67177-31-5Relevant academic research and scientific papers
Synthesis of the Benzotricyclo2,7>heptene Ring System via the Intramolecular -Cycloaddition Reaction of Some Cyclopropene Derivatives
Padwa, Albert,Rieker, William F.,Rosenthal, Robert J.
, p. 4446 - 4456 (2007/10/02)
The photo and thermal reactions of a number of 1,2-diphenyl-3-methyl-3-(o-vinylphenyl)-substituted cyclopropenes have been studied.The thermolysis of these systems gave substituted benzotricyclo2,7> heptenes in good yield by means of a novel intramolecular cycloaddition.The sensitized di-?-methane photorearrangement of several substituted benzonorbornenes was used to independently synthesize the thermal cycloadducts.The observed regiospecificity of the rearrangement is understandable in terms of formation of the most stable diradical intermediate.In contrast to the thermal results, the photosensitized irradiation afforded a mixture of two products.In addition to the cycloadduct, a new compound was isolated whose formation involves attack of the ortho position of the triplet state on the terminal vinyl carbon followed by diradical coupling and subsequent rearomatization.Thermolysis or sensitized photolysis of several unsymmetrically substituted 1,3-diphenyl-2-methyl-2-(o-vinylphenyl)cyclopropenes afforded related cycloadducts.With these systems, the -cycloaddition reaction is highly regiospecific and involves bonding from the cyclopropene carbon bearing the methyl group onto the terminal vinyl carbon.The silver ion and singlet excited-state behavior of several substituted cyclopropenes was also studied, and the results obtained were compared to the reactions which occur on thermolysis or sensitized photolysis.
Photochemistry of Cyclopropene Derivatives. 20. Deuterium Isotope Effects in the Triplet-Induced Photochemistry of Tetrasubstituted Cyclopropenes
Padwa, Albert,Chou, Chuen S.,Rosenthal, Robert J.,Rubin, Byron
, p. 3057 - 3068 (2007/10/02)
The photochemical behavior of a number of 3-(o-alkylphenyl)-substituted cyclopropenes which contain a benzylic hydrogen in the γ-position of the side chain has been studied in mechanistic detail.The results obtained indicate that the products of the direct and triplet-sensitized photolysis are completely different.The singlet states of these systems react by ?-bond cleavage of the ring to give products which are explicable in terms of the chemistry of vinyl carbenes.The triplet state, generated by sensitization techniques, undergoes hydrogen atom abstraction by mechanism analoqous to the well-known Norrish type II process of carbonyl compounds.Rate constants for hydrogen abstraction were obtained by plotting Φo/Φq vs. trans-stilbene at a constant quencher to cyclopropene ratio.In contrast to the symmetrically substituted 1,2-diphenylcyclopropenes, the quantum efficiency of hydrogen abstraction of the 1,3 isomers was found to depend on the concentration of starting material.The primary deuterium isotope effect encountered with the symmetrical 1,2-diphenylcyclopropene systems is significantly larger than any previously reported value for hydrogen transfer to an excited state (kH/kD ca. 20/1).A substantial tunnel effect is proposed to rationalize the results.In contrast to the results obtained with the symmetrical cyclopropenes, a much smaller effect on the quantum efficiency was observed with the unsymmetrical systems (kH/kD = 3.3/1).
Photosensitized Electron-Transfer-Induced Reactions of Some Cyclopropene Derivatives
Padwa, Albert,Chou, Chuen S.,Rieker, William F.
, p. 4555 - 4564 (2007/10/02)
The 9,10-dicyanoanthracene-sensitized rearrangement of several 3-phenyl-substituted cyclopropenes to indenes in acetonitrile has been studied. When an unsymmetrically 1-phenyl-2-methyl-substituted cyclopropene was used, the major indene obtained correspon
