogenic C?B bond. This reaction has a broad scope, enabling the synthesis of various α-amino tertiary boronic esters in excellent yields and, importantly, with universally excellent enantiospecificity (>99 % es) and complete retention of configuration.
- Qi, Qingqing,Yang, Xuena,Fu, Xiaoping,Xu, Shiqing,Negishi, Ei-ichi
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supporting information
p. 15138 - 15142
(2018/10/26)
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- Direct stereospecific amination of alkyl and aryl pinacol boronates
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The direct amination of alkyl and aryl pinacol boronates is accomplished with lithiated methoxyamine. This reaction directly provides aliphatic and aromatic amines, stereospecifically, and without preactivation of the boronate substrate.
- Mlynarski, Scott N.,Karns, Alexander S.,Morken, James P.
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p. 16449 - 16451,3
(2020/09/15)
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- 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
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1-Alkyl-3-methylimidazolium cation based ionic liquids efficiently catalyze N-tert-butyloxycarbonylation of amines with excellent chemoselectivity. The catalytic role of the ionic liquid is envisaged as "electrophilic activation" of di-tert-butyl dicarbonate (Boc2O) through bifurcated hydrogen bond formation with the C-2 hydrogen of the 1-alkyl-3-methylimidazolium cation and has been supported by a downfield shift of the imidazolium C-2 hydrogen of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][NTf2]) from δ 8.39 to 8.66 in the presence of Boc2O in the 1H NMR and a drastic reduction of the catalytic efficiency with 1-butyl-2,3-dimethylimidazolium ionic liquids that are devoid of the C-2 hydrogen. The differential time required for reaction with aromatic and aliphatic amines has offered means for selective N-t-Boc formation during inter and intramolecular competitions. Preferential N-t-Boc formation with secondary aliphatic amine has been achieved in the presence of primary aliphatic amine. Comparison of the catalytic efficiency for N-t-Boc formation with a common substrate revealed that [bmim][NTf2] is superior to the reported Lewis acid catalysts.
- Sarkar, Anirban,Roy, Sudipta Raha,Parikh, Naisargee,Chakraborti, Asit K.
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experimental part
p. 7132 - 7140
(2011/10/08)
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- Propylphosphonic anhydride (T3P)-mediated one-pot rearrangement of carboxylic acids to carbamates
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A simple one-pot conversion of carboxylic acids to carbamates is achieved by propylphosphonic anhydride (T3P) in combination with azidotrimethylsilane and an alcohol via the Curtius rearrangement. Besides diverse primary to tertiary alcohols, t
- Augustine, John Kallikat,Bombrun, Agnes,Mandal, Ashis Baran,Alagarsamy, Padma,Atta, Rajendra Nath,Selvam, Panneer
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experimental part
p. 1477 - 1483
(2011/06/11)
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- New C5-alkylated indolobenzazepinones acting as inhibitors of tubulin polymerization: Cytotoxic and antitumor activities
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A series of 5-alkylindolobenzazepin-7-ones was synthesized by Suzuki coupling between 3-iodoindole-2-carboxylates and the appropriate α-alkylbenzylamino α-boronic acids followed by cyclization to the lactam. Derivatives having a linear alkyl chain at C5 were found to be highly cytotoxic to KB cells with IC50 values in the 30-80 nM range. These compounds also inhibited the polymerization of tubulin with IC50's of 1-2 μM. Compound 4f ((S)-5-ethyl) showed comparable antiproliferative activities (IC50's of 30-70 nM) in a variety of cancer cell lines, cell growth being arrested at the G2/M phase. Compound 4f induced apoptosis in a dose-dependent manner in three different cancer cell lines and was shown to affect cell morphology in a manner consistent with its inhibitory action on tubulin polymerization. Using the experimental model of glioma grafted on the chick chorio-allantoic membrane, local treatment with compound 4f markedly reduced tumor progression.
- Keller, Laurent,Beaumont, Stéphane,Liu, Jian-Miao,Thoret, Sylviane,Bignon, Jér?me S.,Wdzieczak-Bakala, Joanna,Dauban, Philippe,Dodd, Robert H.
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supporting information; experimental part
p. 3414 - 3421
(2009/05/26)
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- N-Acyl glycinates as acyl donors in serine protease-catalyzed kinetic resolution of amines. Improvement of selectivity and reaction rate
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Enzymatic kinetic resolution of aliphatic and benzylic amines leading to (S)-amides was achieved by using alkaline protease as the catalyst and N-octanoyl glycine trifluoroethyl ester as the acyl donor; enantioselectivity ranged between 4 to 244, while reaction times were dramatically shortened and ranged between 15 min to 6 h. The 2008 Royal Society of Chemistry.
- Nechab, Malek,El Blidi, Lahssen,Vanthuyne, Nicolas,Gastaldi, Stephane,Bertrand, Michele P.,Gil, Gerard
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supporting information; experimental part
p. 3917 - 3920
(2009/06/28)
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- Development of column-free alkoxycarbonyl, aryloxycarbonyl, and acyl transfer reagents
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Easy-to-handle alkoxycarbonyl, aryloxycarbonyl, and acyl transfer reagents, which contain 3-nitro-1,2,4-triazole (NT) as a leaving group, were developed. With these reagents (NT reagents), which are stable nonhygroscopic crystalline materials, the reactions can be accomplished in about 5 min, and product can be isolated without tedious column chromatographic purification.
- Shimizu, Mamoru,Sodeoka, Mikiko
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experimental part
p. 1301 - 1312
(2009/07/05)
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- Indium(III) halides as new and highly efficient catalysts for N-tert-butoxycarbonylation of amines
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Indium(III) bromide and chloride efficiently catalysed the N-tert-butoxycarbonylation of amines with (Boc)2O at room temperature and under solvent-free conditions. Various aromatic, heteroaromatic and aliphatic amines were converted to N-tert-butylcarbamates in excellent yields in short times. Chiral amines, esters of α-amino acids and β-amino alcohols afforded optically pure N-t-Boc derivatives in high yields. The reactions were chemoselective and no competitive side reactions such as isocyanate, urea, and N,N-di-t-Boc formation were observed. Chemoselective conversion to N-tert-butylcarbamates took place with amino alcohols without any formation of oxazolidinones. Georg Thieme Verlag Stuttgart.
- Chankeshwara, Sunay V.,Chakraborti, Asit K.
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p. 2784 - 2788
(2008/02/05)
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- HClO4-SiO2 as a new, highly efficient, inexpensive and reusable catalyst for N-tert-butoxycarbonylation of amines
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Perchloric acid adsorbed on silica-gel (HClO4-SiO2) was found to be a new, highly efficient, inexpensive and reusable catalyst for chemoselective N-tert-butoxycarbonylation of amines at room temperature and under solvent-free conditions. The Royal Society of Chemistry 2006.
- Chakraborti, Asit K.,Chankeshwara, Sunay V.
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p. 2769 - 2771
(2008/03/28)
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- A highly chemoselective Boc protection of amines using sulfonic-acid-functionalized silica as an efficient heterogeneous recyclable catalyst
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A facile and versatile method for the chemoselective Boc protection of amines has been developed by a treatment with (Boc)2O in the presence of sulfonic-acid-functionalized silica as a catalyst. The method is general for the preparation of N-Boc derivatives of aliphatic (acyclic and cyclic), aromatic, and heteroaromatic amines; primary and secondary amines; aminols, amino-esters; and sulfonamides. The catalyst works under heterogeneous conditions and can be recycled.
- Das, Biswanath,Venkateswarlu, Katta,Krishnaiah, Maddeboina,Holla, Harish
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p. 7551 - 7556
(2008/02/08)
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- Molecular iodine-catalyzed facile procedure for N-Boc protection of amines
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An efficient and practical protocol for the protection of various structurally and electronically divergent aryl and aliphatic amines using (Boc)2O in the presence of a catalytic amount of molecular iodine (10 mol%) under solvent-free conditions at ambient temperature is presented.
- Varala, Ravi,Nuvula, Sreelatha,Adapa, Srinivas R.
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p. 8283 - 8286
(2007/10/03)
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- A Lewis acid-mediated protocol for the protection of aryl amines as their Boc-derivatives
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A new protocol of protection of poorly reactive aryl amines and functionalized amines with Boc2O in the presence of Zn(ClO 4)2·6H2O as the catalyst is reported. The catalytic action of Zn(ClO4)2·6H2O is specific for the activation of the pyrocarbonates, thus acid sensitive functionalities and stereochemical configurations of the starting materials remain unaltered in the protection process.
- Bartoli, Giuseppe,Bosco, Marcella,Locatelli, Manuela,Marcantoni, Enrico,Massaccesi, Massimo,Melchiorre, Paolo,Sambri, Letizia
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p. 1794 - 1798
(2007/10/03)
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- 'meso-Selective' functionalisation of N-benzyl-α-methylbenzylamine derivatives by α-lithiation and alkylation
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Lithiation and methylation of amide and carbamate derivatives of α-methylbenzylamine proceeds with high diastereoselectivity in favour of meso bis-α-methylbenzylamine derivatives. Carboxylation of the intermediate organolithium is also diastereoselective, and with N-Boc p-methoxy-α-methylbenzylamine as starting material, oxidative cleavage provides a new asymmetric route to phenylglycine. Other electrophiles give a range of stereochemical outcomes, apparently depending on the stereospecificity of their reactions with a pair of diastereoisomeric organolithiums of low to moderate configurational stability.
- Bragg, Ryan A,Clayden, Jonathan,Menet, Christel J
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p. 1955 - 1959
(2007/10/03)
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- Enantioselective Michael reactions of chiral secondary enaminoesters with 2-substituted nitroethylenes. Syntheses of trans,trans-2,4-disubstituted pyrrolidine-3-carboxylates
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The Michael reaction of chiral 3-substituted secondary enaminoesters with 2-substituted nitroethylenes leads to (Z)-adducts, with good to excellent diastereoselectivity. The nitro group of these adducts was catalytically reduced to give, after cyclization and chiral amine elimination, pyrrolines or pyrrolidines after further reduction. In particular, the syntheses of ethyl (2R,3S,4S)-2,4-dimethylpyrrolidine-3-carboxylate and ethyl (2R,3R,4S)-2-(4-methoxyphenyl)-4-(3,4-(methylenedioxy)phenyl)pyrrolidine-3-ca rboxylate are described.
- Revial, Gilbert,Lim, Sethy,Viossat, Bernard,Lemoine, Pascale,Tomas, Alain,Duprat, Arthur F.,Pfau, Michel
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p. 4593 - 4600
(2007/10/03)
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- 163. Chiral diselenides from benzylamines: Catalysts in the diethylzinc addition to aldehydes
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A series of new chiral diselenides with a N-atom in the side chain was prepared by a short synthetic sequence (Scheme 1). Only 1 mol-% of these diselenides catalyzed very effectively the diethylzinc addition to various aromatic and α,β-unsaturated aldehyd
- Wirth, Thomas,Kulicke, Klaus J.,Fragale, Gianfranco
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p. 1957 - 1966
(2007/10/03)
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