Aryl acetylene substituent effects : the synthesis and application of biaryls

Abstract

The work described herein details the synthesis and application of biphenyls that probe the effects of hydrogen, Cl / Br, and methyl substituents on the aryl ring of the terminal acetylenic carbon. From this work, we successfully developed the rapid synthesis of phenyl acetylenes in 3-4 steps from inexpensive commercially available materials. Using these mild conditions, a wide host of functionalized acetylenes has been easily achieved, avoiding complex and or difficult synthetic transformations With the functionalized acetylenes in had, we demonstrated that the subtle change from hydrogen to either methyl or halogen imparts diverse results when subjected to [4+2] or [3+2] cycloadditions. This knowledge has helped to explain other unexplained observations from previous work within this project. These biphenyls were then further investigated by performing various synthetically useful functional group transformations and comparing the differences the substituents have on the corresponding reaction. Noteworthy is the total synthesis of siamenol, a carbazole isolated from the bark of Murriaya siamensis, where the key carbazole forming step is effected by the substituents about the molecule in the synthesis of siamenol derivatives.