Silyl Amides Research Articles

A method for the facile synthesis of ring-A hydroxylated flavones

A general method for the facile synthesis of ring-A hydroxylated flavones is described. Treatment of the hydroxylated acetophenones 6a–d with enough lithium bis(trimethyl)silyl amide to deprotonate all of the phenols as well as to generate the lithium enolate of the ketone, followed by addition of the acid chlorides 7a–d, gave the 1,3-diketones 8a–g, which were cyclized to the desired products 9a–g in high yield.

Reaction of N-trimethyl silyl amides with acid chlorides. an easy synthetic route to nitriles.

Reaction of N-trimethyl silyl amides with acid chlorides. an easy synthetic route to nitriles.

Zur umsetzung von silylaziden mit Grignard-verbindungen

Phenylmagnesium bromide reacts with triphenylsilyl azide (in contrast to organyl azides) in two parallel reactions. One type of reaction is the substitution of the azide group by the magnesium-bound organyl residue. The other is the formation of the adduct, (C 6H 5) 3SiN 3·C 6H 5MgBr, containing an N-diazonium group. At higher temperatures the adduct decomposes by elimination of N 2 to give (C 6H 5) 3SiN(C 6H 5)MgBr. The same type of reaction generally occurs when silyl azicles R 3SiN 3 react with arylmagnesium halides R′MgHal. The hydrolysis of the silyl amide leads to amines R′NH 2. In connection with this the formation of R 3SiNR′(MgHal) by the reaction of R 3SiN 3 with R′MgHal (=R′Hal + Mg) provides a simple procedure to prepare aromatic amines from aromatic halides.

Silyl celluloses: A new class of soluble cellulose derivatives

AbstractTwo general methods for the silylation of cellulose have been developed. Silyl amides undergo silyl—proton exchange reactions with cellulose in polar solvents leading to displacement of 80–90% of the hydroxyl protons by silyl groups. The same products are obtained by reaction of the corresponding chlorosilanes with cellulose in pyridine; however, di‐ and trifunctional impurities present in commercial chlorosilanes have to be removed by scavenging with a carbohydrate in order to avoid crosslinking. Cellulose derivatives with trimethylsilyl, dimethylphenylsilyl, methyldiphenylsilyl, and γ‐cyanopropyldimethylsilyl substituents have been prepared by both methods. The properties of the new soluble polymers are largely dependent on the nature of the silyl substituents. The silyl celluloses exhibit a relatively high degree of hydrolytic stability; methyldiphenylsilyl cellulose is hydrolytically stable even under severe conditions.