Addition Reactions of Polyhalides to Ketene Silyl Acetals and Silyl Enol Ethers under Thermal or Photo-Irradiated Conditions without a Promoter

2002 ◽  
Vol 75 (8) ◽  
pp. 1807-1814 ◽  
Author(s):  
Michiharu Mitani ◽  
Hideo Sakata ◽  
Hisayuki Tabei
Keyword(s):  
Addition Reactions ◽  
Enol Ethers ◽  
Silyl Enol Ethers ◽  
Silyl Acetals

scholarly journals Preparation and facile addition reactions of iminium salts derived from amino ketene silyl acetal and amino silyl enol ether

RSC Advances ◽  
2020 ◽  
Vol 10 (46) ◽  
pp. 27874-27883
Author(s):  
Makoto Shimizu ◽  
Shingo Hata ◽  
Koichi Kondo ◽  
Kazuhiro Murakami ◽  
Isao Mizota ◽  
...  
Keyword(s):  
Addition Reactions ◽  
Amino Ketone ◽  
Enol Ether ◽  
Enol Ethers ◽  
Silyl Enol Ethers ◽  
Iminium Salts ◽  
Silyl Enol Ether ◽  
Silyl Acetals

While iminium salts generated from amino ketene silyl acetals react with silyl enol ethers, those from amino silyl enol ethers also undergo facile addition reactions to give alpha-amino ketone derivatives in good yields.

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.

1,3-Dioxan-5-ones: synthesis, deprotonation, and reactions of their lithium enolates

1995 ◽  
Vol 73 (10) ◽  
pp. 1616-1626 ◽  
Author(s):  
Marek Majewski ◽  
D. Mark Gleave ◽  
Pawel Nowak
Keyword(s):  
Enantiomeric Excess ◽  
Addition Reactions ◽  
Synthetic Route ◽  
Enol Ethers ◽  
Lithium Amide ◽  
Silyl Enol Ethers ◽  
Lithium Amides ◽  
Alkyl Groups ◽  
Lithium Enolates ◽  
Enantioselective Deprotonation

A general synthetic route to 2-alkyl- and 2,2-dialkyl-1,3-dioxan-5-ones, using tris(hydroxymethyl)-nitromethane as the starting material, is described. Deprotonation of these compounds was studied. It was established that these dioxanones could be deprotonated with LDA; however, the reduction of the carbonyl group via a hydride transfer from LDA, giving the corresponding dioxanols, often competed with deprotonation. The reduction could be minimized by using Corey's internal quench procedure to form silyl enol ethers and was less pronounced in 2,2-dialkyldioxanones (ketals) than in 2-alkyldioxanones (acetals). Self-aldol products were observed when dioxanone lithium enolates were quenched with H2O. Addition reactions of lithium enolates of dioxanones to aldehydes were threo-selective as predicted by the Zimmerman–Traxler model. Dioxanones having two different alkyl groups at the 2-position were deprotonated enantioselectively by chiral lithium amide bases with enantiomeric excess (ee) of up to 70%. Keywords: 1,3-dioxan-5-ones, enantioselective deprotonation, chiral lithium amides.

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