Methylenecyclopropene was generated under two different reaction conditions. The passage of 2-chloromethylenecyclopropane through a vertical column containing potassium t-butoxide supported on Chromosorb W (45/60 mesh) at 240(DEGREES)C and 10 mtorr produced methylenecyclopropene nearly free of impurities. The nuclear magnetic resonance spectra (('1)H and ('13)C) were obtained at -100(DEGREES)C in tetrahydrofuran-d(,8). The exocyclic protons appeared at (delta) 3.47 (t, J = 2.2 Hz) and the ring protons at (delta) 8.61 (t, J = 2.2 Hz). The exocyclic carbon appeared at (delta) 59.57 (t, ('1)J(,CH) = 161.5 Hz) and the ring carbons at (delta) 132.90 (t, ('1)J(,CH) = 228.5 Hz). The quaternary carbon was not observed. The infrared spectrum was obtained on an IBM Model 98 FTIR. The characteristic high energy transition appeared at 1770.3 cm('-1). These spectra indicate that 1a contributes significantly to the resonance hybrid.
Methylenecyclopropene was also generated and trapped in a second flask as a Diels-Alder adduct when 2-bromomethylenecyclopropane was injected into a hot solution (75(DEGREES)C) of potassium t-butoxide in dimethyl sulfoxide and the volatiles trapped in a second flask containing cyclopentadiene.
A series of aromatic gem-dichlorocyclopropanes, precursors to the cycloproparenes, were eliminated by potassium t-butoxide in dimethyl sulfoxide in the presence of methyl mercaptide. The major products were the (thiomethyl)methylaromatics. The failure to trap the expected cyclopropenes is seen as evidence of the reaction proceeding via a different mechanism in the higher homologs. This necessitated the development of a synthetic sequence in which the leaving groups were positioned at the bridge-head carbons.
1H-Cycloprop{b}anthracene was synthesized via this new synthetic sequence which involves the Diels-Alder reaction of 1-bromo-2-chlorocyclopropene. The treatment of 1a-bromo-9a-chloro-1a,2,9,9a-tetrahydro-1H-cycloprop{b}anthracene with potassium t-butoxide in tetrahydrofuran at -78 to -30(DEGREES)C afforded 1H-cycloprop{b}anthracene in 41.5% yield. The absence of unusual spectral properties (('1)H NMR, ('13)C NMR, UV, IR) indicates that it does not possess any great degree of bond fixation.
| Identifer | oai:union.ndltd.org:RICE/oai:scholarship.rice.edu:1911/15808 |
| Date | January 1984 |
| Creators | CASSERLY, EDWARD W. |
| Source Sets | Rice University |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | application/pdf |
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