Photochemical nucleophile-olefin, combination aromatic substitution (photo-NOCAS) reaction: Methanol, dienes, 1,4-dicyanobenzene.
Date
1992
Authors
McManus, Kimberly Ann.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
Previous studies of the photo-NOCAS (photochemical nucleophile-olefin, combination aromatic substitution) reaction have focused upon monoalkenes, including prospective ring-opening alkenes. In this thesis, the study has been extended to conjugated dienes and unconjugated dienes (and their potential to undergo ring closure).
The unconjugated dienes studied were 1,5-hexadiene (12), 2-methyl-1,5-hexadiene (13) and 2,5-dimethyl-1,5-hexadiene (14). These dienes were irradiated in the presence of 1,4-dicyanobenzene in acetonitrile-methanol (3:1) solution. The three dienes behaved quite differently. Diene 12 gave cycloaddition to 1,4-dicyanobenzene and dienes 13 and 14 each gave normal acyclic photo-NOCAS products. Addition of the co-donor, biphenyl (9), to the irradiation mixture was found to increase the efficiency of the photo-NOCAS reaction for the latter two dienes. Only for the case of 2,5-dimethyl-1,5-hexadiene with biphenyl present were cyclized products observed. Both cis- and trans-4-(4-cyanophenyl)-1-methoxy-1,4-dimethylcyclohexane (23 and 24) were formed. The mechanism and limitations of the reaction are discussed.
The conjugated dienes studied were 1,3-butadiene (37), 2-methyl-1,3-butadiene (38), 2,3-dimethyl-1,3-butadiene (39) and 2,5-dimethyl-2,4-hexadiene (36). Dienes 37, 38 and 39 were irradiated in the presence of 1,4-dicyanobenzene and biphenyl in acetonitrile-methanol (3:1) solution. Both 1,2- and 1,4-addition products were formed in an approximate equimolar ratio (total yields range from 50-60%). However, irradiation of 2,5-dimethyl-2,4-hexadiene, 1 and 9 in acetonitrile-methanol (3:1) solution yielded 86% 1,4-addition products; trans-2-(4-cyanophenyl)-5-methoxy-2,5-dimethyl-3-hexene (35,82%) and trans-2-(4-cyanophenyl)-2,2,5-trimethyl-3-hexenenitrile (40, 4%). Irradiation of an acetonitrile solution containing 36 and 1 yielded 94% 40. The mechanism of this reaction is discussed. Also, a probable explanation of the regio- and stereoselectivity of the photo-NOCAS reaction involving these conjugated dienes is given.
Thesis (Ph.D.)--Dalhousie University (Canada), 1992.
The unconjugated dienes studied were 1,5-hexadiene (12), 2-methyl-1,5-hexadiene (13) and 2,5-dimethyl-1,5-hexadiene (14). These dienes were irradiated in the presence of 1,4-dicyanobenzene in acetonitrile-methanol (3:1) solution. The three dienes behaved quite differently. Diene 12 gave cycloaddition to 1,4-dicyanobenzene and dienes 13 and 14 each gave normal acyclic photo-NOCAS products. Addition of the co-donor, biphenyl (9), to the irradiation mixture was found to increase the efficiency of the photo-NOCAS reaction for the latter two dienes. Only for the case of 2,5-dimethyl-1,5-hexadiene with biphenyl present were cyclized products observed. Both cis- and trans-4-(4-cyanophenyl)-1-methoxy-1,4-dimethylcyclohexane (23 and 24) were formed. The mechanism and limitations of the reaction are discussed.
The conjugated dienes studied were 1,3-butadiene (37), 2-methyl-1,3-butadiene (38), 2,3-dimethyl-1,3-butadiene (39) and 2,5-dimethyl-2,4-hexadiene (36). Dienes 37, 38 and 39 were irradiated in the presence of 1,4-dicyanobenzene and biphenyl in acetonitrile-methanol (3:1) solution. Both 1,2- and 1,4-addition products were formed in an approximate equimolar ratio (total yields range from 50-60%). However, irradiation of 2,5-dimethyl-2,4-hexadiene, 1 and 9 in acetonitrile-methanol (3:1) solution yielded 86% 1,4-addition products; trans-2-(4-cyanophenyl)-5-methoxy-2,5-dimethyl-3-hexene (35,82%) and trans-2-(4-cyanophenyl)-2,2,5-trimethyl-3-hexenenitrile (40, 4%). Irradiation of an acetonitrile solution containing 36 and 1 yielded 94% 40. The mechanism of this reaction is discussed. Also, a probable explanation of the regio- and stereoselectivity of the photo-NOCAS reaction involving these conjugated dienes is given.
Thesis (Ph.D.)--Dalhousie University (Canada), 1992.
Keywords
Chemistry, Organic.