REACTIONS OF THIOPHENES AND ACETYLENES IN POLAR AND APOLAR SOLVENTS

Abstract

Although the aromatic 6π-electron system of thiophenes is rather unreactive in cycloaddition reactions we have found that several thiophene derivatives react with acetylenes. Alkylthiophenes undergo (2+2)-cycloaddition reactions with electron-deficient acetylenes in apolar solvents in the presence of Lewis acids to give 2-thia-bicyclo [3. 2. 0] hept-3, 6-dienes (1). These compounds show isomerization via an a, a-Cope rearrangement at temperatures of 100 to 150°C.     

The madelung synthesis of dihydro-1H-pyrrolo- and tetrahydropyrido[1,2-a]- indoles under mild conditions

Benzeneacetonitriles substituted with lactam moieties in the ortho-position cyclize under the influence of a base, dependent on the ring-size of the lactam function, to dihydropyrrolo-, tetrahydropyrido[1,2-a]indole or dihydro-1-benzazepin derivatives, respectively.     

On the mechanism of the reaction of enamines and dimethyl acetylenedicarboxylate (DMAD) in polar and apolar solvents

[2+2]-Cycloadducts of enamines and DMAD, formed in apolar solvents, isomerize to pyrrolizine derivatives under mild conditions in protic polar solvents like methanol and 1-butanol.     

Synthesis of pyrrolizines by intramolecular capture of 1,4-dipolar intermediates in reactions of enamines with dimethyl acetylenedicarboxylate

Solvent polarity and reaction temperature strongly influence the reactions of dimethyl acetylenedicar-boxylate (DMAD) with 1-pyrrolidinyl enamines of acyclic and cyclic ketones. Whereas DMAD and 1-[1-phenyl-2-(phenylthio)ethenyl]pyrrolidine (3) give only a mixture of the isomeric 1,3-butadienes (5) in apolar solvents, in methanol the main product is the pyrrolizine 7, together with 5. Again in methanol, DMAD reacts at 0-5° with 8, 9 and 10 to give exclusively 1:1 adducts, the pyrrolizines 11,12 and 13, respectively, whereas at ?50° 8 and 9 give 1:2 (enamine : DMAD) adducts, the pyrrolizines 14 and 15, respectively; a single crystal X-ray analysis of 14 gave the structure of the 1:2 adducts. In the same solvent methyl propiolate and 8 give only the linear Michael adduct 17. The enamine-ketone 18 reacts with DMAD in propylene carbonate at 0–5° to give, via (2 + 2)-cycloaddition and ring expansion, 19, and the linear Michael adduct 20. The mechanism of (2 + 2)-cycloaddition and pyrrolizine formation is discussed in terms of a common tied-ion pair intermediate formed in the first, rate-determining step, followed by a second solvent-dependent step.     

Reduction of nitro groups by ynamines; synthesis and x-ray crystal structure of n,n-diethyl-3,3a-dihydro-3-methylbenzofuro[3,2-c]isoxazole-3-carboxamide

3-Nitrobenzo[b]furan and 1-diethylaminopropyne react thermally at 5–10°C to give a 1:1 addition product ($\text{5}$) in which one of the oxygen atoms of the nitro group is transferred to C-1 of the acetylene. The structure of the benzofuro[3,2-c]isoxazole ($\text{5}$) has been determined by X-ray crystallography.     

Creatine kinase B deficient neurons exhibit an increased fraction of motile mitochondria

Background  

Neurons require an elaborate system of intracellular transport to distribute cargo throughout axonal and dendritic projections. Active anterograde and retrograde transport of mitochondria serves in local energy distribution, but at the same time also requires input of ATP. Here we studied whether brain-type creatine kinase (CK-B), a key enzyme for high-energy phosphoryl transfer between ATP and CrP in brain, has an intermediary role in the reciprocal coordination between mitochondrial motility and energy distribution. Therefore, we analysed the impact of brain-type creatine kinase (CK-B) deficiency on transport activity and velocity of mitochondria in primary murine neurons and made a comparison to the fate of amyloid precursor protein (APP) cargo in these cells, using live cell imaging.