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Research describes the flash vacuum pyrolysis of methoxy-substituted beta-O-4 lignin compounds at 500 C, which involves free-radical reactions, molecular rearrangements, and elimination reactions. Data discuss the reactions with model lignin compounds.

1H-Cyclopropa[b]naphthalene is converted into novel polar olefins 15-19 via reaction of the 1,1-disilyl with anthrone-like ketones. The alkenes so formed are crystalline, polar compounds that range in color from yellow to magenta. Solutions of the 10,10-dimethylanthrylidene 15, the xanthenylidene 16, and N-methylacrydinylidene 18 fluoresce; parent anthrone 19 likely phosphoresces. X-ray crystal structure determinations are reported for 15, 18, and the thioxanthenylidene 17. Theoretical studies using ab initio calculations at the HF/6-31G level have been performed to provide assessments of the structures, charge distributions, and dipole moments of 15-19.

A new synthetic methodology enables the preparation of the permethylated and perspirocycloproponated cyclotetradeca-1,3,6,9,12-pentayne. X-ray crystallographic and spectroscopic studies show that in the permethylated pentayne, compression of the internal C-C-C bond angles at the saturated carbon atoms surrounding the diyne increases the through-space Pi-orbital interactions, resulting in a bathochromic shift. Wider internal C-C-C band angles of perspirocyclopropanated pentayne decrease the through-space Pi-orbital interaction, while spirocyclopropanation increases the through-bond Pi-orbital interactions.

Spectroscopic methods help analyze the structure and rearrangements in an oxaspiropentene derivative, 3',3'-diphenylspiro(1H-cyclo-propa(b)naphthalene-1, 2'-oxirane). Under acidic conditions, this epoxide rearranges to a diol. Use of labeled dimethyldioxirane as an oxygen atom transfer reagent enables the characterization of this derivative.

Synthesizes the permealated and perspirocyclopropanated cyclotetradeca-1,3,6,9,12-pentaynes. Compression of the internal C-C-C bond angles at the saturated carbon atoms flanking the diyne enhances the through-space pi-orbital interactions and causes a bathochromic shift in the long wavelength UV absorption maximum relative to that of reference compounds.

[reaction: see text] The simple bicyclopropenylidene derivative 21b, stabilized by fusion into naphthalene, results from reaction of dimesitylcyclopropenone 20b with the 1-trimethylsilyl-1H-cyclopropa[b]naphthalenyl anion. Although unstable in air, the molecule survives ambient conditions long enough for separation and mass spectral characterization. Aerial oxidation of 21b leads to 2,3-dimesitylanthracene-1,4-dione 22b whose X-ray crystal structure has been determined. While diphenylcyclopropenone 20a does not give identifiable products, the di-tert-butyl analogue 20c gives quinone 22c but in lower yield.