- Efficient and selective cleavage of t-butoxycarbonyl group from carbamates and amides by CeCl3·7H2O-NaI
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A highly selective cleavage of the t-butoxycarbonyl group has been achieved in high yields using CeCl3·7H2O-NaI in acetonitrile at ambient temperature under neutral conditions. This method is mild and compatible with a wide range of
- Yadav,Subba Reddy,Reddy, K. Srinivasa
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- Indium-mediated facile cleavage of the t-butoxycarbonyl group from di-t-butylimidodicarbonate
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Di-t-butylimidodicarbonates are selectively and efficiently deprotected to the corresponding mono-BOC protected amines in high yields using indium or zinc metal in refluxing methanol. Simple BOC and CBz protected amines are unaffected by these conditions.
- Yadav,Reddy,Reddy, K.Srinivasa,Reddy, K.Bhaskar
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- Cobalt-mediated Reduction of C=N Bond. Synthesis of Methyl N-p-Toluenesulfonyl-1-phenylglycinate Catalyzed by Bis(dioximato)cobalt-Quinine Complexes
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Reduction of C=N bond mediated by cobalt complexes was facilitated by the electron withdrawing substituents on the substrate.Catalytic hydrogenation of methyl N-p-toluenesulfonyl-1-imino-1-phenylacetate in the presence of quininium salt afforded the corresponding N-tosyl amino-ester in good yields.
- Kobayashi, Kenji,Okamoto, Tadashi,Oida, Tatsuo,Tanimoto, Shigeo
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- Diiodine-Triethylsilane System: Reduction of N-Sulfonyl Aldimines to N-Alkylsulfonamides
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Because molecular iodine and hydrosilanes are stable to both air and moisture, reactions using these reagents are easy to operate and require mild reaction conditions. Molecular iodine and a hydrosilane were used to reduce N-sulfonyl aldimines to the corr
- Jiang, Jin,Xiao, Lili,Li, Yu-Long
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supporting information
p. 291 - 294
(2020/11/09)
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- Blue light-promoted N–H insertion of amides, isatins, sulfonamides and imides into aryldiazoacetates: Synthesis of unnatural α-aryl amino acid derivatives
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A photochemical protocol using blue light allows the N–H insertion of amides, isatins, sulfonamides and imides into aryldiazoacetates to afford the corresponding α-amino esters. This method is experimentally simple, inexpensive and tolerates numerous functional groups, thus allowing the straightforward preparation of a variety of α-aryl amino acid derivatives in good yields.
- Okada, Celso Y.,dos Santos, Caio Y.,Jurberg, Igor D.
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- Additions of Carbohydrate-Derived Alkoxyallenes to Imines and Subsequent Reactions to Enantiopure 2,5-Dihydropyrrole Derivatives
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The additions of six alkoxyallenes bearing carbohydrate-derived chiral auxiliaries to imines were systematically studied. The reactions of three lithiated 1-alkoxypropa-1,2-dienes with an N-tosyl imine revealed that the diacetone fructose-derived auxiliary provided the highest diastereoselectivity of 91:9. The preferred absolute configuration of the newly formed stereogenic center was determined by subsequent ozonolysis of the allene moiety, transesterification and comparison with literature data. The analogous reactions of three axially chiral 3-nonyl-substituted 1-alkoxyallenes with these auxiliaries confirm these results and also prove that the configuration of the generated stereogenic center was only steered by the auxiliaries, whereas the chiral axis has essentially no influence. In general, four diastereomers were obtained in various portions, depending on the ratio of the two precursor allene diastereomers and on the auxiliary employed. The obtained dia?-stereomeric allenyl amines were cyclized under different conditions. As expected, under basic conditions, a stereospecific cyclization occurred, whereas under silver nitrate catalysis partial isomerization at the allene stage was observed. Under both conditions the 2,5-cis-disubstituted dihydropyrroles were formed faster than the trans-isomers. Several of the 2-substituted or 2,5-disubstituted dihydropyrrole derivatives could be isolated in diastereomerically pure form and were subsequently converted into the expected pyrrolidin-3-ones by removal of the carbohydrate-derived auxiliary under acidic conditions. The desired products were obtained in good yield and with high enantiopurity. They are suitable starting materials for the synthesis of enantiopure pyrrolidine natural products.
- Hausherr, Arndt,Zimmer, Reinhold,Reissig, Hans-Ulrich
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p. 486 - 499
(2019/01/10)
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- Palladium-Catalyzed Enantioselective Three-Component Synthesis of α-Arylglycines
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A general Pd-catalyzed, enantioselective three-component synthesis of α-arylglycines starting from sulfonamides, glyoxylic acid derivatives, and boronic acids was developed. This operationally straightforward procedure enables the preparation of a wide variety of α-arylglycines in high yields and excellent levels of enantioselectivity from a simple set of readily available starting materials. Incorporation of Pbf-amides gives a racemization-free access to N-unprotected α-arylglycines.
- Beisel, Tamara,Diehl, Andreas M.,Manolikakes, Georg
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supporting information
p. 4116 - 4119
(2016/08/30)
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- One-step synthesis of racemic α-amino acids from aldehydes, amine components, and gaseous CO2 by the aid of a bismetal reagent
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α-Amino acids are essential resources for human life and are highly useful as building blocks for organic synthesis. The core framework of an α-amino acid can be divided into three basic components: an aldehyde, an amine, and carbon dioxide (CO2). We report herein that a one-step synthesis of α-amino acids has been successfully achieved from these three basic and inexpensive chemicals with a single operation, in which the mixture of an aldehyde, a sulfonamide, and gaseous CO2 was heated at 100 °C in the presence of Bu3Sn-SnBu3 and CsF. In this one-pot sequential protocol, two important intermediates (imine and α-amino stannane) are involved and the stannyl anion generated in situ plays a crucial role, particularly for the efficient stannylation of the imine in the presence of proton sources and for promoting retrostannylation of the undesired α-alkoxy stannane owing to its high stability and tolerance of the presence of proton sources. This methodology enabled the synthesis of a wide range of racemic arylglycine derivatives in high yields. Go retro! α-Amino acids are essential resources for human life and are highly useful as building blocks for organic synthesis. The core framework of an α-amino acid is retrosynthesized to an aldehyde, an amine, and carbon dioxide. A one-step synthesis of α-amin Copyright
- Mita, Tsuyoshi,Higuchi, Yuki,Sato, Yoshihiro
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p. 1123 - 1128
(2013/02/23)
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- Enantioselective synthesis of diverse sulfinamides and sulfinylferrocenes from phenylglycine-derived chiral sulfinyl transfer agent
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A new chiral sulfinyl transfer auxiliary derived from readily available phenylglycine was developed. This auxiliary is utilized to synthesize a diverse array of alkyl- and arylsulfinamides and sulfinylferrocenes in high yields and excellent ee's. The desired products are produced in a one-pot sequence from the oxathiazolidine 2-oxide by two sequential nucleophilic additions that proceed in a stereospecific manner.
- Han, Zhengxu S.,Meyer, Angelica M.,Xu, Yibo,Zhang, Yongda,Busch, Robert,Shen, Sherry,Grinberg, Nelu,Lu, Bruce Z.,Krishnamurthy, Dhileep,Senanayake, Chris H.
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supporting information; scheme or table
p. 5480 - 5484
(2011/08/09)
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- Transition-metal-free intermolecular amination of sp3 C-H bonds with sulfonamides
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An efficient transition-metal-free intermolecular benzylic amidation with sulfonamides is described. Various valuable nitrogen-containing compounds, including amines, β-chloro amine, amino alcohol, α-, β-amino ester, and N-sulfonyl imine, are generated fr
- Fan, Renhua,Li, Weixun,Pu, Dongming,Zhang, Li
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supporting information; scheme or table
p. 1425 - 1428
(2009/10/06)
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- Three component coupling of α-iminoesters via umpolung addition of organometals: Synthesis of α,α-disubstituted α-amino acids
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The synthesis of α,α-disubstituted α-amino acids by means of a three component coupling is reported. The coupling occurs through umpolung addition of organometallic reagents to the nitrogen of α-iminoesters. The resulting enolate intermediates subsequentl
- Dickstein, Joshua S.,Fennie, Michael W.,Norman, Amber L.,Paulose, Betty J.,Kozlowski, Marisa C.
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scheme or table
p. 15794 - 15795
(2009/05/15)
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- Iron-catalyzed aziridination reactions
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A small quantity of iron(II) triflate (2.5 to 5 mol%) catalyzes the aziridination reactions of enol silyl ethers with tosylimino(iodo)benzene (PhINTs) in acetonitrile to give α-N-tosylamido ketones by subsequent aziridine ring opening. Olefins are convert
- Nakanishi, Masafumi,Salit, Anne-Frederique,Bolm, Carsten
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body text
p. 1835 - 1840
(2009/07/09)
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- Enantioselective amination of silylketene acetals with (N-arylsulfonylimino)phenyliodinanes catalyzed by chiral dirhodium(II) carboxylates: asymmetric synthesis of phenylglycine derivatives
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The first catalytic enantioselective amination of silylketene acetals with (N-arylsulfonylimino)phenyliodinanes is described. The reaction of silylketene acetals derived from methyl phenylacetates with [N-(2-nitrophenylsulfonyl)imino]phenyliodinane (NsN =
- Tanaka, Masahiko,Kurosaki, Yasunobu,Washio, Takuya,Anada, Masahiro,Hashimoto, Shunichi
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p. 8799 - 8802
(2008/03/18)
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- A new and direct asymmetric synthesis of a hindered chiral amine via a novel sulfinate ketimine derived from N-tosyl-1,2,3-oxathiazolidme-2-oxide: Practical asymmetric synthesis of (R)-sibutramine
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A novel and direct approach for the asymmetric synthesis of (R)-sibutramine via chiral amine 5 using N-tosyl-1,2,3-oxathiazolidine-2-oxide (13) as a recyclable chiral auxiliary is described. Chiral sulfinate imine 16e was obtained by treatment of 13e with
- Han, Zhengxu,Krishnamurthy, Dhileepkumar,Senanayake, Chris H.
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p. 327 - 333
(2012/12/22)
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- An expedient synthesis of pyrrole derivatives by reaction of lithiated methoxyallenes with imines
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Addition of lithiated methoxyallene 2 to imines provided the expected allenyl amines in good yield. These could be cyclized with base or with silver nitrate to a variety of 2,5-dihydropyrrole derivatives. Selected examples describe their conversion to pyrrolidin-3-ones or 3-methoxypyrroles. Most importantly, this [3+2] cyclization method could also be applied to the synthesis of 2,5-disubstituted derivatives such as 26-28 and also to the preparation of the enantiopure compound 23.
- Amombo, Marlyse Okala,Hausherr, Arndt,Reissig, Hans-Ulrich
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p. 1871 - 1874
(2007/10/03)
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- Deprotection of sulfonyl aziridines
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The deprotection of the chiral N-sulfonyl aziridines 1-3 has been studied under different desulfonylation conditions. Two methods for the efficient aleprotection of 2-benzyl-, 2-phenyl-, and 2-carboxyl-N- sulfonylaziridines were found. The desulfonylation with lithium and a catalytic amount of di-tert-butyl biphenyl in THF at -78 °C led to the corresponding NH aziridines with yields up to 85%. Alternatively, the desulfonylation could be carried out with magnesium in methanol under ultrasonic conditions. The latter proved to be a very mild method and afforded the desulfonylated aziridines with yields up to 75%, even when the 2-phenyl substituted aziridine 2 was the studied substrate. Furthermore, in all the cases studied, no racemization was observed in the chiral center of the aziridines.
- Alonso, Diego A.,Andersson, Pher G.
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p. 9455 - 9461
(2007/10/03)
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- Diphenylsilane Reduction of C=O and C=N Bearing Electron-Withdrawing Group in the Presence of Aluminium(III) Chloride
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Several α-keto esters and methyl N-p-tolylsulfonyl-2-aryl-2-iminoacetates were reduced to the corresponding α-hydroxy esters and methyl N-p-tolylsulfonyl-2-arylglycinates in high yields by a combination of aluminium(III) chloride and diphenylsilane under operating conditions in which diphenylsilane was added to the pre-formed substrate-aluminium(III) chloride complex in dichloromethane and the mixture stirred.The case of an exactly equivalent amount of aluminium(III) chloride as the substrate resulted in good results.
- Hojo, Makoto,Hojo, Masahiro,Inoue, Yoshihiko,Tanimoto, Shigeo
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p. 2588 - 2592
(2007/10/02)
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