Date of Award

Winter 1997

Project Type

Dissertation

Program or Major

Chemistry

Degree Name

Doctor of Philosophy

First Advisor

Richard Johnson

Abstract

The chemistry of cyclobutyne (20) and 1,2-cyclobutadiene (21) has been investigated. Research efforts were focused on attempting to independently generate and trap these highly reactive species. The trapping experiments were inconclusive in each case.

Calculations using MCSCF theory indicate that perfluorination of cyclobutyne will have a profound effect that stabilizes the cyclobutyne relative to rearrangement. However, experiments designed to generate and trap perfluorocyclobutyne (73) did not provide evidence for this compound.

The development of new routes to strained organic compounds through the extension of known pericyclic reactions is described. These novel pericyclic reactions have been investigated by ab initio calculations and flash vacuum pyrolysis (FVP) experiments.

MP4/6-31G*//MP2/6-31G* calculations support the possibility that strained six-membered rings can be prepared by replacement of a double bond with a triple bond in the prototypical Diels/Alder cycloaddition eq. (1) or electrocyclic reaction eq. (7). The novel cycloadditions explored involve the replacement of the traditional 1,3-butadiene component of (4+2) cycloadditions with vinylacetylene (19), 1,3-butadiyne (160), and strans-butadiene (233). Electrocyclic reactions of 1,2,3-cyclohexatriene (167), 1,2,4-cyclohexatriene (166), cyclohexen-3-yne (247), and 1,2,3,4-cyclohexatetraene (243) have been investigated.

Experimental evidence is presented for the first example of intramolecular diyne + alkene and diyne + alkyne cycloadditions. The latter process is believed to give an o-benzyne intermediate, which is subsequently reduced to indan. This cycloaddition is unique in that it may be considered a cycloaromatization because an aromatic ring is directly generated. The mechanism and generality of diyne cycloadditions is examined.

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