Date of Award

2015

Document Type

Honors Thesis (Open Access)

Department

Colby College. Chemistry Dept.

Advisor(s)

Dasan M. Thamattoor

Second Advisor

Nicholas Boekelheide

Abstract

The photolytic precursor to the sterically hindered β-bis(tert)-butanol carbene, 3-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)-2,2,4,4-tetramethylpentan-3-ol was prepared in three steps from phenanthrene. Photolysis of the precursor generates the desired β-hydroxy carbene, an intermediate, which subsequently rearranges into two different observed products from an intramolecular C-H insertion and alkyl shift. Four intramolecular mechanisms were ultimately considered to account for the possible rearrangement pathways. Computational studies using density functional theory are also presented.

In addition, the photolytic precursors to two cyclic β-hydroxy carbenes, 1-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)cyclopropan-1-ol and 1-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)cyclobutan-1-ol, were also prepared through different synthetic routes from phenanthrene. Photolysis of these alcohols led to the formation of β-cyclopropanol carbene and β-cyclobutanol carbene. Both carbenes were observed to under go an alkyl shift, resulting in a ring expansion, as their major rearrangement product. Additionally, low temperature argon matrix isolation spectroscopy was performed on the β-cyclopropanol carbene in an effort to isolate and study the rearrangement intermediates.

Keywords

carbenes, rearrangements, physical organic chemistry

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