Mathematisch-Naturwissenschaftliche Fakultät

Institut für Chemie

Fachgebiet: Organische Chemie

Betreuer: Prof. Dr. Peter Langer

M. Sc. Mohanad Shkoor
(e-mail: )

Synthesis of Hydroxybenzodioates, Aminophenols and Diaryl Selenides by [3+3] Cyclizations of 1,3-Bis(silyloxy)-1,3-butadienes with 3-Silyloxy- and 3-Alkoxy-2-en-1-ones

Cyclization reactions of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 1,3-dielectrophiles, provide a powerful tool for the synthesis of highly substituted arenes. They proceed with high regioselectivity. I have reported new contributions to the synthesis of highly functionalized arenes starting with acyclic precursors.

I have disclosed a diversity-oriented, convenient and regioselective synthesis of a great variety of 1-hydroxy-2,4-benzodioates (4-hydroxyisophthalates) by the first formal [3+3] cyclizations of 1,3-bis(silyloxy)-1,3-butadienes with 3-silyloxy- and 3-alkoxy-2-alkoxycarbonyl-2-en-1-ones.

I have also reported the synthesis of 3-hydroxy-5-methylphthalates by regioselective chelation-controlled cyclization of 1,3-bis(silyloxy)-1,3-butadienes with 4-silyloxy-2-oxo-3-butenoates derived from acetylpyruvates. The employment of silylated benzoyl- instead of acetylpyruvates results in a change of the regioselectivity and formation of 6-aryl-2-hydroxy-terephthalates. The regiodirecting effect of the aryl group is stronger than the one of the pyruvate-derived ester group. The cyclization of 1,3-bis(silyloxy)-1,3-butadienes with 4-ethoxy-2-oxo-3-butenoates, readily available by condensation of enol ethers with methyl 2-chloro-2-oxoacetate, afforded 3-hydroxyphthalates and 2-hydroxyterephthalates depending on the substitution pattern of the diene.

In addition, I have studied the regioselective synthesis of highly functionalized 4-nitro- and 4-aminophenols based on [3+3] cyclocondensation of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-ethoxy-2-nitro-2-en-1-ones and subsequent reduction of the resulting nitrophenols.

Finally, I have developed a new synthesis of various functionalized unsymmetrical diaryl selenides containing a salicylate substructure by [3+3] cyclocondensation of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-silyloxy-2-phenylselenayl-2-en-1-ones.