Anna Tarli

Date of Graduation

1997

Document Type

Dissertation/Thesis

Abstract

Four acyclic enyne-allenes were synthesized for subsequent chemical elaborations through biradical intermediates. When (Z)-7-methyl-3-propyl-3,5,6-octatrien-1-yne, (Z)-3-butyl-7-methyl-3,5,6-octatrien-1-yne, (Z)-7-methyl-3-(3-methylbutyl)-3,5,6-octatrien-1-yne, and (Z)-9-ethynyl-13-methyl-1,9,11,12-tetradecatetraene were stirred at rt for 18 h in benzene, they underwent facile Myers cycloaromatization reactions to provide {dollar}\\alpha{dollar},3-didehydrotoluene biradical species. Subsequent 1,5-hydrogen shift led to new biradicals species which afforded 7-(dimethylmethylene)spiro (3.5) nona-5,8-dienes via intramolecular radical-radical combination by attacking the ipso carbon of the benzene ring. Seven acyclic enediynyl ethyl ethers were prepared by the Pd(PPh{dollar}\\sb3)\\sb4{dollar}-catalyzed cross coupling between enynyl iodides and 2-ethoxyethynylzinc chloride. On heating to reflux in chlorobenzene for 3 h, the enediynyl ethyl ethers underwent an elimination of a molecule of ethylene, leading to the reactive enyne-ketenes. Subsequent Moore cyclization reactions produced biradicals containing an aryl and a phenoxy radical center followed by a 1,5-hydrogen shift to produce new biradicals which decayed through various intramolecular pathways. For example, thermolysis of (Z)-3-butyl-1-ethoxy-4-ethyl-3-nonene-1,5-diyne produced a chromanol via an intramolecular radical-radical combination, an alkene derived from a second 1,5-hydrogen shift, a phenol which was produced from the acid-catalyzed rearrangement of a spiro intermediate containing a four-membered ring, and a Diels-Alder adduct resulting from the Diels-Alder reaction of an o-quinone methide and the spiro intermediate. Similarly, thermolysis of (Z)-3-butyl-1-ethoxy-4-ethyl-3-decene-1,5-diyne led to a similar mixture of products. Thermolysis of (Z)-3-butyl-1-ethoxy-4-ethyl-7-methoxy-3-heptene-1,5-diyne afforded primarily a trimer via two Diels-Alder reactions of the resulting o-quinone methide, derived from elimination of a molecule of formaldehyde. Thermolysis of (Z)-3-butyl-1-ethoxy-4-ethyl-6-(1-methylphenyl)-3-hexene-1,5-diyne afforded 3-butyl-2-ethyl-6H-dibenzo (b,d) pyran via the radical-radical combination route. Similarly, (Z)-7-(dimethylamino)-1-ethoxy-4-methyl-3-heptene-1,5-diyne led to 3,4-dihydro-3,6-dimethyl-2H-1,3-benzoxazine. In the case of (Z)-1-ethoxy-4-propyl-3-heptene-1,5-diyne, the initial 1,5-hydrogen shift led to a primary radical center located on the tether para to the phenoxy radical center. Subsequent attack on the ipso carbon of the benzene ring for homolytic coupling led to 6-methylspiro (3.5) nona-5,8-dien-7-one which rearranged to two bicyclic phenols. Thermolysis of (Z)-3-butyl-1-ethoxy-4-ethyl-6-(1- methoxyphenyl)-3-hexene-1,5-diyne presents a unique case where the resulting phenol was derived via a zwitterionic intermediate.

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