LE3 .A278 2013

2013

Lukeman, Matthew

Acadia University

Bachelor of Science

Honours

Chemistry

Chemistry

The synthesis, isolation, purification, and photochemical study of two target compounds was successfully achieved. The first compound successfully synthesized was 2-(1-hydroxycyclohexyl)phenol 69, designed to generate a cyclohexyl-fused quinone methide upon photolysis. Compound 69 was synthesized via a one-pot, two-step reaction sequence starting from 2-bromophenol. Attempts to synthesize 70 and 71 via this route, however, were unsuccessful and further efforts are warranted. Following purification by column chromatography, the photoreactions of 69 proceeded smoothly in both aqueous methanol and acetonitrile. The expected quinone methide was generated efficiently with a quantum yield of ~0.5. The quinone methide was observed directly via laser flash photolysis and displayed absorbance maxima at 290 nm and 400 nm, and had a lifetime of 0.9 ms in aqueous acetonitrile and 0.5 ms in aqueous methanol. The second compound successfully synthesized was the cyclic acetal of the photolabile protecting group 2-naphthol (78). This was designed to release 1,3-propanediol upon irradiation, which is a model system for the future release of polyhydroxyl compounds such as many common carbohydrates. This synthesis involved a three-step procedure followed by purification via column chromatography. A variety of photochemical experiments were carried out and the photoproducts were analyzed by 1H NMR, UV-Vis, and GC-MS. Photolysis of 78 in aqueous methanol led to the clean release of the originally caged diol with no undesired by-products as indicated by the GC-MS data obtained and the clean isosbestic points in the UV-Vis spectra. Quantum yield studies indicated that the photorelease proceeded with ~10% efficiency, which compares well with the quantum yields of release for other substrates from the 2-naphthol caging xvi group. Furthermore, the caging process proceeds cleanly at room temperature with good isolated yields (>80%). 78 was also studied with laser flash photolysis and a transient intermediate was detected with an absorbance maximum of 310 nm and a lifetime of 12.5 ms in aqueous acetonitrile. This transient was proposed to be the expected quinone methide intermediate based on comparison with previously studied compounds.

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https://scholar.acadiau.ca/islandora/object/theses:1015