Anellierungsreaktionen zu carbo- und heterocyclischen Ringsystemen
This work is subdivided in three chapters. In the first chapter the synthesis of a 7,7'-bridged 1,1'-Biisoquinoline by a Pomeranz-Fritsch-Reaction is described. This molecule was seperated in its atropisomers which racemice in solution. The influence of the solvent character to the rate of racemization was investigated. It has been shown that the more polar and the more protic the solvent is the higher is the rate of racemization. The second chapter introduces an easy synthetic route to 6-substituted Benzimidazo[2,1-a]isoquinolines and in the single case of a Furyl-substituent to Isoindolo[2,1-a]quinoxalins. The starting materials, ortho-Alkynyl-substituted Benzaldehydes, are prepared by Sonogashira-Coupling of the Bromobenzaldehydes with different substituted terminal Alkynes. The reaction of o,o'- Bis(phenylethinyl)-substituted Benzil with Hydroxylamine Hydrochloride leads to a rearranged Benzofluorenon. The formation is explained by a domino process including a cyclization-step, a Hetero-Diels-Alder reaction and the final rearrangement. In the third chapter the stereochemical outcome of the McMurry reaction is investigated depending on the length of a tether between the meta and meta'-position of an Bisbenzaldehyde. Only the short dioxapentandiyl tethered Bisbenzaldehyde forms streoselectiv the cis-product. Starting with the dioxaoctandiyl- or dioxatetradecandiyl-tethered Bisbenzaldehydes the thermodynamical more stable trans products are obtained. In a second part the regioselectivity of the oxidative photocyclization of these McMurry-products, leading to tethered Phenathrenes, has been investigated. The dioxapentandiyl- and the dioxaoctandiyl-substituted Stilbenes leads regioselectiv to the 4,5-disubstituted Phenathrenes. Whereas the longer dioxatetradecandiyl-tether allows a change in the product ratio and the 2,5-disubstituted Phenanthrene is obtained as the major product. In all cases no 2,7-Phenanthrene could be detected.
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