Date of Award
Spring 1993
Project Type
Dissertation
Program or Major
Chemistry
Degree Name
Doctor of Philosophy
First Advisor
Richard P Johnson
Abstract
The development and implementation of a new chiral triplet sensitizer derived from 1,1$\sp\prime$-binaphthol is described. Irradiation of 1,3-diphenylallene (16) in the presence of 4,5,6,7-tetrahydro-dinaphtho(2,1-g:1$\sp\prime,2\sp\prime$-i) (1,6) dioxecine (10) resulted in 0.66% optical induction. Irradiation of 1,3-cyclooctadiene (17) in the presence of 10 resulted in 11.3% optical induction. The singlet state of 10 could be effectively quenched by higher diene concentration, substantially reducing the optical yield. Irradiation of trans-1,2-diphenyl-cyclopropane (1) in the presence of 10 resulted in very low optical yields.
The mechanism by which triplet excited state allenes react in the vapor phase is investigated through both theory and experiment. Benzene sensitized vapor phase irradiation of cyclohexylallene (63) yields cis and trans-1,3,8-nonatriene (82) as the primary products. Triene 82 undergoes triplet sensitized (4+2) cycloaddition reactions yielding bicyclic alkenes 45 and 83. Additionally, 82 undergoes a series of triplet sensitized (2+2) cycloadditions, yielding bicyclic alkenes 84-86. The absence of any observed tricyclics argues for the intermediacy of planar triplet allene 89, instead of triplet cyclopropylidene 88. Benzene sensitized vapor phase irradiation of vinylidenecycloheptane (64) yielded only starting material. Models indicated that neither intermediate, triplet cyclopropylidene 99 or planar triplet allene 100, was particularly well suited for hydrogen abstraction to occur. Benzene sensitized solution phase irradiation of either 63 or 64 yielded only starting material.
Ab initio calculations at the UMP3/6-31G*//UHF/3-21G level are reported for hydrogen abstraction from methane by triplet cyclopropylidene (52), and planar triplet allene (61). The calculations predict E$\sb{\rm a}$ = 16.7 and 18.8 kcal/mol for hydrogen abstraction by 52 and 61, respectively.
The syntheses and trapping of 1-phenyl-1,2-cyclohexadiene (137) is described. Several pathways directed toward the synthesis of 1,2-cyclopentadiene (131) are also described. Additionally, the development of a new, and presumably general route to cyclic allenes is presented.
The syntheses and trapping of 1,2,3-cyclohexatriene (199) and cyclohexen-3-yne (240) are described. Both are prepared by introduction of the strained $\pi$ bond through fluoride induced elimination of vicinal trimethylsilyl, and triflate or halide groups. Both syntheses are general and should be applicable to different ring sizes.
Recommended Citation
Shakespeare, William Calvin, "I Asymmetric photochemistry II Exploratory and mechanistic studies on the triplet sensitized vapor phase photochemistry of allenes III Developments in the synthesis of strained cyclic cumulenes" (1993). Doctoral Dissertations. 1740.
https://scholars.unh.edu/dissertation/1740