Study of heteroaromatic enediyne and substituted benzothiophene synthesis with a study of unusual H NMR signals in neomenthyl halides

Abstract

The synthesis of a number of heteroaromatic enediynes has been examined using the Sonogashira coupling reaction. Alkynes were coupled to 2,3-dibromothiophene to yield a number o f hetero- and homo-disubstituted enediynes. Both thermal and photochemical Bergman cyclizations were attempted with these enediynes in an attempt to produce substituted fused bicyclic heteroaromatic products. Through this method, benzothiophene was prepared. The enediyne functionality and its cyclization is of synthetic interest given that a variety of naturally occurring compounds containing this unit demonstrate the ability to cleave DNA. In addition, a solvent effect study on neomenthyl halides was undertaken. In this study, the effect of various solvents on the ’H NMR spectra of neomenthyl halides was investigated. During the course of the study an unusual low field proton resonance was discovered.