Uwe Beifuss

Asymmetric induction in intramolecular ene reactions of 1,7-dienes

Abstract Chiral, double-activated enophiles in 1,7-dienes 6a - d undergo thermal and Lewis-acid catalyzed intramolecular ene reactions yielding trans-cyclohexanes 7a-d and 8a-d . The extent of diastereoselectivity depends on the reaction temperature. The 1,7-dienes 6 are obtained via Knoevenagel condensation of citronellal 5 with acyclic 1,3-dicarbonyls and analogous compounds 4 . Starting with the diene 6e , however, an intramolecular hetero-Diels-Alder reaction takes place.

Efficient allylation of 4-silyloxyquinolinium triflates and other positively charged heteroaromatic systems

Abstract The regioselective allylation of 4-silyloxyquinolinium triflates with allyltri- n -butyltin has been performed to give 2-allyl-4-silyloxy-1,2-dihydroquinolines with excellent yields. Similiar results have been obtained with 4-silyloxy-1-benzopyrylium triflates and 4-silyloxy-1-benzothiopyrylium triflates.

Intermolecular polar [4π++ 2π] cycloadditions of cationic 2-azabutadienes from thiomethylamines: a new and efficient method for the regio- and diastereo-selective synthesis of 1,2,3,4-tetrahydroquinolines

Substituted 1,2,3,4-tetrahydioquinolines and related condensed nitrogen-heterocycles are formed highly regio- and diastereo-selectively with yields ranging from 57 to 100% by intermolecular polar [4π++ 2π] cycloadditions of cationic 2-azabutadienes from thiomethylamines and various dienophiles.

On the total synthesis of (S)-methanophenazine and the formal synthesis of (R)-methanophenazine from a common precursor†

Abstract Methanophenazine is a new cofactor from methanogenic archaea. ( S )-Methanophenazine has been synthesized from three building blocks, i.e. 2-hydroxy-phenazine, ethyl ( R )-3-methylglutarate and ( E , E )-farnesyl acetone; a stereodivergent approach from ethyl ( R )-3-methylglutarate warrants the formal synthesis of ( R )-methanophenazine.

Regioselective Synthesis of 3-O-Alkyl Ethers of Ascorbic Acid without Protecting Groups in a Single Step

Abstract The direct alkylation of l -ascorbic acid (vitamin C) with alkyl mesylates using sodium hydrogen carbonate as a base without protecting groups proceeds regioselectively and yields the corresponding 3-O-alkyl ethers of l -ascorbic acid exclusively.

Highly diastereoselective synthesis of octahydroacridines by domino imine condensation–intramolecular polar [4π++ 2π]-cycloaddition of anilines and ω-unsaturated aldehydes

Substituted 1,2,3,4,4a,9,9a,10-octahydroacridines with five stereogenic centres are formed highly diastereoselectively by the domino imine condensation–intramolecular polar [4π++ 2π]-cycloaddition of anilines and ω-unsaturated aldehydes.

Stereoselective Multiple Functionalization of Pyrylium Salts by Domino Reactions with 2‐Silyloxybuta‐1,3‐dienes

Six at a time! Up to six stereogenic centers can be diastereoselectively formed in one step in three-component domino reactions of 4-silyloxypyrylium triflates with 2-silyloxybuta-1,3-dienes. Annulated or bridged ring systems such as 1 and 2, respectively, can be formed with high selectivity. R1 =silyl group; R2 , R3 =organyl group.

Oxidation of α,β-unsaturated carbonyl groups with ruthenium (III)-chloride and peracetic acid: a new access to α-oxo-ene-diols

Abstract A one pot oxidation of cyclic unsaturated carbonyl and carboxylic compounds with ruthenium (III)-chloride and peracetic acid to the corresponding α-oxo-ene-diols (aci-reductones) has been developed.

Biosynthesis of porphyrins and related macrocycles. Part 35. Discovery of a novel dipyrrolic cofactor essential for the catalytic action of hydroxymethylbilane synthase (porphobilinogen deaminase)

The enzyme hydroxymethylbilane synthase constructs the open-chain hydroxymethylbilane by assembly of four porphobilinogen units head-to-tail, the first of these being covalently bound to the enzyme through a group X. The surprising discovery is made that X is a novel dipyrromethane cofactor constructed from two porphobilinogen units and bound to the protein via the sulphur of cysteine. This cofactor does not turn over in the catalytic process but acts as an anchor for the assembly of a hexapyrrole from which the tetrapyrrolic hydroxymethylbilane is cleaved leaving the dipyrromethane cofactor in place for a further building cycle.

2-Aminobuta-1,3-dienes as annulation reagents for 4-quinolones and benzothiopyran-4-ones: an attractive route for the highly diastereoselective synthesis of acridine- and thioxanthene-derivatives

Enamines regioselectively add to the CN+-bond of 4-silyloxyquinolinium triflates with high yields, and the BF3·Et2O mediated annulations of 4-quinolones with 2-aminobuta-1,3-dienes proceed with high diastereoselectivity to give substituted 1,2,3,4,4a,9,9a,10-octahydroacridine-3,9-dione derivatives; 4-silyloxy-1-benzothiopyrylium triflates and benzothiopyran-4-ones behave analogously.