Ulf Annby

Palladium-catalysed synthesis of heterocondensed pyrroles

Abstract The palladium-catalysed preparation of some heterocondensed pyrroles from ortho nitrogen containing hetaryl iodides and derivatives of propargyl alcohol is described.

A novel approach to bz-substituted tryptophans via Pd-catalysed coupling / annulation.

Abstract The Pd-catalysed preparation of bz-substituted tryptophans and their derivatives, starting from 2-iodoanilines and γ,δ-acetylenic amino acid derivatives, is reported.

Indole-3-Acetic Acids and Hetero Analogues by One Pot Synthesis including Heck Cyclisation

Abstract Bz-substituted indole-3-acetic acid ethyl esters (14e-g) and heteroanalogues, i.e. thienopyrroles (14a, c) and selenolopyrrole (14d), were prepared starting from N-BOC protected o-iodo aryl amines. Allylation with ethyl 4-bromocrolonate, followed by palladium-catalysed ring closure in a one pot reaction, yielded N-BOC protected indoles (13e-g), thienopyrroles (13a-c), and selenolopyrrole (13d). The BOC group was readily removed thermally after adsorption on silica. Oxothienopyrroles (11a-c) were similarly prepared.

BENZYLIDENE PROTECTED BIS-MPA: A CONVENIENT DENDRIMER BUILDING BLOCK

Abstract Benzylidene protected bis-MPA, 2,2-bis(hydroxymethyl)propanoic acid, was synthesised and evaluated as building block in the construction of dendrimers. It was found that the anhydride of benzylidene protected bis-MPA reacts with neopentylic alcohols to give high yields of acylated products. Purification is facilitated by the crystalline nature of most ester products. Deprotection by hydrogenolysis gives polyol dendrimers in good yields.

Enzymatic synthesis of Thia-L-tryptophans

Abstract Thia analogs of L-tryptophan ( β -3-thieno[2,3- b ]pyrrolyl-L-alanine and β -3-thieno[3,2- b ]pyrrolyl-L-alanine) have been prepared by the reaction of L-serine and thienopyrroles catalysed by Salmonella typhimurium tryptophan synthase.

Regiochemistry of Palladium(II)-assisted oxidative lactonisation reactions.

Abstract The Pd(II)-assisted lactonisation of alkenoic acids has been studied. The selectivity, persisting to formation of 5- and 6-membered unsaturated lactones, can be governed by the change of solvent and/or base.

Hydrozirconation of 1-arylalkenes

The hydrozirconation of 1-arylhexenes with Cp2Zr(H)Cl has been studied at various temperatures. 1-Phenyl-1-hexene and its ortho-methoxyl derivative both react significantly more slowly at room temperature than simple alkenes. Furthermore, the tendency of zirconium to migrate towards the terminal position, in these compounds is very low at room temperature, as concluded from 2H NMR analysis after deuterolysis. Instead, the α-deuterated arylhexanes predominate. This is in contrast to the behaviour of simple alkenes, which are known to give terminal σ-alkylzirconium compounds. At elevated temperature (60°C), 1-phenyl-1-hexene gives about 50% of deuterated phenylhexane with a reversed isomer ratio (α-Dω-D1090). 1-Phenyl-3-Z-hexene reacts much faster than 1-phenyl-1-hexene at room temperature, but the reaction is unselective unless the temperature is slightly raised (45°C; 26 α-D74 ω-D). 2-(3-Z-Hexenyl)thiophene gives about 55% of deuterated 2-hexylthiophene at 25°C, with deuterium incorporated almost exclusively at the ω-position. In contrast, 2- and 3-(1-hexenyl)-thiophene, are hydrogenated, and give hexylthiophenes with low deuterium incorporation.

Reaction of the aromatic olefin 1-(1-hexenyl)-2-thiomethyl-benzene with Cp2Zr(H)Cl. Unexpected cleavage of the methylsulphur bond

Abstract Reaction of the aromatic olefin 1-(1-hexenyl)-2-thiomethylbenzene with Cp2Zr(H)Cl results in cleavage of the sulphurmethyl bond. When the 2-hexylthiophenol thus formed is exposed to air, it is oxidized to the corresponding disulphide, which is produced in about 70% yield (based on starting olefin). Such a reaction does not take place with 1-(1-hexenyl)-2-methoxybenzene as substrate.

Synthesis of new monofunctional and oligofunctional oxetane acetals

Derivatives of 3-ethyl-3-(hydroxymethyl)oxetane (trimethylolpropane oxetane), potentially useful in cationic UV-curable formulations, were prepared by the simple acid-catalyzed addition of alcohols to 1-alkenyl ethers. Examples include several difunctional oxetane derivatives along with one fluorinated and one acryloylated oxetane derivative. These new materials may find use as reactive diluents or binders in several applications. A preliminary assessment of the curing was made.

Aspects of the hydrozirconation-isomerisation reaction☆

Abstract Aspects of the hydrozirconation-isomerization of nonfunctionalised olefins are discussed. Cyclooctene and 1-methyl-1-cyclohexene were previously reported not to react with Cp 2 Zr(H)Cl. In the present work after treatment of the former with Cp 2 Zr(D)Cl, and subsequent hydrolysis, no cyclooctane could be detected. Although the olefin seemed not to have reacted, it was deduced that the corresponding cyclooctylzirconium was in fact formed, since the amount of deuterium incorporated in cyclooctene was roughly the same as the amount of zirconium deuteride used. Total scrambling of deuterium was observed. Cycloheptene and 2,2,11,11-tetramethyl-6-dodecene gave similar results. 1-Methyl-1-cyclohexene, on the other hand, was very unreactive. No evidence for deuterium incorporation in the recovered olefin (80–90%) was obtained. When Z -5-decene was used as substrate, zirconium migration towards the terminal carbon, and cis-trans isomerisation, were slower than expected. No internal alkylzirconium derivatives could be trapped. Competing hydrogenation of 1- and Z -5-decene is favoured when a deficiency of the zirconium hydride is used.