TRIPLE BOND PARTICIPATION IN THE OXY-COPE REARRANGEMENT John Harry MacMillan Ph.D. Northeastern University, 1970

As a part of the study of oxy-Cope systems in this laboratory, some examples of triple bond participation in these reactions have been investigated. In general, the experimental results indicate that acetylenes and allenes participate readily in cyclic six membered transition states and that triple bond participation in electrocyclic reactions leads to increased rates in comparison with the corresponding olefinic structures. 1-Hexen-5-yn-3-ol was subjected to vapor phase thermolysis in a flow system over the range of 350-90 degrees centigrate and under various pressres. The extent of beta-hydroxyolefin cleavage, which leads to formation of acrolein and allene, is independent of residence time in the thermolysis zone but increases with temperature, indicative of a higher activation energy than for the competing rearrangement processes. One of these processes affords 4,5-hexadienal via an acetylenic analog of the oxy-Cope reaction. Also produced is 3-cyclopentenecarboxaldehyde in amounts increasing with increasing temperature and/or residence time. The data is consistent with an electrocylic reaction involving the enolic progenitor of the oxy-Cope product, which ketonizes only upon condensation in the product trap. The thermolysis of 3-methyl-1-hexen-5-yn-3-ol was reinvestgated due to conflicting literature reports concerning product formation. The production of both vinyl acetylcyclopropane and 4-acetylcyclopentene has been verified in this laboratory. The effect of the methyl group upon product composition is interpreted on the basis of a torsional effect in the transition state. Thermolysis of 5-hexen-1-yn-3-ol affords 2- and 3- cyclopentenecarboxaldehydes, trans-2,5-hexadienal and sorbaldehyde in varying amounts dependent upon temperature and contact time. Since the competing beta-hydroxyolefin cleavage is completely absent, kinetic parameters could be determined. The Arrhenius energy of 30 kcal/mol and activation entropy of -14 e.u. are indicative of a concerted mechanism. The kinetic data, the effects of temperature and contact time upon product distribution and the results of a deut- erium tracer study indicate the intermediacy of the primary oxy-Cope product in the formation of all observed products. These reactions constitute the chemistry of an allenol intermediate, 1-hydroxy-1,2,5-hexatriene. Thermolysis of 1-phenyl-3-butyn-1-ol and 1-phenyl-2-methyl-3-butyn- 2-ol gave no trace of oxy-Cope rearrangement products, indicating the unwillingness of the phenyl group to participate in the oxy-Cope rearrangement. Thermolysis of 1,5-hexadiyn-3-ol at 350 degrees gives 4-methylene-2-cyclobutene-1-carboxaldehyde and phenol. The hydroxy group greatly facilitates the aromatization pathway. Phenol production increases with increasing temperature or residence time. 3-Methyl or 4,4-dimethyl substitution blocks the pathway leading to aromatization. 4-Methyl substitution gives o-cresol as the only aromatic product. The data indicate the absence of hydroxy migration or carbon skeletal rearrangements in the formation of phenol. Prismane or benzvalene intermediacy is ruled out on the basis of this data. A mechanism for phenol formation is presented involving the intermediacy of the primary oxy-Cope product. Thermolysis of 5-hexyn-3-ol and 2-methyl-4-pentyn-2-ol afford quantitative conversions to cleavage products. Kinetic studies show both reactions to be first order and to possess highly negative entropies of activation, indicative of concerted mechanisms with cyclic transition states. Both alcohols gave faster cleavage rates and lower activation energies than the corresponding literature values of their olefinic analogs. Grignard reagents are found to add to the internal carbon atom of the triple bond in propargylic alcohols to yield 2-methylene substituted alcohols. The presence of a carbinol function bonded to the internal alkyne carbon atom is necessary for the addition to occur. Dissert. Abstr. Int. B, Vol.XXXII, No. 10, 1972 Order No. 72-13,297, 222 pages

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