Reinhart Keese

The addition of perfluorobutyl iodide to carbon-carbon multiple bonds and the preparation of perfluorobutylalkenes

Abstract Addition of perfluorobutyl iodide to CC multiple bonds is efficiently achieved by sodium dithionite under ultrasonic irradiation or phase transfer conditions. Perfluorobutyl substituted alkenes are obtained from the β-iodo-perfluoroalkanes resp.-alkenes by base-catalyzed elimination resp. reductive cleavage.

Synthesis of 2,3-dimethyltetra-cyclo(5.5.1.04,13.010,13)trideca-2,5-dien-9-one, a new derivative of all-cis-(5.5.5.5)fenestrane

Abstract Intramolecular arene-olefin photoreaction of methyl-6-methyl-2-phenylhept-5-enoate (9a) leads to the tetracyclic product 10a, from which the fenestra-dienone, 2, has been obtained. Mechanistic aspects of the photoreaction are discussed.

Synthesis of [5.5.5.5]fenestranes by Pd-catalyzed carbonylation-cyclisation

Pd-catalyzed reaction of 3-acetoxy-8-butenyl- (9) and 8-but-3-inyl-bicyclo[3.3.0]oct-1-ene (11) with CO in CH3COOH lead via double annulation to all-cis[5.5.5.5]fenestranes.

PHOTOCHEMISTRY OF SUBSTITUTED 1-(BUT-3-ENYL)-INDANES

Abstract The intramolecular arene-olefin photocycloaddition was studied with 1-substituted indanes. The chemo- as well as the regioselectivity is primarily controlled by donor substituents in the indane moiety. Selected transformations of the photoproducts are described.

Methanol and dimethylaniline as methylating agents of Co(I) corrinoids under acidic conditions

Abstract Methyl transfer from methanol and dimethylaniline to Co(I) corrinoids is an efficient process, when the corresponding Co(II) complexes are electrochemically reduced in the presence of acids.

First Synthesis and Structure of a Tetraazasilafenestrane

A shift from the computational to the synthetic side has taken place in the quest for compounds containing planar-tetracoordinate silicon: The first tetraazasilaspiro[4.4]nonane with two alkylene bridges has been prepared [Eq. (1)]. According to the X-ray structure analysis, the angle between the two diazasilacyclopentene rings is 84.7°. AIBN=azobisisobutyronitrile, X=Br.

The structural basis of the geminal-dimethyl effect

Abstract A systematic analysis of the X-ray structures of cyclohexanes, cylcopentanes and open-chain compounds containing gem.-dimethyl groups has revealed that a static scissor-type deformation at the quaternary C atom is absent. Unexpectedly the CCC bond angles in α-position to the quaternary C atom are significantly larger than the standard values in the unsubstituted reference structures. This distortion is interpreted in terms of gauche interactions. Based on the presently available data for structures containing gem.-dimethyl groups, the structure-reactivity relationship observed by Thorpe and Ingold for this class of compounds, has an origin different from static scissor-like distortions at the quaternary C atom.

Synthesis ofω-Substituted Alkanethiols and (Bromomethyl)methylthiomalonates

Several multifunctional derivatives of methylthiomalonic acid (=2-(thiocarboxy)acetic acid), i.e.20a, b, 21, 22a, b, and 24, were prepared from thiols bearing a functionalized head group, i.e. from 9a, b, 12, and 16d, f (Schemes 4 and 5). The association constants of the two dithio podands 8b and 11 with K+ were determined.

METHYL TRANSFER FROM METHANOL TO CO-COBYRINATE : A MODEL FOR THE COENZYME B12 DEPENDENT METHYLTRANSFERASE ?

With CoI corrins as supernucleophiles, methylation by methanol is achieved when the leaving group is activated by Zn2+ ions at elevated temperatures (see reaction below). This methylation reaction is the first model for the Co-dependent methyltransferase.

Synthesis of cyclododeca-2,8-diyne-1,7-dione

Abstract The 12-membered carbocyclic compounds 5 , containing 2 α,β-unsaturated alkynone functionalities is prepared from 5-hexyn-1-ol in 9 steps. Ring closure is achieve by C-C bond formation between the terminal iodoalkyne and aldehyde group using CrC1 2 in a yield of 62%.