Date of Award

2-1-1994

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Abstract

The original goal of this study was to use ($\eta\sp6$-arene)chromium tricarbonyl (Cr(CO)$\sb3$) chemistry to develop a scheme for benzyl-aryl bond cleavage in coal model compounds. Specifically, the regioselective formation and rearrangement of a benzyl alcohol was proposed as a means for accomplishing this goal. The application of such a method to coal could give the valuable structural information necessary for efficient use of the world's vast coal reserves.The enhanced acidity of the benzyl proton in ($\eta\sp6$-arylalkyl)Cr(CO)$\sb3$ complexes allowed for the ready generation of the benzylic anions of several complexes which were then treated with many aprotic reagents in the hopes of forming the benzyl alcohol. The greatest success came with ($\eta\sp6$-hexamethylbenzene)Cr(CO)$\sb3$ (1), where treatment of the benzylic anion with tributylborate (B(OBu)$\sb3$) gave pentamethylbenzyl alcohol in 79% yield. However, the Cr(CO)$\sb3$ complexes of tetralin and diphenylmethane gave little or no benzylic hydroxylation under these conditions, indicating a lack of generality with benzyl substitution by trialkoxyborates. The benzylic anions of the complexes of hexamethylbenzene and diphenylmethane gave 30% and 70% benzylic oxidation, respectively, when treated with pure O$\sb2$.An in situ aromatic hydroxylation procedure was developed and was shown to be successful across a wide range of aromatic compounds from mono-cyclics to polycyclic aromatic hydrocarbons (PAH). In most cases, the hydroxylation was regioselective and occurred in good to excellent yields. The following phenols were prepared: Benzylphenol (90%, mixture of isomers) 5,6,7,8-tetrahydro-2-naphthol (83%), 2-naphthol (94%), 2-hydroxy-9,10-anthraquinone (71%), phenanthrol (82%, mixture of isomers), 2-pyrenol (59%), 8-hydroxyfluoranthene (78%), 7,9-dihydroxyfluoranthene (21%), N-methyloxindole (89%),N-methylcarbazol-2-ol (55%).The in situ method was further extended to silylations and carboethoxylations of ($\eta\sp6$-naphthalene)Cr(CO)$\sb3$ and ($\eta\sp6$-pyrene)Cr(CO)$\sb3$. With the pyrene complex this led to the synthesis of 3 new compounds; 2-(trimethylsilyl)pyrene (98%), 1,2-bis(carboethoxy)-pyrene(27%), and 1,2,3-tris(carboethoxy)pyrene (71%). The conditions by which 1, 2, or 3 carboethoxy groups could be introduced were also determined. The observed selectivity in the mono-functionalization procedures appears to be steric in nature, but conformational effects of the Cr(CO)$\sb3$ moiety may also play an important role.

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