Bernd Giese

Tris(trimethylsilyl)silane as mediator in organic synthesis via radicals

Abstract Silane3 is an effective mediator in organic synthesis via radicals. Reactions with this silane give smaller amounts of unwanted reduction products than reactions with toxic stannanes.

Anomeric effect of radicals

Abstract The glucosyl radical 1 is attacked predominately at the axial position. This can be explained by an anomeric effect that stabilizes σ-radical 5.

Diastereoselective synthesis of branched 2-deoxy sugars via radical c-c bond formation reactions

Abstract From glycals 1 and 6, 2-deoxy sugars can be synthesized in 40–72% yields. With 1,2-disubstituted alkenes 3 this radical C-C bond formation reaction leads with high stereoselectivity to the isomers 4 and 8.

Biomimetic chain elongation of carbohydrates via radical carbon-carbon bond formation

Abstract Radical bond forming reactions can be used to mimic enzymatic aldol reactions between phosphoenol pyruvate and carbohydrates.

Synthesis of 1,6-heterosubstituted products via radicals

Abstract Ketones and electron deficient alkenes are combined with each other via a methylene group to yield 1,6-heterosubstituted products in a radical chain reaction.

Generation and synthetic use of alkyl radicals with [CpFe(CO)2]2 as mediator

Abstract Irradiation of dimeric iron complex 1 in the presence of alkyl halides yields alkyl radicals that are useful in organic synthesis.

CC Bond formation reactions with umpolung of aldehydes via radicals

Abstract Aldehydes 4 and alkenes 2 yield 1,6-heterosubstituted products 7 and/or 9. The CC bond formation occurs by reactions of radicals 10 which rearrange very rapidly to radicals 12.

Diastereoselectivity of the mercuration of acyclic allylic alcohols

Abstract The diastereoselectivity of the mercuration of acyclic alkenes 4 can be reversed by changing the substituent in the allylic position; with alcohols the erythro isomers 5 and with esters or hemiacetals the threo isomers 6 and 8 are formed predominantly (Table I).

Carbon-carbon bond formation between alkylated alkenes and acrylic ester via 2-methoxyalkyl radicals

Abstract Methoxymercuration/demercuration reactions of alkenes 10 in 10 in the presence of acrylic ester yield products 11 in a carbon-carbon bond formation reaction.

The influence of alkoxy groups on the nucleophilicity of alkyl radicals

Abstract One alkoxy substituent increases the nucleophilicity of alkyl radicals in addition reactions at alkenes more than three methyl groups.