Synthesis of α,α-Disubstituted α-Amino Esters: Nucleophilic Addition to Iminium Salts Generated from Amino Ketene Silyl Acetals

2011 ◽  
Vol 76 (23) ◽  
pp. 9670-9677 ◽  
Author(s):  
Shingo Hata ◽  
Hiroshi Koyama ◽  
Makoto Shimizu
Keyword(s):  
Nucleophilic Addition ◽  
Amino Esters ◽  
Iminium Salts ◽  
Silyl Acetals

Integrated reactions using addition to conjugated imines and iminium salts

2012 ◽  
Vol 84 (12) ◽  
pp. 2609-2617 ◽  
Author(s):  
Takafumi Nishi ◽  
Isao Mizota ◽  
Makoto Shimizu
Keyword(s):  
Nucleophilic Addition ◽  
Claisen Rearrangement ◽  
Functional Materials ◽  
Addition Reactions ◽  
Iminium Salts ◽  
Silyl Acetals ◽  
Imino Esters

Recently, nucleophilic addition reactions to imino functions have been utilized in many crucial steps for the synthesis of bioactive and functional materials. This article summarizes the integrated “umpolung” reactions of α-imino esters and the use of iminium salts as reactive electrophiles. Regarding the umpolung reactions, the following five reactions are discussed: (1) N-alkylation/homocoupling; (2) tandem N-ethylation/C-allylation; (3) tandem N-ethylation/C-cyanation; (4) reduction of imines with tris(trimethylsilyl)aluminum; and (5) N-alkylation and Claisen rearrangement. Moreover, the generation and reactions of alkoxycarbonyl iminium species are also discussed. These are prepared easily from trisubstituted amino ketene silyl acetals by oxidation, and the subsequent nucleophilic addition of various nucleophiles readily affords the addition products.

Unexpected and intriguing reactivity of α-imino esters and iminium salts

2006 ◽  
Vol 78 (10) ◽  
pp. 1867-1876 ◽  
Author(s):  
Makoto Shimizu
Keyword(s):  
Benzoyl Peroxide ◽  
Nucleophilic Addition ◽  
Coupling Reaction ◽  
Grignard Reagents ◽  
Tandem Reaction ◽  
Amino Esters ◽  
Iminium Salts ◽  
Iminium Salt ◽  
Oxidative Removal ◽  
Imino Esters

An intriguing umpolung of the reactivity of imines possessing electron-withdrawing groups was observed. For example, N-alkylation-coupling reaction of the imines derived from glyoxylates was conducted with dialkylaluminum chloride in acetonitrile to give N-monoalkylated 1,2-diamines in good yields. On treatment of various α-imino esters with organoaluminum reagents and allyltributyltin in the presence of benzoyl peroxide (BPO), the tandem reaction proceeded to give the N-alkylation/C-allylation products in good yields. Diethyl 2-[N-(p-methoxyphenyl)imino]-malonate underwent amination reactions with alkyl Grignard reagents to give N-alkylation products in good yields. The obtained N-alkylation products were readily converted into N-alkyl-p-anisidines by the oxidative removal of the malonate moiety. In order to enhance the reactivity of imines, an iminium salt was prepared using the oxidation of amino ketene silyl acetal with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and the subsequent nucleophilic addition to this iminium species proceeded to afford α-amino esters in good yields.

scholarly journals Asymmetric organocatalytic synthesis of tertiary azomethyl alcohols: key intermediates towards azoxy compounds and α-hydroxy-β-amino esters

2017 ◽  
Vol 15 (14) ◽  
pp. 2993-3005 ◽  
Author(s):  
José A. Carmona ◽  
Gonzalo de Gonzalo ◽  
Inmaculada Serrano ◽  
Ana M. Crespo-Peña ◽  
Michal Šimek ◽  
...  
Keyword(s):  
Nucleophilic Addition ◽  
Keto Esters ◽  
Amino Esters ◽  
Azoxy Compounds

New carbohydrate based organocatalysts have been developed for the asymmetric nucleophilic addition of formaldehyde tert-butylhydrazone to α-keto esters.

ChemInform Abstract: Double Nucleophilic Addition to Acrolein with Ketene Silyl Acetals and Allylborolanes Catalyzed by Proline.

ChemInform ◽  
2011 ◽  
Vol 43 (2) ◽  
pp. no-no
Author(s):  
Makoto Shimizu ◽  
Mami Kawanishi ◽  
Akinori Itoh ◽  
Isao Mizota ◽  
Iwao Hachiya
Keyword(s):  
Nucleophilic Addition ◽  
Silyl Acetals

Aminoboranes as new iminium ion generators in amination reactions

2006 ◽  
Vol 78 (7) ◽  
pp. 1377-1387 ◽  
Author(s):  
Michinori Suginome
Keyword(s):  
Reductive Amination ◽  
Carbonyl Carbon Atom ◽  
Amino Groups ◽  
Boron Compounds ◽  
Enol Ethers ◽  
Silyl Enol Ethers ◽  
Amino Esters ◽  
Iminium Ions ◽  
Iminium Ion ◽  
Silyl Acetals

The utilization of aminoborane derivatives in amination reactions such as Strecker-type aminative cyanation, Mannich-type reaction, and reductive amination is described. Bis(dialkylamino)cyanoboranes and bis(dialkylamino)boron enolates underwent the concurrent transfer of the amino group and either the cyano or the enoxy group from the boron to carbonyl carbon atom in their reaction with aldehydes, leading to the formation of α-amino nitriles and β-amino ketones, respectively. Bis(dialkylamino)borane derivatives that lack the additional nucleophilic groups on the boron atoms were found to serve as effective generators of iminium ions from aldehydes. In the presence of these aminoboranes, reactions of aldehydes with ketene silyl acetals or silyl enol ethers take place, giving Mannich-type products, i.e., β-amino esters and ketones, selectively. Using diisopropylamino-substituted boron compounds, which are designed as "universal" iminium ion generators, reactions of free sec-amines, aldehydes, and ketene silyl acetals proceed efficiently, giving β-amino esters in which the amino groups are derived exclusively from the free amines. The use of the universal iminium ion generator is also effective for reductive amination of aldehydes, in which NaBH4 is used as a hydride donor.

Thiourea-catalyzed nucleophilic addition of TMSCN and ketene silyl acetals to nitrones and aldehydes

2003 ◽  
Vol 44 (14) ◽  
pp. 2817-2821 ◽  
Author(s):  
Tomotaka Okino ◽  
Yasutaka Hoashi ◽  
Yoshiji Takemoto
Keyword(s):  
Nucleophilic Addition ◽  
Silyl Acetals

ChemInform Abstract: Preparation of β-Amino Esters from Ketene Silyl Acetals and N-( Alkylamino)benzotriazoles.

ChemInform ◽  
2010 ◽  
Vol 22 (37) ◽  
pp. no-no
Author(s):  
A. R. KATRITZKY ◽  
N. SHOBANA ◽  
P. A. HARRIS
Keyword(s):  
Amino Esters ◽  
Silyl Acetals
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