نتایج جستجو برای: aldehydes
تعداد نتایج: 7935 فیلتر نتایج به سال:
A direct asymmetric Mannich reaction using a novel axially chiral amino trifluoromethanesulfonamide (S)-3 has been developed in highly anti-selective and enantioselective manners. Thus, in the presence of a catalytic amount of (S)-3, the reactions between aldehydes and the alpha-imino ester 4 proceed smoothly to give the functional beta-amino aldehydes with significantly higher anti/syn ratio a...
Lividamine and paromamine were converted into two key intermediate ethylenic aldehydes 10a and 10b. Reductive amination of the two aldehydes yielded the protected sisamine 11a and the three analogs 11b, 12a and 12b. These four derivatives were deprotected to yield the four pseudodisaccharides 1a, 1b, 2a and 2b which were less active in vitro than neamine against Escherichia coli ATCC 9637 and S...
S U M M A R Y Phospholipid-free milk fat, beef tallow, and ox heart fat contain approximately 50 (calculated aa tetradecanal), 05, and loo0 mg per kg (calculated as hexadecanal), respectively, of aldehydes. The aldehydes are bound as enol-ethers, and are located mostly in the a-position of the glycerol molecule. A sample of milk fat was found to contain 45 mg per kg glycerol ether (calculated &...
A mild and efficient method catalyzed by α-chymotrypsin was developed for the synthesis of bis(indolyl)methanes through a cascade process between indole and aromatic aldehydes. In the ethanol aqueous solution, a green medium, a wide range of aromatic aldehydes could react with indole to afford the desired products with moderate to good yields (from 68% to 95%) using a little α-chymotrypsin as c...
An enantioselective aldol reaction of N-propionylthiazolidinethione and representative aldehydes is disclosed. The reaction is catalyzed by [Ni(S,S)-t-BuBox](Otf)2. Enolization is effected by 2,6-lutidine, and TMSOTf facilitates catalyst turnover. Syn diastereoselectivities range from 88:12 to 97:3, and enantioselectivities are 90% or greater. Both aromatic and enolizable aliphatic aldehydes ar...
The development of a catalytic asymmetric method for the direct aminoallylation of aldehydes is described that gives high asymmetric inductions for a broad range of substrates including both aromatic and aliphatic aldehydes. This method allows for direct isolation of unprotected analytically pure homoallylic amines without chromatography. The unique catalyst system developed for this process in...
A novel bicyclization of 2-(2-(hydroxymethyl)-1-methylene-2,3-dihydro-1H-inden-2-yl)ethanol with aldehydes in the presence of 10 mol% BF3·OEt2 in dichloromethane at 0-25 °C affords the biologically relevant indeno[2,1-c]pyran scaffolds in good yields with high selectivity. Similarly the bicyclization of 2-(1-(hydroxymethyl)-2-methylenecyclopentyl)ethanol with aldehydes generates the correspondi...
This review describes the first method to prepare imidazolines from aldehydes and 1,2-diamines by condensation and successive oxidation using NBS in one-pot operation. The reaction proceeds under mild conditions and can be applied to various aromatic and aliphatic aldehydes and 1,2-diamines. The utility of this method is also demonstrated in the total synthesis of spongotine A and the preparati...
Quantitative results are reported for gas-liquid chromatography of mixtures of free tetra-, hexa-, and octadecanals and cis-9-octadecenal on polar and nonpolar liquid phases. Stability of the fatty aldehydes during chromatographic analysis and up to 1 year of storage appears to be related to the solvent (carbon disulfide) used. Analysis of the free aldehydes by gas-liquid chromatography elimina...
A metal-free oxidative decarbonylative coupling of aromatic aldehydes with electron-rich or electron-deficient arenes to produce biaryl compounds was developed. This novel coupling was proposed to proceed via a non-chain radical homolytic aromatic substitution (HAS) type mechanism, based on the substrate scope, ortho-regioselectivity, radical trapping experiments and DFT calculation studies. Wi...
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